linux-ext4 - [PATCH v5 08/12] ext4: update direct I/O read to do trylock in IOCB

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Date:   Mon, 21 Oct 2019 20:18:46 +1100
From:   Matthew Bobrowski <mbobrowski@...browski.org>
To:     tytso@....edu, jack@...e.cz, adilger.kernel@...ger.ca
Cc:     linux-ext4@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        hch@...radead.org, david@...morbit.com, darrick.wong@...cle.com
Subject: [PATCH v5 08/12] ext4: update direct I/O read to do trylock in
 IOCB_NOWAIT cases

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@...browski.org>
---
 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);
 		/*
-- 
2.20.1

--<M>--