From: Miklos Szeredi <miklos@szeredi.hu>
This patch fixes a bug noticed by Al Viro:
However, we still have a problem here - just what would
happen if vfsmount is detached while we were grabbing namespace
semaphore? Refcount alone is not useful here - we might be held by
whoever had detached the vfsmount. IOW, we should check that it's
still attached (i.e. that mnt->mnt_parent != mnt). If it's not -
just leave it alone, do mntput() and let whoever holds it deal with
the sucker. No need to put it back on lists.
Signed-off-by: Miklos Szeredi <miklos@szeredi.hu>
Cc: <viro@parcelfarce.linux.theplanet.co.uk>
Signed-off-by: Andrew Morton <akpm@osdl.org>
---
fs/namespace.c | 7 +++++++
1 files changed, 7 insertions(+)
diff -puN fs/namespace.c~namespacec-fix-expiring-of-detached-mount fs/namespace.c
--- 25/fs/namespace.c~namespacec-fix-expiring-of-detached-mount Mon May 23 16:16:53 2005
+++ 25-akpm/fs/namespace.c Mon May 23 16:16:53 2005
@@ -829,6 +829,13 @@ static void expire_mount(struct vfsmount
{
spin_lock(&vfsmount_lock);
+ /* check if mount is still attached, if not, let whoever holds
+ it deal with the sucker */
+ if (mnt->mnt_parent == mnt) {
+ spin_unlock(&vfsmount_lock);
+ return;
+ }
+
/* check that it is still dead: the count should now be 2 - as
* contributed by the vfsmount parent and the mntget above */
if (atomic_read(&mnt->mnt_count) == 2) {
_