From: Matthew Bobrowski <mbobrowski@xxxxxxxxxxxxxx>
[ Upstream commit 548feebec7e93e58b647dba70b3303dcb569c914 ]
This patch updates the lock pattern in ext4_direct_IO_read() to not
block on inode lock in cases of IOCB_NOWAIT direct I/O reads. The
locking condition implemented here is similar to that of 942491c9e6d6
("xfs: fix AIM7 regression").
Fixes: 16c54688592c ("ext4: Allow parallel DIO reads")
Signed-off-by: Matthew Bobrowski <mbobrowski@xxxxxxxxxxxxxx>
Reviewed-by: Jan Kara <jack@xxxxxxx>
Reviewed-by: Ritesh Harjani <riteshh@xxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/c5d5e759f91747359fbd2c6f9a36240cf75ad79f.1572949325.git.mbobrowski@xxxxxxxxxxxxxx
Signed-off-by: Theodore Ts'o <tytso@xxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
fs/ext4/inode.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index f8a0af11a31e8..00d25a0643913 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -3839,7 +3839,13 @@ static ssize_t ext4_direct_IO_read(struct kiocb *iocb, struct iov_iter *iter)
* writes & truncates and since we take care of writing back page cache,
* we are protected against page writeback as well.
*/
- inode_lock_shared(inode);
+ if (iocb->ki_flags & IOCB_NOWAIT) {
+ if (!inode_trylock_shared(inode))
+ return -EAGAIN;
+ } else {
+ inode_lock_shared(inode);
+ }
+
ret = filemap_write_and_wait_range(mapping, iocb->ki_pos,
iocb->ki_pos + count - 1);
if (ret)
--
2.20.1
