[PATCH 3.4 12/92] NFSv4: don't set SETATTR for O_RDONLY|O_EXCL

[lizf]

From: NeilBrown <neilb@xxxxxxxx>

3.4.112-rc1 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@xxxxxxxx>
Signed-off-by: Trond Myklebust <trond.myklebust@xxxxxxxxxxxxxxx>
[lizf: Backported to 3.4: adjust context]
Signed-off-by: Zefan Li <lizefan@xxxxxxxxxx>
---
 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 3d344ab..92eff4d 100644
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -1851,7 +1851,7 @@ static int _nfs4_do_open(struct inode *dir, struct dentry *dentry, fmode_t fmode
 	if (server->caps & NFS_CAP_POSIX_LOCK)
 		set_bit(NFS_STATE_POSIX_LOCKS, &state->flags);
 
-	if (opendata->o_arg.open_flags & O_EXCL) {
+	if ((opendata->o_arg.open_flags & (O_CREAT|O_EXCL)) == (O_CREAT|O_EXCL)) {
 		nfs4_exclusive_attrset(opendata, sattr);
 
 		nfs_fattr_init(opendata->o_res.f_attr);
-- 
1.9.1