mirror of https://gitee.com/openkylin/linux.git
3163 lines
85 KiB
C
3163 lines
85 KiB
C
/*
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* linux/mm/filemap.c
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*
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* Copyright (C) 1994-1999 Linus Torvalds
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*/
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/*
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* This file handles the generic file mmap semantics used by
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* most "normal" filesystems (but you don't /have/ to use this:
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* the NFS filesystem used to do this differently, for example)
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*/
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#include <linux/export.h>
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#include <linux/compiler.h>
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#include <linux/dax.h>
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#include <linux/fs.h>
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#include <linux/sched/signal.h>
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#include <linux/uaccess.h>
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#include <linux/capability.h>
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#include <linux/kernel_stat.h>
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#include <linux/gfp.h>
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#include <linux/mm.h>
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#include <linux/swap.h>
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#include <linux/mman.h>
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#include <linux/pagemap.h>
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#include <linux/file.h>
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#include <linux/uio.h>
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#include <linux/hash.h>
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#include <linux/writeback.h>
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#include <linux/backing-dev.h>
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#include <linux/pagevec.h>
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#include <linux/blkdev.h>
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#include <linux/security.h>
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#include <linux/cpuset.h>
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#include <linux/hardirq.h> /* for BUG_ON(!in_atomic()) only */
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#include <linux/hugetlb.h>
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#include <linux/memcontrol.h>
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#include <linux/cleancache.h>
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#include <linux/rmap.h>
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#include "internal.h"
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#define CREATE_TRACE_POINTS
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#include <trace/events/filemap.h>
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/*
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* FIXME: remove all knowledge of the buffer layer from the core VM
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*/
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#include <linux/buffer_head.h> /* for try_to_free_buffers */
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#include <asm/mman.h>
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/*
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* Shared mappings implemented 30.11.1994. It's not fully working yet,
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* though.
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*
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* Shared mappings now work. 15.8.1995 Bruno.
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*
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* finished 'unifying' the page and buffer cache and SMP-threaded the
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* page-cache, 21.05.1999, Ingo Molnar <mingo@redhat.com>
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*
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* SMP-threaded pagemap-LRU 1999, Andrea Arcangeli <andrea@suse.de>
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*/
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/*
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* Lock ordering:
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*
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* ->i_mmap_rwsem (truncate_pagecache)
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* ->private_lock (__free_pte->__set_page_dirty_buffers)
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* ->swap_lock (exclusive_swap_page, others)
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* ->mapping->tree_lock
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*
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* ->i_mutex
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* ->i_mmap_rwsem (truncate->unmap_mapping_range)
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*
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* ->mmap_sem
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* ->i_mmap_rwsem
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* ->page_table_lock or pte_lock (various, mainly in memory.c)
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* ->mapping->tree_lock (arch-dependent flush_dcache_mmap_lock)
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*
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* ->mmap_sem
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* ->lock_page (access_process_vm)
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*
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* ->i_mutex (generic_perform_write)
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* ->mmap_sem (fault_in_pages_readable->do_page_fault)
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*
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* bdi->wb.list_lock
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* sb_lock (fs/fs-writeback.c)
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* ->mapping->tree_lock (__sync_single_inode)
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*
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* ->i_mmap_rwsem
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* ->anon_vma.lock (vma_adjust)
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*
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* ->anon_vma.lock
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* ->page_table_lock or pte_lock (anon_vma_prepare and various)
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*
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* ->page_table_lock or pte_lock
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* ->swap_lock (try_to_unmap_one)
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* ->private_lock (try_to_unmap_one)
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* ->tree_lock (try_to_unmap_one)
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* ->zone_lru_lock(zone) (follow_page->mark_page_accessed)
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* ->zone_lru_lock(zone) (check_pte_range->isolate_lru_page)
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* ->private_lock (page_remove_rmap->set_page_dirty)
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* ->tree_lock (page_remove_rmap->set_page_dirty)
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* bdi.wb->list_lock (page_remove_rmap->set_page_dirty)
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* ->inode->i_lock (page_remove_rmap->set_page_dirty)
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* ->memcg->move_lock (page_remove_rmap->lock_page_memcg)
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* bdi.wb->list_lock (zap_pte_range->set_page_dirty)
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* ->inode->i_lock (zap_pte_range->set_page_dirty)
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* ->private_lock (zap_pte_range->__set_page_dirty_buffers)
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*
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* ->i_mmap_rwsem
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* ->tasklist_lock (memory_failure, collect_procs_ao)
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*/
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static int page_cache_tree_insert(struct address_space *mapping,
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struct page *page, void **shadowp)
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{
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struct radix_tree_node *node;
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void **slot;
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int error;
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error = __radix_tree_create(&mapping->page_tree, page->index, 0,
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&node, &slot);
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if (error)
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return error;
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if (*slot) {
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void *p;
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p = radix_tree_deref_slot_protected(slot, &mapping->tree_lock);
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if (!radix_tree_exceptional_entry(p))
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return -EEXIST;
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mapping->nrexceptional--;
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if (!dax_mapping(mapping)) {
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if (shadowp)
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*shadowp = p;
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} else {
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/* DAX can replace empty locked entry with a hole */
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WARN_ON_ONCE(p !=
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dax_radix_locked_entry(0, RADIX_DAX_EMPTY));
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/* Wakeup waiters for exceptional entry lock */
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dax_wake_mapping_entry_waiter(mapping, page->index, p,
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true);
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}
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}
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__radix_tree_replace(&mapping->page_tree, node, slot, page,
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workingset_update_node, mapping);
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mapping->nrpages++;
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return 0;
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}
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static void page_cache_tree_delete(struct address_space *mapping,
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struct page *page, void *shadow)
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{
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int i, nr;
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/* hugetlb pages are represented by one entry in the radix tree */
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nr = PageHuge(page) ? 1 : hpage_nr_pages(page);
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VM_BUG_ON_PAGE(!PageLocked(page), page);
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VM_BUG_ON_PAGE(PageTail(page), page);
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VM_BUG_ON_PAGE(nr != 1 && shadow, page);
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for (i = 0; i < nr; i++) {
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struct radix_tree_node *node;
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void **slot;
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__radix_tree_lookup(&mapping->page_tree, page->index + i,
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&node, &slot);
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VM_BUG_ON_PAGE(!node && nr != 1, page);
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radix_tree_clear_tags(&mapping->page_tree, node, slot);
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__radix_tree_replace(&mapping->page_tree, node, slot, shadow,
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workingset_update_node, mapping);
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}
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if (shadow) {
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mapping->nrexceptional += nr;
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/*
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* Make sure the nrexceptional update is committed before
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* the nrpages update so that final truncate racing
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* with reclaim does not see both counters 0 at the
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* same time and miss a shadow entry.
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*/
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smp_wmb();
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}
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mapping->nrpages -= nr;
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}
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/*
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* Delete a page from the page cache and free it. Caller has to make
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* sure the page is locked and that nobody else uses it - or that usage
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* is safe. The caller must hold the mapping's tree_lock.
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*/
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void __delete_from_page_cache(struct page *page, void *shadow)
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{
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struct address_space *mapping = page->mapping;
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int nr = hpage_nr_pages(page);
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trace_mm_filemap_delete_from_page_cache(page);
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/*
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* if we're uptodate, flush out into the cleancache, otherwise
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* invalidate any existing cleancache entries. We can't leave
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* stale data around in the cleancache once our page is gone
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*/
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if (PageUptodate(page) && PageMappedToDisk(page))
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cleancache_put_page(page);
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else
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cleancache_invalidate_page(mapping, page);
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VM_BUG_ON_PAGE(PageTail(page), page);
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VM_BUG_ON_PAGE(page_mapped(page), page);
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if (!IS_ENABLED(CONFIG_DEBUG_VM) && unlikely(page_mapped(page))) {
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int mapcount;
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pr_alert("BUG: Bad page cache in process %s pfn:%05lx\n",
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current->comm, page_to_pfn(page));
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dump_page(page, "still mapped when deleted");
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dump_stack();
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add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE);
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mapcount = page_mapcount(page);
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if (mapping_exiting(mapping) &&
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page_count(page) >= mapcount + 2) {
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/*
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* All vmas have already been torn down, so it's
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* a good bet that actually the page is unmapped,
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* and we'd prefer not to leak it: if we're wrong,
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* some other bad page check should catch it later.
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*/
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page_mapcount_reset(page);
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page_ref_sub(page, mapcount);
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}
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}
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page_cache_tree_delete(mapping, page, shadow);
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page->mapping = NULL;
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/* Leave page->index set: truncation lookup relies upon it */
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/* hugetlb pages do not participate in page cache accounting. */
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if (PageHuge(page))
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return;
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__mod_node_page_state(page_pgdat(page), NR_FILE_PAGES, -nr);
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if (PageSwapBacked(page)) {
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__mod_node_page_state(page_pgdat(page), NR_SHMEM, -nr);
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if (PageTransHuge(page))
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__dec_node_page_state(page, NR_SHMEM_THPS);
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} else {
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VM_BUG_ON_PAGE(PageTransHuge(page), page);
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}
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/*
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* At this point page must be either written or cleaned by truncate.
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* Dirty page here signals a bug and loss of unwritten data.
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*
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* This fixes dirty accounting after removing the page entirely but
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* leaves PageDirty set: it has no effect for truncated page and
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* anyway will be cleared before returning page into buddy allocator.
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*/
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if (WARN_ON_ONCE(PageDirty(page)))
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account_page_cleaned(page, mapping, inode_to_wb(mapping->host));
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}
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/**
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* delete_from_page_cache - delete page from page cache
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* @page: the page which the kernel is trying to remove from page cache
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*
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* This must be called only on pages that have been verified to be in the page
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* cache and locked. It will never put the page into the free list, the caller
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* has a reference on the page.
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*/
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void delete_from_page_cache(struct page *page)
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{
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struct address_space *mapping = page_mapping(page);
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unsigned long flags;
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void (*freepage)(struct page *);
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BUG_ON(!PageLocked(page));
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freepage = mapping->a_ops->freepage;
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spin_lock_irqsave(&mapping->tree_lock, flags);
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__delete_from_page_cache(page, NULL);
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spin_unlock_irqrestore(&mapping->tree_lock, flags);
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if (freepage)
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freepage(page);
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if (PageTransHuge(page) && !PageHuge(page)) {
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page_ref_sub(page, HPAGE_PMD_NR);
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VM_BUG_ON_PAGE(page_count(page) <= 0, page);
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} else {
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put_page(page);
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}
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}
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EXPORT_SYMBOL(delete_from_page_cache);
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int filemap_check_errors(struct address_space *mapping)
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{
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int ret = 0;
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/* Check for outstanding write errors */
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if (test_bit(AS_ENOSPC, &mapping->flags) &&
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test_and_clear_bit(AS_ENOSPC, &mapping->flags))
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ret = -ENOSPC;
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if (test_bit(AS_EIO, &mapping->flags) &&
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test_and_clear_bit(AS_EIO, &mapping->flags))
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ret = -EIO;
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return ret;
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}
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EXPORT_SYMBOL(filemap_check_errors);
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static int filemap_check_and_keep_errors(struct address_space *mapping)
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{
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/* Check for outstanding write errors */
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if (test_bit(AS_EIO, &mapping->flags))
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return -EIO;
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if (test_bit(AS_ENOSPC, &mapping->flags))
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return -ENOSPC;
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return 0;
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}
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/**
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* __filemap_fdatawrite_range - start writeback on mapping dirty pages in range
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* @mapping: address space structure to write
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* @start: offset in bytes where the range starts
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* @end: offset in bytes where the range ends (inclusive)
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* @sync_mode: enable synchronous operation
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*
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* Start writeback against all of a mapping's dirty pages that lie
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* within the byte offsets <start, end> inclusive.
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*
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* If sync_mode is WB_SYNC_ALL then this is a "data integrity" operation, as
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* opposed to a regular memory cleansing writeback. The difference between
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* these two operations is that if a dirty page/buffer is encountered, it must
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* be waited upon, and not just skipped over.
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*/
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int __filemap_fdatawrite_range(struct address_space *mapping, loff_t start,
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loff_t end, int sync_mode)
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{
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int ret;
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struct writeback_control wbc = {
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.sync_mode = sync_mode,
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.nr_to_write = LONG_MAX,
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.range_start = start,
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.range_end = end,
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};
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if (!mapping_cap_writeback_dirty(mapping))
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return 0;
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wbc_attach_fdatawrite_inode(&wbc, mapping->host);
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ret = do_writepages(mapping, &wbc);
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wbc_detach_inode(&wbc);
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return ret;
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}
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static inline int __filemap_fdatawrite(struct address_space *mapping,
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int sync_mode)
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{
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return __filemap_fdatawrite_range(mapping, 0, LLONG_MAX, sync_mode);
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}
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int filemap_fdatawrite(struct address_space *mapping)
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{
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return __filemap_fdatawrite(mapping, WB_SYNC_ALL);
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}
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EXPORT_SYMBOL(filemap_fdatawrite);
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int filemap_fdatawrite_range(struct address_space *mapping, loff_t start,
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loff_t end)
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{
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return __filemap_fdatawrite_range(mapping, start, end, WB_SYNC_ALL);
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}
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EXPORT_SYMBOL(filemap_fdatawrite_range);
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/**
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* filemap_flush - mostly a non-blocking flush
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* @mapping: target address_space
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*
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* This is a mostly non-blocking flush. Not suitable for data-integrity
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* purposes - I/O may not be started against all dirty pages.
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*/
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int filemap_flush(struct address_space *mapping)
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{
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return __filemap_fdatawrite(mapping, WB_SYNC_NONE);
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}
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EXPORT_SYMBOL(filemap_flush);
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/**
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* filemap_range_has_page - check if a page exists in range.
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* @mapping: address space within which to check
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* @start_byte: offset in bytes where the range starts
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* @end_byte: offset in bytes where the range ends (inclusive)
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*
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* Find at least one page in the range supplied, usually used to check if
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* direct writing in this range will trigger a writeback.
