[PATCH 2/3] fsnotify: Remove mark->free_list

[Jan Kara <jack@suse.com>]

Free list is used when all marks on given inode / mount should be
destroyed when inode / mount is going away. However we can free all of
the marks without using a special list with some care.

Signed-off-by: Jan Kara <jack@suse.com>
---
 fs/notify/fsnotify.c             |  1 -
 fs/notify/fsnotify.h             | 21 +++++++++++++++------
 fs/notify/inode_mark.c           | 20 --------------------
 fs/notify/mark.c                 | 40 +++++++++++++++++++++++++---------------
 fs/notify/vfsmount_mark.c        | 19 -------------------
 include/linux/fsnotify_backend.h |  2 --
 6 files changed, 40 insertions(+), 63 deletions(-)

diff --git a/fs/notify/fsnotify.c b/fs/notify/fsnotify.c
index dd3fb0b17be7..0771c1ed9525 100644
--- a/fs/notify/fsnotify.c
+++ b/fs/notify/fsnotify.c
@@ -26,7 +26,6 @@
 
 #include <linux/fsnotify_backend.h>
 #include "fsnotify.h"
-#include "../mount.h"
 
 /*
  * Clear all of the marks on an inode when it is being evicted from core
diff --git a/fs/notify/fsnotify.h b/fs/notify/fsnotify.h
index 13a00be516d2..b44c68a857e7 100644
--- a/fs/notify/fsnotify.h
+++ b/fs/notify/fsnotify.h
@@ -6,6 +6,8 @@
 #include <linux/srcu.h>
 #include <linux/types.h>
 
+#include "../mount.h"
+
 /* destroy all events sitting in this groups notification queue */
 extern void fsnotify_flush_notify(struct fsnotify_group *group);
 
@@ -38,15 +40,22 @@ extern int fsnotify_add_vfsmount_mark(struct fsnotify_mark *mark,
 extern void fsnotify_destroy_vfsmount_mark(struct fsnotify_mark *mark);
 /* inode specific destruction of a mark */
 extern void fsnotify_destroy_inode_mark(struct fsnotify_mark *mark);
-/* Destroy all marks in the given list */
-extern void fsnotify_destroy_marks(struct list_head *to_free);
 /* Find mark belonging to given group in the list of marks */
 extern struct fsnotify_mark *fsnotify_find_mark(struct hlist_head *head,
 						struct fsnotify_group *group);
-/* run the list of all marks associated with inode and flag them to be freed */
-extern void fsnotify_clear_marks_by_inode(struct inode *inode);
-/* run the list of all marks associated with vfsmount and flag them to be freed */
-extern void fsnotify_clear_marks_by_mount(struct vfsmount *mnt);
+/* Destroy all marks in the given list protected by 'lock' */
+extern void fsnotify_destroy_marks(struct hlist_head *head, spinlock_t *lock);
+/* run the list of all marks associated with inode and destroy them */
+static inline void fsnotify_clear_marks_by_inode(struct inode *inode)
+{
+	fsnotify_destroy_marks(&inode->i_fsnotify_marks, &inode->i_lock);
+}
+/* run the list of all marks associated with vfsmount and destroy them */
+static inline void fsnotify_clear_marks_by_mount(struct vfsmount *mnt)
+{
+	fsnotify_destroy_marks(&real_mount(mnt)->mnt_fsnotify_marks,
+			       &mnt->mnt_root->d_lock);
+}
 /*
  * update the dentry->d_flags of all of inode's children to indicate if inode cares
  * about events that happen to its children.
diff --git a/fs/notify/inode_mark.c b/fs/notify/inode_mark.c
index 3daf513ee99e..474a3ce1b5e1 100644
--- a/fs/notify/inode_mark.c
+++ b/fs/notify/inode_mark.c
@@ -65,26 +65,6 @@ void fsnotify_destroy_inode_mark(struct fsnotify_mark *mark)
 }
 
