md: fix and update workqueue usage
Workqueue usage in md has two problems.
* Flush can be used during or depended upon by memory reclaim, but md
uses the system workqueue for flush_work which may lead to deadlock.
* md depends on flush_scheduled_work() to achieve exclusion against
completion of removal of previous instances. flush_scheduled_work()
may incur unexpected amount of delay and is scheduled to be removed.
This patch adds two workqueues to md - md_wq and md_misc_wq. The
former is guaranteed to make forward progress under memory pressure
and serves flush_work. The latter serves as the flush domain for
other works.
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: NeilBrown <neilb@suse.de>
diff --git a/drivers/md/md.c b/drivers/md/md.c
index 2399168..0b6fa2a 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -67,6 +67,8 @@
static void md_print_devices(void);
static DECLARE_WAIT_QUEUE_HEAD(resync_wait);
+static struct workqueue_struct *md_wq;
+static struct workqueue_struct *md_misc_wq;
#define MD_BUG(x...) { printk("md: bug in file %s, line %d\n", __FILE__, __LINE__); md_print_devices(); }
@@ -298,7 +300,7 @@
if (atomic_dec_and_test(&mddev->flush_pending)) {
/* The pre-request flush has finished */
- schedule_work(&mddev->flush_work);
+ queue_work(md_wq, &mddev->flush_work);
}
bio_put(bio);
}
@@ -367,7 +369,7 @@
submit_flushes(mddev);
if (atomic_dec_and_test(&mddev->flush_pending))
- schedule_work(&mddev->flush_work);
+ queue_work(md_wq, &mddev->flush_work);
}
EXPORT_SYMBOL(md_flush_request);
@@ -434,14 +436,13 @@
* so destroy it */
list_del(&mddev->all_mddevs);
if (mddev->gendisk) {
- /* we did a probe so need to clean up.
- * Call schedule_work inside the spinlock
- * so that flush_scheduled_work() after
- * mddev_find will succeed in waiting for the
- * work to be done.
+ /* We did a probe so need to clean up. Call
+ * queue_work inside the spinlock so that
+ * flush_workqueue() after mddev_find will
+ * succeed in waiting for the work to be done.
*/
INIT_WORK(&mddev->del_work, mddev_delayed_delete);
- schedule_work(&mddev->del_work);
+ queue_work(md_misc_wq, &mddev->del_work);
} else
kfree(mddev);
}
@@ -1848,7 +1849,7 @@
synchronize_rcu();
INIT_WORK(&rdev->del_work, md_delayed_delete);
kobject_get(&rdev->kobj);
- schedule_work(&rdev->del_work);
+ queue_work(md_misc_wq, &rdev->del_work);
}
/*
@@ -4192,10 +4193,10 @@
shift = partitioned ? MdpMinorShift : 0;
unit = MINOR(mddev->unit) >> shift;
- /* wait for any previous instance if this device
- * to be completed removed (mddev_delayed_delete).
+ /* wait for any previous instance of this device to be
+ * completely removed (mddev_delayed_delete).
*/
- flush_scheduled_work();
+ flush_workqueue(md_misc_wq);
mutex_lock(&disks_mutex);
error = -EEXIST;
@@ -5891,7 +5892,7 @@
*/
mddev_put(mddev);
/* Wait until bdev->bd_disk is definitely gone */
- flush_scheduled_work();
+ flush_workqueue(md_misc_wq);
/* Then retry the open from the top */
return -ERESTARTSYS;
}
@@ -6047,7 +6048,7 @@
set_bit(MD_RECOVERY_NEEDED, &mddev->recovery);
md_wakeup_thread(mddev->thread);
if (mddev->event_work.func)
- schedule_work(&mddev->event_work);
+ queue_work(md_misc_wq, &mddev->event_work);
md_new_event_inintr(mddev);
}
@@ -7207,12 +7208,23 @@
static int __init md_init(void)
{
- if (register_blkdev(MD_MAJOR, "md"))
- return -1;
- if ((mdp_major=register_blkdev(0, "mdp"))<=0) {
- unregister_blkdev(MD_MAJOR, "md");
- return -1;
- }
+ int ret = -ENOMEM;
+
+ md_wq = alloc_workqueue("md", WQ_RESCUER, 0);
+ if (!md_wq)
+ goto err_wq;
+
+ md_misc_wq = alloc_workqueue("md_misc", 0, 0);
+ if (!md_misc_wq)
+ goto err_misc_wq;
+
+ if ((ret = register_blkdev(MD_MAJOR, "md")) < 0)
+ goto err_md;
+
+ if ((ret = register_blkdev(0, "mdp")) < 0)
+ goto err_mdp;
+ mdp_major = ret;
+
blk_register_region(MKDEV(MD_MAJOR, 0), 1UL<<MINORBITS, THIS_MODULE,
md_probe, NULL, NULL);
blk_register_region(MKDEV(mdp_major, 0), 1UL<<MINORBITS, THIS_MODULE,
@@ -7223,8 +7235,16 @@
md_geninit();
return 0;
-}
+err_mdp:
+ unregister_blkdev(MD_MAJOR, "md");
+err_md:
+ destroy_workqueue(md_misc_wq);
+err_misc_wq:
+ destroy_workqueue(md_wq);
+err_wq:
+ return ret;
+}
#ifndef MODULE
@@ -7311,6 +7331,8 @@
export_array(mddev);
mddev->hold_active = 0;
}
+ destroy_workqueue(md_misc_wq);
+ destroy_workqueue(md_wq);
}
subsys_initcall(md_init);