1257 lines
35 KiB
C
1257 lines
35 KiB
C
/*
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* fs/direct-io.c
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*
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* Copyright (C) 2002, Linus Torvalds.
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*
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* O_DIRECT
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*
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* 04Jul2002 akpm@zip.com.au
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* Initial version
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* 11Sep2002 janetinc@us.ibm.com
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* added readv/writev support.
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* 29Oct2002 akpm@zip.com.au
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* rewrote bio_add_page() support.
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* 30Oct2002 pbadari@us.ibm.com
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* added support for non-aligned IO.
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* 06Nov2002 pbadari@us.ibm.com
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* added asynchronous IO support.
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* 21Jul2003 nathans@sgi.com
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* added IO completion notifier.
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*/
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#include <linux/kernel.h>
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#include <linux/module.h>
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#include <linux/types.h>
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#include <linux/fs.h>
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#include <linux/mm.h>
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#include <linux/slab.h>
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#include <linux/highmem.h>
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#include <linux/pagemap.h>
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#include <linux/task_io_accounting_ops.h>
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#include <linux/bio.h>
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#include <linux/wait.h>
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#include <linux/err.h>
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#include <linux/blkdev.h>
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#include <linux/buffer_head.h>
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#include <linux/rwsem.h>
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#include <linux/uio.h>
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#include <asm/atomic.h>
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/*
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* How many user pages to map in one call to get_user_pages(). This determines
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* the size of a structure on the stack.
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*/
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#define DIO_PAGES 64
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/*
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* This code generally works in units of "dio_blocks". A dio_block is
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* somewhere between the hard sector size and the filesystem block size. it
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* is determined on a per-invocation basis. When talking to the filesystem
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* we need to convert dio_blocks to fs_blocks by scaling the dio_block quantity
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* down by dio->blkfactor. Similarly, fs-blocksize quantities are converted
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* to bio_block quantities by shifting left by blkfactor.
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*
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* If blkfactor is zero then the user's request was aligned to the filesystem's
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* blocksize.
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*
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* lock_type is DIO_LOCKING for regular files on direct-IO-naive filesystems.
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* This determines whether we need to do the fancy locking which prevents
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* direct-IO from being able to read uninitialised disk blocks. If its zero
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* (blockdev) this locking is not done, and if it is DIO_OWN_LOCKING i_mutex is
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* not held for the entire direct write (taken briefly, initially, during a
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* direct read though, but its never held for the duration of a direct-IO).
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*/
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struct dio {
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/* BIO submission state */
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struct bio *bio; /* bio under assembly */
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struct inode *inode;
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int rw;
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loff_t i_size; /* i_size when submitted */
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int lock_type; /* doesn't change */
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unsigned blkbits; /* doesn't change */
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unsigned blkfactor; /* When we're using an alignment which
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is finer than the filesystem's soft
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blocksize, this specifies how much
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finer. blkfactor=2 means 1/4-block
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alignment. Does not change */
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unsigned start_zero_done; /* flag: sub-blocksize zeroing has
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been performed at the start of a
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write */
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int pages_in_io; /* approximate total IO pages */
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size_t size; /* total request size (doesn't change)*/
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sector_t block_in_file; /* Current offset into the underlying
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file in dio_block units. */
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unsigned blocks_available; /* At block_in_file. changes */
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sector_t final_block_in_request;/* doesn't change */
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unsigned first_block_in_page; /* doesn't change, Used only once */
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int boundary; /* prev block is at a boundary */
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int reap_counter; /* rate limit reaping */
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get_block_t *get_block; /* block mapping function */
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dio_iodone_t *end_io; /* IO completion function */
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sector_t final_block_in_bio; /* current final block in bio + 1 */
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sector_t next_block_for_io; /* next block to be put under IO,
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in dio_blocks units */
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struct buffer_head map_bh; /* last get_block() result */
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/*
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* Deferred addition of a page to the dio. These variables are
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* private to dio_send_cur_page(), submit_page_section() and
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* dio_bio_add_page().
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*/
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struct page *cur_page; /* The page */
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unsigned cur_page_offset; /* Offset into it, in bytes */
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unsigned cur_page_len; /* Nr of bytes at cur_page_offset */
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sector_t cur_page_block; /* Where it starts */
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/*
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* Page fetching state. These variables belong to dio_refill_pages().
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*/
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int curr_page; /* changes */
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int total_pages; /* doesn't change */
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unsigned long curr_user_address;/* changes */
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/*
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* Page queue. These variables belong to dio_refill_pages() and
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* dio_get_page().
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*/
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struct page *pages[DIO_PAGES]; /* page buffer */
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unsigned head; /* next page to process */
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unsigned tail; /* last valid page + 1 */
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int page_errors; /* errno from get_user_pages() */
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/* BIO completion state */
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spinlock_t bio_lock; /* protects BIO fields below */
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unsigned long refcount; /* direct_io_worker() and bios */
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struct bio *bio_list; /* singly linked via bi_private */
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struct task_struct *waiter; /* waiting task (NULL if none) */
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/* AIO related stuff */
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struct kiocb *iocb; /* kiocb */
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int is_async; /* is IO async ? */
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int io_error; /* IO error in completion path */
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ssize_t result; /* IO result */
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};
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/*
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* How many pages are in the queue?
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*/
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static inline unsigned dio_pages_present(struct dio *dio)
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{
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return dio->tail - dio->head;
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}
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/*
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* Go grab and pin some userspace pages. Typically we'll get 64 at a time.