 /*
- * Given an inode, destroy all of the marks associated with that inode.
- */
-void fsnotify_clear_marks_by_inode(struct inode *inode)
-{
-	struct fsnotify_mark *mark;
-	struct hlist_node *n;
-	LIST_HEAD(free_list);
-
-	spin_lock(&inode->i_lock);
-	hlist_for_each_entry_safe(mark, n, &inode->i_fsnotify_marks, obj_list) {
-		list_add(&mark->free_list, &free_list);
-		hlist_del_init_rcu(&mark->obj_list);
-		fsnotify_get_mark(mark);
-	}
-	spin_unlock(&inode->i_lock);
-
-	fsnotify_destroy_marks(&free_list);
-}
-
-/*
  * Given a group clear all of the inode marks associated with that group.
  */
 void fsnotify_clear_inode_marks_by_group(struct fsnotify_group *group)
diff --git a/fs/notify/mark.c b/fs/notify/mark.c
index 39ddcaf0918f..3b2d1ba41e7b 100644
--- a/fs/notify/mark.c
+++ b/fs/notify/mark.c
@@ -203,24 +203,34 @@ void fsnotify_destroy_mark(struct fsnotify_mark *mark,
 	mutex_unlock(&group->mark_mutex);
 }
 
-/*
- * Destroy all marks in the given list. The marks must be already detached from
- * the original inode / vfsmount.
- */
-void fsnotify_destroy_marks(struct list_head *to_free)
+void fsnotify_destroy_marks(struct hlist_head *head, spinlock_t *lock)
 {
-	struct fsnotify_mark *mark, *lmark;
-	struct fsnotify_group *group;
-
-	list_for_each_entry_safe(mark, lmark, to_free, free_list) {
-		spin_lock(&mark->lock);
-		fsnotify_get_group(mark->group);
-		group = mark->group;
-		spin_unlock(&mark->lock);
+	struct fsnotify_mark *mark;
 
-		fsnotify_destroy_mark(mark, group);
+	while (1) {
+		/*
+		 * We have to be careful since we can race with e.g.
+		 * fsnotify_clear_marks_by_group() and once we drop 'lock',
+		 * mark can get removed from the obj_list and destroyed. But
+		 * we are holding mark reference so mark cannot be freed and
+		 * calling fsnotify_destroy_mark() more than once is fine.
+		 */
+		spin_lock(lock);
+		if (hlist_empty(head)) {
+			spin_unlock(lock);
+			break;
+		}
+		mark = hlist_entry(head->first, struct fsnotify_mark, obj_list);
+		/*
+		 * We don't update i_fsnotify_mask / mnt_fsnotify_mask here
+		 * since inode / mount is going away anyway. So just remove
+		 * mark from the list.
+		 */
+		hlist_del_init_rcu(&mark->obj_list);
+		fsnotify_get_mark(mark);
+		spin_unlock(lock);
+		fsnotify_destroy_mark(mark, mark->group);
 		fsnotify_put_mark(mark);
-		fsnotify_put_group(group);
 	}
 }
 
diff --git a/fs/notify/vfsmount_mark.c b/fs/notify/vfsmount_mark.c
index 326b148e623c..a8fcab68faef 100644
--- a/fs/notify/vfsmount_mark.c
+++ b/fs/notify/vfsmount_mark.c
@@ -28,25 +28,6 @@
 
 #include <linux/fsnotify_backend.h>
 #include "fsnotify.h"
-#include "../mount.h"
-
-void fsnotify_clear_marks_by_mount(struct vfsmount *mnt)
-{
-	struct fsnotify_mark *mark;
-	struct hlist_node *n;
-	struct mount *m = real_mount(mnt);
-	LIST_HEAD(free_list);
-
-	spin_lock(&mnt->mnt_root->d_lock);
-	hlist_for_each_entry_safe(mark, n, &m->mnt_fsnotify_marks, obj_list) {
-		list_add(&mark->free_list, &free_list);
-		hlist_del_init_rcu(&mark->obj_list);
-		fsnotify_get_mark(mark);
-	}
-	spin_unlock(&mnt->mnt_root->d_lock);
-
-	fsnotify_destroy_marks(&free_list);
-}
 
 void fsnotify_clear_vfsmount_marks_by_group(struct fsnotify_group *group)
 {
diff --git a/include/linux/fsnotify_backend.h b/include/linux/fsnotify_backend.h
index dd6ddb0287ed..f044fe30e8c3 100644
--- a/include/linux/fsnotify_backend.h
+++ b/include/linux/fsnotify_backend.h
@@ -225,8 +225,6 @@ struct fsnotify_mark {
 	spinlock_t lock;
 	/* List of marks for inode / vfsmount [obj_lock] */
 	struct hlist_node obj_list;
-	/* tmp list used when freeing this mark */
-	struct list_head free_list;
 	union {	/* Object pointer [mark->lock, group->mark_mutex] */
 		struct inode *inode;	/* inode this mark is associated with */
 		struct vfsmount *mnt;	/* vfsmount this mark is associated with */
-- 
2.1.4