Commit b27652d9 authored by Matthew Wilcox (Oracle)'s avatar Matthew Wilcox (Oracle)
Browse files

mm/filemap: Add FGP_STABLE 



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: default avatarMatthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: default avatarDavid Howells <dhowells@redhat.com>
Acked-by: default avatarVlastimil Babka <vbabka@suse.cz>
parent 3f0c6a07

include/linux/pagemap.h

+1 −0
Original line number Diff line number Diff line
@@ -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);

mm/filemap.c

+3 −22
Original line number Diff line number Diff line
@@ -1872,6 +1872,7 @@ static void *mapping_get_entry(struct address_space *mapping, pgoff_t index) 
 * * %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 @@ struct folio *__filemap_get_folio(struct address_space *mapping, pgoff_t index, 
			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 @@ generic_file_direct_write(struct kiocb *iocb, struct iov_iter *from) 
}

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)

{

mm/folio-compat.c

+13 −0
Original line number Diff line number Diff line
@@ -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);