linux-kernel - [PATCH AUTOSEL 4.18 126/131] NFSv4.1: Fix a potential layoutget/layoutrecall deadlock

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Message-ID: <20180902064601.183036-126-alexander.levin@microsoft.com>
Date:   Sun, 2 Sep 2018 13:05:41 +0000
From:   Sasha Levin <Alexander.Levin@...rosoft.com>
To:     "stable@...r.kernel.org" <stable@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC:     Trond Myklebust <trond.myklebust@...merspace.com>,
        Sasha Levin <Alexander.Levin@...rosoft.com>
Subject: [PATCH AUTOSEL 4.18 126/131] NFSv4.1: Fix a potential
 layoutget/layoutrecall deadlock

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

[ Upstream commit bd3d16a887b0c19a2a20d35ffed499e3a3637feb ]

If the client is sending a layoutget, but the server issues a callback
to recall what it thinks may be an outstanding layout, then we may find
an uninitialised layout attached to the inode due to the layoutget.
In that case, it is appropriate to return NFS4ERR_NOMATCHING_LAYOUT
rather than NFS4ERR_DELAY, as the latter can end up deadlocking.

Signed-off-by: Trond Myklebust <trond.myklebust@...merspace.com>
Signed-off-by: Sasha Levin <alexander.levin@...rosoft.com>
---
 fs/nfs/callback_proc.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/nfs/callback_proc.c b/fs/nfs/callback_proc.c
index 64c214fb9da6..14333c482f86 100644
--- a/fs/nfs/callback_proc.c
+++ b/fs/nfs/callback_proc.c
@@ -215,9 +215,9 @@ static u32 pnfs_check_callback_stateid(struct pnfs_layout_hdr *lo,
 {
 	u32 oldseq, newseq;
 
-	/* Is the stateid still not initialised? */
+	/* Is the stateid not initialised? */
 	if (!pnfs_layout_is_valid(lo))
-		return NFS4ERR_DELAY;
+		return NFS4ERR_NOMATCHING_LAYOUT;
 
 	/* Mismatched stateid? */
 	if (!nfs4_stateid_match_other(&lo->plh_stateid, new))
-- 
2.17.1