[PATCH 06/10] fsnotify: use a mutex instead of a spinlock to protect a groups mark list

[Andy Whitcroft]

From: Lino Sanfilippo <LinoSanfilippo at gmx.de>

Replaces the groups mark_lock spinlock with a mutex. Using a mutex instead
of a spinlock results in more flexibility (i.e it allows to sleep while the
lock is held).

Signed-off-by: Lino Sanfilippo <LinoSanfilippo at gmx.de>
Signed-off-by: Eric Paris <eparis at redhat.com>

(cherry-picked from commit 5d7c7ca90faa2717cc1a425d558893bc9df59ea2 git://git.infradead.org/users/eparis/notify.git)
BugLink: http://bugs.launchpad.net/bugs/922906
Signed-off-by: Andy Whitcroft <apw at canonical.com>
---
 fs/notify/group.c                |    2 +-
 fs/notify/inode_mark.c           |    4 ++--
 fs/notify/mark.c                 |   18 +++++++++---------
 fs/notify/vfsmount_mark.c        |    4 ++--
 include/linux/fsnotify_backend.h |    2 +-
 5 files changed, 15 insertions(+), 15 deletions(-)

diff --git a/fs/notify/group.c b/fs/notify/group.c
index 37569ec..2d47100 100644
--- a/fs/notify/group.c
+++ b/fs/notify/group.c
@@ -97,7 +97,7 @@ struct fsnotify_group *fsnotify_alloc_group(const struct fsnotify_ops *ops)
 	init_waitqueue_head(&group->notification_waitq);
 	group->max_events = UINT_MAX;
 
-	spin_lock_init(&group->mark_lock);
+	mutex_init(&group->mark_mutex);
 	INIT_LIST_HEAD(&group->marks_list);
 
 	group->ops = ops;
diff --git a/fs/notify/inode_mark.c b/fs/notify/inode_mark.c
index b13c00a..4e9071e 100644
--- a/fs/notify/inode_mark.c
+++ b/fs/notify/inode_mark.c
@@ -63,8 +63,8 @@ void fsnotify_destroy_inode_mark(struct fsnotify_mark *mark)
 {
 	struct inode *inode = mark->i.inode;
 
+	BUG_ON(!mutex_is_locked(&mark->group->mark_mutex));
 	assert_spin_locked(&mark->lock);
-	assert_spin_locked(&mark->group->mark_lock);
 
 	spin_lock(&inode->i_lock);
 
@@ -191,8 +191,8 @@ int fsnotify_add_inode_mark(struct fsnotify_mark *mark,
 
 	mark->flags |= FSNOTIFY_MARK_FLAG_INODE;
 
+	BUG_ON(!mutex_is_locked(&group->mark_mutex));
 	assert_spin_locked(&mark->lock);
-	assert_spin_locked(&group->mark_lock);
 
 	spin_lock(&inode->i_lock);
 
diff --git a/fs/notify/mark.c b/fs/notify/mark.c
index 3f6cdbd..d4512e1 100644
--- a/fs/notify/mark.c
+++ b/fs/notify/mark.c
@@ -137,13 +137,13 @@ void fsnotify_destroy_mark(struct fsnotify_mark *mark)
 	group = mark->group;
 	spin_unlock(&mark->lock);
 
-	spin_lock(&group->mark_lock);
+	mutex_lock(&group->mark_mutex);
 	spin_lock(&mark->lock);
 
 	/* something else already called this function on this mark */
 	if (!(mark->flags & FSNOTIFY_MARK_FLAG_ALIVE)) {
 		spin_unlock(&mark->lock);
-		spin_unlock(&group->mark_lock);
+		mutex_unlock(&group->mark_mutex);
 		goto put_group;
 	}
 
@@ -160,7 +160,7 @@ void fsnotify_destroy_mark(struct fsnotify_mark *mark)
 	list_del_init(&mark->g_list);
 
 	spin_unlock(&mark->lock);
-	spin_unlock(&group->mark_lock);
+	mutex_unlock(&group->mark_mutex);
 
 	spin_lock(&destroy_lock);
 	list_add(&mark->destroy_list, &destroy_list);
@@ -234,11 +234,11 @@ int fsnotify_add_mark(struct fsnotify_mark *mark,
 
