linux-kernel - [PATCH 4.14 149/178] IB/core: Fix use workqueue without WQ_MEM

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Message-Id: <20171218152927.058095024@linuxfoundation.org>
Date:   Mon, 18 Dec 2017 16:49:45 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Parav Pandit <parav@...lanox.com>,
        Daniel Jurgens <danielj@...lanox.com>,
        Leon Romanovsky <leon@...nel.org>,
        Doug Ledford <dledford@...hat.com>,
        Sasha Levin <alexander.levin@...izon.com>
Subject: [PATCH 4.14 149/178] IB/core: Fix use workqueue without WQ_MEM_RECLAIM

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

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

From: Parav Pandit <parav@...lanox.com>

[ Upstream commit 39baf10310e6669564a485b55267fae70a4e44ae ]

The IB/core provides address resolution service and invokes callback
handler when address resolve request completes of requester in worker
thread context.

Such caller might allocate or free memory in callback handler
depending on the completion status to make further progress or to
terminate a connection. Most ULPs resolve route which involves
allocating route entry and path record elements in callback event handler.

It has been noticed that WQ_MEM_RECLAIM flag should not be used for
workers that tend to allocate memory in this [1] thread discussion.

In order to mitigate this situation, WQ_MEM_RECLAIM flag was dropped for
other such WQs in this [2] patch.

Similar problem might arise with address resolution path, though its not
yet noticed. The ib_addr workqueue is not memory reclaim path due to its
nature of invoking callback that might allocate memory or don't free any
memory under memory pressure.

[1] https://www.spinics.net/lists/linux-rdma/msg53239.html
[2] https://www.spinics.net/lists/linux-rdma/msg53416.html

Fixes: f54816261c2b ("IB/addr: Remove deprecated create_singlethread_workqueue")
Fixes: 5fff41e1f89d ("IB/core: Fix race condition in resolving IP to MAC")
Signed-off-by: Parav Pandit <parav@...lanox.com>
Reviewed-by: Daniel Jurgens <danielj@...lanox.com>
Signed-off-by: Leon Romanovsky <leon@...nel.org>
Signed-off-by: Doug Ledford <dledford@...hat.com>
Signed-off-by: Sasha Levin <alexander.levin@...izon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 drivers/infiniband/core/addr.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/infiniband/core/addr.c
+++ b/drivers/infiniband/core/addr.c
@@ -852,7 +852,7 @@ static struct notifier_block nb = {

 int addr_init(void)
 {
-	addr_wq = alloc_ordered_workqueue("ib_addr", WQ_MEM_RECLAIM);
+	addr_wq = alloc_ordered_workqueue("ib_addr", 0);
 	if (!addr_wq)
 		return -ENOMEM;