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*/
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bool filemap_range_has_page(struct address_space *mapping,
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loff_t start_byte, loff_t end_byte)
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{
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pgoff_t index = start_byte >> PAGE_SHIFT;
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pgoff_t end = end_byte >> PAGE_SHIFT;
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struct pagevec pvec;
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bool ret;
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if (end_byte < start_byte)
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return false;
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if (mapping->nrpages == 0)
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return false;
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pagevec_init(&pvec, 0);
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if (!pagevec_lookup(&pvec, mapping, index, 1))
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return false;
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ret = (pvec.pages[0]->index <= end);
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pagevec_release(&pvec);
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return ret;
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}
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EXPORT_SYMBOL(filemap_range_has_page);
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static void __filemap_fdatawait_range(struct address_space *mapping,
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loff_t start_byte, loff_t end_byte)
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{
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pgoff_t index = start_byte >> PAGE_SHIFT;
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pgoff_t end = end_byte >> PAGE_SHIFT;
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struct pagevec pvec;
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int nr_pages;
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if (end_byte < start_byte)
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return;
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pagevec_init(&pvec, 0);
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while ((index <= end) &&
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(nr_pages = pagevec_lookup_tag(&pvec, mapping, &index,
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PAGECACHE_TAG_WRITEBACK,
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min(end - index, (pgoff_t)PAGEVEC_SIZE-1) + 1)) != 0) {
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unsigned i;
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for (i = 0; i < nr_pages; i++) {
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struct page *page = pvec.pages[i];
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/* until radix tree lookup accepts end_index */
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if (page->index > end)
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continue;
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wait_on_page_writeback(page);
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ClearPageError(page);
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}
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pagevec_release(&pvec);
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cond_resched();
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}
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}
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/**
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* filemap_fdatawait_range - wait for writeback to complete
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* @mapping: address space structure to wait for
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* @start_byte: offset in bytes where the range starts
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* @end_byte: offset in bytes where the range ends (inclusive)
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*
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* Walk the list of under-writeback pages of the given address space
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* in the given range and wait for all of them. Check error status of
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* the address space and return it.
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*
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* Since the error status of the address space is cleared by this function,
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* callers are responsible for checking the return value and handling and/or
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* reporting the error.
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*/
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int filemap_fdatawait_range(struct address_space *mapping, loff_t start_byte,
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loff_t end_byte)
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{
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__filemap_fdatawait_range(mapping, start_byte, end_byte);
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return filemap_check_errors(mapping);
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}
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EXPORT_SYMBOL(filemap_fdatawait_range);
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/**
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* filemap_fdatawait_keep_errors - wait for writeback without clearing errors
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* @mapping: address space structure to wait for
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*
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* Walk the list of under-writeback pages of the given address space
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* and wait for all of them. Unlike filemap_fdatawait(), this function
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* does not clear error status of the address space.
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*
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* Use this function if callers don't handle errors themselves. Expected
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* call sites are system-wide / filesystem-wide data flushers: e.g. sync(2),
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* fsfreeze(8)
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*/
|
|
int filemap_fdatawait_keep_errors(struct address_space *mapping)
|
|
{
|
|
loff_t i_size = i_size_read(mapping->host);
|
|
|
|
if (i_size == 0)
|
|
return 0;
|
|
|
|
__filemap_fdatawait_range(mapping, 0, i_size - 1);
|
|
return filemap_check_and_keep_errors(mapping);
|
|
}
|
|
EXPORT_SYMBOL(filemap_fdatawait_keep_errors);
|
|
|
|
/**
|
|
* filemap_fdatawait - wait for all under-writeback pages to complete
|
|
* @mapping: address space structure to wait for
|
|
*
|
|
* Walk the list of under-writeback pages of the given address space
|
|
* and wait for all of them. Check error status of the address space
|
|
* and return it.
|
|
*
|
|
* Since the error status of the address space is cleared by this function,
|
|
* callers are responsible for checking the return value and handling and/or
|
|
* reporting the error.
|
|
*/
|
|
int filemap_fdatawait(struct address_space *mapping)
|
|
{
|
|
loff_t i_size = i_size_read(mapping->host);
|
|
|
|
if (i_size == 0)
|
|
return 0;
|
|
|
|
return filemap_fdatawait_range(mapping, 0, i_size - 1);
|
|
}
|
|
EXPORT_SYMBOL(filemap_fdatawait);
|
|
|
|
int filemap_write_and_wait(struct address_space *mapping)
|
|
{
|
|
int err = 0;
|
|
|
|
if ((!dax_mapping(mapping) && mapping->nrpages) ||
|
|
(dax_mapping(mapping) && mapping->nrexceptional)) {
|
|
err = filemap_fdatawrite(mapping);
|
|
/*
|
|
* Even if the above returned error, the pages may be
|
|
* written partially (e.g. -ENOSPC), so we wait for it.
|
|
* But the -EIO is special case, it may indicate the worst
|
|
* thing (e.g. bug) happened, so we avoid waiting for it.
|
|
*/
|
|
if (err != -EIO) {
|
|
int err2 = filemap_fdatawait(mapping);
|
|
if (!err)
|
|
err = err2;
|
|
} else {
|
|
/* Clear any previously stored errors */
|
|
filemap_check_errors(mapping);
|
|
}
|
|
} else {
|
|
err = filemap_check_errors(mapping);
|
|
}
|
|
return err;
|
|
}
|
|
EXPORT_SYMBOL(filemap_write_and_wait);
|
|
|
|
/**
|
|
* filemap_write_and_wait_range - write out & wait on a file range
|
|
* @mapping: the address_space for the pages
|
|
* @lstart: offset in bytes where the range starts
|
|
* @lend: offset in bytes where the range ends (inclusive)
|
|
*
|
|
* Write out and wait upon file offsets lstart->lend, inclusive.
|
|
*
|
|
* Note that @lend is inclusive (describes the last byte to be written) so
|
|
* that this function can be used to write to the very end-of-file (end = -1).
|
|
*/
|
|
int filemap_write_and_wait_range(struct address_space *mapping,
|
|
loff_t lstart, loff_t lend)
|
|
{
|
|
int err = 0;
|
|
|
|
if ((!dax_mapping(mapping) && mapping->nrpages) ||
|
|
(dax_mapping(mapping) && mapping->nrexceptional)) {
|
|
err = __filemap_fdatawrite_range(mapping, lstart, lend,
|
|
WB_SYNC_ALL);
|
|
/* See comment of filemap_write_and_wait() */
|
|
if (err != -EIO) {
|
|
int err2 = filemap_fdatawait_range(mapping,
|
|
lstart, lend);
|
|
if (!err)
|
|
err = err2;
|
|
} else {
|
|
/* Clear any previously stored errors */
|
|
filemap_check_errors(mapping);
|
|
}
|
|
} else {
|
|
err = filemap_check_errors(mapping);
|
|
}
|
|
return err;
|
|
}
|
|
EXPORT_SYMBOL(filemap_write_and_wait_range);
|
|
|
|
void __filemap_set_wb_err(struct address_space *mapping, int err)
|
|
{
|
|
errseq_t eseq = __errseq_set(&mapping->wb_err, err);
|
|
|
|
trace_filemap_set_wb_err(mapping, eseq);
|
|
}
|
|
EXPORT_SYMBOL(__filemap_set_wb_err);
|
|
|
|
/**
|
|
* file_check_and_advance_wb_err - report wb error (if any) that was previously
|
|
* and advance wb_err to current one
|
|
* @file: struct file on which the error is being reported
|
|
*
|
|
* When userland calls fsync (or something like nfsd does the equivalent), we
|
|
* want to report any writeback errors that occurred since the last fsync (or
|
|
* since the file was opened if there haven't been any).
|
|
*
|
|
* Grab the wb_err from the mapping. If it matches what we have in the file,
|
|
* then just quickly return 0. The file is all caught up.
|
|
*
|
|
* If it doesn't match, then take the mapping value, set the "seen" flag in
|
|
* it and try to swap it into place. If it works, or another task beat us
|
|
* to it with the new value, then update the f_wb_err and return the error
|
|
* portion. The error at this point must be reported via proper channels
|
|
* (a'la fsync, or NFS COMMIT operation, etc.).
|
|
*
|
|
* While we handle mapping->wb_err with atomic operations, the f_wb_err
|
|
* value is protected by the f_lock since we must ensure that it reflects
|
|
* the latest value swapped in for this file descriptor.
|
|
*/
|
|
int file_check_and_advance_wb_err(struct file *file)
|
|
{
|
|
int err = 0;
|
|
errseq_t old = READ_ONCE(file->f_wb_err);
|
|
struct address_space *mapping = file->f_mapping;
|
|
|
|
/* Locklessly handle the common case where nothing has changed */
|
|
if (errseq_check(&mapping->wb_err, old)) {
|
|
/* Something changed, must use slow path */
|
|
spin_lock(&file->f_lock);
|
|
old = file->f_wb_err;
|
|
err = errseq_check_and_advance(&mapping->wb_err,
|
|
&file->f_wb_err);
|
|
trace_file_check_and_advance_wb_err(file, old);
|
|
spin_unlock(&file->f_lock);
|
|
}
|
|
return err;
|
|
}
|
|
EXPORT_SYMBOL(file_check_and_advance_wb_err);
|
|
|
|
/**
|
|
* file_write_and_wait_range - write out & wait on a file range
|
|
* @file: file pointing to address_space with pages
|
|
* @lstart: offset in bytes where the range starts
|
|
* @lend: offset in bytes where the range ends (inclusive)
|
|
*
|
|
* Write out and wait upon file offsets lstart->lend, inclusive.
|
|
*
|
|
* Note that @lend is inclusive (describes the last byte to be written) so
|
|
* that this function can be used to write to the very end-of-file (end = -1).
|
|
*
|
|
* After writing out and waiting on the data, we check and advance the
|
|
* f_wb_err cursor to the latest value, and return any errors detected there.
|
|
*/
|
|
int file_write_and_wait_range(struct file *file, loff_t lstart, loff_t lend)
|
|
{
|
|
int err = 0, err2;
|
|
struct address_space *mapping = file->f_mapping;
|
|
|
|
if ((!dax_mapping(mapping) && mapping->nrpages) ||
|
|
(dax_mapping(mapping) && mapping->nrexceptional)) {
|
|
err = __filemap_fdatawrite_range(mapping, lstart, lend,
|
|
WB_SYNC_ALL);
|
|
/* See comment of filemap_write_and_wait() */
|
|
if (err != -EIO)
|
|
__filemap_fdatawait_range(mapping, lstart, lend);
|
|
}
|
|
err2 = file_check_and_advance_wb_err(file);
|
|
if (!err)
|
|
err = err2;
|
|
return err;
|
|
}
|
|
EXPORT_SYMBOL(file_write_and_wait_range);
|
|
|
|
/**
|
|
* replace_page_cache_page - replace a pagecache page with a new one
|
|
* @old: page to be replaced
|
|
* @new: page to replace with
|
|
* @gfp_mask: allocation mode
|
|
*
|
|
* This function replaces a page in the pagecache with a new one. On
|
|
* success it acquires the pagecache reference for the new page and
|
|
* drops it for the old page. Both the old and new pages must be
|
|
* locked. This function does not add the new page to the LRU, the
|
|
* caller must do that.
|
|
*
|
|
* The remove + add is atomic. The only way this function can fail is
|
|
* memory allocation failure.
|
|
*/
|
|
int replace_page_cache_page(struct page *old, struct page *new, gfp_t gfp_mask)
|
|
{
|
|
int error;
|
|
|
|
VM_BUG_ON_PAGE(!PageLocked(old), old);
|
|
VM_BUG_ON_PAGE(!PageLocked(new), new);
|
|
VM_BUG_ON_PAGE(new->mapping, new);
|
|
|
|
error = radix_tree_preload(gfp_mask & ~__GFP_HIGHMEM);
|
|
if (!error) {
|
|
struct address_space *mapping = old->mapping;
|
|
void (*freepage)(struct page *);
|
|
unsigned long flags;
|
|
|
|
pgoff_t offset = old->index;
|
|
freepage = mapping->a_ops->freepage;
|
|
|
|
get_page(new);
|
|
new->mapping = mapping;
|
|
new->index = offset;
|
|
|
|
spin_lock_irqsave(&mapping->tree_lock, flags);
|
|
__delete_from_page_cache(old, NULL);
|
|
error = page_cache_tree_insert(mapping, new, NULL);
|
|
BUG_ON(error);
|
|
|
|
/*
|
|
* hugetlb pages do not participate in page cache accounting.
|
|
*/
|
|
if (!PageHuge(new))
|
|
__inc_node_page_state(new, NR_FILE_PAGES);
|
|
if (PageSwapBacked(new))
|
|
__inc_node_page_state(new, NR_SHMEM);
|
|
spin_unlock_irqrestore(&mapping->tree_lock, flags);
|
|
mem_cgroup_migrate(old, new);
|
|
radix_tree_preload_end();
|
|
if (freepage)
|
|
freepage(old);
|
|
put_page(old);
|
|
}
|
|
|
|
return error;
|
|
}
|
|
EXPORT_SYMBOL_GPL(replace_page_cache_page);
|
|
|
|
static int __add_to_page_cache_locked(struct page *page,
|
|
struct address_space *mapping,
|
|
pgoff_t offset, gfp_t gfp_mask,
|
|
void **shadowp)
|
|
{
|
|
int huge = PageHuge(page);
|
|
struct mem_cgroup *memcg;
|
|
int error;
|
|
|
|
VM_BUG_ON_PAGE(!PageLocked(page), page);
|
|
VM_BUG_ON_PAGE(PageSwapBacked(page), page);
|
|
|
|
if (!huge) {
|
|
error = mem_cgroup_try_charge(page, current->mm,
|
|
gfp_mask, &memcg, false);
|
|
if (error)
|
|
return error;
|
|
}
|
|
|
|
error = radix_tree_maybe_preload(gfp_mask & ~__GFP_HIGHMEM);
|
|
if (error) {
|
|
if (!huge)
|
|
mem_cgroup_cancel_charge(page, memcg, false);
|
|
return error;
|
|
}
|
|
|
|
get_page(page);
|
|
page->mapping = mapping;
|
|
page->index = offset;
|
|
|
|
spin_lock_irq(&mapping->tree_lock);
|
|
error = page_cache_tree_insert(mapping, page, shadowp);
|
|
radix_tree_preload_end();
|
|
if (unlikely(error))
|
|
goto err_insert;
|
|
|
|
/* hugetlb pages do not participate in page cache accounting. */
|
|
if (!huge)
|
|
__inc_node_page_state(page, NR_FILE_PAGES);
|
|
spin_unlock_irq(&mapping->tree_lock);
|
|
if (!huge)
|
|
mem_cgroup_commit_charge(page, memcg, false, false);
|
|
trace_mm_filemap_add_to_page_cache(page);
|
|
return 0;
|
|
err_insert:
|
|
page->mapping = NULL;
|
|
/* Leave page->index set: truncation relies upon it */
|
|
spin_unlock_irq(&mapping->tree_lock);
|
|
if (!huge)
|
|
mem_cgroup_cancel_charge(page, memcg, false);
|
|
put_page(page);
|
|
return error;
|
|
}
|
|
|
|
/**
|
|
* add_to_page_cache_locked - add a locked page to the pagecache
|
|
* @page: page to add
|
|
* @mapping: the page's address_space
|
|
* @offset: page index
|
|
* @gfp_mask: page allocation mode
|
|
*
|
|
* This function is used to add a page to the pagecache. It must be locked.
