[PATCH 01/13] iomap: clear the per-folio dirty bits on all writeback failures

Christoph Hellwig
2023-11-26T12:47:35Z

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>
---
fs/iomap/buffered-io.c | 10 ++++++----
1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
index f72df2babe561a..98d52feb220f0a 100644
--- a/fs/iomap/buffered-io.c
+++ b/fs/iomap/buffered-io.c
@@ -1849,10 +1849,6 @@ iomap_writepage_map(struct iomap_writepage_ctx *wpc,
*/
if (wpc->ops->discard_folio)
wpc->ops->discard_folio(folio, pos);
- if (!count) {
- folio_unlock(folio);
- goto done;
- }
}

/*
@@ -1861,6 +1857,12 @@ 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 (error && !count) {
+ folio_unlock(folio);
+ goto done;
+ }
+
folio_start_writeback(folio);
folio_unlock(folio);

--
2.39.2