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mm/shmem: return head page from find_lock_entry 

Convert shmem_getpage_gfp() (the only remaining caller of
find_lock_entry()) to cope with a head page being returned instead of
the subpage for the index.

[willy@infradead.org: fix BUG()s]
  Link https://lore.kernel.org/linux-mm/20200912032042.GA6583@casper.infradead.org/

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Huang Ying <ying.huang@intel.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Matthew Auld <matthew.auld@intel.com>
Cc: William Kucharski <william.kucharski@oracle.com>
Link: https://lkml.kernel.org/r/20200910183318.20139-8-willy@infradead.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Matthew Wilcox (Oracle) 2020-10-13 16:51:38 -07:00 committed by Linus Torvalds
parent a6de4b4873
commit 63ec1973dd
3 changed files with 30 additions and 23 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

9
include/linux/pagemap.h
View File

@ -372,6 +372,15 @@ static inline struct page *grab_cache_page_nowait(struct address_space *mapping,
mapping_gfp_mask(mapping));
}
/* Does this page contain this index? */
static inline bool thp_contains(struct page *head, pgoff_t index)
{
/* HugeTLBfs indexes the page cache in units of hpage_size */
if (PageHuge(head))
return head->index == index;
return page_index(head) == (index & ~(thp_nr_pages(head) - 1UL));
}
/*
* Given the page we found in the page cache, return the page corresponding
* to this index in the file

25
mm/filemap.c
View File

@ -1692,37 +1692,34 @@ struct page *find_get_entry(struct address_space *mapping, pgoff_t index)
}
/**
* find_lock_entry - locate, pin and lock a page cache entry
* @mapping: the address_space to search
* @offset: the page cache index
* find_lock_entry - Locate and lock a page cache entry.
* @mapping: The address_space to search.
* @index: 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.
* Looks up the page at @mapping & @index. If there is a page in the
* cache, the head page 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.
*
* find_lock_entry() may sleep.
*
* Return: the found page or shadow entry, %NULL if nothing is found.
* Context: May sleep.
* Return: The head page or shadow entry, %NULL if nothing is found.
*/
struct page *find_lock_entry(struct address_space *mapping, pgoff_t offset)
struct page *find_lock_entry(struct address_space *mapping, pgoff_t index)
{
struct page *page;
repeat:
page = find_get_entry(mapping, offset);
page = find_get_entry(mapping, index);
if (page && !xa_is_value(page)) {
lock_page(page);
/* Has the page been truncated? */
if (unlikely(page_mapping(page) != mapping)) {
if (unlikely(page->mapping != mapping)) {
unlock_page(page);
put_page(page);
goto repeat;
}
page = find_subpage(page, offset);
VM_BUG_ON_PAGE(page_to_pgoff(page) != offset, page);
VM_BUG_ON_PAGE(!thp_contains(page, index), page);
}
return page;
}

19
mm/shmem.c
View File

@ -1830,6 +1830,8 @@ static int shmem_getpage_gfp(struct inode *inode, pgoff_t index,
return error;
}
if (page)
hindex = page->index;
if (page && sgp == SGP_WRITE)
mark_page_accessed(page);
@ -1840,11 +1842,10 @@ static int shmem_getpage_gfp(struct inode *inode, pgoff_t index,
unlock_page(page);
put_page(page);
page = NULL;
hindex = index;
}
if (page || sgp == SGP_READ) {
*pagep = page;
return 0;
}
if (page || sgp == SGP_READ)
goto out;
/*
* Fast cache lookup did not find it:
@ -1969,14 +1970,13 @@ static int shmem_getpage_gfp(struct inode *inode, pgoff_t index,
* it now, lest undo on failure cancel our earlier guarantee.
*/
if (sgp != SGP_WRITE && !PageUptodate(page)) {
struct page *head = compound_head(page);
int i;
for (i = 0; i < compound_nr(head); i++) {
clear_highpage(head + i);
flush_dcache_page(head + i);
for (i = 0; i < compound_nr(page); i++) {
clear_highpage(page + i);
flush_dcache_page(page + i);
}
SetPageUptodate(head);
SetPageUptodate(page);
}
/* Perhaps the file has been truncated since we checked */
@ -1992,6 +1992,7 @@ static int shmem_getpage_gfp(struct inode *inode, pgoff_t index,
error = -EINVAL;
goto unlock;
}
out:
*pagep = page + index - hindex;
return 0;