|
|
* This function does not add the page to the LRU. The caller must do that.
|
|
*/
|
|
int add_to_page_cache_locked(struct page *page, struct address_space *mapping,
|
|
pgoff_t offset, gfp_t gfp_mask)
|
|
{
|
|
return __add_to_page_cache_locked(page, mapping, offset,
|
|
gfp_mask, NULL);
|
|
}
|
|
EXPORT_SYMBOL(add_to_page_cache_locked);
|
|
|
|
int add_to_page_cache_lru(struct page *page, struct address_space *mapping,
|
|
pgoff_t offset, gfp_t gfp_mask)
|
|
{
|
|
void *shadow = NULL;
|
|
int ret;
|
|
|
|
__SetPageLocked(page);
|
|
ret = __add_to_page_cache_locked(page, mapping, offset,
|
|
gfp_mask, &shadow);
|
|
if (unlikely(ret))
|
|
__ClearPageLocked(page);
|
|
else {
|
|
/*
|
|
* The page might have been evicted from cache only
|
|
* recently, in which case it should be activated like
|
|
* any other repeatedly accessed page.
|
|
* The exception is pages getting rewritten; evicting other
|
|
* data from the working set, only to cache data that will
|
|
* get overwritten with something else, is a waste of memory.
|
|
*/
|
|
if (!(gfp_mask & __GFP_WRITE) &&
|
|
shadow && workingset_refault(shadow)) {
|
|
SetPageActive(page);
|
|
workingset_activation(page);
|
|
} else
|
|
ClearPageActive(page);
|
|
lru_cache_add(page);
|
|
}
|
|
return ret;
|
|
}
|
|
EXPORT_SYMBOL_GPL(add_to_page_cache_lru);
|
|
|
|
#ifdef CONFIG_NUMA
|
|
struct page *__page_cache_alloc(gfp_t gfp)
|
|
{
|
|
int n;
|
|
struct page *page;
|
|
|
|
if (cpuset_do_page_mem_spread()) {
|
|
unsigned int cpuset_mems_cookie;
|
|
do {
|
|
cpuset_mems_cookie = read_mems_allowed_begin();
|
|
n = cpuset_mem_spread_node();
|
|
page = __alloc_pages_node(n, gfp, 0);
|
|
} while (!page && read_mems_allowed_retry(cpuset_mems_cookie));
|
|
|
|
return page;
|
|
}
|
|
return alloc_pages(gfp, 0);
|
|
}
|
|
EXPORT_SYMBOL(__page_cache_alloc);
|
|
#endif
|
|
|
|
/*
|
|
* In order to wait for pages to become available there must be
|
|
* waitqueues associated with pages. By using a hash table of
|
|
* waitqueues where the bucket discipline is to maintain all
|
|
* waiters on the same queue and wake all when any of the pages
|
|
* become available, and for the woken contexts to check to be
|
|
* sure the appropriate page became available, this saves space
|
|
* at a cost of "thundering herd" phenomena during rare hash
|
|
* collisions.
|
|
*/
|
|
#define PAGE_WAIT_TABLE_BITS 8
|
|
#define PAGE_WAIT_TABLE_SIZE (1 << PAGE_WAIT_TABLE_BITS)
|
|
static wait_queue_head_t page_wait_table[PAGE_WAIT_TABLE_SIZE] __cacheline_aligned;
|
|
|
|
static wait_queue_head_t *page_waitqueue(struct page *page)
|
|
{
|
|
return &page_wait_table[hash_ptr(page, PAGE_WAIT_TABLE_BITS)];
|
|
}
|
|
|
|
void __init pagecache_init(void)
|
|
{
|
|
int i;
|
|
|
|
for (i = 0; i < PAGE_WAIT_TABLE_SIZE; i++)
|
|
init_waitqueue_head(&page_wait_table[i]);
|
|
|
|
page_writeback_init();
|
|
}
|
|
|
|
struct wait_page_key {
|
|
struct page *page;
|
|
int bit_nr;
|
|
int page_match;
|
|
};
|
|
|
|
struct wait_page_queue {
|
|
struct page *page;
|
|
int bit_nr;
|
|
wait_queue_entry_t wait;
|
|
};
|
|
|
|
static int wake_page_function(wait_queue_entry_t *wait, unsigned mode, int sync, void *arg)
|
|
{
|
|
struct wait_page_key *key = arg;
|
|
struct wait_page_queue *wait_page
|
|
= container_of(wait, struct wait_page_queue, wait);
|
|
|
|
if (wait_page->page != key->page)
|
|
return 0;
|
|
key->page_match = 1;
|
|
|
|
if (wait_page->bit_nr != key->bit_nr)
|
|
return 0;
|
|
if (test_bit(key->bit_nr, &key->page->flags))
|
|
return 0;
|
|
|
|
return autoremove_wake_function(wait, mode, sync, key);
|
|
}
|
|
|
|
static void wake_up_page_bit(struct page *page, int bit_nr)
|
|
{
|
|
wait_queue_head_t *q = page_waitqueue(page);
|
|
struct wait_page_key key;
|
|
unsigned long flags;
|
|
|
|
key.page = page;
|
|
key.bit_nr = bit_nr;
|
|
key.page_match = 0;
|
|
|
|
spin_lock_irqsave(&q->lock, flags);
|
|
__wake_up_locked_key(q, TASK_NORMAL, &key);
|
|
/*
|
|
* It is possible for other pages to have collided on the waitqueue
|
|
* hash, so in that case check for a page match. That prevents a long-
|
|
* term waiter
|
|
*
|
|
* It is still possible to miss a case here, when we woke page waiters
|
|
* and removed them from the waitqueue, but there are still other
|
|
* page waiters.
|
|
*/
|
|
if (!waitqueue_active(q) || !key.page_match) {
|
|
ClearPageWaiters(page);
|
|
/*
|
|
* It's possible to miss clearing Waiters here, when we woke
|
|
* our page waiters, but the hashed waitqueue has waiters for
|
|
* other pages on it.
|
|
*
|
|
* That's okay, it's a rare case. The next waker will clear it.
|
|
*/
|
|
}
|
|
spin_unlock_irqrestore(&q->lock, flags);
|
|
}
|
|
|
|
static void wake_up_page(struct page *page, int bit)
|
|
{
|
|
if (!PageWaiters(page))
|
|
return;
|
|
wake_up_page_bit(page, bit);
|
|
}
|
|
|
|
static inline int wait_on_page_bit_common(wait_queue_head_t *q,
|
|
struct page *page, int bit_nr, int state, bool lock)
|
|
{
|
|
struct wait_page_queue wait_page;
|
|
wait_queue_entry_t *wait = &wait_page.wait;
|
|
int ret = 0;
|
|
|
|
init_wait(wait);
|
|
wait->func = wake_page_function;
|
|
wait_page.page = page;
|
|
wait_page.bit_nr = bit_nr;
|
|
|
|
for (;;) {
|
|
spin_lock_irq(&q->lock);
|
|
|
|
if (likely(list_empty(&wait->entry))) {
|
|
if (lock)
|
|
__add_wait_queue_entry_tail_exclusive(q, wait);
|
|
else
|
|
__add_wait_queue(q, wait);
|
|
SetPageWaiters(page);
|
|
}
|
|
|
|
set_current_state(state);
|
|
|
|
spin_unlock_irq(&q->lock);
|
|
|
|
if (likely(test_bit(bit_nr, &page->flags))) {
|
|
io_schedule();
|
|
if (unlikely(signal_pending_state(state, current))) {
|
|
ret = -EINTR;
|
|
break;
|
|
}
|
|
}
|
|
|
|
if (lock) {
|
|
if (!test_and_set_bit_lock(bit_nr, &page->flags))
|
|
break;
|
|
} else {
|
|
if (!test_bit(bit_nr, &page->flags))
|
|
break;
|
|
}
|
|
}
|
|
|
|
finish_wait(q, wait);
|
|
|
|
/*
|
|
* A signal could leave PageWaiters set. Clearing it here if
|
|
* !waitqueue_active would be possible (by open-coding finish_wait),
|
|
* but still fail to catch it in the case of wait hash collision. We
|
|
* already can fail to clear wait hash collision cases, so don't
|
|
* bother with signals either.
|
|
*/
|
|
|
|
return ret;
|
|
}
|
|
|
|
void wait_on_page_bit(struct page *page, int bit_nr)
|
|
{
|
|
wait_queue_head_t *q = page_waitqueue(page);
|
|
wait_on_page_bit_common(q, page, bit_nr, TASK_UNINTERRUPTIBLE, false);
|
|
}
|
|
EXPORT_SYMBOL(wait_on_page_bit);
|
|
|
|
int wait_on_page_bit_killable(struct page *page, int bit_nr)
|
|
{
|
|
wait_queue_head_t *q = page_waitqueue(page);
|
|
return wait_on_page_bit_common(q, page, bit_nr, TASK_KILLABLE, false);
|
|
}
|
|
|
|
/**
|
|
* add_page_wait_queue - Add an arbitrary waiter to a page's wait queue
|
|
* @page: Page defining the wait queue of interest
|
|
* @waiter: Waiter to add to the queue
|
|
*
|
|
* Add an arbitrary @waiter to the wait queue for the nominated @page.
|
|
*/
|
|
void add_page_wait_queue(struct page *page, wait_queue_entry_t *waiter)
|
|
{
|
|
wait_queue_head_t *q = page_waitqueue(page);
|
|
unsigned long flags;
|
|
|
|
spin_lock_irqsave(&q->lock, flags);
|
|
__add_wait_queue(q, waiter);
|
|
SetPageWaiters(page);
|
|
spin_unlock_irqrestore(&q->lock, flags);
|
|
}
|
|
EXPORT_SYMBOL_GPL(add_page_wait_queue);
|
|
|
|
#ifndef clear_bit_unlock_is_negative_byte
|
|
|
|
/*
|
|
* PG_waiters is the high bit in the same byte as PG_lock.
|
|
*
|
|
* On x86 (and on many other architectures), we can clear PG_lock and
|
|
* test the sign bit at the same time. But if the architecture does
|
|
* not support that special operation, we just do this all by hand
|
|
* instead.
|
|
*
|
|
* The read of PG_waiters has to be after (or concurrently with) PG_locked
|
|
* being cleared, but a memory barrier should be unneccssary since it is
|
|
* in the same byte as PG_locked.
|
|
*/
|
|
static inline bool clear_bit_unlock_is_negative_byte(long nr, volatile void *mem)
|
|
{
|
|
clear_bit_unlock(nr, mem);
|
|
/* smp_mb__after_atomic(); */
|
|
return test_bit(PG_waiters, mem);
|
|
}
|
|
|
|
#endif
|
|
|
|
/**
|
|
* unlock_page - unlock a locked page
|
|
* @page: the page
|
|
*
|
|
* Unlocks the page and wakes up sleepers in ___wait_on_page_locked().
|
|
* Also wakes sleepers in wait_on_page_writeback() because the wakeup
|
|
* mechanism between PageLocked pages and PageWriteback pages is shared.
|
|
* But that's OK - sleepers in wait_on_page_writeback() just go back to sleep.
|
|
*
|
|
* Note that this depends on PG_waiters being the sign bit in the byte
|
|
* that contains PG_locked - thus the BUILD_BUG_ON(). That allows us to
|
|
* clear the PG_locked bit and test PG_waiters at the same time fairly
|
|
* portably (architectures that do LL/SC can test any bit, while x86 can
|
|
* test the sign bit).
|
|
*/
|
|
void unlock_page(struct page *page)
|
|
{
|
|
BUILD_BUG_ON(PG_waiters != 7);
|
|
page = compound_head(page);
|
|
VM_BUG_ON_PAGE(!PageLocked(page), page);
|
|
if (clear_bit_unlock_is_negative_byte(PG_locked, &page->flags))
|
|
wake_up_page_bit(page, PG_locked);
|
|
}
|
|
EXPORT_SYMBOL(unlock_page);
|
|
|
|
/**
|
|
* end_page_writeback - end writeback against a page
|
|
* @page: the page
|
|
*/
|
|
void end_page_writeback(struct page *page)
|
|
{
|
|
/*
|
|
* TestClearPageReclaim could be used here but it is an atomic
|
|
* operation and overkill in this particular case. Failing to
|
|
* shuffle a page marked for immediate reclaim is too mild to
|
|
* justify taking an atomic operation penalty at the end of
|
|
* ever page writeback.
|
|
*/
|
|
if (PageReclaim(page)) {
|
|
ClearPageReclaim(page);
|
|
rotate_reclaimable_page(page);
|
|
}
|
|
|
|
if (!test_clear_page_writeback(page))
|
|
BUG();
|
|
|
|
smp_mb__after_atomic();
|
|
wake_up_page(page, PG_writeback);
|
|
}
|
|
EXPORT_SYMBOL(end_page_writeback);
|
|
|
|
/*
|
|
* After completing I/O on a page, call this routine to update the page
|
|
* flags appropriately
|
|
*/
|
|
void page_endio(struct page *page, bool is_write, int err)
|
|
{
|
|
if (!is_write) {
|
|
if (!err) {
|
|
SetPageUptodate(page);
|
|
} else {
|
|
ClearPageUptodate(page);
|
|
SetPageError(page);
|
|
}
|
|
unlock_page(page);
|
|
} else {
|
|
if (err) {
|
|
struct address_space *mapping;
|
|
|
|
SetPageError(page);
|
|
mapping = page_mapping(page);
|
|
if (mapping)
|
|
mapping_set_error(mapping, err);
|
|
}
|
|
end_page_writeback(page);
|
|
}
|
|
}
|
|
EXPORT_SYMBOL_GPL(page_endio);
|
|
|
|
/**
|
|
* __lock_page - get a lock on the page, assuming we need to sleep to get it
|
|
* @__page: the page to lock
|
|
*/
|
|
void __lock_page(struct page *__page)
|
|
{
|
|
struct page *page = compound_head(__page);
|
|
wait_queue_head_t *q = page_waitqueue(page);
|
|
wait_on_page_bit_common(q, page, PG_locked, TASK_UNINTERRUPTIBLE, true);
|
|
}
|
|
EXPORT_SYMBOL(__lock_page);
|
|
|
|
int __lock_page_killable(struct page *__page)
|
|
{
|
|
struct page *page = compound_head(__page);
|
|
wait_queue_head_t *q = page_waitqueue(page);
|
|
return wait_on_page_bit_common(q, page, PG_locked, TASK_KILLABLE, true);
|
|
}
|
|
EXPORT_SYMBOL_GPL(__lock_page_killable);
|
|
|
|
/*
|
|
* Return values:
|
|
* 1 - page is locked; mmap_sem is still held.
|
|
* 0 - page is not locked.
