Commit 566d3362 authored by Hugh Dickins's avatar Hugh Dickins Committed by Linus Torvalds
Browse files

mm: warn on deleting redirtied only if accounted 

filemap_unaccount_folio() has a WARN_ON_ONCE(folio_test_dirty(folio)).  It
is good to warn of late dirtying on a persistent filesystem, but late
dirtying on tmpfs can only lose data which is expected to be thrown away;
and it's a pity if that warning comes ONCE on tmpfs, then hides others
which really matter.  Make it conditional on mapping_cap_writeback().

Cleanup: then folio_account_cleaned() no longer needs to check that for
itself, and so no longer needs to know the mapping.

Link: https://lkml.kernel.org/r/b5a1106c-7226-a5c6-ad41-ad4832cae1f@google.com


Signed-off-by: default avatarHugh Dickins <hughd@google.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Jan Kara <jack@suse.de>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 7f760917

include/linux/pagemap.h

+1 −2
Original line number Diff line number Diff line
@@ -1009,8 +1009,7 @@ static inline void __set_page_dirty(struct page *page, 
{

	__folio_mark_dirty(page_folio(page), mapping, warn);

}

void folio_account_cleaned(struct folio *folio, struct address_space *mapping,

			  struct bdi_writeback *wb);

void folio_account_cleaned(struct folio *folio, struct bdi_writeback *wb);

void __folio_cancel_dirty(struct folio *folio);

static inline void folio_cancel_dirty(struct folio *folio)

{

mm/filemap.c

+9 −5
Original line number Diff line number Diff line
@@ -193,16 +193,20 @@ static void filemap_unaccount_folio(struct address_space *mapping, 
	/*

	 * At this point folio must be either written or cleaned by

	 * truncate.  Dirty folio here signals a bug and loss of

	 * unwritten data.

	 * unwritten data - on ordinary filesystems.

	 *

	 * This fixes dirty accounting after removing the folio entirely

	 * But it's harmless on in-memory filesystems like tmpfs; and can

	 * occur when a driver which did get_user_pages() sets page dirty

	 * before putting it, while the inode is being finally evicted.

	 *

	 * Below fixes dirty accounting after removing the folio entirely

	 * but leaves the dirty flag set: it has no effect for truncated

	 * folio and anyway will be cleared before returning folio to

	 * buddy allocator.

	 */

	if (WARN_ON_ONCE(folio_test_dirty(folio)))

		folio_account_cleaned(folio, mapping,

					inode_to_wb(mapping->host));

	if (WARN_ON_ONCE(folio_test_dirty(folio) &&

			 mapping_can_writeback(mapping)))

		folio_account_cleaned(folio, inode_to_wb(mapping->host));

}



/*

mm/page-writeback.c

+8 −10
Original line number Diff line number Diff line
@@ -2465,17 +2465,15 @@ static void folio_account_dirtied(struct folio *folio, 
 *

 * Caller must hold lock_page_memcg().

 */

void folio_account_cleaned(struct folio *folio, struct address_space *mapping,

			  struct bdi_writeback *wb)

void folio_account_cleaned(struct folio *folio, struct bdi_writeback *wb)

{

	if (mapping_can_writeback(mapping)) {

	long nr = folio_nr_pages(folio);



	lruvec_stat_mod_folio(folio, NR_FILE_DIRTY, -nr);

	zone_stat_mod_folio(folio, NR_ZONE_WRITE_PENDING, -nr);

	wb_stat_mod(wb, WB_RECLAIMABLE, -nr);

	task_io_account_cancelled_write(nr * PAGE_SIZE);

}

}



/*

 * Mark the folio dirty, and set it dirty in the page cache, and mark
@@ -2683,7 +2681,7 @@ void __folio_cancel_dirty(struct folio *folio) 
		wb = unlocked_inode_to_wb_begin(inode, &cookie);



		if (folio_test_clear_dirty(folio))

			folio_account_cleaned(folio, mapping, wb);

			folio_account_cleaned(folio, wb);



		unlocked_inode_to_wb_end(inode, &cookie);

		folio_memcg_unlock(folio);