3.16.62-rc1 review patch.  If anyone has any objections, please let me know.

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

From: piaojun <[email protected]>

commit 3111784bee81591ea2815011688d28b65df03627 upstream.

In my testing, v9fs_fid_xattr_set will return successfully even if the
backend ext4 filesystem has no space to store xattr key-value. That will
cause inconsistent behavior between front end and back end. The reason is
that lsetxattr will be triggered by p9_client_clunk, and unfortunately we
did not catch the error. This patch will catch the error to notify upper
caller.

p9_client_clunk (in 9p)
  p9_client_rpc(clnt, P9_TCLUNK, "d", fid->fid);
    v9fs_clunk (in qemu)
      put_fid
        free_fid
          v9fs_xattr_fid_clunk
            v9fs_co_lsetxattr
              s->ops->lsetxattr
                ext4_xattr_user_set (in host ext4 filesystem)

Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Jun Piao <[email protected]>
Cc: Eric Van Hensbergen <[email protected]>
Cc: Ron Minnich <[email protected]>
Cc: Latchesar Ionkov <[email protected]>
Cc: Andrew Morton <[email protected]>
Signed-off-by: Dominique Martinet <[email protected]>
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings <[email protected]>
---
 fs/9p/xattr.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

--- a/fs/9p/xattr.c
+++ b/fs/9p/xattr.c
@@ -121,7 +121,7 @@ int v9fs_fid_xattr_set(struct p9_fid *fi
                   const void *value, size_t value_len, int flags)
 {
        u64 offset = 0;
-       int retval, msize, write_count;
+       int retval, err, msize, write_count;
 
        p9_debug(P9_DEBUG_VFS, "name = %s value_len = %zu flags = %d\n",
                 name, value_len, flags);
@@ -158,7 +158,9 @@ int v9fs_fid_xattr_set(struct p9_fid *fi
        }
        retval = 0;
 err:
-       p9_client_clunk(fid);
+       err = p9_client_clunk(fid);
+       if (!retval && err)
+               retval = err;
        return retval;
 }
 

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