linux-kernel - [PATCH 3.12 15/40] nfs: increment i_dio

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Date:	Wed,  2 Apr 2014 22:13:01 +0200
From:	Jiri Slaby <jslaby@...e.cz>
To:	stable@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org,
	Christoph Hellwig <hch@...radead.org>,
	Christoph Hellwig <hch@....de>,
	Trond Myklebust <trond.myklebust@...marydata.com>,
	Jiri Slaby <jslaby@...e.cz>
Subject: [PATCH 3.12 15/40] nfs: increment i_dio_count for reads, too

From: Christoph Hellwig <hch@...radead.org>

3.12-stable review patch.  If anyone has any objections, please let me know.

===============

commit 1f90ee27461e31a1c18e5d819f6ea6f5c7304b16 upstream.

i_dio_count is used to protect dio access against truncate.  We want
to make sure there are no dio reads pending either when doing a
truncate.  I suspect on plain NFS things might work even without
this, but once we use a pnfs layout driver that access backing devices
directly things will go bad without the proper synchronization.

Signed-off-by: Christoph Hellwig <hch@....de>
Signed-off-by: Trond Myklebust <trond.myklebust@...marydata.com>
Signed-off-by: Jiri Slaby <jslaby@...e.cz>
---
 fs/nfs/direct.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/fs/nfs/direct.c b/fs/nfs/direct.c
index 2adc0094cde8..af5f3ffcb157 100644
--- a/fs/nfs/direct.c
+++ b/fs/nfs/direct.c
@@ -236,10 +236,10 @@ static void nfs_direct_complete(struct nfs_direct_req *dreq, bool write)
 		spin_unlock(&inode->i_lock);
 	}
 
-	if (write) {
+	if (write)
 		nfs_zap_mapping(inode, inode->i_mapping);
-		inode_dio_done(inode);
-	}
+
+	inode_dio_done(inode);
 
 	if (dreq->iocb) {
 		long res = (long) dreq->error;
@@ -420,6 +420,7 @@ static ssize_t nfs_direct_read_schedule_iovec(struct nfs_direct_req *dreq,
 					      loff_t pos, bool uio)
 {
 	struct nfs_pageio_descriptor desc;
+	struct inode *inode = dreq->inode;
 	ssize_t result = -EINVAL;
 	size_t requested_bytes = 0;
 	unsigned long seg;
@@ -428,6 +429,7 @@ static ssize_t nfs_direct_read_schedule_iovec(struct nfs_direct_req *dreq,
 			     &nfs_direct_read_completion_ops);
 	get_dreq(dreq);
 	desc.pg_dreq = dreq;
+	atomic_inc(&inode->i_dio_count);
 
 	for (seg = 0; seg < nr_segs; seg++) {
 		const struct iovec *vec = &iov[seg];
@@ -447,6 +449,7 @@ static ssize_t nfs_direct_read_schedule_iovec(struct nfs_direct_req *dreq,
 	 * generic layer handle the completion.
 	 */
 	if (requested_bytes == 0) {
+		inode_dio_done(inode);
 		nfs_direct_req_release(dreq);
 		return result < 0 ? result : -EIO;
 	}
-- 
1.9.1

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