diff options
authorMikulas Patocka <mpatocka@redhat.com>2014-06-14 13:44:31 -0400
committerMike Snitzer <snitzer@redhat.com>2014-07-10 16:44:13 -0400
commitacfe0ad74d2e1bfc81d1d7bf5e15b043985d3650 (patch)
parent4c834452aad01531db949414f94f817a86348d59 (diff)
dm: allocate a special workqueue for deferred device removal
The commit 2c140a246dc ("dm: allow remove to be deferred") introduced a deferred removal feature for the device mapper. When this feature is used (by passing a flag DM_DEFERRED_REMOVE to DM_DEV_REMOVE_CMD ioctl) and the user tries to remove a device that is currently in use, the device will be removed automatically in the future when the last user closes it. Device mapper used the system workqueue to perform deferred removals. However, some targets (dm-raid1, dm-mpath, dm-stripe) flush work items scheduled for the system workqueue from their destructor. If the destructor itself is called from the system workqueue during deferred removal, it introduces a possible deadlock - the workqueue tries to flush itself. Fix this possible deadlock by introducing a new workqueue for deferred removals. We allocate just one workqueue for all dm targets. The ability of dm targets to process IOs isn't dependent on deferred removal of unused targets, so a deadlock due to shared workqueue isn't possible. Also, cleanup local_init() to eliminate potential for returning success on failure. Signed-off-by: Mikulas Patocka <mpatocka@redhat.com> Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com> Cc: stable@vger.kernel.org # 3.13+
1 files changed, 13 insertions, 2 deletions
diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 437d99045ef2..32b958dbc499 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -54,6 +54,8 @@ static void do_deferred_remove(struct work_struct *w);
static DECLARE_WORK(deferred_remove_work, do_deferred_remove);
+static struct workqueue_struct *deferred_remove_workqueue;
* For bio-based dm.
* One of these is allocated per bio.
@@ -276,16 +278,24 @@ static int __init local_init(void)
if (r)
goto out_free_rq_tio_cache;
+ deferred_remove_workqueue = alloc_workqueue("kdmremove", WQ_UNBOUND, 1);
+ if (!deferred_remove_workqueue) {
+ r = -ENOMEM;
+ goto out_uevent_exit;
+ }
_major = major;
r = register_blkdev(_major, _name);
if (r < 0)
- goto out_uevent_exit;
+ goto out_free_workqueue;
if (!_major)
_major = r;
return 0;
+ destroy_workqueue(deferred_remove_workqueue);
@@ -299,6 +309,7 @@ out_free_io_cache:
static void local_exit(void)
+ destroy_workqueue(deferred_remove_workqueue);
@@ -407,7 +418,7 @@ static void dm_blk_close(struct gendisk *disk, fmode_t mode)
if (atomic_dec_and_test(&md->open_count) &&
(test_bit(DMF_DEFERRED_REMOVE, &md->flags)))
- schedule_work(&deferred_remove_work);
+ queue_work(deferred_remove_workqueue, &deferred_remove_work);

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