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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Mike Galbraith <efault@gmx.de>,
        Trond Myklebust <trond.myklebust@primarydata.com>
Subject: [PATCH 4.9 23/88] NFS: Add a cond_resched() to nfs_commit_release_pages()
Date:   Thu, 15 Feb 2018 16:16:50 +0100
Message-Id: <20180215151225.894700764@linuxfoundation.org>
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4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Trond Myklebust <trond.myklebust@primarydata.com>

commit 7f1bda447c9bd48b415acedba6b830f61591601f upstream.

The commit list can get very large, and so we need a cond_resched()
in nfs_commit_release_pages() in order to ensure we don't hog the CPU
for excessive periods of time.

Reported-by: Mike Galbraith <efault@gmx.de>
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 fs/nfs/write.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/fs/nfs/write.c
+++ b/fs/nfs/write.c
@@ -1806,6 +1806,8 @@ static void nfs_commit_release_pages(str
 		set_bit(NFS_CONTEXT_RESEND_WRITES, &req->wb_context->flags);
 	next:
 		nfs_unlock_and_release_request(req);
+		/* Latency breaker */
+		cond_resched();
 	}
 	nfss = NFS_SERVER(data->inode);
 	if (atomic_long_read(&nfss->writeback) < NFS_CONGESTION_OFF_THRESH)