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>
This commit is contained in:
Eric Paris
2010-07-28 10:18:38 -04:00
parent 700307a29a
commit 75c1be487a
5 changed files with 111 additions and 40 deletions

View File

@@ -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);