Re: [PATCH v5 08/12] ext4: update direct I/O read to do trylock in IOCB_NOWAIT cases

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On 10/21/19 2:48 PM, Matthew Bobrowski wrote:
This patch updates the lock pattern in ext4_dio_read_iter() to only
perform the trylock in IOCB_NOWAIT cases.

Signed-off-by: Matthew Bobrowski <mbobrowski@xxxxxxxxxxxxxx>

This shall need a rebase (as mentioned in patch-1 discussion).
It will be good to mention that the locking condition
is kept similar to 942491c9e6d6 ("xfs: fix AIM7 regression").

Also, I think it may also need a fixes tag.
It seems unconditional inode_lock_shared was added by below commit.

Fixes: 16c54688592c ("ext4: Allow parallel DIO reads")


Otherwise, this patch looks good to me. You may add:

Reviewed-by: Ritesh Harjani <riteshh@xxxxxxxxxxxxx>


---
  fs/ext4/file.c | 8 +++++++-
  1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/fs/ext4/file.c b/fs/ext4/file.c
index 6ea7e00e0204..8420686b90f5 100644
--- a/fs/ext4/file.c
+++ b/fs/ext4/file.c
@@ -52,7 +52,13 @@ static int ext4_dio_read_iter(struct kiocb *iocb, struct iov_iter *to)
  	ssize_t ret;
  	struct inode *inode = file_inode(iocb->ki_filp);
- inode_lock_shared(inode);
+	if (iocb->ki_flags & IOCB_NOWAIT) {
+		if (!inode_trylock_shared(inode))
+			return -EAGAIN;
+	} else {
+		inode_lock_shared(inode);
+	}
+
  	if (!ext4_dio_supported(inode)) {
  		inode_unlock_shared(inode);
  		/*





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