linux-kernel - [PATCH 5.4 145/168] SUNRPC: Set memalloc_nofs

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Date:   Mon, 15 Mar 2021 14:56:17 +0100
From:   gregkh@...uxfoundation.org
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Benjamin Coddington <bcodding@...hat.com>,
        Anna Schumaker <Anna.Schumaker@...app.com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.4 145/168] SUNRPC: Set memalloc_nofs_save() for sync tasks

From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

From: Benjamin Coddington <bcodding@...hat.com>

[ Upstream commit f0940f4b3284a00f38a5d42e6067c2aaa20e1f2e ]

We could recurse into NFS doing memory reclaim while sending a sync task,
which might result in a deadlock.  Set memalloc_nofs_save for sync task
execution.

Fixes: a1231fda7e94 ("SUNRPC: Set memalloc_nofs_save() on all rpciod/xprtiod jobs")
Signed-off-by: Benjamin Coddington <bcodding@...hat.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@...app.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 net/sunrpc/sched.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/net/sunrpc/sched.c b/net/sunrpc/sched.c
index 7afbf15bcbd9..4beb6d2957c3 100644
--- a/net/sunrpc/sched.c
+++ b/net/sunrpc/sched.c
@@ -990,8 +990,11 @@ void rpc_execute(struct rpc_task *task)
 
 	rpc_set_active(task);
 	rpc_make_runnable(rpciod_workqueue, task);
-	if (!is_async)
+	if (!is_async) {
+		unsigned int pflags = memalloc_nofs_save();
 		__rpc_execute(task);
+		memalloc_nofs_restore(pflags);
+	}
 }
 
 static void rpc_async_schedule(struct work_struct *work)
-- 
2.30.1