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mm/filemap: Add FGP_STABLE

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Allow filemap_get_folio() to wait for writeback to complete (if the
filesystem wants that behaviour).  This is the folio equivalent of
grab_cache_page_write_begin(), which is moved into the folio-compat
file as a reminder to migrate all the code using it.  This paves the
way for getting rid of AOP_FLAG_NOFS once grab_cache_page_write_begin()
is removed.

Kernel grows by 11 bytes.  filemap_get_folio() grows by 33 bytes but
grab_cache_page_write_begin() shrinks by 22 bytes to make up for it.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: David Howells <dhowells@redhat.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
This commit is contained in:
Matthew Wilcox (Oracle) 2020-12-24 12:55:56 -05:00
parent 3f0c6a07fe
commit b27652d935
3 changed files with 17 additions and 22 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
include/linux/pagemap.h
View File

@ -301,6 +301,7 @@ pgoff_t page_cache_prev_miss(struct address_space *mapping,
#define FGP_FOR_MMAP 0x00000040
#define FGP_HEAD 0x00000080
#define FGP_ENTRY 0x00000100
#define FGP_STABLE 0x00000200
struct folio *__filemap_get_folio(struct address_space *mapping, pgoff_t index,
int fgp_flags, gfp_t gfp);

25
mm/filemap.c
View File

@ -1872,6 +1872,7 @@ out:
* * %FGP_WRITE - The page will be written to by the caller.
* * %FGP_NOFS - __GFP_FS will get cleared in gfp.
* * %FGP_NOWAIT - Don't get blocked by page lock.
* * %FGP_STABLE - Wait for the folio to be stable (finished writeback)
*
* If %FGP_LOCK or %FGP_CREAT are specified then the function may sleep even
* if the %GFP flags specified for %FGP_CREAT are atomic.
@ -1922,6 +1923,8 @@ repeat:
folio_clear_idle(folio);
}
if (fgp_flags & FGP_STABLE)
folio_wait_stable(folio);
no_page:
if (!folio && (fgp_flags & FGP_CREAT)) {
int err;
@ -3704,28 +3707,6 @@ out:
}
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)
{

13
mm/folio-compat.c
View File

@ -116,6 +116,7 @@ int add_to_page_cache_lru(struct page *page, struct address_space *mapping,
}
EXPORT_SYMBOL(add_to_page_cache_lru);
noinline
struct page *pagecache_get_page(struct address_space *mapping, pgoff_t index,
int fgp_flags, gfp_t gfp)
{
@ -127,3 +128,15 @@ struct page *pagecache_get_page(struct address_space *mapping, pgoff_t index,
return folio_file_page(folio, index);
}
EXPORT_SYMBOL(pagecache_get_page);
struct page *grab_cache_page_write_begin(struct address_space *mapping,
pgoff_t index, unsigned flags)
{
unsigned fgp_flags = FGP_LOCK | FGP_WRITE | FGP_CREAT | FGP_STABLE;
if (flags & AOP_FLAG_NOFS)
fgp_flags |= FGP_NOFS;
return pagecache_get_page(mapping, index, fgp_flags,
mapping_gfp_mask(mapping));
}
EXPORT_SYMBOL(grab_cache_page_write_begin);