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authorHugh Dickins <hughd@google.com>2022-03-24 18:13:59 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2022-03-24 19:06:51 -0700
commit566d3362885aab04d6b0f885f12db3176ca3a032 (patch)
tree25ac4e4fd25635a26587151d6b54a90a9e86888d /mm/filemap.c
parent7f7609175ff2339a2cffa48ba2474ef928d7eafd (diff)
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: Hugh 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: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/filemap.c')
-rw-r--r--mm/filemap.c14
1 files changed, 9 insertions, 5 deletions
diff --git a/mm/filemap.c b/mm/filemap.c
index c5c169c16bae..8426434042f4 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -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));
}
/*