fsnotify: srcu to protect read side of inode and vfsmount locks
Currently reading the inode->i_fsnotify_marks or
vfsmount->mnt_fsnotify_marks lists are protected by a spinlock on both the
read and the write side. This patch protects the read side of those lists
with a new single srcu.
Signed-off-by: Eric Paris <eparis@redhat.com>
diff --git a/fs/notify/mark.c b/fs/notify/mark.c
index 69c5a16..41f3990 100644
--- 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 @@
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 @@
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 @@
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);