[PATCH] iomap: Fix direct I/O write consistency check

[Andreas Gruenbacher]

When a direct I/O write falls back to buffered I/O entirely, dio->size
will be 0 in iomap_dio_complete.  Function invalidate_inode_pages2_range
will try to invalidate the rest of the address space.  If there are any
dirty pages in that range, the write will fail and a "Page cache
invalidation failure on direct I/O" error will be logged.

On gfs2, this can be reproduced as follows:

  xfs_io \
    -c "open -ft foo" -c "pwrite 4k 4k" -c "close" \
    -c "open -d foo" -c "pwrite 0 4k"

Fix this by recognizing 0-length writes.

Signed-off-by: Andreas Gruenbacher <agruenba@xxxxxxxxxx>
---
 fs/iomap/direct-io.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/iomap/direct-io.c b/fs/iomap/direct-io.c
index c1aafb2ab990..c9d6b4eecdb7 100644
--- a/fs/iomap/direct-io.c
+++ b/fs/iomap/direct-io.c
@@ -108,7 +108,7 @@ static ssize_t iomap_dio_complete(struct iomap_dio *dio)
 	 * ->end_io() when necessary, otherwise a racing buffer read would cache
 	 * zeros from unwritten extents.
 	 */
-	if (!dio->error &&
+	if (!dio->error && dio->size &&
 	    (dio->flags & IOMAP_DIO_WRITE) && inode->i_mapping->nrpages) {
 		int err;
 		err = invalidate_inode_pages2_range(inode->i_mapping,
-- 
2.26.2