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*/
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static int dio_refill_pages(struct dio *dio)
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{
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int ret;
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int nr_pages;
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nr_pages = min(dio->total_pages - dio->curr_page, DIO_PAGES);
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down_read(¤t->mm->mmap_sem);
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ret = get_user_pages(
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current, /* Task for fault acounting */
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current->mm, /* whose pages? */
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dio->curr_user_address, /* Where from? */
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nr_pages, /* How many pages? */
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dio->rw == READ, /* Write to memory? */
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0, /* force (?) */
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&dio->pages[0],
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NULL); /* vmas */
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up_read(¤t->mm->mmap_sem);
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if (ret < 0 && dio->blocks_available && (dio->rw & WRITE)) {
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struct page *page = ZERO_PAGE(dio->curr_user_address);
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/*
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* A memory fault, but the filesystem has some outstanding
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* mapped blocks. We need to use those blocks up to avoid
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* leaking stale data in the file.
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*/
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if (dio->page_errors == 0)
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dio->page_errors = ret;
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page_cache_get(page);
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dio->pages[0] = page;
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dio->head = 0;
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dio->tail = 1;
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ret = 0;
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goto out;
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}
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if (ret >= 0) {
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dio->curr_user_address += ret * PAGE_SIZE;
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dio->curr_page += ret;
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dio->head = 0;
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dio->tail = ret;
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ret = 0;
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}
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out:
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return ret;
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}
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/*
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* Get another userspace page. Returns an ERR_PTR on error. Pages are
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* buffered inside the dio so that we can call get_user_pages() against a
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* decent number of pages, less frequently. To provide nicer use of the
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* L1 cache.
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*/
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static struct page *dio_get_page(struct dio *dio)
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{
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if (dio_pages_present(dio) == 0) {
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int ret;
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ret = dio_refill_pages(dio);
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if (ret)
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return ERR_PTR(ret);
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BUG_ON(dio_pages_present(dio) == 0);
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}
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return dio->pages[dio->head++];
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}
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/**
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* dio_complete() - called when all DIO BIO I/O has been completed
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* @offset: the byte offset in the file of the completed operation
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*
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* This releases locks as dictated by the locking type, lets interested parties
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* know that a DIO operation has completed, and calculates the resulting return
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* code for the operation.
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*
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* It lets the filesystem know if it registered an interest earlier via
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* get_block. Pass the private field of the map buffer_head so that
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* filesystems can use it to hold additional state between get_block calls and
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* dio_complete.
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*/
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static int dio_complete(struct dio *dio, loff_t offset, int ret)
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{
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ssize_t transferred = 0;
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/*
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* AIO submission can race with bio completion to get here while
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* expecting to have the last io completed by bio completion.
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* In that case -EIOCBQUEUED is in fact not an error we want
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* to preserve through this call.
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*/
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if (ret == -EIOCBQUEUED)
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ret = 0;
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if (dio->result) {
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transferred = dio->result;
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/* Check for short read case */
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if ((dio->rw == READ) && ((offset + transferred) > dio->i_size))
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transferred = dio->i_size - offset;
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}
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if (dio->end_io && dio->result)
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dio->end_io(dio->iocb, offset, transferred,
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dio->map_bh.b_private);
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if (dio->lock_type == DIO_LOCKING)
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/* lockdep: non-owner release */
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up_read_non_owner(&dio->inode->i_alloc_sem);
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if (ret == 0)
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ret = dio->page_errors;
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if (ret == 0)
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ret = dio->io_error;
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if (ret == 0)
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ret = transferred;
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return ret;
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}
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static int dio_bio_complete(struct dio *dio, struct bio *bio);
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/*
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* Asynchronous IO callback.
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*/
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static int dio_bio_end_aio(struct bio *bio, unsigned int bytes_done, int error)
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{
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struct dio *dio = bio->bi_private;
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unsigned long remaining;
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unsigned long flags;
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if (bio->bi_size)
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return 1;
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/* cleanup the bio */
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dio_bio_complete(dio, bio);
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spin_lock_irqsave(&dio->bio_lock, flags);
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remaining = --dio->refcount;
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if (remaining == 1 && dio->waiter)
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wake_up_process(dio->waiter);
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spin_unlock_irqrestore(&dio->bio_lock, flags);
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if (remaining == 0) {
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int ret = dio_complete(dio, dio->iocb->ki_pos, 0);
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aio_complete(dio->iocb, ret, 0);
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kfree(dio);
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}
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return 0;
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}
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/*
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* The BIO completion handler simply queues the BIO up for the process-context
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* handler.
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*
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* During I/O bi_private points at the dio. After I/O, bi_private is used to
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* implement a singly-linked list of completed BIOs, at dio->bio_list.
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*/
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static int dio_bio_end_io(struct bio *bio, unsigned int bytes_done, int error)
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{
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struct dio *dio = bio->bi_private;
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unsigned long flags;
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if (bio->bi_size)
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return 1;
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spin_lock_irqsave(&dio->bio_lock, flags);
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bio->bi_private = dio->bio_list;
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dio->bio_list = bio;
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if (--dio->refcount == 1 && dio->waiter)
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wake_up_process(dio->waiter);
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spin_unlock_irqrestore(&dio->bio_lock, flags);
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return 0;
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}
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static int
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dio_bio_alloc(struct dio *dio, struct block_device *bdev,
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sector_t first_sector, int nr_vecs)
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{
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struct bio *bio;
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bio = bio_alloc(GFP_KERNEL, nr_vecs);
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if (bio == NULL)
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return -ENOMEM;
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bio->bi_bdev = bdev;
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bio->bi_sector = first_sector;
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if (dio->is_async)
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bio->bi_end_io = dio_bio_end_aio;
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else
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bio->bi_end_io = dio_bio_end_io;
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dio->bio = bio;
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return 0;
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}
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/*
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* In the AIO read case we speculatively dirty the pages before starting IO.
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* During IO completion, any of these pages which happen to have been written
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* back will be redirtied by bio_check_pages_dirty().
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*
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* bios hold a dio reference between submit_bio and ->end_io.
