linux-kernel - [PATCH] NFS: Use an appropriate work queue for direct-write completion

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Message-ID: <878t5hydb1.fsf@notabene.neil.brown.name>
Date:   Wed, 08 Aug 2018 09:20:02 +1000
From:   NeilBrown <neilb@...e.com>
To:     Trond Myklebust <trond.myklebust@...merspace.com>,
        Anna Schumaker <anna.schumaker@...app.com>
cc:     linux-nfs@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] NFS: Use an appropriate work queue for direct-write completion


When a direct-write completes, a work_struct is schedule to handle
the completion.
When NFS is being used for swap, the direct write might be a swap-out,
so memory allocation can block until the write completes.
The work queue currently used is not WQ_MEM_RECLAIM, so tasks
can block waiting for memory - this leads to deadlock.

So use nfsiod_workqueue instead.  This will always have a running
thread, and work items should never block waiting for memory.

Signed-off-by: Neil Brown <neilb@...e.com>
---
 fs/nfs/direct.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/nfs/direct.c b/fs/nfs/direct.c
index 621c517b325c..aa12c3063bae 100644
--- a/fs/nfs/direct.c
+++ b/fs/nfs/direct.c
@@ -758,7 +758,7 @@ static void nfs_direct_write_schedule_work(struct work_struct *work)
 
 static void nfs_direct_write_complete(struct nfs_direct_req *dreq)
 {
-	schedule_work(&dreq->work); /* Calls nfs_direct_write_schedule_work */
+	queue_work(nfsiod_workqueue, &dreq->work); /* Calls nfs_direct_write_schedule_work */
 }
 
 static void nfs_direct_write_completion(struct nfs_pgio_header *hdr)
-- 
2.14.0.rc0.dirty


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