Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs

Pull assorted fixes - mostly vfs - from Al Viro:
 "Assorted fixes, with an unexpected detour into vfio refcounting logics
  (fell out when digging in an analog of eventpoll race in there)."

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
  task_work: add a scheduling point in task_work_run()
  fs: fix fs/namei.c kernel-doc warnings
  eventpoll: use-after-possible-free in epoll_create1()
  vfio: grab vfio_device reference *before* exposing the sucker via fd_install()
  vfio: get rid of vfio_device_put()/vfio_group_get_device* races
  vfio: get rid of open-coding kref_put_mutex
  introduce kref_put_mutex()
  vfio: don't dereference after kfree...
  mqueue: lift mnt_want_write() outside ->i_mutex, clean up a bit

1 files changed, 18 insertions, 0 deletions

diff --git a/include/linux/kref.h b/include/linux/kref.h
index 9c07dcebded7..65af6887872f 100644
--- a/include/linux/kref.h
+++ b/include/linux/kref.h
@@ -18,6 +18,7 @@
 #include <linux/bug.h>
 #include <linux/atomic.h>
 #include <linux/kernel.h>
+#include <linux/mutex.h>
 
 struct kref {
 	atomic_t refcount;
@@ -93,4 +94,21 @@ static inline int kref_put(struct kref *kref, void (*release)(struct kref *kref)
 {
 	return kref_sub(kref, 1, release);
 }
+
+static inline int kref_put_mutex(struct kref *kref,
+				 void (*release)(struct kref *kref),
+				 struct mutex *lock)
+{
+	WARN_ON(release == NULL);
+        if (unlikely(!atomic_add_unless(&kref->refcount, -1, 1))) {
+		mutex_lock(lock);
+		if (unlikely(!atomic_dec_and_test(&kref->refcount))) {
+			mutex_unlock(lock);
+			return 0;
+		}
+		release(kref);
+		return 1;
+	}
+	return 0;
+}
 #endif /* _KREF_H_ */