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*/
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static void dio_bio_submit(struct dio *dio)
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{
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struct bio *bio = dio->bio;
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unsigned long flags;
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bio->bi_private = dio;
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spin_lock_irqsave(&dio->bio_lock, flags);
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dio->refcount++;
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spin_unlock_irqrestore(&dio->bio_lock, flags);
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if (dio->is_async && dio->rw == READ)
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bio_set_pages_dirty(bio);
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submit_bio(dio->rw, bio);
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dio->bio = NULL;
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dio->boundary = 0;
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}
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/*
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* Release any resources in case of a failure
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*/
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static void dio_cleanup(struct dio *dio)
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{
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while (dio_pages_present(dio))
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page_cache_release(dio_get_page(dio));
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}
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/*
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* Wait for the next BIO to complete. Remove it and return it. NULL is
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* returned once all BIOs have been completed. This must only be called once
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* all bios have been issued so that dio->refcount can only decrease. This
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* requires that that the caller hold a reference on the dio.
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*/
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static struct bio *dio_await_one(struct dio *dio)
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{
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unsigned long flags;
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struct bio *bio = NULL;
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spin_lock_irqsave(&dio->bio_lock, flags);
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/*
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* Wait as long as the list is empty and there are bios in flight. bio
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* completion drops the count, maybe adds to the list, and wakes while
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* holding the bio_lock so we don't need set_current_state()'s barrier
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* and can call it after testing our condition.
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*/
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while (dio->refcount > 1 && dio->bio_list == NULL) {
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__set_current_state(TASK_UNINTERRUPTIBLE);
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dio->waiter = current;
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spin_unlock_irqrestore(&dio->bio_lock, flags);
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io_schedule();
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/* wake up sets us TASK_RUNNING */
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spin_lock_irqsave(&dio->bio_lock, flags);
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dio->waiter = NULL;
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}
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if (dio->bio_list) {
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bio = dio->bio_list;
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dio->bio_list = bio->bi_private;
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}
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spin_unlock_irqrestore(&dio->bio_lock, flags);
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return bio;
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}
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/*
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* Process one completed BIO. No locks are held.
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*/
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static int dio_bio_complete(struct dio *dio, struct bio *bio)
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{
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const int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags);
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struct bio_vec *bvec = bio->bi_io_vec;
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int page_no;
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if (!uptodate)
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dio->io_error = -EIO;
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if (dio->is_async && dio->rw == READ) {
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bio_check_pages_dirty(bio); /* transfers ownership */
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} else {
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for (page_no = 0; page_no < bio->bi_vcnt; page_no++) {
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struct page *page = bvec[page_no].bv_page;
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if (dio->rw == READ && !PageCompound(page))
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set_page_dirty_lock(page);
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page_cache_release(page);
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}
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bio_put(bio);
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}
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return uptodate ? 0 : -EIO;
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}
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/*
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* Wait on and process all in-flight BIOs. This must only be called once
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* all bios have been issued so that the refcount can only decrease.
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* This just waits for all bios to make it through dio_bio_complete. IO
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* errors are propogated through dio->io_error and should be propogated via
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* dio_complete().
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*/
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static void dio_await_completion(struct dio *dio)
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{
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struct bio *bio;
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do {
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bio = dio_await_one(dio);
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if (bio)
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dio_bio_complete(dio, bio);
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} while (bio);
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}
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/*
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* A really large O_DIRECT read or write can generate a lot of BIOs. So
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* to keep the memory consumption sane we periodically reap any completed BIOs
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* during the BIO generation phase.
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*
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* This also helps to limit the peak amount of pinned userspace memory.
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*/
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static int dio_bio_reap(struct dio *dio)
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{
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int ret = 0;
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if (dio->reap_counter++ >= 64) {
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while (dio->bio_list) {
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unsigned long flags;
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struct bio *bio;
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int ret2;
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spin_lock_irqsave(&dio->bio_lock, flags);
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bio = dio->bio_list;
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dio->bio_list = bio->bi_private;
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spin_unlock_irqrestore(&dio->bio_lock, flags);
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ret2 = dio_bio_complete(dio, bio);
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if (ret == 0)
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ret = ret2;
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}
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dio->reap_counter = 0;
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}
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return ret;
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}
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|
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/*
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* Call into the fs to map some more disk blocks. We record the current number
|
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* of available blocks at dio->blocks_available. These are in units of the
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* fs blocksize, (1 << inode->i_blkbits).
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*
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* The fs is allowed to map lots of blocks at once. If it wants to do that,
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* it uses the passed inode-relative block number as the file offset, as usual.
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*
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* get_block() is passed the number of i_blkbits-sized blocks which direct_io
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* has remaining to do. The fs should not map more than this number of blocks.
|
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*
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* If the fs has mapped a lot of blocks, it should populate bh->b_size to
|
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* indicate how much contiguous disk space has been made available at
|
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* bh->b_blocknr.
|
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*
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* If *any* of the mapped blocks are new, then the fs must set buffer_new().
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* This isn't very efficient...
|
|
*
|
|
* In the case of filesystem holes: the fs may return an arbitrarily-large
|
|
* hole by returning an appropriate value in b_size and by clearing
|
|
* buffer_mapped(). However the direct-io code will only process holes one
|
|
* block at a time - it will repeatedly call get_block() as it walks the hole.