|
|
* mmap_sem has been released (up_read()), unless flags had both
|
|
* FAULT_FLAG_ALLOW_RETRY and FAULT_FLAG_RETRY_NOWAIT set, in
|
|
* which case mmap_sem is still held.
|
|
*
|
|
* If neither ALLOW_RETRY nor KILLABLE are set, will always return 1
|
|
* with the page locked and the mmap_sem unperturbed.
|
|
*/
|
|
int __lock_page_or_retry(struct page *page, struct mm_struct *mm,
|
|
unsigned int flags)
|
|
{
|
|
if (flags & FAULT_FLAG_ALLOW_RETRY) {
|
|
/*
|
|
* CAUTION! In this case, mmap_sem is not released
|
|
* even though return 0.
|
|
*/
|
|
if (flags & FAULT_FLAG_RETRY_NOWAIT)
|
|
return 0;
|
|
|
|
up_read(&mm->mmap_sem);
|
|
if (flags & FAULT_FLAG_KILLABLE)
|
|
wait_on_page_locked_killable(page);
|
|
else
|
|
wait_on_page_locked(page);
|
|
return 0;
|
|
} else {
|
|
if (flags & FAULT_FLAG_KILLABLE) {
|
|
int ret;
|
|
|
|
ret = __lock_page_killable(page);
|
|
if (ret) {
|
|
up_read(&mm->mmap_sem);
|
|
return 0;
|
|
}
|
|
} else
|
|
__lock_page(page);
|
|
return 1;
|
|
}
|
|
}
|
|
|
|
/**
|
|
* page_cache_next_hole - find the next hole (not-present entry)
|
|
* @mapping: mapping
|
|
* @index: index
|
|
* @max_scan: maximum range to search
|
|
*
|
|
* Search the set [index, min(index+max_scan-1, MAX_INDEX)] for the
|
|
* lowest indexed hole.
|
|
*
|
|
* Returns: the index of the hole if found, otherwise returns an index
|
|
* outside of the set specified (in which case 'return - index >=
|
|
* max_scan' will be true). In rare cases of index wrap-around, 0 will
|
|
* be returned.
|
|
*
|
|
* page_cache_next_hole may be called under rcu_read_lock. However,
|
|
* like radix_tree_gang_lookup, this will not atomically search a
|
|
* snapshot of the tree at a single point in time. For example, if a
|
|
* hole is created at index 5, then subsequently a hole is created at
|
|
* index 10, page_cache_next_hole covering both indexes may return 10
|
|
* if called under rcu_read_lock.
|
|
*/
|
|
pgoff_t page_cache_next_hole(struct address_space *mapping,
|
|
pgoff_t index, unsigned long max_scan)
|
|
{
|
|
unsigned long i;
|
|
|
|
for (i = 0; i < max_scan; i++) {
|
|
struct page *page;
|
|
|
|
page = radix_tree_lookup(&mapping->page_tree, index);
|
|
if (!page || radix_tree_exceptional_entry(page))
|
|
break;
|
|
index++;
|
|
if (index == 0)
|
|
break;
|
|
}
|
|
|
|
return index;
|
|
}
|
|
EXPORT_SYMBOL(page_cache_next_hole);
|
|
|
|
/**
|
|
* page_cache_prev_hole - find the prev hole (not-present entry)
|
|
* @mapping: mapping
|
|
* @index: index
|
|
* @max_scan: maximum range to search
|
|
*
|
|
* Search backwards in the range [max(index-max_scan+1, 0), index] for
|
|
* the first hole.
|
|
*
|
|
* Returns: the index of the hole if found, otherwise returns an index
|
|
* outside of the set specified (in which case 'index - return >=
|
|
* max_scan' will be true). In rare cases of wrap-around, ULONG_MAX
|
|
* will be returned.
|
|
*
|
|
* page_cache_prev_hole may be called under rcu_read_lock. However,
|
|
* like radix_tree_gang_lookup, this will not atomically search a
|
|
* snapshot of the tree at a single point in time. For example, if a
|
|
* hole is created at index 10, then subsequently a hole is created at
|
|
* index 5, page_cache_prev_hole covering both indexes may return 5 if
|
|
* called under rcu_read_lock.
|
|
*/
|
|
pgoff_t page_cache_prev_hole(struct address_space *mapping,
|
|
pgoff_t index, unsigned long max_scan)
|
|
{
|
|
unsigned long i;
|
|
|
|
for (i = 0; i < max_scan; i++) {
|
|
struct page *page;
|
|
|
|
page = radix_tree_lookup(&mapping->page_tree, index);
|
|
if (!page || radix_tree_exceptional_entry(page))
|
|
break;
|
|
index--;
|
|
if (index == ULONG_MAX)
|
|
break;
|
|
}
|
|
|
|
return index;
|
|
}
|
|
EXPORT_SYMBOL(page_cache_prev_hole);
|
|
|
|
/**
|
|
* find_get_entry - find and get a page cache entry
|
|
* @mapping: the address_space to search
|
|
* @offset: the page cache index
|
|
*
|
|
* Looks up the page cache slot at @mapping & @offset. If there is a
|
|
* page cache page, it is returned with an increased refcount.
|
|
*
|
|
* If the slot holds a shadow entry of a previously evicted page, or a
|
|
* swap entry from shmem/tmpfs, it is returned.
|
|
*
|
|
* Otherwise, %NULL is returned.
|
|
*/
|
|
struct page *find_get_entry(struct address_space *mapping, pgoff_t offset)
|
|
{
|
|
void **pagep;
|
|
struct page *head, *page;
|
|
|
|
rcu_read_lock();
|
|
repeat:
|
|
page = NULL;
|
|
pagep = radix_tree_lookup_slot(&mapping->page_tree, offset);
|
|
if (pagep) {
|
|
page = radix_tree_deref_slot(pagep);
|
|
if (unlikely(!page))
|
|
goto out;
|
|
if (radix_tree_exception(page)) {
|
|
if (radix_tree_deref_retry(page))
|
|
goto repeat;
|
|
/*
|
|
* A shadow entry of a recently evicted page,
|
|
* or a swap entry from shmem/tmpfs. Return
|
|
* it without attempting to raise page count.
|
|
*/
|
|
goto out;
|
|
}
|
|
|
|
head = compound_head(page);
|
|
if (!page_cache_get_speculative(head))
|
|
goto repeat;
|
|
|
|
/* The page was split under us? */
|
|
if (compound_head(page) != head) {
|
|
put_page(head);
|
|
goto repeat;
|
|
}
|
|
|
|
/*
|
|
* Has the page moved?
|
|
* This is part of the lockless pagecache protocol. See
|
|
* include/linux/pagemap.h for details.
|
|
*/
|
|
if (unlikely(page != *pagep)) {
|
|
put_page(head);
|
|
goto repeat;
|
|
}
|
|
}
|
|
out:
|
|
rcu_read_unlock();
|
|
|
|
return page;
|
|
}
|
|
EXPORT_SYMBOL(find_get_entry);
|
|
|
|
/**
|
|
* find_lock_entry - locate, pin and lock a page cache entry
|
|
* @mapping: the address_space to search
|
|
* @offset: the page cache index
|
|
*
|
|
* Looks up the page cache slot at @mapping & @offset. If there is a
|
|
* page cache page, it is returned locked and with an increased
|
|
* refcount.
|
|
*
|
|
* If the slot holds a shadow entry of a previously evicted page, or a
|
|
* swap entry from shmem/tmpfs, it is returned.
|
|
*
|
|
* Otherwise, %NULL is returned.
|
|
*
|
|
* find_lock_entry() may sleep.
|
|
*/
|
|
struct page *find_lock_entry(struct address_space *mapping, pgoff_t offset)
|
|
{
|
|
struct page *page;
|
|
|
|
repeat:
|
|
page = find_get_entry(mapping, offset);
|
|
if (page && !radix_tree_exception(page)) {
|
|
lock_page(page);
|
|
/* Has the page been truncated? */
|
|
if (unlikely(page_mapping(page) != mapping)) {
|
|
unlock_page(page);
|
|
put_page(page);
|
|
goto repeat;
|
|
}
|
|
VM_BUG_ON_PAGE(page_to_pgoff(page) != offset, page);
|
|
}
|
|
return page;
|
|
}
|
|
EXPORT_SYMBOL(find_lock_entry);
|
|
|
|
/**
|
|
* pagecache_get_page - find and get a page reference
|
|
* @mapping: the address_space to search
|
|
* @offset: the page index
|
|
* @fgp_flags: PCG flags
|
|
* @gfp_mask: gfp mask to use for the page cache data page allocation
|
|
*
|
|
* Looks up the page cache slot at @mapping & @offset.
|
|
*
|
|
* PCG flags modify how the page is returned.
|
|
*
|
|
* @fgp_flags can be:
|
|
*
|
|
* - FGP_ACCESSED: the page will be marked accessed
|
|
* - FGP_LOCK: Page is return locked
|
|
* - FGP_CREAT: If page is not present then a new page is allocated using
|
|
* @gfp_mask and added to the page cache and the VM's LRU
|
|
* list. The page is returned locked and with an increased
|
|
* refcount. Otherwise, NULL is returned.
|
|
*
|
|
* If FGP_LOCK or FGP_CREAT are specified then the function may sleep even
|
|
* if the GFP flags specified for FGP_CREAT are atomic.
|
|
*
|
|
* If there is a page cache page, it is returned with an increased refcount.
|
|
*/
|
|
struct page *pagecache_get_page(struct address_space *mapping, pgoff_t offset,
|
|
int fgp_flags, gfp_t gfp_mask)
|
|
{
|
|
struct page *page;
|
|
|
|
repeat:
|
|
page = find_get_entry(mapping, offset);
|
|
if (radix_tree_exceptional_entry(page))
|
|
page = NULL;
|
|
if (!page)
|
|
goto no_page;
|
|
|
|
if (fgp_flags & FGP_LOCK) {
|
|
if (fgp_flags & FGP_NOWAIT) {
|
|
if (!trylock_page(page)) {
|
|
put_page(page);
|
|
return NULL;
|
|
}
|
|
} else {
|
|
lock_page(page);
|
|
}
|
|
|
|
/* Has the page been truncated? */
|
|
if (unlikely(page->mapping != mapping)) {
|
|
unlock_page(page);
|
|
put_page(page);
|
|
goto repeat;
|
|
}
|
|
VM_BUG_ON_PAGE(page->index != offset, page);
|
|
}
|
|
|
|
if (page && (fgp_flags & FGP_ACCESSED))
|
|
mark_page_accessed(page);
|
|
|
|
no_page:
|
|
if (!page && (fgp_flags & FGP_CREAT)) {
|
|
int err;
|
|
if ((fgp_flags & FGP_WRITE) && mapping_cap_account_dirty(mapping))
|
|
gfp_mask |= __GFP_WRITE;
|
|
if (fgp_flags & FGP_NOFS)
|
|
gfp_mask &= ~__GFP_FS;
|
|
|
|
page = __page_cache_alloc(gfp_mask);
|
|
if (!page)
|
|
return NULL;
|
|
|
|
if (WARN_ON_ONCE(!(fgp_flags & FGP_LOCK)))
|
|
fgp_flags |= FGP_LOCK;
|
|
|
|
/* Init accessed so avoid atomic mark_page_accessed later */
|
|
if (fgp_flags & FGP_ACCESSED)
|
|
__SetPageReferenced(page);
|
|
|
|
err = add_to_page_cache_lru(page, mapping, offset,
|
|
gfp_mask & GFP_RECLAIM_MASK);
|
|
if (unlikely(err)) {
|
|
put_page(page);
|
|
page = NULL;
|
|
if (err == -EEXIST)
|
|
goto repeat;
|
|
}
|
|
}
|
|
|
|
return page;
|
|
}
|
|
EXPORT_SYMBOL(pagecache_get_page);
|
|
|
|
/**
|
|
* find_get_entries - gang pagecache lookup
|
|
* @mapping: The address_space to search
|
|
* @start: The starting page cache index
|
|
* @nr_entries: The maximum number of entries
|
|
* @entries: Where the resulting entries are placed
|
|
* @indices: The cache indices corresponding to the entries in @entries
|
|
*
|
|
* find_get_entries() will search for and return a group of up to
|
|
* @nr_entries entries in the mapping. The entries are placed at
|
|
* @entries. find_get_entries() takes a reference against any actual
|
|
* pages it returns.
|
|
*
|
|
* The search returns a group of mapping-contiguous page cache entries
|
|
* with ascending indexes. There may be holes in the indices due to
|
|
* not-present pages.
|
|
*
|
|
* Any shadow entries of evicted pages, or swap entries from
|
|
* shmem/tmpfs, are included in the returned array.
|
|
*
|
|
* find_get_entries() returns the number of pages and shadow entries
|
|
* which were found.
|
|
*/
|
|
unsigned find_get_entries(struct address_space *mapping,
|
|
pgoff_t start, unsigned int nr_entries,
|
|
struct page **entries, pgoff_t *indices)
|
|
{
|
|
void **slot;
|
|
unsigned int ret = 0;
|
|
struct radix_tree_iter iter;
|
|
|
|
if (!nr_entries)
|
|
return 0;
|
|
|
|
rcu_read_lock();
|
|
radix_tree_for_each_slot(slot, &mapping->page_tree, &iter, start) {
|
|
struct page *head, *page;
|
|
repeat:
|
|
page = radix_tree_deref_slot(slot);
|
|
if (unlikely(!page))
|
|
continue;
|
|
if (radix_tree_exception(page)) {
|
|
if (radix_tree_deref_retry(page)) {
|
|
slot = radix_tree_iter_retry(&iter);
|
|
continue;
|
|
}
|
|
/*
|
|
* A shadow entry of a recently evicted page, a swap
|
|
* entry from shmem/tmpfs or a DAX entry. Return it
|
|
* without attempting to raise page count.
|
|
*/
|
|
goto export;
|
|
}
|
|
|
|
head = compound_head(page);
|
|
if (!page_cache_get_speculative(head))
|
|
goto repeat;
|
|
|
|
/* The page was split under us? */
|
|
if (compound_head(page) != head) {
|
|
put_page(head);
|
|
goto repeat;
|
|
}
|
|
|
|
/* Has the page moved? */
|
|
if (unlikely(page != *slot)) {
|
|
put_page(head);
|
|
goto repeat;
|
|
}
|
|
export:
|
|
indices[ret] = iter.index;
|
|
entries[ret] = page;
|
|
if (++ret == nr_entries)
|
|
break;
|
|
}
|
|
rcu_read_unlock();
|
|
return ret;
|
|
}
|
|
|
|
/**
|
|
* find_get_pages - gang pagecache lookup
|
|
* @mapping: The address_space to search
|
|
* @start: The starting page index
|
|
* @nr_pages: The maximum number of pages
|
|
* @pages: Where the resulting pages are placed
|
|
*
|
|
* find_get_pages() will search for and return a group of up to
|
|
* @nr_pages pages in the mapping. The pages are placed at @pages.
