fsnotify: srcu to protect read side of inode and vfsmount locks

[net-next-2.6.git] / fs / notify / mark.c

diff --git a/fs/notify/mark.c b/fs/notify/mark.c
index 69c5a166930c153f8b1844bce7e012e9dda3749b..41f3990f900ba9c25f355cd3e80374cf5642ffd5 100644 (file)
--- a/fs/notify/mark.c
+++ b/fs/notify/mark.c
@@ -85,10 +85,12 @@
 #include <linux/fs.h>
 #include <linux/init.h>
 #include <linux/kernel.h>
+#include <linux/kthread.h>
 #include <linux/module.h>
 #include <linux/mutex.h>
 #include <linux/slab.h>
 #include <linux/spinlock.h>
+#include <linux/srcu.h>
 #include <linux/writeback.h> /* for inode_lock */
 
 #include <asm/atomic.h>
@@ -96,6 +98,11 @@
 #include <linux/fsnotify_backend.h>
 #include "fsnotify.h"
 
+struct srcu_struct fsnotify_mark_srcu;
+static DEFINE_SPINLOCK(destroy_lock);
+static LIST_HEAD(destroy_list);
+static DECLARE_WAIT_QUEUE_HEAD(destroy_waitq);
+
 void fsnotify_get_mark(struct fsnotify_mark *mark)
 {
        atomic_inc(&mark->refcnt);
@@ -144,11 +151,14 @@ void fsnotify_destroy_mark(struct fsnotify_mark *mark)
 
        list_del_init(&mark->g_list);
 
-       fsnotify_put_mark(mark); /* for i_list and g_list */
-
        spin_unlock(&group->mark_lock);
        spin_unlock(&mark->lock);
 
+       spin_lock(&destroy_lock);
+       list_add(&mark->destroy_list, &destroy_list);
+       spin_unlock(&destroy_lock);
+       wake_up(&destroy_waitq);
+
        /*
         * Some groups like to know that marks are being freed.  This is a
         * callback to the group function to let it know that this mark
@@ -263,12 +273,17 @@ int fsnotify_add_mark(struct fsnotify_mark *mark,
 err:
        mark->flags &= ~FSNOTIFY_MARK_FLAG_ALIVE;
        list_del_init(&mark->g_list);
+       mark->group = NULL;
        atomic_dec(&group->num_marks);
-       fsnotify_put_mark(mark);
 
        spin_unlock(&group->mark_lock);
        spin_unlock(&mark->lock);
 
+       spin_lock(&destroy_lock);
+       list_add(&mark->destroy_list, &destroy_list);
+       spin_unlock(&destroy_lock);
+       wake_up(&destroy_waitq);
+
        return ret;
 }
 
@@ -326,3 +341,42 @@ void fsnotify_init_mark(struct fsnotify_mark *mark,
        atomic_set(&mark->refcnt, 1);
        mark->free_mark = free_mark;
 }
+
+static int fsnotify_mark_destroy(void *ignored)
+{
+       struct fsnotify_mark *mark, *next;
+       LIST_HEAD(private_destroy_list);
+
+       for (;;) {
+               spin_lock(&destroy_lock);
+               list_for_each_entry_safe(mark, next, &destroy_list, destroy_list) {
+                       list_del(&mark->destroy_list);
+                       list_add(&mark->destroy_list, &private_destroy_list);
+               }
+               spin_unlock(&destroy_lock);
+
+               synchronize_srcu(&fsnotify_mark_srcu);
+
+               list_for_each_entry_safe(mark, next, &private_destroy_list, destroy_list) {
+                       list_del_init(&mark->destroy_list);
+                       fsnotify_put_mark(mark);
+               }
+
+               wait_event_interruptible(destroy_waitq, !list_empty(&destroy_list));
+       }
+
+       return 0;
+}
+
+static int __init fsnotify_mark_init(void)
+{
+       struct task_struct *thread;
+
+       thread = kthread_run(fsnotify_mark_destroy, NULL,
+                            "fsnotify_mark");
+       if (IS_ERR(thread))
+               panic("unable to start fsnotify mark destruction thread.");
+
+       return 0;
+}
+device_initcall(fsnotify_mark_init);