|
|
*/
|
|
static int get_more_blocks(struct dio *dio)
|
|
{
|
|
int ret;
|
|
struct buffer_head *map_bh = &dio->map_bh;
|
|
sector_t fs_startblk; /* Into file, in filesystem-sized blocks */
|
|
unsigned long fs_count; /* Number of filesystem-sized blocks */
|
|
unsigned long dio_count;/* Number of dio_block-sized blocks */
|
|
unsigned long blkmask;
|
|
int create;
|
|
|
|
/*
|
|
* If there was a memory error and we've overwritten all the
|
|
* mapped blocks then we can now return that memory error
|
|
*/
|
|
ret = dio->page_errors;
|
|
if (ret == 0) {
|
|
BUG_ON(dio->block_in_file >= dio->final_block_in_request);
|
|
fs_startblk = dio->block_in_file >> dio->blkfactor;
|
|
dio_count = dio->final_block_in_request - dio->block_in_file;
|
|
fs_count = dio_count >> dio->blkfactor;
|
|
blkmask = (1 << dio->blkfactor) - 1;
|
|
if (dio_count & blkmask)
|
|
fs_count++;
|
|
|
|
map_bh->b_state = 0;
|
|
map_bh->b_size = fs_count << dio->inode->i_blkbits;
|
|
|
|
create = dio->rw & WRITE;
|
|
if (dio->lock_type == DIO_LOCKING) {
|
|
if (dio->block_in_file < (i_size_read(dio->inode) >>
|
|
dio->blkbits))
|
|
create = 0;
|
|
} else if (dio->lock_type == DIO_NO_LOCKING) {
|
|
create = 0;
|
|
}
|
|
|
|
/*
|
|
* For writes inside i_size we forbid block creations: only
|
|
* overwrites are permitted. We fall back to buffered writes
|
|
* at a higher level for inside-i_size block-instantiating
|
|
* writes.
|
|
*/
|
|
ret = (*dio->get_block)(dio->inode, fs_startblk,
|
|
map_bh, create);
|
|
}
|
|
return ret;
|
|
}
|
|
|
|
/*
|
|
* There is no bio. Make one now.
|
|
*/
|
|
static int dio_new_bio(struct dio *dio, sector_t start_sector)
|
|
{
|
|
sector_t sector;
|
|
int ret, nr_pages;
|
|
|
|
ret = dio_bio_reap(dio);
|
|
if (ret)
|
|
goto out;
|
|
sector = start_sector << (dio->blkbits - 9);
|
|
nr_pages = min(dio->pages_in_io, bio_get_nr_vecs(dio->map_bh.b_bdev));
|
|
BUG_ON(nr_pages <= 0);
|
|
ret = dio_bio_alloc(dio, dio->map_bh.b_bdev, sector, nr_pages);
|
|
dio->boundary = 0;
|
|
out:
|
|
return ret;
|
|
}
|
|
|
|
/*
|
|
* Attempt to put the current chunk of 'cur_page' into the current BIO. If
|
|
* that was successful then update final_block_in_bio and take a ref against
|
|
* the just-added page.
|
|
*
|
|
* Return zero on success. Non-zero means the caller needs to start a new BIO.
|
|
*/
|
|
static int dio_bio_add_page(struct dio *dio)
|
|
{
|
|
int ret;
|
|
|
|
ret = bio_add_page(dio->bio, dio->cur_page,
|
|
dio->cur_page_len, dio->cur_page_offset);
|
|
if (ret == dio->cur_page_len) {
|
|
/*
|
|
* Decrement count only, if we are done with this page
|
|
*/
|
|
if ((dio->cur_page_len + dio->cur_page_offset) == PAGE_SIZE)
|
|
dio->pages_in_io--;
|
|
page_cache_get(dio->cur_page);
|
|
dio->final_block_in_bio = dio->cur_page_block +
|
|
(dio->cur_page_len >> dio->blkbits);
|
|
ret = 0;
|
|
} else {
|
|
ret = 1;
|
|
}
|
|
return ret;
|
|
}
|
|
|
|
/*
|
|
* Put cur_page under IO. The section of cur_page which is described by
|
|
* cur_page_offset,cur_page_len is put into a BIO. The section of cur_page
|
|
* starts on-disk at cur_page_block.
|
|
*
|
|
* We take a ref against the page here (on behalf of its presence in the bio).
|
|
*
|
|
* The caller of this function is responsible for removing cur_page from the
|
|
* dio, and for dropping the refcount which came from that presence.
|
|
*/
|
|
static int dio_send_cur_page(struct dio *dio)
|
|
{
|
|
int ret = 0;
|
|
|
|
if (dio->bio) {
|
|
/*
|
|
* See whether this new request is contiguous with the old
|
|
*/
|
|
if (dio->final_block_in_bio != dio->cur_page_block)
|
|
dio_bio_submit(dio);
|
|
/*
|
|
* Submit now if the underlying fs is about to perform a
|
|
* metadata read
|
|
*/
|
|
if (dio->boundary)
|
|
dio_bio_submit(dio);
|
|
}
|
|
|
|
if (dio->bio == NULL) {
|
|
ret = dio_new_bio(dio, dio->cur_page_block);
|
|
if (ret)
|
|
goto out;
|
|
}
|
|
|
|
if (dio_bio_add_page(dio) != 0) {
|
|
dio_bio_submit(dio);
|
|
ret = dio_new_bio(dio, dio->cur_page_block);
|
|
if (ret == 0) {
|
|
ret = dio_bio_add_page(dio);
|
|
BUG_ON(ret != 0);
|
|
}
|
|
}
|
|
out:
|
|
return ret;
|
|
}
|
|
|
|
/*
|
|
* An autonomous function to put a chunk of a page under deferred IO.
|
|
*
|
|
* The caller doesn't actually know (or care) whether this piece of page is in
|
|
* a BIO, or is under IO or whatever. We just take care of all possible
|
|
* situations here. The separation between the logic of do_direct_IO() and
|
|
* that of submit_page_section() is important for clarity. Please don't break.
|
|
*
|
|
* The chunk of page starts on-disk at blocknr.
|
|
*
|
|
* We perform deferred IO, by recording the last-submitted page inside our
|
|
* private part of the dio structure. If possible, we just expand the IO
|
|
* across that page here.
|
|
*
|
|
* If that doesn't work out then we put the old page into the bio and add this
|
|
* page to the dio instead.
|
|
*/
|
|
static int
|
|
submit_page_section(struct dio *dio, struct page *page,
|
|
unsigned offset, unsigned len, sector_t blocknr)
|
|
{
|
|
int ret = 0;
|
|
|
|
if (dio->rw & WRITE) {
|
|
/*
|
|
* Read accounting is performed in submit_bio()
|
|
*/
|
|
task_io_account_write(len);
|
|
}
|
|
|
|
/*
|
|
* Can we just grow the current page's presence in the dio?
