iomap: handle a post-direct I/O invalidate race in iomap_write_delalloc_release

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>

diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
index de47698a029ac6dd15152582175d67dbb21288a2..db7a3ff92e61e6efbd4efb6efab16abbd370c08b 100644 (file)
--- a/fs/iomap/buffered-io.c
+++ b/fs/iomap/buffered-io.c
@@ -1242,7 +1242,15 @@ 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,