 	/*
 	 * LOCKING ORDER!!!!
-	 * group->mark_lock
+	 * group->mark_mutex
 	 * mark->lock
 	 * inode->i_lock
 	 */
-	spin_lock(&group->mark_lock);
+	mutex_lock(&group->mark_mutex);
 
 	spin_lock(&mark->lock);
 	mark->flags |= FSNOTIFY_MARK_FLAG_ALIVE;
@@ -265,7 +265,7 @@ int fsnotify_add_mark(struct fsnotify_mark *mark,
 	fsnotify_set_mark_mask_locked(mark, mark->mask);
 	spin_unlock(&mark->lock);
 
-	spin_unlock(&group->mark_lock);
+	mutex_unlock(&group->mark_mutex);
 
 	if (inode)
 		__fsnotify_update_child_dentry_flags(inode);
@@ -279,7 +279,7 @@ err:
 	atomic_dec(&group->num_marks);
 
 	spin_unlock(&mark->lock);
-	spin_unlock(&group->mark_lock);
+	mutex_unlock(&group->mark_mutex);
 
 	spin_lock(&destroy_lock);
 	list_add(&mark->destroy_list, &destroy_list);
@@ -299,7 +299,7 @@ void fsnotify_clear_marks_by_group_flags(struct fsnotify_group *group,
 	struct fsnotify_mark *lmark, *mark;
 	LIST_HEAD(free_list);
 
-	spin_lock(&group->mark_lock);
+	mutex_lock(&group->mark_mutex);
 	list_for_each_entry_safe(mark, lmark, &group->marks_list, g_list) {
 		if (mark->flags & flags) {
 			list_add(&mark->free_g_list, &free_list);
@@ -307,7 +307,7 @@ void fsnotify_clear_marks_by_group_flags(struct fsnotify_group *group,
 			fsnotify_get_mark(mark);
 		}
 	}
-	spin_unlock(&group->mark_lock);
+	mutex_unlock(&group->mark_mutex);
 
 	list_for_each_entry_safe(mark, lmark, &free_list, free_g_list) {
 		fsnotify_destroy_mark(mark);
diff --git a/fs/notify/vfsmount_mark.c b/fs/notify/vfsmount_mark.c
index 778fe6c..5feee17 100644
--- a/fs/notify/vfsmount_mark.c
+++ b/fs/notify/vfsmount_mark.c
@@ -85,8 +85,8 @@ void fsnotify_destroy_vfsmount_mark(struct fsnotify_mark *mark)
 {
 	struct vfsmount *mnt = mark->m.mnt;
 
+	BUG_ON(!mutex_is_locked(&mark->group->mark_mutex));
 	assert_spin_locked(&mark->lock);
-	assert_spin_locked(&mark->group->mark_lock);
 
 	spin_lock(&mnt->mnt_root->d_lock);
 
@@ -146,8 +146,8 @@ int fsnotify_add_vfsmount_mark(struct fsnotify_mark *mark,
 
 	mark->flags |= FSNOTIFY_MARK_FLAG_VFSMOUNT;
 
+	BUG_ON(!mutex_is_locked(&group->mark_mutex));
 	assert_spin_locked(&mark->lock);
-	assert_spin_locked(&group->mark_lock);
 
 	spin_lock(&mnt->mnt_root->d_lock);
 
diff --git a/include/linux/fsnotify_backend.h b/include/linux/fsnotify_backend.h
index a1450b3..b48eccf 100644
--- a/include/linux/fsnotify_backend.h
+++ b/include/linux/fsnotify_backend.h
@@ -141,7 +141,7 @@ struct fsnotify_group {
 	unsigned int priority;
 
 	/* stores all fastpath marks assoc with this group so they can be cleaned on unregister */
-	spinlock_t mark_lock;		/* protect marks_list */
+	struct mutex mark_mutex;	/* protect marks_list */
 	atomic_t num_marks;		/* 1 for each mark and 1 for not being
 					 * past the point of no return when freeing
 					 * a group */
-- 
1.7.9.5