|
|
* find_get_pages() takes a reference against the returned pages.
|
|
*
|
|
* The search returns a group of mapping-contiguous pages with ascending
|
|
* indexes. There may be holes in the indices due to not-present pages.
|
|
*
|
|
* find_get_pages() returns the number of pages which were found.
|
|
*/
|
|
unsigned find_get_pages(struct address_space *mapping, pgoff_t start,
|
|
unsigned int nr_pages, struct page **pages)
|
|
{
|
|
struct radix_tree_iter iter;
|
|
void **slot;
|
|
unsigned ret = 0;
|
|
|
|
if (unlikely(!nr_pages))
|
|
return 0;
|
|
|
|
rcu_read_lock();
|
|
radix_tree_for_each_slot(slot, &mapping->page_tree, &iter, start) {
|
|
struct page *head, *page;
|
|
repeat:
|
|
page = radix_tree_deref_slot(slot);
|
|
if (unlikely(!page))
|
|
continue;
|
|
|
|
if (radix_tree_exception(page)) {
|
|
if (radix_tree_deref_retry(page)) {
|
|
slot = radix_tree_iter_retry(&iter);
|
|
continue;
|
|
}
|
|
/*
|
|
* A shadow entry of a recently evicted page,
|
|
* or a swap entry from shmem/tmpfs. Skip
|
|
* over it.
|
|
*/
|
|
continue;
|
|
}
|
|
|
|
head = compound_head(page);
|
|
if (!page_cache_get_speculative(head))
|
|
goto repeat;
|
|
|
|
/* The page was split under us? */
|
|
if (compound_head(page) != head) {
|
|
put_page(head);
|
|
goto repeat;
|
|
}
|
|
|
|
/* Has the page moved? */
|
|
if (unlikely(page != *slot)) {
|
|
put_page(head);
|
|
goto repeat;
|
|
}
|
|
|
|
pages[ret] = page;
|
|
if (++ret == nr_pages)
|
|
break;
|
|
}
|
|
|
|
rcu_read_unlock();
|
|
return ret;
|
|
}
|
|
|
|
/**
|
|
* find_get_pages_contig - gang contiguous pagecache lookup
|
|
* @mapping: The address_space to search
|
|
* @index: The starting page index
|
|
* @nr_pages: The maximum number of pages
|
|
* @pages: Where the resulting pages are placed
|
|
*
|
|
* find_get_pages_contig() works exactly like find_get_pages(), except
|
|
* that the returned number of pages are guaranteed to be contiguous.
|
|
*
|
|
* find_get_pages_contig() returns the number of pages which were found.
|
|
*/
|
|
unsigned find_get_pages_contig(struct address_space *mapping, pgoff_t index,
|
|
unsigned int nr_pages, struct page **pages)
|
|
{
|
|
struct radix_tree_iter iter;
|
|
void **slot;
|
|
unsigned int ret = 0;
|
|
|
|
if (unlikely(!nr_pages))
|
|
return 0;
|
|
|
|
rcu_read_lock();
|
|
radix_tree_for_each_contig(slot, &mapping->page_tree, &iter, index) {
|
|
struct page *head, *page;
|
|
repeat:
|
|
page = radix_tree_deref_slot(slot);
|
|
/* The hole, there no reason to continue */
|
|
if (unlikely(!page))
|
|
break;
|
|
|
|
if (radix_tree_exception(page)) {
|
|
if (radix_tree_deref_retry(page)) {
|
|
slot = radix_tree_iter_retry(&iter);
|
|
continue;
|
|
}
|
|
/*
|
|
* A shadow entry of a recently evicted page,
|
|
* or a swap entry from shmem/tmpfs. Stop
|
|
* looking for contiguous pages.
|
|
*/
|
|
break;
|
|
}
|
|
|
|
head = compound_head(page);
|
|
if (!page_cache_get_speculative(head))
|
|
goto repeat;
|
|
|
|
/* The page was split under us? */
|
|
if (compound_head(page) != head) {
|
|
put_page(head);
|
|
goto repeat;
|
|
}
|
|
|
|
/* Has the page moved? */
|
|
if (unlikely(page != *slot)) {
|
|
put_page(head);
|
|
goto repeat;
|
|
}
|
|
|
|
/*
|
|
* must check mapping and index after taking the ref.
|
|
* otherwise we can get both false positives and false
|
|
* negatives, which is just confusing to the caller.
|
|
*/
|
|
if (page->mapping == NULL || page_to_pgoff(page) != iter.index) {
|
|
put_page(page);
|
|
break;
|
|
}
|
|
|
|
pages[ret] = page;
|
|
if (++ret == nr_pages)
|
|
break;
|
|
}
|
|
rcu_read_unlock();
|
|
return ret;
|
|
}
|
|
EXPORT_SYMBOL(find_get_pages_contig);
|
|
|
|
/**
|
|
* find_get_pages_tag - find and return pages that match @tag
|
|
* @mapping: the address_space to search
|
|
* @index: the starting page index
|
|
* @tag: the tag index
|
|
* @nr_pages: the maximum number of pages
|
|
* @pages: where the resulting pages are placed
|
|
*
|
|
* Like find_get_pages, except we only return pages which are tagged with
|
|
* @tag. We update @index to index the next page for the traversal.
|
|
*/
|
|
unsigned find_get_pages_tag(struct address_space *mapping, pgoff_t *index,
|
|
int tag, unsigned int nr_pages, struct page **pages)
|
|
{
|
|
struct radix_tree_iter iter;
|
|
void **slot;
|
|
unsigned ret = 0;
|
|
|
|
if (unlikely(!nr_pages))
|
|
return 0;
|
|
|
|
rcu_read_lock();
|
|
radix_tree_for_each_tagged(slot, &mapping->page_tree,
|
|
&iter, *index, tag) {
|
|
struct page *head, *page;
|
|
repeat:
|
|
page = radix_tree_deref_slot(slot);
|
|
if (unlikely(!page))
|
|
continue;
|
|
|
|
if (radix_tree_exception(page)) {
|
|
if (radix_tree_deref_retry(page)) {
|
|
slot = radix_tree_iter_retry(&iter);
|
|
continue;
|
|
}
|
|
/*
|
|
* A shadow entry of a recently evicted page.
|
|
*
|
|
* Those entries should never be tagged, but
|
|
* this tree walk is lockless and the tags are
|
|
* looked up in bulk, one radix tree node at a
|
|
* time, so there is a sizable window for page
|
|
* reclaim to evict a page we saw tagged.
|
|
*
|
|
* Skip over it.
|
|
*/
|
|
continue;
|
|
}
|
|
|
|
head = compound_head(page);
|
|
if (!page_cache_get_speculative(head))
|
|
goto repeat;
|
|
|
|
/* The page was split under us? */
|
|
if (compound_head(page) != head) {
|
|
put_page(head);
|
|
goto repeat;
|
|
}
|
|
|
|
/* Has the page moved? */
|
|
if (unlikely(page != *slot)) {
|
|
put_page(head);
|
|
goto repeat;
|
|
}
|
|
|
|
pages[ret] = page;
|
|
if (++ret == nr_pages)
|
|
break;
|
|
}
|
|
|
|
rcu_read_unlock();
|
|
|
|
if (ret)
|
|
*index = pages[ret - 1]->index + 1;
|
|
|
|
return ret;
|
|
}
|
|
EXPORT_SYMBOL(find_get_pages_tag);
|
|
|
|
/**
|
|
* find_get_entries_tag - find and return entries that match @tag
|
|
* @mapping: the address_space to search
|
|
* @start: the starting page cache index
|
|
* @tag: the tag index
|
|
* @nr_entries: the maximum number of entries
|
|
* @entries: where the resulting entries are placed
|
|
* @indices: the cache indices corresponding to the entries in @entries
|
|
*
|
|
* Like find_get_entries, except we only return entries which are tagged with
|
|
* @tag.
|
|
*/
|
|
unsigned find_get_entries_tag(struct address_space *mapping, pgoff_t start,
|
|
int tag, unsigned int nr_entries,
|
|
struct page **entries, pgoff_t *indices)
|
|
{
|
|
void **slot;
|
|
unsigned int ret = 0;
|
|
struct radix_tree_iter iter;
|
|
|
|
if (!nr_entries)
|
|
return 0;
|
|
|
|
rcu_read_lock();
|
|
radix_tree_for_each_tagged(slot, &mapping->page_tree,
|
|
&iter, start, tag) {
|
|
struct page *head, *page;
|
|
repeat:
|
|
page = radix_tree_deref_slot(slot);
|
|
if (unlikely(!page))
|
|
continue;
|
|
if (radix_tree_exception(page)) {
|
|
if (radix_tree_deref_retry(page)) {
|
|
slot = radix_tree_iter_retry(&iter);
|
|
continue;
|
|
}
|
|
|
|
/*
|
|
* A shadow entry of a recently evicted page, a swap
|
|
* entry from shmem/tmpfs or a DAX entry. Return it
|
|
* without attempting to raise page count.
|
|
*/
|
|
goto export;
|
|
}
|
|
|
|
head = compound_head(page);
|
|
if (!page_cache_get_speculative(head))
|
|
goto repeat;
|
|
|
|
/* The page was split under us? */
|
|
if (compound_head(page) != head) {
|
|
put_page(head);
|
|
goto repeat;
|
|
}
|
|
|
|
/* Has the page moved? */
|
|
if (unlikely(page != *slot)) {
|
|
put_page(head);
|
|
goto repeat;
|
|
}
|
|
export:
|
|
indices[ret] = iter.index;
|
|
entries[ret] = page;
|
|
if (++ret == nr_entries)
|
|
break;
|
|
}
|
|
rcu_read_unlock();
|
|
return ret;
|
|
}
|
|
EXPORT_SYMBOL(find_get_entries_tag);
|
|
|
|
/*
|
|
* CD/DVDs are error prone. When a medium error occurs, the driver may fail
|
|
* a _large_ part of the i/o request. Imagine the worst scenario:
|
|
*
|
|
* ---R__________________________________________B__________
|
|
* ^ reading here ^ bad block(assume 4k)
|
|
*
|
|
* read(R) => miss => readahead(R...B) => media error => frustrating retries
|
|
* => failing the whole request => read(R) => read(R+1) =>
|
|
* readahead(R+1...B+1) => bang => read(R+2) => read(R+3) =>
|
|
* readahead(R+3...B+2) => bang => read(R+3) => read(R+4) =>
|
|
* readahead(R+4...B+3) => bang => read(R+4) => read(R+5) => ......
|
|
*
|
|
* It is going insane. Fix it by quickly scaling down the readahead size.
|
|
*/
|
|
static void shrink_readahead_size_eio(struct file *filp,
|
|
struct file_ra_state *ra)
|
|
{
|
|
ra->ra_pages /= 4;
|
|
}
|
|
|
|
/**
|
|
* do_generic_file_read - generic file read routine
|
|
* @filp: the file to read
|
|
* @ppos: current file position
|
|
* @iter: data destination
|
|
* @written: already copied
|
|
*
|
|
* This is a generic file read routine, and uses the
|
|
* mapping->a_ops->readpage() function for the actual low-level stuff.
|
|
*
|
|
* This is really ugly. But the goto's actually try to clarify some
|
|
* of the logic when it comes to error handling etc.
|
|
*/
|
|
static ssize_t do_generic_file_read(struct file *filp, loff_t *ppos,
|
|
struct iov_iter *iter, ssize_t written)
|
|
{
|
|
struct address_space *mapping = filp->f_mapping;
|
|
struct inode *inode = mapping->host;
|
|
struct file_ra_state *ra = &filp->f_ra;
|
|
pgoff_t index;
|
|
pgoff_t last_index;
|
|
pgoff_t prev_index;
|
|
unsigned long offset; /* offset into pagecache page */
|
|
unsigned int prev_offset;
|
|
int error = 0;
|
|
|
|
if (unlikely(*ppos >= inode->i_sb->s_maxbytes))
|
|
return 0;
|
|
iov_iter_truncate(iter, inode->i_sb->s_maxbytes);
|
|
|
|
index = *ppos >> PAGE_SHIFT;
|
|
prev_index = ra->prev_pos >> PAGE_SHIFT;
|
|
prev_offset = ra->prev_pos & (PAGE_SIZE-1);
|
|
last_index = (*ppos + iter->count + PAGE_SIZE-1) >> PAGE_SHIFT;
|
|
offset = *ppos & ~PAGE_MASK;
|
|
|
|
for (;;) {
|
|
struct page *page;
|
|
pgoff_t end_index;
|
|
loff_t isize;
|
|
unsigned long nr, ret;
|
|
|
|
cond_resched();
|
|
find_page:
|
|
if (fatal_signal_pending(current)) {
|
|
error = -EINTR;
|
|
goto out;
|
|
}
|
|
|
|
page = find_get_page(mapping, index);
|
|
if (!page) {
|
|
page_cache_sync_readahead(mapping,
|
|
ra, filp,
|
|
index, last_index - index);
|
|
page = find_get_page(mapping, index);
|
|
if (unlikely(page == NULL))
|
|
goto no_cached_page;
|
|
}
|
|
if (PageReadahead(page)) {
|
|
page_cache_async_readahead(mapping,
|
|
ra, filp, page,
|
|
index, last_index - index);
|
|
}
|
|
if (!PageUptodate(page)) {
|
|
/*
|
|
* See comment in do_read_cache_page on why
|
|
* wait_on_page_locked is used to avoid unnecessarily
|
|
* serialisations and why it's safe.
|
|
*/
|
|
error = wait_on_page_locked_killable(page);
|
|
if (unlikely(error))
|
|
goto readpage_error;
|
|
if (PageUptodate(page))
|
|
goto page_ok;
|
|
|
|
if (inode->i_blkbits == PAGE_SHIFT ||
|
|
!mapping->a_ops->is_partially_uptodate)
|
|
goto page_not_up_to_date;
|
|
/* pipes can't handle partially uptodate pages */
|
|
if (unlikely(iter->type & ITER_PIPE))
|
|
goto page_not_up_to_date;
|
|
if (!trylock_page(page))
|
|
goto page_not_up_to_date;
|
|
/* Did it get truncated before we got the lock? */
|
|
if (!page->mapping)
|
|
goto page_not_up_to_date_locked;
|
|
if (!mapping->a_ops->is_partially_uptodate(page,
|
|
offset, iter->count))
|
|
goto page_not_up_to_date_locked;
|
|
unlock_page(page);
|
|
}
|
|
page_ok:
|
|
/*
|
|
* i_size must be checked after we know the page is Uptodate.
