[PATCH AUTOSEL 6.11 242/244] iomap: handle a post-direct I/O invalidate race in iomap_write_delalloc_release

Sasha Levin
2024-09-25T11:53:30Z

From: Christoph Hellwig <hch@lst.de>

[ Upstream commit 7a9d43eace888a0ee6095035997bb138425844d3 ]

When direct I/O completions invalidates the page cache it holds neither the
i_rwsem nor the invalidate_lock so it can be racing with
iomap_write_delalloc_release. If the search for the end of the region that
contains data returns the start offset we hit such a race and just need to
look for the end of the newly created hole instead.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20240910043949.3481298-2-hch@lst.de
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
fs/iomap/buffered-io.c | 10 +++++++++-
1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
index d745f718bcde8..ca928cc9be49a 100644
--- a/fs/iomap/buffered-io.c
+++ b/fs/iomap/buffered-io.c
@@ -1241,7 +1241,15 @@ static int iomap_write_delalloc_release(struct inode *inode,
error = data_end;
goto out_unlock;
}
- WARN_ON_ONCE(data_end <= start_byte);
+
+ /*
+ * If we race with post-direct I/O invalidation of the page cache,
+ * there might be no data left at start_byte.
+ */
+ if (data_end == start_byte)
+ continue;
+
+ WARN_ON_ONCE(data_end < start_byte);
WARN_ON_ONCE(data_end > scan_end_byte);

error = iomap_write_delalloc_scan(inode, &punch_start_byte,
--
2.43.0