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authorTejun Heo <tj@kernel.org>2010-10-15 15:36:08 +0200
committerNeilBrown <neilb@suse.de>2010-10-28 17:32:29 +1100
commite804ac780e2f01cb3b914daca2fd4780d1743db1 (patch)
tree60447c76ea9dbaa526c8cabc14898e4df4498bf6 /drivers/md
parent57dab0bdf689d42972975ec646d862b0900a4bf3 (diff)
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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>
Diffstat (limited to 'drivers/md')
-rw-r--r--drivers/md/md.c64
1 files changed, 43 insertions, 21 deletions
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 DEFINE_SPINLOCK(pers_lock);
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 @@ static void md_end_flush(struct bio *bio, int err)
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 @@ void md_flush_request(mddev_t *mddev, struct bio *bio)
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 @@ static void mddev_put(mddev_t *mddev)
* 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 @@ static void unbind_rdev_from_array(mdk_rdev_t * rdev)
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 @@ static int md_alloc(dev_t dev, char *name)
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 @@ static int md_open(struct block_device *bdev, fmode_t mode)
*/
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 @@ void md_error(mddev_t *mddev, mdk_rdev_t *rdev)
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 void md_geninit(void)
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 @@ static int __init md_init(void)
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 @@ static __exit void md_exit(void)
export_array(mddev);
mddev->hold_active = 0;
}
+ destroy_workqueue(md_misc_wq);
+ destroy_workqueue(md_wq);
}
subsys_initcall(md_init);