fs: Fix namespace related hangs

Nick converted the dentry->d_mounted counter to a flag, however with
namespaces, dentries can be mounted multiple times (and more
importantly unmounted multiple times).

If a namespace was created and then released, the unmount_tree would
remove the DCACHE_MOUNTED flag and that would make d_mountpoint fail,
causing the mounts to be lost.

This patch coverts it back to a counter, and adds some extra WARN_ONs
to make sure things are accounted properly.

Signed-off-by: John Stultz <johnstul@us.ibm.com>
Cc: "Luis Claudio R. Goncalves" <lclaudio@uudg.org>
Cc: Nick Piggin <npiggin@suse.de>
LKML-Reference: <1272522942.1967.12.camel@work-vm>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

1 files changed, 2 insertions, 1 deletions

diff --git a/include/linux/dcache.h b/include/linux/dcache.h
index 39872ea86c6a..bc5a5ff141c8 100644
--- a/include/linux/dcache.h
+++ b/include/linux/dcache.h
@@ -99,6 +99,7 @@ struct dentry {
         atomic_t d_count;
         unsigned int d_flags;           /* protected by d_lock */
         spinlock_t d_lock;              /* per dentry lock */
+        int d_mounted;
         seqcount_t d_seq;               /* per dentry seqlock */
         struct inode *d_inode;          /* Where the name belongs to - NULL is
                                          * negative */
@@ -364,7 +365,7 @@ extern void dput(struct dentry *);
 
 static inline int d_mountpoint(struct dentry *dentry)
 {
-        return dentry->d_flags & DCACHE_MOUNTED;
+        return dentry->d_mounted;
 }
 
 extern struct vfsmount *lookup_mnt(struct path *);