From: NeilBrown <neilb@suse.de>
Date: Fri, 9 Nov 2012 00:09:37 +0000 (-0800)
Subject: vfs: d_obtain_alias() needs to use "/" as default name.
X-Git-Tag: v3.2.36~31
X-Git-Url: https://git.kernelconcepts.de/?a=commitdiff_plain;h=150086ca6bd7493e7753f923a3f55e73701253b3;p=karo-tx-linux.git

vfs: d_obtain_alias() needs to use "/" as default name.

commit b911a6bdeef5848c468597d040e3407e0aee04ce upstream.

NFS appears to use d_obtain_alias() to create the root dentry rather than
d_make_root.  This can cause 'prepend_path()' to complain that the root
has a weird name if an NFS filesystem is lazily unmounted.  e.g.  if
"/mnt" is an NFS mount then

 { cd /mnt; umount -l /mnt ; ls -l /proc/self/cwd; }

will cause a WARN message like
   WARNING: at /home/git/linux/fs/dcache.c:2624 prepend_path+0x1d7/0x1e0()
   ...
   Root dentry has weird name <>

to appear in kernel logs.

So change d_obtain_alias() to use "/" rather than "" as the anonymous
name.

Signed-off-by: NeilBrown <neilb@suse.de>
Cc: Trond Myklebust <Trond.Myklebust@netapp.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
[bwh: Backported to 3.2: use named initialisers instead of QSTR_INIT()]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---

diff --git a/fs/dcache.c b/fs/dcache.c
index 63c0c6b9b82e..bb7f4ccdfbde 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -1492,7 +1492,7 @@ static struct dentry * d_find_any_alias(struct inode *inode)
  */
 struct dentry *d_obtain_alias(struct inode *inode)
 {
-	static const struct qstr anonstring = { .name = "" };
+	static const struct qstr anonstring = { .name = "/", .len = 1 };
 	struct dentry *tmp;
 	struct dentry *res;