|
|
*
|
|
* Checking i_size after the check allows us to calculate
|
|
* the correct value for "nr", which means the zero-filled
|
|
* part of the page is not copied back to userspace (unless
|
|
* another truncate extends the file - this is desired though).
|
|
*/
|
|
|
|
isize = i_size_read(inode);
|
|
end_index = (isize - 1) >> PAGE_SHIFT;
|
|
if (unlikely(!isize || index > end_index)) {
|
|
put_page(page);
|
|
goto out;
|
|
}
|
|
|
|
/* nr is the maximum number of bytes to copy from this page */
|
|
nr = PAGE_SIZE;
|
|
if (index == end_index) {
|
|
nr = ((isize - 1) & ~PAGE_MASK) + 1;
|
|
if (nr <= offset) {
|
|
put_page(page);
|
|
goto out;
|
|
}
|
|
}
|
|
nr = nr - offset;
|
|
|
|
/* If users can be writing to this page using arbitrary
|
|
* virtual addresses, take care about potential aliasing
|
|
* before reading the page on the kernel side.
|
|
*/
|
|
if (mapping_writably_mapped(mapping))
|
|
flush_dcache_page(page);
|
|
|
|
/*
|
|
* When a sequential read accesses a page several times,
|
|
* only mark it as accessed the first time.
|
|
*/
|
|
if (prev_index != index || offset != prev_offset)
|
|
mark_page_accessed(page);
|
|
prev_index = index;
|
|
|
|
/*
|
|
* Ok, we have the page, and it's up-to-date, so
|
|
* now we can copy it to user space...
|
|
*/
|
|
|
|
ret = copy_page_to_iter(page, offset, nr, iter);
|
|
offset += ret;
|
|
index += offset >> PAGE_SHIFT;
|
|
offset &= ~PAGE_MASK;
|
|
prev_offset = offset;
|
|
|
|
put_page(page);
|
|
written += ret;
|
|
if (!iov_iter_count(iter))
|
|
goto out;
|
|
if (ret < nr) {
|
|
error = -EFAULT;
|
|
goto out;
|
|
}
|
|
continue;
|
|
|
|
page_not_up_to_date:
|
|
/* Get exclusive access to the page ... */
|
|
error = lock_page_killable(page);
|
|
if (unlikely(error))
|
|
goto readpage_error;
|
|
|
|
page_not_up_to_date_locked:
|
|
/* Did it get truncated before we got the lock? */
|
|
if (!page->mapping) {
|
|
unlock_page(page);
|
|
put_page(page);
|
|
continue;
|
|
}
|
|
|
|
/* Did somebody else fill it already? */
|
|
if (PageUptodate(page)) {
|
|
unlock_page(page);
|
|
goto page_ok;
|
|
}
|
|
|
|
readpage:
|
|
/*
|
|
* A previous I/O error may have been due to temporary
|
|
* failures, eg. multipath errors.
|
|
* PG_error will be set again if readpage fails.
|
|
*/
|
|
ClearPageError(page);
|
|
/* Start the actual read. The read will unlock the page. */
|
|
error = mapping->a_ops->readpage(filp, page);
|
|
|
|
if (unlikely(error)) {
|
|
if (error == AOP_TRUNCATED_PAGE) {
|
|
put_page(page);
|
|
error = 0;
|
|
goto find_page;
|
|
}
|
|
goto readpage_error;
|
|
}
|
|
|
|
if (!PageUptodate(page)) {
|
|
error = lock_page_killable(page);
|
|
if (unlikely(error))
|
|
goto readpage_error;
|
|
if (!PageUptodate(page)) {
|
|
if (page->mapping == NULL) {
|
|
/*
|
|
* invalidate_mapping_pages got it
|
|
*/
|
|
unlock_page(page);
|
|
put_page(page);
|
|
goto find_page;
|
|
}
|
|
unlock_page(page);
|
|
shrink_readahead_size_eio(filp, ra);
|
|
error = -EIO;
|
|
goto readpage_error;
|
|
}
|
|
unlock_page(page);
|
|
}
|
|
|
|
goto page_ok;
|
|
|
|
readpage_error:
|
|
/* UHHUH! A synchronous read error occurred. Report it */
|
|
put_page(page);
|
|
goto out;
|
|
|
|
no_cached_page:
|
|
/*
|
|
* Ok, it wasn't cached, so we need to create a new
|
|
* page..
|
|
*/
|
|
page = page_cache_alloc_cold(mapping);
|
|
if (!page) {
|
|
error = -ENOMEM;
|
|
goto out;
|
|
}
|
|
error = add_to_page_cache_lru(page, mapping, index,
|
|
mapping_gfp_constraint(mapping, GFP_KERNEL));
|
|
if (error) {
|
|
put_page(page);
|
|
if (error == -EEXIST) {
|
|
error = 0;
|
|
goto find_page;
|
|
}
|
|
goto out;
|
|
}
|
|
goto readpage;
|
|
}
|
|
|
|
out:
|
|
ra->prev_pos = prev_index;
|
|
ra->prev_pos <<= PAGE_SHIFT;
|
|
ra->prev_pos |= prev_offset;
|
|
|
|
*ppos = ((loff_t)index << PAGE_SHIFT) + offset;
|
|
file_accessed(filp);
|
|
return written ? written : error;
|
|
}
|
|
|
|
/**
|
|
* generic_file_read_iter - generic filesystem read routine
|
|
* @iocb: kernel I/O control block
|
|
* @iter: destination for the data read
|
|
*
|
|
* This is the "read_iter()" routine for all filesystems
|
|
* that can use the page cache directly.
|
|
*/
|
|
ssize_t
|
|
generic_file_read_iter(struct kiocb *iocb, struct iov_iter *iter)
|
|
{
|
|
struct file *file = iocb->ki_filp;
|
|
ssize_t retval = 0;
|
|
size_t count = iov_iter_count(iter);
|
|
|
|
if (!count)
|
|
goto out; /* skip atime */
|
|
|
|
if (iocb->ki_flags & IOCB_DIRECT) {
|
|
struct address_space *mapping = file->f_mapping;
|
|
struct inode *inode = mapping->host;
|
|
loff_t size;
|
|
|
|
size = i_size_read(inode);
|
|
if (iocb->ki_flags & IOCB_NOWAIT) {
|
|
if (filemap_range_has_page(mapping, iocb->ki_pos,
|
|
iocb->ki_pos + count - 1))
|
|
return -EAGAIN;
|
|
} else {
|
|
retval = filemap_write_and_wait_range(mapping,
|
|
iocb->ki_pos,
|
|
iocb->ki_pos + count - 1);
|
|
if (retval < 0)
|
|
goto out;
|
|
}
|
|
|
|
file_accessed(file);
|
|
|
|
retval = mapping->a_ops->direct_IO(iocb, iter);
|
|
if (retval >= 0) {
|
|
iocb->ki_pos += retval;
|
|
count -= retval;
|
|
}
|
|
iov_iter_revert(iter, count - iov_iter_count(iter));
|
|
|
|
/*
|
|
* Btrfs can have a short DIO read if we encounter
|
|
* compressed extents, so if there was an error, or if
|
|
* we've already read everything we wanted to, or if
|
|
* there was a short read because we hit EOF, go ahead
|
|
* and return. Otherwise fallthrough to buffered io for
|
|
* the rest of the read. Buffered reads will not work for
|
|
* DAX files, so don't bother trying.
|
|
*/
|
|
if (retval < 0 || !count || iocb->ki_pos >= size ||
|
|
IS_DAX(inode))
|
|
goto out;
|
|
}
|
|
|
|
retval = do_generic_file_read(file, &iocb->ki_pos, iter, retval);
|
|
out:
|
|
return retval;
|
|
}
|
|
EXPORT_SYMBOL(generic_file_read_iter);
|
|
|
|
#ifdef CONFIG_MMU
|
|
/**
|
|
* page_cache_read - adds requested page to the page cache if not already there
|
|
* @file: file to read
|
|
* @offset: page index
|
|
* @gfp_mask: memory allocation flags
|
|
*
|
|
* This adds the requested page to the page cache if it isn't already there,
|
|
* and schedules an I/O to read in its contents from disk.
|
|
*/
|
|
static int page_cache_read(struct file *file, pgoff_t offset, gfp_t gfp_mask)
|
|
{
|
|
struct address_space *mapping = file->f_mapping;
|
|
struct page *page;
|
|
int ret;
|
|
|
|
do {
|
|
page = __page_cache_alloc(gfp_mask|__GFP_COLD);
|
|
if (!page)
|
|
return -ENOMEM;
|
|
|
|
ret = add_to_page_cache_lru(page, mapping, offset, gfp_mask & GFP_KERNEL);
|
|
if (ret == 0)
|
|
ret = mapping->a_ops->readpage(file, page);
|
|
else if (ret == -EEXIST)
|
|
ret = 0; /* losing race to add is OK */
|
|
|
|
put_page(page);
|
|
|
|
} while (ret == AOP_TRUNCATED_PAGE);
|
|
|
|
return ret;
|
|
}
|
|
|
|
#define MMAP_LOTSAMISS (100)
|
|
|
|
/*
|
|
* Synchronous readahead happens when we don't even find
|
|
* a page in the page cache at all.
|
|
*/
|
|
static void do_sync_mmap_readahead(struct vm_area_struct *vma,
|
|
struct file_ra_state *ra,
|
|
struct file *file,
|
|
pgoff_t offset)
|
|
{
|
|
struct address_space *mapping = file->f_mapping;
|
|
|
|
/* If we don't want any read-ahead, don't bother */
|
|
if (vma->vm_flags & VM_RAND_READ)
|
|
return;
|
|
if (!ra->ra_pages)
|
|
return;
|
|
|
|
if (vma->vm_flags & VM_SEQ_READ) {
|
|
page_cache_sync_readahead(mapping, ra, file, offset,
|
|
ra->ra_pages);
|
|
return;
|
|
}
|
|
|
|
/* Avoid banging the cache line if not needed */
|
|
if (ra->mmap_miss < MMAP_LOTSAMISS * 10)
|
|
ra->mmap_miss++;
|
|
|
|
/*
|
|
* Do we miss much more than hit in this file? If so,
|
|
* stop bothering with read-ahead. It will only hurt.
|
|
*/
|
|
if (ra->mmap_miss > MMAP_LOTSAMISS)
|
|
return;
|
|
|
|
/*
|
|
* mmap read-around
|
|
*/
|
|
ra->start = max_t(long, 0, offset - ra->ra_pages / 2);
|
|
ra->size = ra->ra_pages;
|
|
ra->async_size = ra->ra_pages / 4;
|
|
ra_submit(ra, mapping, file);
|
|
}
|
|
|
|
/*
|
|
* Asynchronous readahead happens when we find the page and PG_readahead,
|
|
* so we want to possibly extend the readahead further..
|
|
*/
|
|
static void do_async_mmap_readahead(struct vm_area_struct *vma,
|
|
struct file_ra_state *ra,
|
|
struct file *file,
|
|
struct page *page,
|
|
pgoff_t offset)
|
|
{
|
|
struct address_space *mapping = file->f_mapping;
|
|
|
|
/* If we don't want any read-ahead, don't bother */
|
|
if (vma->vm_flags & VM_RAND_READ)
|
|
return;
|
|
if (ra->mmap_miss > 0)
|
|
ra->mmap_miss--;
|
|
if (PageReadahead(page))
|
|
page_cache_async_readahead(mapping, ra, file,
|
|
page, offset, ra->ra_pages);
|
|
}
|
|
|
|
/**
|
|
* filemap_fault - read in file data for page fault handling
|
|
* @vmf: struct vm_fault containing details of the fault
|
|
*
|
|
* filemap_fault() is invoked via the vma operations vector for a
|
|
* mapped memory region to read in file data during a page fault.
|
|
*
|
|
* The goto's are kind of ugly, but this streamlines the normal case of having
|
|
* it in the page cache, and handles the special cases reasonably without
|
|
* having a lot of duplicated code.
|
|
*
|
|
* vma->vm_mm->mmap_sem must be held on entry.
|
|
*
|
|
* If our return value has VM_FAULT_RETRY set, it's because
|
|
* lock_page_or_retry() returned 0.
|
|
* The mmap_sem has usually been released in this case.
|
|
* See __lock_page_or_retry() for the exception.
|
|
*
|
|
* If our return value does not have VM_FAULT_RETRY set, the mmap_sem
|
|
* has not been released.
|
|
*
|
|
* We never return with VM_FAULT_RETRY and a bit from VM_FAULT_ERROR set.
|
|
*/
|
|
int filemap_fault(struct vm_fault *vmf)
|
|
{
|
|
int error;
|
|
struct file *file = vmf->vma->vm_file;
|
|
struct address_space *mapping = file->f_mapping;
|
|
struct file_ra_state *ra = &file->f_ra;
|
|
struct inode *inode = mapping->host;
|
|
pgoff_t offset = vmf->pgoff;
|
|
pgoff_t max_off;
|
|
struct page *page;
|
|
int ret = 0;
|
|
|
|
max_off = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE);
|
|
if (unlikely(offset >= max_off))
|
|
return VM_FAULT_SIGBUS;
|
|
|
|
/*
|
|
* Do we have something in the page cache already?
|
|
*/
|
|
page = find_get_page(mapping, offset);
|
|
if (likely(page) && !(vmf->flags & FAULT_FLAG_TRIED)) {
|
|
/*
|
|
* We found the page, so try async readahead before
|
|
* waiting for the lock.
|
|
*/
|
|
do_async_mmap_readahead(vmf->vma, ra, file, page, offset);
|
|
} else if (!page) {
|
|
/* No page in the page cache at all */
|
|
do_sync_mmap_readahead(vmf->vma, ra, file, offset);
|
|
count_vm_event(PGMAJFAULT);
|
|
count_memcg_event_mm(vmf->vma->vm_mm, PGMAJFAULT);
|
|
ret = VM_FAULT_MAJOR;
|
|
retry_find:
|
|
page = find_get_page(mapping, offset);
|
|
if (!page)
|
|
goto no_cached_page;
|
|
}
|
|
|
|
if (!lock_page_or_retry(page, vmf->vma->vm_mm, vmf->flags)) {
|
|
put_page(page);
|
|
return ret | VM_FAULT_RETRY;
|
|
}
|
|
|
|
/* Did it get truncated? */
|
|
if (unlikely(page->mapping != mapping)) {
|
|
unlock_page(page);
|
|
put_page(page);
|
|
goto retry_find;
|
|
}
|
|
VM_BUG_ON_PAGE(page->index != offset, page);
|
|
|
|
/*
|
|
* We have a locked page in the page cache, now we need to check
|
|
* that it's up-to-date. If not, it is going to be due to an error.
|
|
*/
|
|
if (unlikely(!PageUptodate(page)))
|
|
goto page_not_uptodate;
|
|
|
|
/*
|
|
* Found the page and have a reference on it.
