linux-kernel - [PATCH 3.12 54/84] NFSv4: don't set SETATTR for O_RDONLY|O

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Message-Id: <d71ea882b4c5e2f23b6631f6f546b6b1756a7d93.1443792303.git.jslaby@suse.cz>
Date:	Fri,  2 Oct 2015 15:24:59 +0200
From:	Jiri Slaby <jslaby@...e.cz>
To:	stable@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, NeilBrown <neilb@...e.com>,
	Trond Myklebust <trond.myklebust@...marydata.com>,
	Jiri Slaby <jslaby@...e.cz>
Subject: [PATCH 3.12 54/84] NFSv4: don't set SETATTR for O_RDONLY|O_EXCL

From: NeilBrown <neilb@...e.com>

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

===============

commit efcbc04e16dfa95fef76309f89710dd1d99a5453 upstream.

It is unusual to combine the open flags O_RDONLY and O_EXCL, but
it appears that libre-office does just that.

[pid  3250] stat("/home/USER/.config", {st_mode=S_IFDIR|0700, st_size=8192, ...}) = 0
[pid  3250] open("/home/USER/.config/libreoffice/4-suse/user/extensions/buildid", O_RDONLY|O_EXCL <unfinished ...>

NFSv4 takes O_EXCL as a sign that a setattr command should be sent,
probably to reset the timestamps.

When it was an O_RDONLY open, the SETATTR command does not
identify any actual attributes to change.
If no delegation was provided to the open, the SETATTR uses the
all-zeros stateid and the request is accepted (at least by the
Linux NFS server - no harm, no foul).

If a read-delegation was provided, this is used in the SETATTR
request, and a Netapp filer will justifiably claim
NFS4ERR_BAD_STATEID, which the Linux client takes as a sign
to retry - indefinitely.

So only treat O_EXCL specially if O_CREAT was also given.

Signed-off-by: NeilBrown <neilb@...e.com>
Signed-off-by: Trond Myklebust <trond.myklebust@...marydata.com>
Signed-off-by: Jiri Slaby <jslaby@...e.cz>
---
 fs/nfs/nfs4proc.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index 36a72b59d7c8..794af58b388f 100644
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -2267,7 +2267,7 @@ static int _nfs4_do_open(struct inode *dir,
 		goto err_free_label;
 	state = ctx->state;

-	if ((opendata->o_arg.open_flags & O_EXCL) &&
+	if ((opendata->o_arg.open_flags & (O_CREAT|O_EXCL)) == (O_CREAT|O_EXCL) &&
 	    (opendata->o_arg.createmode != NFS4_CREATE_GUARDED)) {
 		nfs4_exclusive_attrset(opendata, sattr);

-- 
2.6.0

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