|
|
*/
|
|
if ( (dio->cur_page == page) &&
|
|
(dio->cur_page_offset + dio->cur_page_len == offset) &&
|
|
(dio->cur_page_block +
|
|
(dio->cur_page_len >> dio->blkbits) == blocknr)) {
|
|
dio->cur_page_len += len;
|
|
|
|
/*
|
|
* If dio->boundary then we want to schedule the IO now to
|
|
* avoid metadata seeks.
|
|
*/
|
|
if (dio->boundary) {
|
|
ret = dio_send_cur_page(dio);
|
|
page_cache_release(dio->cur_page);
|
|
dio->cur_page = NULL;
|
|
}
|
|
goto out;
|
|
}
|
|
|
|
/*
|
|
* If there's a deferred page already there then send it.
|
|
*/
|
|
if (dio->cur_page) {
|
|
ret = dio_send_cur_page(dio);
|
|
page_cache_release(dio->cur_page);
|
|
dio->cur_page = NULL;
|
|
if (ret)
|
|
goto out;
|
|
}
|
|
|
|
page_cache_get(page); /* It is in dio */
|
|
dio->cur_page = page;
|
|
dio->cur_page_offset = offset;
|
|
dio->cur_page_len = len;
|
|
dio->cur_page_block = blocknr;
|
|
out:
|
|
return ret;
|
|
}
|
|
|
|
/*
|
|
* Clean any dirty buffers in the blockdev mapping which alias newly-created
|
|
* file blocks. Only called for S_ISREG files - blockdevs do not set
|
|
* buffer_new
|
|
*/
|
|
static void clean_blockdev_aliases(struct dio *dio)
|
|
{
|
|
unsigned i;
|
|
unsigned nblocks;
|
|
|
|
nblocks = dio->map_bh.b_size >> dio->inode->i_blkbits;
|
|
|
|
for (i = 0; i < nblocks; i++) {
|
|
unmap_underlying_metadata(dio->map_bh.b_bdev,
|
|
dio->map_bh.b_blocknr + i);
|
|
}
|
|
}
|
|
|
|
/*
|
|
* If we are not writing the entire block and get_block() allocated
|
|
* the block for us, we need to fill-in the unused portion of the
|
|
* block with zeros. This happens only if user-buffer, fileoffset or
|
|
* io length is not filesystem block-size multiple.
|
|
*
|
|
* `end' is zero if we're doing the start of the IO, 1 at the end of the
|
|
* IO.
|
|
*/
|
|
static void dio_zero_block(struct dio *dio, int end)
|
|
{
|
|
unsigned dio_blocks_per_fs_block;
|
|
unsigned this_chunk_blocks; /* In dio_blocks */
|
|
unsigned this_chunk_bytes;
|
|
struct page *page;
|
|
|
|
dio->start_zero_done = 1;
|
|
if (!dio->blkfactor || !buffer_new(&dio->map_bh))
|
|
return;
|
|
|
|
dio_blocks_per_fs_block = 1 << dio->blkfactor;
|
|
this_chunk_blocks = dio->block_in_file & (dio_blocks_per_fs_block - 1);
|
|
|
|
if (!this_chunk_blocks)
|
|
return;
|
|
|
|
/*
|
|
* We need to zero out part of an fs block. It is either at the
|
|
* beginning or the end of the fs block.
|
|
*/
|
|
if (end)
|
|
this_chunk_blocks = dio_blocks_per_fs_block - this_chunk_blocks;
|
|
|
|
this_chunk_bytes = this_chunk_blocks << dio->blkbits;
|
|
|
|
page = ZERO_PAGE(dio->curr_user_address);
|
|
if (submit_page_section(dio, page, 0, this_chunk_bytes,
|
|
dio->next_block_for_io))
|
|
return;
|
|
|
|
dio->next_block_for_io += this_chunk_blocks;
|
|
}
|
|
|
|
/*
|
|
* Walk the user pages, and the file, mapping blocks to disk and generating
|
|
* a sequence of (page,offset,len,block) mappings. These mappings are injected
|
|
* into submit_page_section(), which takes care of the next stage of submission
|
|
*
|
|
* Direct IO against a blockdev is different from a file. Because we can
|
|
* happily perform page-sized but 512-byte aligned IOs. It is important that
|
|
* blockdev IO be able to have fine alignment and large sizes.
|
|
*
|
|
* So what we do is to permit the ->get_block function to populate bh.b_size
|
|
* with the size of IO which is permitted at this offset and this i_blkbits.
|
|
*
|
|
* For best results, the blockdev should be set up with 512-byte i_blkbits and
|
|
* it should set b_size to PAGE_SIZE or more inside get_block(). This gives
|
|
* fine alignment but still allows this function to work in PAGE_SIZE units.