|
|
* We must recheck i_size under page lock.
|
|
*/
|
|
max_off = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE);
|
|
if (unlikely(offset >= max_off)) {
|
|
unlock_page(page);
|
|
put_page(page);
|
|
return VM_FAULT_SIGBUS;
|
|
}
|
|
|
|
vmf->page = page;
|
|
return ret | VM_FAULT_LOCKED;
|
|
|
|
no_cached_page:
|
|
/*
|
|
* We're only likely to ever get here if MADV_RANDOM is in
|
|
* effect.
|
|
*/
|
|
error = page_cache_read(file, offset, vmf->gfp_mask);
|
|
|
|
/*
|
|
* The page we want has now been added to the page cache.
|
|
* In the unlikely event that someone removed it in the
|
|
* meantime, we'll just come back here and read it again.
|
|
*/
|
|
if (error >= 0)
|
|
goto retry_find;
|
|
|
|
/*
|
|
* An error return from page_cache_read can result if the
|
|
* system is low on memory, or a problem occurs while trying
|
|
* to schedule I/O.
|
|
*/
|
|
if (error == -ENOMEM)
|
|
return VM_FAULT_OOM;
|
|
return VM_FAULT_SIGBUS;
|
|
|
|
page_not_uptodate:
|
|
/*
|
|
* Umm, take care of errors if the page isn't up-to-date.
|
|
* Try to re-read it _once_. We do this synchronously,
|
|
* because there really aren't any performance issues here
|
|
* and we need to check for errors.
|
|
*/
|
|
ClearPageError(page);
|
|
error = mapping->a_ops->readpage(file, page);
|
|
if (!error) {
|
|
wait_on_page_locked(page);
|
|
if (!PageUptodate(page))
|
|
error = -EIO;
|
|
}
|
|
put_page(page);
|
|
|
|
if (!error || error == AOP_TRUNCATED_PAGE)
|
|
goto retry_find;
|
|
|
|
/* Things didn't work out. Return zero to tell the mm layer so. */
|
|
shrink_readahead_size_eio(file, ra);
|
|
return VM_FAULT_SIGBUS;
|
|
}
|
|
EXPORT_SYMBOL(filemap_fault);
|
|
|
|
void filemap_map_pages(struct vm_fault *vmf,
|
|
pgoff_t start_pgoff, pgoff_t end_pgoff)
|
|
{
|
|
struct radix_tree_iter iter;
|
|
void **slot;
|
|
struct file *file = vmf->vma->vm_file;
|
|
struct address_space *mapping = file->f_mapping;
|
|
pgoff_t last_pgoff = start_pgoff;
|
|
unsigned long max_idx;
|
|
struct page *head, *page;
|
|
|
|
rcu_read_lock();
|
|
radix_tree_for_each_slot(slot, &mapping->page_tree, &iter,
|
|
start_pgoff) {
|
|
if (iter.index > end_pgoff)
|
|
break;
|
|
repeat:
|
|
page = radix_tree_deref_slot(slot);
|
|
if (unlikely(!page))
|
|
goto next;
|
|
if (radix_tree_exception(page)) {
|
|
if (radix_tree_deref_retry(page)) {
|
|
slot = radix_tree_iter_retry(&iter);
|
|
continue;
|
|
}
|
|
goto next;
|
|
}
|
|
|
|
head = compound_head(page);
|
|
if (!page_cache_get_speculative(head))
|
|
goto repeat;
|
|
|
|
/* The page was split under us? */
|
|
if (compound_head(page) != head) {
|
|
put_page(head);
|
|
goto repeat;
|
|
}
|
|
|
|
/* Has the page moved? */
|
|
if (unlikely(page != *slot)) {
|
|
put_page(head);
|
|
goto repeat;
|
|
}
|
|
|
|
if (!PageUptodate(page) ||
|
|
PageReadahead(page) ||
|
|
PageHWPoison(page))
|
|
goto skip;
|
|
if (!trylock_page(page))
|
|
goto skip;
|
|
|
|
if (page->mapping != mapping || !PageUptodate(page))
|
|
goto unlock;
|
|
|
|
max_idx = DIV_ROUND_UP(i_size_read(mapping->host), PAGE_SIZE);
|
|
if (page->index >= max_idx)
|
|
goto unlock;
|
|
|
|
if (file->f_ra.mmap_miss > 0)
|
|
file->f_ra.mmap_miss--;
|
|
|
|
vmf->address += (iter.index - last_pgoff) << PAGE_SHIFT;
|
|
if (vmf->pte)
|
|
vmf->pte += iter.index - last_pgoff;
|
|
last_pgoff = iter.index;
|
|
if (alloc_set_pte(vmf, NULL, page))
|
|
goto unlock;
|
|
unlock_page(page);
|
|
goto next;
|
|
unlock:
|
|
unlock_page(page);
|
|
skip:
|
|
put_page(page);
|
|
next:
|
|
/* Huge page is mapped? No need to proceed. */
|
|
if (pmd_trans_huge(*vmf->pmd))
|
|
break;
|
|
if (iter.index == end_pgoff)
|
|
break;
|
|
}
|
|
rcu_read_unlock();
|
|
}
|
|
EXPORT_SYMBOL(filemap_map_pages);
|
|
|
|
int filemap_page_mkwrite(struct vm_fault *vmf)
|
|
{
|
|
struct page *page = vmf->page;
|
|
struct inode *inode = file_inode(vmf->vma->vm_file);
|
|
int ret = VM_FAULT_LOCKED;
|
|
|
|
sb_start_pagefault(inode->i_sb);
|
|
file_update_time(vmf->vma->vm_file);
|
|
lock_page(page);
|
|
if (page->mapping != inode->i_mapping) {
|
|
unlock_page(page);
|
|
ret = VM_FAULT_NOPAGE;
|
|
goto out;
|
|
}
|
|
/*
|
|
* We mark the page dirty already here so that when freeze is in
|
|
* progress, we are guaranteed that writeback during freezing will
|
|
* see the dirty page and writeprotect it again.
|
|
*/
|
|
set_page_dirty(page);
|
|
wait_for_stable_page(page);
|
|
out:
|
|
sb_end_pagefault(inode->i_sb);
|
|
return ret;
|
|
}
|
|
EXPORT_SYMBOL(filemap_page_mkwrite);
|
|
|
|
const struct vm_operations_struct generic_file_vm_ops = {
|
|
.fault = filemap_fault,
|
|
.map_pages = filemap_map_pages,
|
|
.page_mkwrite = filemap_page_mkwrite,
|
|
};
|
|
|
|
/* This is used for a general mmap of a disk file */
|
|
|
|
int generic_file_mmap(struct file * file, struct vm_area_struct * vma)
|
|
{
|
|
struct address_space *mapping = file->f_mapping;
|
|
|
|
if (!mapping->a_ops->readpage)
|
|
return -ENOEXEC;
|
|
file_accessed(file);
|
|
vma->vm_ops = &generic_file_vm_ops;
|
|
return 0;
|
|
}
|
|
|
|
/*
|
|
* This is for filesystems which do not implement ->writepage.
|
|
*/
|
|
int generic_file_readonly_mmap(struct file *file, struct vm_area_struct *vma)
|
|
{
|
|
if ((vma->vm_flags & VM_SHARED) && (vma->vm_flags & VM_MAYWRITE))
|
|
return -EINVAL;
|
|
return generic_file_mmap(file, vma);
|
|
}
|
|
#else
|
|
int generic_file_mmap(struct file * file, struct vm_area_struct * vma)
|
|
{
|
|
return -ENOSYS;
|
|
}
|
|
int generic_file_readonly_mmap(struct file * file, struct vm_area_struct * vma)
|
|
{
|
|
return -ENOSYS;
|
|
}
|
|
#endif /* CONFIG_MMU */
|
|
|
|
EXPORT_SYMBOL(generic_file_mmap);
|
|
EXPORT_SYMBOL(generic_file_readonly_mmap);
|
|
|
|
static struct page *wait_on_page_read(struct page *page)
|
|
{
|
|
if (!IS_ERR(page)) {
|
|
wait_on_page_locked(page);
|
|
if (!PageUptodate(page)) {
|
|
put_page(page);
|
|
page = ERR_PTR(-EIO);
|
|
}
|
|
}
|
|
return page;
|
|
}
|
|
|
|
static struct page *do_read_cache_page(struct address_space *mapping,
|
|
pgoff_t index,
|
|
int (*filler)(void *, struct page *),
|
|
void *data,
|
|
gfp_t gfp)
|
|
{
|
|
struct page *page;
|
|
int err;
|
|
repeat:
|
|
page = find_get_page(mapping, index);
|
|
if (!page) {
|
|
page = __page_cache_alloc(gfp | __GFP_COLD);
|
|
if (!page)
|
|
return ERR_PTR(-ENOMEM);
|
|
err = add_to_page_cache_lru(page, mapping, index, gfp);
|
|
if (unlikely(err)) {
|
|
put_page(page);
|
|
if (err == -EEXIST)
|
|
goto repeat;
|
|
/* Presumably ENOMEM for radix tree node */
|
|
return ERR_PTR(err);
|
|
}
|
|
|
|
filler:
|
|
err = filler(data, page);
|
|
if (err < 0) {
|
|
put_page(page);
|
|
return ERR_PTR(err);
|
|
}
|
|
|
|
page = wait_on_page_read(page);
|
|
if (IS_ERR(page))
|
|
return page;
|
|
goto out;
|
|
}
|
|
if (PageUptodate(page))
|
|
goto out;
|
|
|
|
/*
|
|
* Page is not up to date and may be locked due one of the following
|
|
* case a: Page is being filled and the page lock is held
|
|
* case b: Read/write error clearing the page uptodate status
|
|
* case c: Truncation in progress (page locked)
|
|
* case d: Reclaim in progress
|
|
*
|
|
* Case a, the page will be up to date when the page is unlocked.
|
|
* There is no need to serialise on the page lock here as the page
|
|
* is pinned so the lock gives no additional protection. Even if the
|
|
* the page is truncated, the data is still valid if PageUptodate as
|
|
* it's a race vs truncate race.
|
|
* Case b, the page will not be up to date
|
|
* Case c, the page may be truncated but in itself, the data may still
|
|
* be valid after IO completes as it's a read vs truncate race. The
|
|
* operation must restart if the page is not uptodate on unlock but
|
|
* otherwise serialising on page lock to stabilise the mapping gives
|
|
* no additional guarantees to the caller as the page lock is
|
|
* released before return.
|
|
* Case d, similar to truncation. If reclaim holds the page lock, it
|
|
* will be a race with remove_mapping that determines if the mapping
|
|
* is valid on unlock but otherwise the data is valid and there is
|
|
* no need to serialise with page lock.
|
|
*
|
|
* As the page lock gives no additional guarantee, we optimistically
|
|
* wait on the page to be unlocked and check if it's up to date and
|
|
* use the page if it is. Otherwise, the page lock is required to
|
|
* distinguish between the different cases. The motivation is that we
|
|
* avoid spurious serialisations and wakeups when multiple processes
|
|
* wait on the same page for IO to complete.
|
|
*/
|
|
wait_on_page_locked(page);
|
|
if (PageUptodate(page))
|
|
goto out;
|
|
|
|
/* Distinguish between all the cases under the safety of the lock */
|
|
lock_page(page);
|
|
|
|
/* Case c or d, restart the operation */
|
|
if (!page->mapping) {
|
|
unlock_page(page);
|
|
put_page(page);
|
|
goto repeat;
|
|
}
|
|
|
|
/* Someone else locked and filled the page in a very small window */
|
|
if (PageUptodate(page)) {
|
|
unlock_page(page);
|
|
goto out;
|
|
}
|
|
goto filler;
|
|
|
|
out:
|
|
mark_page_accessed(page);
|
|
return page;
|
|
}
|
|
|
|
/**
|
|
* read_cache_page - read into page cache, fill it if needed
|
|
* @mapping: the page's address_space
|
|
* @index: the page index
|
|
* @filler: function to perform the read
|
|
* @data: first arg to filler(data, page) function, often left as NULL
|
|
*
|
|
* Read into the page cache. If a page already exists, and PageUptodate() is
|
|
* not set, try to fill the page and wait for it to become unlocked.
|
|
*
|
|
* If the page does not get brought uptodate, return -EIO.
|
|
*/
|
|
struct page *read_cache_page(struct address_space *mapping,
|
|
pgoff_t index,
|
|
int (*filler)(void *, struct page *),
|
|
void *data)
|
|
{
|
|
return do_read_cache_page(mapping, index, filler, data, mapping_gfp_mask(mapping));
|
|
}
|
|
EXPORT_SYMBOL(read_cache_page);
|
|
|
|
/**
|
|
* read_cache_page_gfp - read into page cache, using specified page allocation flags.
|
|
* @mapping: the page's address_space
|
|
* @index: the page index
|
|
* @gfp: the page allocator flags to use if allocating
|
|
*
|
|
* This is the same as "read_mapping_page(mapping, index, NULL)", but with
|
|
* any new page allocations done using the specified allocation flags.
|
|
*
|
|
* If the page does not get brought uptodate, return -EIO.
|
|
*/
|
|
struct page *read_cache_page_gfp(struct address_space *mapping,
|
|
pgoff_t index,
|
|
gfp_t gfp)
|
|
{
|
|
filler_t *filler = (filler_t *)mapping->a_ops->readpage;
|
|
|
|
return do_read_cache_page(mapping, index, filler, NULL, gfp);
|
|
}
|
|
EXPORT_SYMBOL(read_cache_page_gfp);
|
|
|
|
/*
|
|
* Performs necessary checks before doing a write
|
|
*
|
|
* Can adjust writing position or amount of bytes to write.
|
|
* Returns appropriate error code that caller should return or
|
|
* zero in case that write should be allowed.
|
|
*/
|
|
inline ssize_t generic_write_checks(struct kiocb *iocb, struct iov_iter *from)
|
|
{
|
|
struct file *file = iocb->ki_filp;
|
|
struct inode *inode = file->f_mapping->host;
|
|
unsigned long limit = rlimit(RLIMIT_FSIZE);
|
|
loff_t pos;
|
|
|
|
if (!iov_iter_count(from))
|
|
return 0;
|
|
|
|
/* FIXME: this is for backwards compatibility with 2.4 */
|
|
if (iocb->ki_flags & IOCB_APPEND)
|
|
iocb->ki_pos = i_size_read(inode);
|
|
|
|
pos = iocb->ki_pos;
|
|
|
|
if ((iocb->ki_flags & IOCB_NOWAIT) && !(iocb->ki_flags & IOCB_DIRECT))
|
|
return -EINVAL;
|
|
|
|
if (limit != RLIM_INFINITY) {
|
|
if (iocb->ki_pos >= limit) {
|
|
send_sig(SIGXFSZ, current, 0);
|
|
return -EFBIG;
|
|
}
|
|
iov_iter_truncate(from, limit - (unsigned long)pos);
|
|
}
|
|
|
|
/*
|
|
* LFS rule
|
|
*/
|
|
if (unlikely(pos + iov_iter_count(from) > MAX_NON_LFS &&
|
|
!(file->f_flags & O_LARGEFILE))) {
|
|
if (pos >= MAX_NON_LFS)
|
|
return -EFBIG;
|
|
iov_iter_truncate(from, MAX_NON_LFS - (unsigned long)pos);
|
|
}
|
|
|
|
/*
|
|
* Are we about to exceed the fs block limit ?
