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Commit 718822c1 authored by Mikulas Patocka's avatar Mikulas Patocka Committed by Mike Snitzer
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dm delay: fix a possible deadlock due to shared workqueue 



The dm-delay target uses a shared workqueue for multiple instances.  This
can cause deadlock if two or more dm-delay targets are stacked on the top
of each other.

This patch changes dm-delay to use a per-instance workqueue.

Cc: stable@vger.kernel.org # 2.6.22+

Signed-off-by: default avatarMikulas Patocka <mpatocka@redhat.com>
Signed-off-by: default avatarMike Snitzer <snitzer@redhat.com>
parent 7b6b2bc9

drivers/md/dm-delay.c

+11 −12
Original line number Diff line number Diff line
@@ -20,6 +20,7 @@ 
struct delay_c {

	struct timer_list delay_timer;

	struct mutex timer_lock;

	struct workqueue_struct *kdelayd_wq;

	struct work_struct flush_expired_bios;

	struct list_head delayed_bios;

	atomic_t may_delay;
@@ -45,14 +46,13 @@ struct dm_delay_info { 


static DEFINE_MUTEX(delayed_bios_lock);



static struct workqueue_struct *kdelayd_wq;

static struct kmem_cache *delayed_cache;



static void handle_delayed_timer(unsigned long data)

{

	struct delay_c *dc = (struct delay_c *)data;



	queue_work(kdelayd_wq, &dc->flush_expired_bios);

	queue_work(dc->kdelayd_wq, &dc->flush_expired_bios);

}



static void queue_timeout(struct delay_c *dc, unsigned long expires)
@@ -191,6 +191,12 @@ out: 
		goto bad_dev_write;

	}



	dc->kdelayd_wq = alloc_workqueue("kdelayd", WQ_MEM_RECLAIM, 0);

	if (!dc->kdelayd_wq) {

		DMERR("Couldn't start kdelayd");

		goto bad_queue;

	}



	setup_timer(&dc->delay_timer, handle_delayed_timer, (unsigned long)dc);



	INIT_WORK(&dc->flush_expired_bios, flush_expired_bios);
@@ -203,6 +209,8 @@ out: 
	ti->private = dc;

	return 0;



bad_queue:

	mempool_destroy(dc->delayed_pool);

bad_dev_write:

	if (dc->dev_write)

		dm_put_device(ti, dc->dev_write);
@@ -217,7 +225,7 @@ static void delay_dtr(struct dm_target *ti) 
{

	struct delay_c *dc = ti->private;



	flush_workqueue(kdelayd_wq);

	destroy_workqueue(dc->kdelayd_wq);



	dm_put_device(ti, dc->dev_read);
@@ -350,12 +358,6 @@ static int __init dm_delay_init(void) 
{

	int r = -ENOMEM;



	kdelayd_wq = alloc_workqueue("kdelayd", WQ_MEM_RECLAIM, 0);

	if (!kdelayd_wq) {

		DMERR("Couldn't start kdelayd");

		goto bad_queue;

	}



	delayed_cache = KMEM_CACHE(dm_delay_info, 0);

	if (!delayed_cache) {

		DMERR("Couldn't create delayed bio cache.");
@@ -373,8 +375,6 @@ static int __init dm_delay_init(void) 
bad_register:

	kmem_cache_destroy(delayed_cache);

bad_memcache:

	destroy_workqueue(kdelayd_wq);

bad_queue:

	return r;

}
@@ -382,7 +382,6 @@ static void __exit dm_delay_exit(void) 
{

	dm_unregister_target(&delay_target);

	kmem_cache_destroy(delayed_cache);

	destroy_workqueue(kdelayd_wq);

}



/* Module hooks */