Patch "NFSv4: don't set SETATTR for O_RDONLY|O_EXCL" has been added to the 3.10-stable tree

This is a note to let you know that I've just added the patch titled

NFSv4: don't set SETATTR for O_RDONLY|O_EXCL

to the 3.10-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
nfsv4-don-t-set-setattr-for-o_rdonly-o_excl.patch
and it can be found in the queue-3.10 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: NeilBrown <[email protected]>
Date: Thu, 30 Jul 2015 13:00:56 +1000
Subject: NFSv4: don't set SETATTR for O_RDONLY|O_EXCL

From: NeilBrown <[email protected]>

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.

---
 fs/nfs/nfs4proc.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

@@ -2043,7 +2043,7 @@ static int _nfs4_do_open(struct inode *d
 	if (status != 0)
 		goto err_opendata_put;
 
-	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);
 

Patches currently in stable-queue which might be from [email protected] are

queue-3.10/nfsv4-don-t-set-setattr-for-o_rdonly-o_excl.patch