* [PATCH 1/2] dm-delay: fix a possible deadlock due to shared workqueue
@ 2013-11-15 21:12 Mikulas Patocka
2013-11-15 21:12 ` [PATCH 2/2] dm-delay: use per-bio data instead of a mempool and slab cache Mikulas Patocka
0 siblings, 1 reply; 2+ messages in thread
From: Mikulas Patocka @ 2013-11-15 21:12 UTC (permalink / raw)
To: Alasdair G. Kergon, Mike Snitzer; +Cc: dm-devel
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 per-instance workqueue.
Cc: stable@kernel.org # 2.6.22+
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
---
drivers/md/dm-delay.c | 23 +++++++++++------------
1 file changed, 11 insertions(+), 12 deletions(-)
Index: linux-3.12-fast/drivers/md/dm-delay.c
===================================================================
--- linux-3.12-fast.orig/drivers/md/dm-delay.c 2013-11-15 20:56:09.000000000 +0100
+++ linux-3.12-fast/drivers/md/dm-delay.c 2013-11-15 22:10:21.000000000 +0100
@@ -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 *
{
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 */
^ permalink raw reply [flat|nested] 2+ messages in thread
* [PATCH 2/2] dm-delay: use per-bio data instead of a mempool and slab cache
2013-11-15 21:12 [PATCH 1/2] dm-delay: fix a possible deadlock due to shared workqueue Mikulas Patocka
@ 2013-11-15 21:12 ` Mikulas Patocka
0 siblings, 0 replies; 2+ messages in thread
From: Mikulas Patocka @ 2013-11-15 21:12 UTC (permalink / raw)
To: Alasdair G. Kergon, Mike Snitzer; +Cc: dm-devel
Starting with commit c0820cf5ad09522bdd9ff68e84841a09c9f339d8, device
mapper has capability to pre-allocate target-specific structure with the
bio.
This patch changes dm-delay to use this facility instead of a slab cache
and mempool.
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
---
drivers/md/dm-delay.c | 35 +++++++----------------------------
1 file changed, 7 insertions(+), 28 deletions(-)
Index: linux-3.12-fast/drivers/md/dm-delay.c
===================================================================
--- linux-3.12-fast.orig/drivers/md/dm-delay.c 2013-11-15 22:10:21.000000000 +0100
+++ linux-3.12-fast/drivers/md/dm-delay.c 2013-11-15 22:10:27.000000000 +0100
@@ -24,7 +24,6 @@ struct delay_c {
struct work_struct flush_expired_bios;
struct list_head delayed_bios;
atomic_t may_delay;
- mempool_t *delayed_pool;
struct dm_dev *dev_read;
sector_t start_read;
@@ -40,14 +39,11 @@ struct delay_c {
struct dm_delay_info {
struct delay_c *context;
struct list_head list;
- struct bio *bio;
unsigned long expires;
};
static DEFINE_MUTEX(delayed_bios_lock);
-static struct kmem_cache *delayed_cache;
-
static void handle_delayed_timer(unsigned long data)
{
struct delay_c *dc = (struct delay_c *)data;
@@ -87,13 +83,14 @@ static struct bio *flush_delayed_bios(st
mutex_lock(&delayed_bios_lock);
list_for_each_entry_safe(delayed, next, &dc->delayed_bios, list) {
if (flush_all || time_after_eq(jiffies, delayed->expires)) {
+ struct bio *bio = dm_bio_from_per_bio_data(delayed,
+ sizeof(struct dm_delay_info));
list_del(&delayed->list);
- bio_list_add(&flush_bios, delayed->bio);
- if ((bio_data_dir(delayed->bio) == WRITE))
+ bio_list_add(&flush_bios, bio);
+ if ((bio_data_dir(bio) == WRITE))
delayed->context->writes--;
else
delayed->context->reads--;
- mempool_free(delayed, dc->delayed_pool);
continue;
}
@@ -185,12 +182,6 @@ static int delay_ctr(struct dm_target *t
}
out:
- dc->delayed_pool = mempool_create_slab_pool(128, delayed_cache);
- if (!dc->delayed_pool) {
- DMERR("Couldn't create delayed bio pool.");
- goto bad_dev_write;
- }
-
dc->kdelayd_wq = alloc_workqueue("kdelayd", WQ_MEM_RECLAIM, 0);
if (!dc->kdelayd_wq) {
DMERR("Couldn't start kdelayd");
@@ -206,12 +197,11 @@ out:
ti->num_flush_bios = 1;
ti->num_discard_bios = 1;
+ ti->per_bio_data_size = sizeof(struct dm_delay_info);
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);
bad_dev_read:
@@ -232,7 +222,6 @@ static void delay_dtr(struct dm_target *
if (dc->dev_write)
dm_put_device(ti, dc->dev_write);
- mempool_destroy(dc->delayed_pool);
kfree(dc);
}
@@ -244,10 +233,9 @@ static int delay_bio(struct delay_c *dc,
if (!delay || !atomic_read(&dc->may_delay))
return 1;
- delayed = mempool_alloc(dc->delayed_pool, GFP_NOIO);
+ delayed = dm_per_bio_data(bio, sizeof(struct dm_delay_info));
delayed->context = dc;
- delayed->bio = bio;
delayed->expires = expires = jiffies + (delay * HZ / 1000);
mutex_lock(&delayed_bios_lock);
@@ -356,13 +344,7 @@ static struct target_type delay_target =
static int __init dm_delay_init(void)
{
- int r = -ENOMEM;
-
- delayed_cache = KMEM_CACHE(dm_delay_info, 0);
- if (!delayed_cache) {
- DMERR("Couldn't create delayed bio cache.");
- goto bad_memcache;
- }
+ int r;
r = dm_register_target(&delay_target);
if (r < 0) {
@@ -373,15 +355,12 @@ static int __init dm_delay_init(void)
return 0;
bad_register:
- kmem_cache_destroy(delayed_cache);
-bad_memcache:
return r;
}
static void __exit dm_delay_exit(void)
{
dm_unregister_target(&delay_target);
- kmem_cache_destroy(delayed_cache);
}
/* Module hooks */
^ permalink raw reply [flat|nested] 2+ messages in thread
end of thread, other threads:[~2013-11-15 21:12 UTC | newest]
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2013-11-15 21:12 [PATCH 1/2] dm-delay: fix a possible deadlock due to shared workqueue Mikulas Patocka
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