|
|
*/
|
|
static int do_direct_IO(struct dio *dio)
|
|
{
|
|
const unsigned blkbits = dio->blkbits;
|
|
const unsigned blocks_per_page = PAGE_SIZE >> blkbits;
|
|
struct page *page;
|
|
unsigned block_in_page;
|
|
struct buffer_head *map_bh = &dio->map_bh;
|
|
int ret = 0;
|
|
|
|
/* The I/O can start at any block offset within the first page */
|
|
block_in_page = dio->first_block_in_page;
|
|
|
|
while (dio->block_in_file < dio->final_block_in_request) {
|
|
page = dio_get_page(dio);
|
|
if (IS_ERR(page)) {
|
|
ret = PTR_ERR(page);
|
|
goto out;
|
|
}
|
|
|
|
while (block_in_page < blocks_per_page) {
|
|
unsigned offset_in_page = block_in_page << blkbits;
|
|
unsigned this_chunk_bytes; /* # of bytes mapped */
|
|
unsigned this_chunk_blocks; /* # of blocks */
|
|
unsigned u;
|
|
|
|
if (dio->blocks_available == 0) {
|
|
/*
|
|
* Need to go and map some more disk
|
|
*/
|
|
unsigned long blkmask;
|
|
unsigned long dio_remainder;
|
|
|
|
ret = get_more_blocks(dio);
|
|
if (ret) {
|
|
page_cache_release(page);
|
|
goto out;
|
|
}
|
|
if (!buffer_mapped(map_bh))
|
|
goto do_holes;
|
|
|
|
dio->blocks_available =
|
|
map_bh->b_size >> dio->blkbits;
|
|
dio->next_block_for_io =
|
|
map_bh->b_blocknr << dio->blkfactor;
|
|
if (buffer_new(map_bh))
|
|
clean_blockdev_aliases(dio);
|
|
|
|
if (!dio->blkfactor)
|
|
goto do_holes;
|
|
|
|
blkmask = (1 << dio->blkfactor) - 1;
|
|
dio_remainder = (dio->block_in_file & blkmask);
|
|
|
|
/*
|
|
* If we are at the start of IO and that IO
|
|
* starts partway into a fs-block,
|
|
* dio_remainder will be non-zero. If the IO
|
|
* is a read then we can simply advance the IO
|
|
* cursor to the first block which is to be
|
|
* read. But if the IO is a write and the
|
|
* block was newly allocated we cannot do that;
|
|
* the start of the fs block must be zeroed out
|
|
* on-disk
|
|
*/
|
|
if (!buffer_new(map_bh))
|
|
dio->next_block_for_io += dio_remainder;
|
|
dio->blocks_available -= dio_remainder;
|
|
}
|
|
do_holes:
|
|
/* Handle holes */
|
|
if (!buffer_mapped(map_bh)) {
|
|
char *kaddr;
|
|
loff_t i_size_aligned;
|
|
|
|
/* AKPM: eargh, -ENOTBLK is a hack */
|
|
if (dio->rw & WRITE) {
|
|
page_cache_release(page);
|
|
return -ENOTBLK;
|
|
}
|
|
|
|
/*
|
|
* Be sure to account for a partial block as the
|
|
* last block in the file
|
|
*/
|
|
i_size_aligned = ALIGN(i_size_read(dio->inode),
|
|
1 << blkbits);
|
|
if (dio->block_in_file >=
|
|
i_size_aligned >> blkbits) {
|
|
/* We hit eof */
|
|
page_cache_release(page);
|
|
goto out;
|
|
}
|
|
kaddr = kmap_atomic(page, KM_USER0);
|
|
memset(kaddr + (block_in_page << blkbits),
|
|
0, 1 << blkbits);
|
|
flush_dcache_page(page);
|
|
kunmap_atomic(kaddr, KM_USER0);
|
|
dio->block_in_file++;
|
|
block_in_page++;
|
|
goto next_block;
|
|
}
|
|
|
|
/*
|
|
* If we're performing IO which has an alignment which
|
|
* is finer than the underlying fs, go check to see if
|
|
* we must zero out the start of this block.
|
|
*/
|
|
if (unlikely(dio->blkfactor && !dio->start_zero_done))
|
|
dio_zero_block(dio, 0);
|
|
|
|
/*
|
|
* Work out, in this_chunk_blocks, how much disk we
|
|
* can add to this page
|
|
*/
|
|
this_chunk_blocks = dio->blocks_available;
|
|
u = (PAGE_SIZE - offset_in_page) >> blkbits;
|
|
if (this_chunk_blocks > u)
|
|
this_chunk_blocks = u;
|
|
u = dio->final_block_in_request - dio->block_in_file;
|
|
if (this_chunk_blocks > u)
|
|
this_chunk_blocks = u;
|
|
this_chunk_bytes = this_chunk_blocks << blkbits;
|
|
BUG_ON(this_chunk_bytes == 0);
|
|
|
|
dio->boundary = buffer_boundary(map_bh);
|
|
ret = submit_page_section(dio, page, offset_in_page,
|
|
this_chunk_bytes, dio->next_block_for_io);
|
|
if (ret) {
|
|
page_cache_release(page);
|
|
goto out;
|
|
}
|
|
dio->next_block_for_io += this_chunk_blocks;
|
|
|
|
dio->block_in_file += this_chunk_blocks;
|
|
block_in_page += this_chunk_blocks;
|
|
dio->blocks_available -= this_chunk_blocks;
|
|
next_block:
|
|
BUG_ON(dio->block_in_file > dio->final_block_in_request);
|
|
if (dio->block_in_file == dio->final_block_in_request)
|
|
break;
|
|
}
|
|
|
|
/* Drop the ref which was taken in get_user_pages() */
|
|
page_cache_release(page);
|
|
block_in_page = 0;
|
|
}
|
|
out:
|
|
return ret;
|
|
}
|
|
|
|
/*
|
|
* Releases both i_mutex and i_alloc_sem
|
|
*/
|
|
static ssize_t
|
|
direct_io_worker(int rw, struct kiocb *iocb, struct inode *inode,
|
|
const struct iovec *iov, loff_t offset, unsigned long nr_segs,
|
|
unsigned blkbits, get_block_t get_block, dio_iodone_t end_io,
|
|
struct dio *dio)
|
|
{
|
|
unsigned long user_addr;
|
|
unsigned long flags;
|
|
int seg;
|
|
ssize_t ret = 0;
|
|
ssize_t ret2;
|
|
size_t bytes;
|
|
|
|
dio->bio = NULL;
|
|
dio->inode = inode;
|
|
dio->rw = rw;
|
|
dio->blkbits = blkbits;
|
|
dio->blkfactor = inode->i_blkbits - blkbits;
|
|
dio->start_zero_done = 0;
|
|
dio->size = 0;
|
|
dio->block_in_file = offset >> blkbits;
|
|
dio->blocks_available = 0;
|
|
dio->cur_page = NULL;
|
|
|
|
dio->boundary = 0;
|
|
dio->reap_counter = 0;
|
|
dio->get_block = get_block;
|
|
dio->end_io = end_io;
|
|
dio->map_bh.b_private = NULL;
|
|
dio->final_block_in_bio = -1;
|
|
dio->next_block_for_io = -1;
|
|
|
|
dio->page_errors = 0;
|
|
dio->io_error = 0;
|
|
dio->result = 0;
|
|
dio->iocb = iocb;
|
|
dio->i_size = i_size_read(inode);
|
|
|
|
spin_lock_init(&dio->bio_lock);
|
|
dio->refcount = 1;
|
|
dio->bio_list = NULL;
|
|
dio->waiter = NULL;
|
|
|
|
/*
|
|
* In case of non-aligned buffers, we may need 2 more
|
|
* pages since we need to zero out first and last block.