|
|
*
|
|
* If we have written data it becomes a short write. If we have
|
|
* exceeded without writing data we send a signal and return EFBIG.
|
|
* Linus frestrict idea will clean these up nicely..
|
|
*/
|
|
if (unlikely(pos >= inode->i_sb->s_maxbytes))
|
|
return -EFBIG;
|
|
|
|
iov_iter_truncate(from, inode->i_sb->s_maxbytes - pos);
|
|
return iov_iter_count(from);
|
|
}
|
|
EXPORT_SYMBOL(generic_write_checks);
|
|
|
|
int pagecache_write_begin(struct file *file, struct address_space *mapping,
|
|
loff_t pos, unsigned len, unsigned flags,
|
|
struct page **pagep, void **fsdata)
|
|
{
|
|
const struct address_space_operations *aops = mapping->a_ops;
|
|
|
|
return aops->write_begin(file, mapping, pos, len, flags,
|
|
pagep, fsdata);
|
|
}
|
|
EXPORT_SYMBOL(pagecache_write_begin);
|
|
|
|
int pagecache_write_end(struct file *file, struct address_space *mapping,
|
|
loff_t pos, unsigned len, unsigned copied,
|
|
struct page *page, void *fsdata)
|
|
{
|
|
const struct address_space_operations *aops = mapping->a_ops;
|
|
|
|
return aops->write_end(file, mapping, pos, len, copied, page, fsdata);
|
|
}
|
|
EXPORT_SYMBOL(pagecache_write_end);
|
|
|
|
ssize_t
|
|
generic_file_direct_write(struct kiocb *iocb, struct iov_iter *from)
|
|
{
|
|
struct file *file = iocb->ki_filp;
|
|
struct address_space *mapping = file->f_mapping;
|
|
struct inode *inode = mapping->host;
|
|
loff_t pos = iocb->ki_pos;
|
|
ssize_t written;
|
|
size_t write_len;
|
|
pgoff_t end;
|
|
|
|
write_len = iov_iter_count(from);
|
|
end = (pos + write_len - 1) >> PAGE_SHIFT;
|
|
|
|
if (iocb->ki_flags & IOCB_NOWAIT) {
|
|
/* If there are pages to writeback, return */
|
|
if (filemap_range_has_page(inode->i_mapping, pos,
|
|
pos + iov_iter_count(from)))
|
|
return -EAGAIN;
|
|
} else {
|
|
written = filemap_write_and_wait_range(mapping, pos,
|
|
pos + write_len - 1);
|
|
if (written)
|
|
goto out;
|
|
}
|
|
|
|
/*
|
|
* After a write we want buffered reads to be sure to go to disk to get
|
|
* the new data. We invalidate clean cached page from the region we're
|
|
* about to write. We do this *before* the write so that we can return
|
|
* without clobbering -EIOCBQUEUED from ->direct_IO().
|
|
*/
|
|
written = invalidate_inode_pages2_range(mapping,
|
|
pos >> PAGE_SHIFT, end);
|
|
/*
|
|
* If a page can not be invalidated, return 0 to fall back
|
|
* to buffered write.
|
|
*/
|
|
if (written) {
|
|
if (written == -EBUSY)
|
|
return 0;
|
|
goto out;
|
|
}
|
|
|
|
written = mapping->a_ops->direct_IO(iocb, from);
|
|
|
|
/*
|
|
* Finally, try again to invalidate clean pages which might have been
|
|
* cached by non-direct readahead, or faulted in by get_user_pages()
|
|
* if the source of the write was an mmap'ed region of the file
|
|
* we're writing. Either one is a pretty crazy thing to do,
|
|
* so we don't support it 100%. If this invalidation
|
|
* fails, tough, the write still worked...
|
|
*/
|
|
invalidate_inode_pages2_range(mapping,
|
|
pos >> PAGE_SHIFT, end);
|
|
|
|
if (written > 0) {
|
|
pos += written;
|
|
write_len -= written;
|
|
if (pos > i_size_read(inode) && !S_ISBLK(inode->i_mode)) {
|
|
i_size_write(inode, pos);
|
|
mark_inode_dirty(inode);
|
|
}
|
|
iocb->ki_pos = pos;
|
|
}
|
|
iov_iter_revert(from, write_len - iov_iter_count(from));
|
|
out:
|
|
return written;
|
|
}
|
|
EXPORT_SYMBOL(generic_file_direct_write);
|
|
|
|
/*
|
|
* Find or create a page at the given pagecache position. Return the locked
|
|
* page. This function is specifically for buffered writes.
|
|
*/
|
|
struct page *grab_cache_page_write_begin(struct address_space *mapping,
|
|
pgoff_t index, unsigned flags)
|
|
{
|
|
struct page *page;
|
|
int fgp_flags = FGP_LOCK|FGP_WRITE|FGP_CREAT;
|
|
|
|
if (flags & AOP_FLAG_NOFS)
|
|
fgp_flags |= FGP_NOFS;
|
|
|
|
page = pagecache_get_page(mapping, index, fgp_flags,
|
|
mapping_gfp_mask(mapping));
|
|
if (page)
|
|
wait_for_stable_page(page);
|
|
|
|
return page;
|
|
}
|
|
EXPORT_SYMBOL(grab_cache_page_write_begin);
|
|
|
|
ssize_t generic_perform_write(struct file *file,
|
|
struct iov_iter *i, loff_t pos)
|
|
{
|
|
struct address_space *mapping = file->f_mapping;
|
|
const struct address_space_operations *a_ops = mapping->a_ops;
|
|
long status = 0;
|
|
ssize_t written = 0;
|
|
unsigned int flags = 0;
|
|
|
|
do {
|
|
struct page *page;
|
|
unsigned long offset; /* Offset into pagecache page */
|
|
unsigned long bytes; /* Bytes to write to page */
|
|
size_t copied; /* Bytes copied from user */
|
|
void *fsdata;
|
|
|
|
offset = (pos & (PAGE_SIZE - 1));
|
|
bytes = min_t(unsigned long, PAGE_SIZE - offset,
|
|
iov_iter_count(i));
|
|
|
|
again:
|
|
/*
|
|
* Bring in the user page that we will copy from _first_.
|
|
* Otherwise there's a nasty deadlock on copying from the
|
|
* same page as we're writing to, without it being marked
|
|
* up-to-date.
|
|
*
|
|
* Not only is this an optimisation, but it is also required
|
|
* to check that the address is actually valid, when atomic
|
|
* usercopies are used, below.
|
|
*/
|
|
if (unlikely(iov_iter_fault_in_readable(i, bytes))) {
|
|
status = -EFAULT;
|
|
break;
|
|
}
|
|
|
|
if (fatal_signal_pending(current)) {
|
|
status = -EINTR;
|
|
break;
|
|
}
|
|
|
|
status = a_ops->write_begin(file, mapping, pos, bytes, flags,
|
|
&page, &fsdata);
|
|
if (unlikely(status < 0))
|
|
break;
|
|
|
|
if (mapping_writably_mapped(mapping))
|
|
flush_dcache_page(page);
|
|
|
|
copied = iov_iter_copy_from_user_atomic(page, i, offset, bytes);
|
|
flush_dcache_page(page);
|
|
|
|
status = a_ops->write_end(file, mapping, pos, bytes, copied,
|
|
page, fsdata);
|
|
if (unlikely(status < 0))
|
|
break;
|
|
copied = status;
|
|
|
|
cond_resched();
|
|
|
|
iov_iter_advance(i, copied);
|
|
if (unlikely(copied == 0)) {
|
|
/*
|
|
* If we were unable to copy any data at all, we must
|
|
* fall back to a single segment length write.
|
|
*
|
|
* If we didn't fallback here, we could livelock
|
|
* because not all segments in the iov can be copied at
|
|
* once without a pagefault.
|
|
*/
|
|
bytes = min_t(unsigned long, PAGE_SIZE - offset,
|
|
iov_iter_single_seg_count(i));
|
|
goto again;
|
|
}
|
|
pos += copied;
|
|
written += copied;
|
|
|
|
balance_dirty_pages_ratelimited(mapping);
|
|
} while (iov_iter_count(i));
|
|
|
|
return written ? written : status;
|
|
}
|
|
EXPORT_SYMBOL(generic_perform_write);
|
|
|
|
/**
|
|
* __generic_file_write_iter - write data to a file
|
|
* @iocb: IO state structure (file, offset, etc.)
|
|
* @from: iov_iter with data to write
|
|
*
|
|
* This function does all the work needed for actually writing data to a
|
|
* file. It does all basic checks, removes SUID from the file, updates
|
|
* modification times and calls proper subroutines depending on whether we
|
|
* do direct IO or a standard buffered write.
|
|
*
|
|
* It expects i_mutex to be grabbed unless we work on a block device or similar
|
|
* object which does not need locking at all.
|
|
*
|
|
* This function does *not* take care of syncing data in case of O_SYNC write.
|
|
* A caller has to handle it. This is mainly due to the fact that we want to
|
|
* avoid syncing under i_mutex.
|
|
*/
|
|
ssize_t __generic_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
|
|
{
|
|
struct file *file = iocb->ki_filp;
|
|
struct address_space * mapping = file->f_mapping;
|
|
struct inode *inode = mapping->host;
|
|
ssize_t written = 0;
|
|
ssize_t err;
|
|
ssize_t status;
|
|
|
|
/* We can write back this queue in page reclaim */
|
|
current->backing_dev_info = inode_to_bdi(inode);
|
|
err = file_remove_privs(file);
|
|
if (err)
|
|
goto out;
|
|
|
|
err = file_update_time(file);
|
|
if (err)
|
|
goto out;
|
|
|
|
if (iocb->ki_flags & IOCB_DIRECT) {
|
|
loff_t pos, endbyte;
|
|
|
|
written = generic_file_direct_write(iocb, from);
|
|
/*
|
|
* If the write stopped short of completing, fall back to
|
|
* buffered writes. Some filesystems do this for writes to
|
|
* holes, for example. For DAX files, a buffered write will
|
|
* not succeed (even if it did, DAX does not handle dirty
|
|
* page-cache pages correctly).
|
|
*/
|
|
if (written < 0 || !iov_iter_count(from) || IS_DAX(inode))
|
|
goto out;
|
|
|
|
status = generic_perform_write(file, from, pos = iocb->ki_pos);
|
|
/*
|
|
* If generic_perform_write() returned a synchronous error
|
|
* then we want to return the number of bytes which were
|
|
* direct-written, or the error code if that was zero. Note
|
|
* that this differs from normal direct-io semantics, which
|
|
* will return -EFOO even if some bytes were written.
|
|
*/
|
|
if (unlikely(status < 0)) {
|
|
err = status;
|
|
goto out;
|
|
}
|
|
/*
|
|
* We need to ensure that the page cache pages are written to
|
|
* disk and invalidated to preserve the expected O_DIRECT
|
|
* semantics.
|
|
*/
|
|
endbyte = pos + status - 1;
|
|
err = filemap_write_and_wait_range(mapping, pos, endbyte);
|
|
if (err == 0) {
|
|
iocb->ki_pos = endbyte + 1;
|
|
written += status;
|
|
invalidate_mapping_pages(mapping,
|
|
pos >> PAGE_SHIFT,
|
|
endbyte >> PAGE_SHIFT);
|
|
} else {
|
|
/*
|
|
* We don't know how much we wrote, so just return
|
|
* the number of bytes which were direct-written
|
|
*/
|
|
}
|
|
} else {
|
|
written = generic_perform_write(file, from, iocb->ki_pos);
|
|
if (likely(written > 0))
|
|
iocb->ki_pos += written;
|
|
}
|
|
out:
|
|
current->backing_dev_info = NULL;
|
|
return written ? written : err;
|
|
}
|
|
EXPORT_SYMBOL(__generic_file_write_iter);
|
|
|
|
/**
|
|
* generic_file_write_iter - write data to a file
|
|
* @iocb: IO state structure
|
|
* @from: iov_iter with data to write
|
|
*
|
|
* This is a wrapper around __generic_file_write_iter() to be used by most
|
|
* filesystems. It takes care of syncing the file in case of O_SYNC file
|
|
* and acquires i_mutex as needed.
|
|
*/
|
|
ssize_t generic_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
|
|
{
|
|
struct file *file = iocb->ki_filp;
|
|
struct inode *inode = file->f_mapping->host;
|
|
ssize_t ret;
|
|
|
|
inode_lock(inode);
|
|
ret = generic_write_checks(iocb, from);
|
|
if (ret > 0)
|
|
ret = __generic_file_write_iter(iocb, from);
|
|
inode_unlock(inode);
|
|
|
|
if (ret > 0)
|
|
ret = generic_write_sync(iocb, ret);
|
|
return ret;
|
|
}
|
|
EXPORT_SYMBOL(generic_file_write_iter);
|
|
|
|
/**
|
|
* try_to_release_page() - release old fs-specific metadata on a page
|
|
*
|
|
* @page: the page which the kernel is trying to free
|
|
* @gfp_mask: memory allocation flags (and I/O mode)
|
|
*
|
|
* The address_space is to try to release any data against the page
|
|
* (presumably at page->private). If the release was successful, return '1'.
|
|
* Otherwise return zero.
|
|
*
|
|
* This may also be called if PG_fscache is set on a page, indicating that the
|
|
* page is known to the local caching routines.
|
|
*
|
|
* The @gfp_mask argument specifies whether I/O may be performed to release
|
|
* this page (__GFP_IO), and whether the call may block (__GFP_RECLAIM & __GFP_FS).
|
|
*
|
|
*/
|
|
int try_to_release_page(struct page *page, gfp_t gfp_mask)
|
|
{
|
|
struct address_space * const mapping = page->mapping;
|
|
|
|
BUG_ON(!PageLocked(page));
|
|
if (PageWriteback(page))
|
|
return 0;
|
|
|
|
if (mapping && mapping->a_ops->releasepage)
|
|
return mapping->a_ops->releasepage(page, gfp_mask);
|
|
return try_to_free_buffers(page);
|
|
}
|
|
|
|
EXPORT_SYMBOL(try_to_release_page);
|