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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org,
        Tigran Mkrtchyan <tigran.mkrtchyan@desy.de>,
        Trond Myklebust <trond.myklebust@primarydata.com>
Subject: [PATCH 4.15 097/202] nfs41: do not return ENOMEM on LAYOUTUNAVAILABLE
Date:   Thu, 15 Feb 2018 16:16:37 +0100
Message-Id: <20180215151718.430400589@linuxfoundation.org>
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4.15-stable review patch.  If anyone has any objections, please let me know.

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

From: Tigran Mkrtchyan <tigran.mkrtchyan@desy.de>

commit 7ff4cff637aa0bd2abbd81f53b2a6206c50afd95 upstream.

A pNFS server may return LAYOUTUNAVAILABLE error on LAYOUTGET for files
which don't have any layout. In this situation pnfs_update_layout
currently returns NULL. As this NULL is converted into ENOMEM, IO
requests fails instead of falling back to MDS.

Do not return ENOMEM on LAYOUTUNAVAILABLE and let client retry through
MDS.

Fixes 8d40b0f14846f. I will suggest to backport this fix to affected
stable branches.

Signed-off-by: Tigran Mkrtchyan <tigran.mkrtchyan@desy.de>
[trondmy: Use IS_ERR_OR_NULL()]
Fixes: 8d40b0f14846 ("NFS filelayout:call GETDEVICEINFO after...")
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 fs/nfs/filelayout/filelayout.c |    4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

--- a/fs/nfs/filelayout/filelayout.c
+++ b/fs/nfs/filelayout/filelayout.c
@@ -895,9 +895,7 @@ fl_pnfs_update_layout(struct inode *ino,
 
 	lseg = pnfs_update_layout(ino, ctx, pos, count, iomode, strict_iomode,
 				  gfp_flags);
-	if (!lseg)
-		lseg = ERR_PTR(-ENOMEM);
-	if (IS_ERR(lseg))
+	if (IS_ERR_OR_NULL(lseg))
 		goto out;
 
 	lo = NFS_I(ino)->layout;