|
|
*/
|
|
if (unlikely(dio->blkfactor))
|
|
dio->pages_in_io = 2;
|
|
else
|
|
dio->pages_in_io = 0;
|
|
|
|
for (seg = 0; seg < nr_segs; seg++) {
|
|
user_addr = (unsigned long)iov[seg].iov_base;
|
|
dio->pages_in_io +=
|
|
((user_addr+iov[seg].iov_len +PAGE_SIZE-1)/PAGE_SIZE
|
|
- user_addr/PAGE_SIZE);
|
|
}
|
|
|
|
for (seg = 0; seg < nr_segs; seg++) {
|
|
user_addr = (unsigned long)iov[seg].iov_base;
|
|
dio->size += bytes = iov[seg].iov_len;
|
|
|
|
/* Index into the first page of the first block */
|
|
dio->first_block_in_page = (user_addr & ~PAGE_MASK) >> blkbits;
|
|
dio->final_block_in_request = dio->block_in_file +
|
|
(bytes >> blkbits);
|
|
/* Page fetching state */
|
|
dio->head = 0;
|
|
dio->tail = 0;
|
|
dio->curr_page = 0;
|
|
|
|
dio->total_pages = 0;
|
|
if (user_addr & (PAGE_SIZE-1)) {
|
|
dio->total_pages++;
|
|
bytes -= PAGE_SIZE - (user_addr & (PAGE_SIZE - 1));
|
|
}
|
|
dio->total_pages += (bytes + PAGE_SIZE - 1) / PAGE_SIZE;
|
|
dio->curr_user_address = user_addr;
|
|
|
|
ret = do_direct_IO(dio);
|
|
|
|
dio->result += iov[seg].iov_len -
|
|
((dio->final_block_in_request - dio->block_in_file) <<
|
|
blkbits);
|
|
|
|
if (ret) {
|
|
dio_cleanup(dio);
|
|
break;
|
|
}
|
|
} /* end iovec loop */
|
|
|
|
if (ret == -ENOTBLK && (rw & WRITE)) {
|
|
/*
|
|
* The remaining part of the request will be
|
|
* be handled by buffered I/O when we return
|
|
*/
|
|
ret = 0;
|
|
}
|
|
/*
|
|
* There may be some unwritten disk at the end of a part-written
|
|
* fs-block-sized block. Go zero that now.
|
|
*/
|
|
dio_zero_block(dio, 1);
|
|
|
|
if (dio->cur_page) {
|
|
ret2 = dio_send_cur_page(dio);
|
|
if (ret == 0)
|
|
ret = ret2;
|
|
page_cache_release(dio->cur_page);
|
|
dio->cur_page = NULL;
|
|
}
|
|
if (dio->bio)
|
|
dio_bio_submit(dio);
|
|
|
|
/* All IO is now issued, send it on its way */
|
|
blk_run_address_space(inode->i_mapping);
|
|
|
|
/*
|
|
* It is possible that, we return short IO due to end of file.
|
|
* In that case, we need to release all the pages we got hold on.
|
|
*/
|
|
dio_cleanup(dio);
|
|
|
|
/*
|
|
* All block lookups have been performed. For READ requests
|
|
* we can let i_mutex go now that its achieved its purpose
|
|
* of protecting us from looking up uninitialized blocks.
|
|
*/
|
|
if ((rw == READ) && (dio->lock_type == DIO_LOCKING))
|
|
mutex_unlock(&dio->inode->i_mutex);
|
|
|
|
/*
|
|
* The only time we want to leave bios in flight is when a successful
|
|
* partial aio read or full aio write have been setup. In that case
|
|
* bio completion will call aio_complete. The only time it's safe to
|
|
* call aio_complete is when we return -EIOCBQUEUED, so we key on that.
|
|
* This had *better* be the only place that raises -EIOCBQUEUED.
|
|
*/
|
|
BUG_ON(ret == -EIOCBQUEUED);
|
|
if (dio->is_async && ret == 0 && dio->result &&
|
|
((rw & READ) || (dio->result == dio->size)))
|
|
ret = -EIOCBQUEUED;
|
|
|
|
if (ret != -EIOCBQUEUED)
|
|
dio_await_completion(dio);
|
|
|
|
/*
|
|
* Sync will always be dropping the final ref and completing the
|
|
* operation. AIO can if it was a broken operation described above or
|
|
* in fact if all the bios race to complete before we get here. In
|
|
* that case dio_complete() translates the EIOCBQUEUED into the proper
|
|
* return code that the caller will hand to aio_complete().
|
|
*
|
|
* This is managed by the bio_lock instead of being an atomic_t so that
|
|
* completion paths can drop their ref and use the remaining count to
|
|
* decide to wake the submission path atomically.
|
|
*/
|
|
spin_lock_irqsave(&dio->bio_lock, flags);
|
|
ret2 = --dio->refcount;
|
|
spin_unlock_irqrestore(&dio->bio_lock, flags);
|
|
BUG_ON(!dio->is_async && ret2 != 0);
|
|
if (ret2 == 0) {
|
|
ret = dio_complete(dio, offset, ret);
|
|
kfree(dio);
|
|
} else
|
|
BUG_ON(ret != -EIOCBQUEUED);
|
|
|
|
return ret;
|
|
}
|
|
|
|
/*
|
|
* This is a library function for use by filesystem drivers.
