linux-kernel - [PATCH 4.18 151/158] NFSv4.1: Fix a potential layoutget/layoutrecall deadlock

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Message-Id: <20180917211718.064732534@linuxfoundation.org>
Date:   Tue, 18 Sep 2018 00:43:01 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Trond Myklebust <trond.myklebust@...merspace.com>,
        Sasha Levin <alexander.levin@...rosoft.com>
Subject: [PATCH 4.18 151/158] NFSv4.1: Fix a potential layoutget/layoutrecall deadlock

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

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

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 fs/nfs/callback_proc.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/fs/nfs/callback_proc.c
+++ b/fs/nfs/callback_proc.c
@@ -215,9 +215,9 @@ static u32 pnfs_check_callback_stateid(s
 {
 	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))