Fix inc/dec_mnt_count for -rt

With Nick's vfs patches, inc/dec_mnt_count use per-cpu counters, so
this patch makes sure we disable preemption before calling.

Its not a great fix, but works because count_mnt_count() sums all the
percpu values, so each one individually doesn't need to be 0'ed out.

I suspect the better fix for -rt is to revert the mnt_count back to an atomic
counter.

Signed-off-by: John Stultz <johnstul@us.ibm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

1 files changed, 7 insertions, 1 deletions

diff --git a/fs/namespace.c b/fs/namespace.c
index 7fb7fe3da44e..c1632069b06c 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -757,7 +757,9 @@ void mntput_no_expire(struct vfsmount *mnt)
                         vfsmount_read_unlock(cpu);
                         goto repeat;
                 }
+                preempt_disable();
                 dec_mnt_count(mnt);
+                preempt_enable();
                 vfsmount_read_unlock(cpu);
 
                 return;
@@ -766,7 +768,9 @@ void mntput_no_expire(struct vfsmount *mnt)
 repeat:
         vfsmount_write_lock();
         BUG_ON(mnt->mnt_flags & MNT_MOUNTED);
+        preempt_disable();
         dec_mnt_count(mnt);
+        preempt_enable();
         if (count_mnt_count(mnt)) {
                 vfsmount_write_unlock();
                 return;
@@ -819,7 +823,9 @@ void mnt_unpin(struct vfsmount *mnt)
 {
         vfsmount_write_lock();
         if (mnt->mnt_pinned) {
-                inc_mnt_count(mnt);
+                preempt_disable();
+                dec_mnt_count(mnt);
+                preempt_enable();
                 mnt->mnt_pinned--;
         }
         vfsmount_write_unlock();