linux-ext4 - [PATCH 2/8] nowait aio: Return if cannot get hold of i

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Date:   Tue, 28 Feb 2017 17:36:04 -0600
From:   Goldwyn Rodrigues <rgoldwyn@...e.de>
To:     jack@...e.com
Cc:     hch@...radead.org, linux-fsdevel@...r.kernel.org,
        linux-block@...r.kernel.org, linux-btrfs@...r.kernel.org,
        linux-ext4@...r.kernel.org, linux-xfs@...r.kernel.org,
        Goldwyn Rodrigues <rgoldwyn@...e.com>
Subject: [PATCH 2/8] nowait aio: Return if cannot get hold of i_rwsem

From: Goldwyn Rodrigues <rgoldwyn@...e.com>

A failure to lock i_rwsem would mean there is I/O being performed
by another thread. So, let's bail.

Signed-off-by: Goldwyn Rodrigues <rgoldwyn@...e.com>
---
 mm/filemap.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/mm/filemap.c b/mm/filemap.c
index 3f9afde..78dd50e 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -2973,7 +2973,12 @@ ssize_t generic_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
 	struct inode *inode = file->f_mapping->host;
 	ssize_t ret;
 
-	inode_lock(inode);
+	if (!inode_trylock(inode)) {
+		/* Don't sleep on inode rwsem */
+		if (iocb->ki_flags & IOCB_NOWAIT)
+			return -EAGAIN;
+		inode_lock(inode);
+	}
 	ret = generic_write_checks(iocb, from);
 	if (ret > 0)
 		ret = __generic_file_write_iter(iocb, from);
-- 
2.10.2