|
|
* The locking rules are governed by the dio_lock_type parameter.
|
|
*
|
|
* DIO_NO_LOCKING (no locking, for raw block device access)
|
|
* For writes, i_mutex is not held on entry; it is never taken.
|
|
*
|
|
* DIO_LOCKING (simple locking for regular files)
|
|
* For writes we are called under i_mutex and return with i_mutex held, even
|
|
* though it is internally dropped.
|
|
* For reads, i_mutex is not held on entry, but it is taken and dropped before
|
|
* returning.
|
|
*
|
|
* DIO_OWN_LOCKING (filesystem provides synchronisation and handling of
|
|
* uninitialised data, allowing parallel direct readers and writers)
|
|
* For writes we are called without i_mutex, return without it, never touch it.
|
|
* For reads we are called under i_mutex and return with i_mutex held, even
|
|
* though it may be internally dropped.
|
|
*
|
|
* Additional i_alloc_sem locking requirements described inline below.
|
|
*/
|
|
ssize_t
|
|
__blockdev_direct_IO(int rw, struct kiocb *iocb, struct inode *inode,
|
|
struct block_device *bdev, const struct iovec *iov, loff_t offset,
|
|
unsigned long nr_segs, get_block_t get_block, dio_iodone_t end_io,
|
|
int dio_lock_type)
|
|
{
|
|
int seg;
|
|
size_t size;
|
|
unsigned long addr;
|
|
unsigned blkbits = inode->i_blkbits;
|
|
unsigned bdev_blkbits = 0;
|
|
unsigned blocksize_mask = (1 << blkbits) - 1;
|
|
ssize_t retval = -EINVAL;
|
|
loff_t end = offset;
|
|
struct dio *dio;
|
|
int release_i_mutex = 0;
|
|
int acquire_i_mutex = 0;
|
|
|
|
if (rw & WRITE)
|
|
rw = WRITE_SYNC;
|
|
|
|
if (bdev)
|
|
bdev_blkbits = blksize_bits(bdev_hardsect_size(bdev));
|
|
|
|
if (offset & blocksize_mask) {
|
|
if (bdev)
|
|
blkbits = bdev_blkbits;
|
|
blocksize_mask = (1 << blkbits) - 1;
|
|
if (offset & blocksize_mask)
|
|
goto out;
|
|
}
|
|
|
|
/* Check the memory alignment. Blocks cannot straddle pages */
|
|
for (seg = 0; seg < nr_segs; seg++) {
|
|
addr = (unsigned long)iov[seg].iov_base;
|
|
size = iov[seg].iov_len;
|
|
end += size;
|
|
if ((addr & blocksize_mask) || (size & blocksize_mask)) {
|
|
if (bdev)
|
|
blkbits = bdev_blkbits;
|
|
blocksize_mask = (1 << blkbits) - 1;
|
|
if ((addr & blocksize_mask) || (size & blocksize_mask))
|
|
goto out;
|
|
}
|
|
}
|
|
|
|
dio = kmalloc(sizeof(*dio), GFP_KERNEL);
|
|
retval = -ENOMEM;
|
|
if (!dio)
|
|
goto out;
|
|
|
|
/*
|
|
* For block device access DIO_NO_LOCKING is used,
|
|
* neither readers nor writers do any locking at all
|
|
* For regular files using DIO_LOCKING,
|
|
* readers need to grab i_mutex and i_alloc_sem
|
|
* writers need to grab i_alloc_sem only (i_mutex is already held)
|
|
* For regular files using DIO_OWN_LOCKING,
|
|
* neither readers nor writers take any locks here
|
|
*/
|
|
dio->lock_type = dio_lock_type;
|
|
if (dio_lock_type != DIO_NO_LOCKING) {
|
|
/* watch out for a 0 len io from a tricksy fs */
|
|
if (rw == READ && end > offset) {
|
|
struct address_space *mapping;
|
|
|
|
mapping = iocb->ki_filp->f_mapping;
|
|
if (dio_lock_type != DIO_OWN_LOCKING) {
|
|
mutex_lock(&inode->i_mutex);
|
|
release_i_mutex = 1;
|
|
}
|
|
|
|
retval = filemap_write_and_wait_range(mapping, offset,
|
|
end - 1);
|
|
if (retval) {
|
|
kfree(dio);
|
|
goto out;
|
|
}
|
|
|
|
if (dio_lock_type == DIO_OWN_LOCKING) {
|
|
mutex_unlock(&inode->i_mutex);
|
|
acquire_i_mutex = 1;
|
|
}
|
|
}
|
|
|
|
if (dio_lock_type == DIO_LOCKING)
|
|
/* lockdep: not the owner will release it */
|
|
down_read_non_owner(&inode->i_alloc_sem);
|
|
}
|
|
|
|
/*
|
|
* For file extending writes updating i_size before data
|
|
* writeouts complete can expose uninitialized blocks. So
|
|
* even for AIO, we need to wait for i/o to complete before
|
|
* returning in this case.
|
|
*/
|
|
dio->is_async = !is_sync_kiocb(iocb) && !((rw & WRITE) &&
|
|
(end > i_size_read(inode)));
|
|
|
|
retval = direct_io_worker(rw, iocb, inode, iov, offset,
|
|
nr_segs, blkbits, get_block, end_io, dio);
|
|
|
|
if (rw == READ && dio_lock_type == DIO_LOCKING)
|
|
release_i_mutex = 0;
|
|
|
|
out:
|
|
if (release_i_mutex)
|
|
mutex_unlock(&inode->i_mutex);
|
|
else if (acquire_i_mutex)
|
|
mutex_lock(&inode->i_mutex);
|
|
return retval;
|
|
}
|
|
EXPORT_SYMBOL(__blockdev_direct_IO);
|