[PATCH 6.6 078/638] iomap: clear the per-folio dirty bits on all writeback failures

Sasha Levin
2024-03-24T23:02:33Z

From: Christoph Hellwig <hch@lst.de>

[ Upstream commit 7ea1d9b4a840c2dd01d1234663d4a8ef256cfe39 ]

write_cache_pages always clear the page dirty bit before calling into the
file systems, and leaves folios with a writeback failure without the
dirty bit after return. We also clear the per-block writeback bits for
writeback failures unless no I/O has submitted, which will leave the
folio in an inconsistent state where it doesn't have the folio dirty,
but one or more per-block dirty bits. This seems to be due the place
where the iomap_clear_range_dirty call was inserted into the existing
not very clearly structured code when adding per-block dirty bit support
and not actually intentional. Switch to always clearing the dirty on
writeback failure.

Fixes: 4ce02c679722 ("iomap: Add per-block dirty state tracking to improve performance")
Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20231207072710.176093-2-hch@lst.de
Signed-off-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
fs/iomap/buffered-io.c | 18 +++++++++++-------
1 file changed, 11 insertions(+), 7 deletions(-)

diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
index 2bc0aa23fde3b..1c63e48230aed 100644
--- a/fs/iomap/buffered-io.c
+++ b/fs/iomap/buffered-io.c
@@ -1830,16 +1830,10 @@ iomap_writepage_map(struct iomap_writepage_ctx *wpc,
if (unlikely(error)) {
/*
* Let the filesystem know what portion of the current page
- * failed to map. If the page hasn't been added to ioend, it
- * won't be affected by I/O completion and we must unlock it
- * now.
+ * failed to map.
*/
if (wpc->ops->discard_folio)
wpc->ops->discard_folio(folio, pos);
- if (!count) {
- folio_unlock(folio);
- goto done;
- }
}

/*
@@ -1848,6 +1842,16 @@ iomap_writepage_map(struct iomap_writepage_ctx *wpc,
* all the dirty bits in the folio here.
*/
iomap_clear_range_dirty(folio, 0, folio_size(folio));
+
+ /*
+ * If the page hasn't been added to the ioend, it won't be affected by
+ * I/O completion and we must unlock it now.
+ */
+ if (error && !count) {
+ folio_unlock(folio);
+ goto done;
+ }
+
folio_start_writeback(folio);
folio_unlock(folio);

--
2.43.0