Commit 30b8feb7 authored by NeilBrown's avatar NeilBrown
Browse files

md/raid5: avoid deadlock when raid5 array has unack badblocks during md_stop_writes. 



When raid5 recovery hits a fresh badblock, this badblock will flagged as unack
badblock until md_update_sb() is called.
But md_stop will take reconfig lock which means raid5d can't call
md_update_sb() in md_check_recovery(), the badblock will always
be unack, so raid5d thread enters an infinite loop and md_stop_write()
can never stop sync_thread. This causes deadlock.

To solve this, when STOP_ARRAY ioctl is issued and sync_thread is
running, we need set md->recovery FROZEN and INTR flags and wait for
sync_thread to stop before we (re)take reconfig lock.

This requires that raid5 reshape_request notices MD_RECOVERY_INTR
(which it probably should have noticed anyway) and stops waiting for a
metadata update in that case.

Reported-by: default avatarJianpeng Ma <majianpeng@gmail.com>
Reported-by: default avatarBian Yu <bianyu@kedacom.com>
Signed-off-by: default avatarNeilBrown <neilb@suse.de>
parent c91abf5a

drivers/md/md.c

+49 −19
Original line number Diff line number Diff line
@@ -5340,20 +5340,35 @@ EXPORT_SYMBOL_GPL(md_stop); 
static int md_set_readonly(struct mddev *mddev, struct block_device *bdev)

{

	int err = 0;

	int did_freeze = 0;



	if (!test_bit(MD_RECOVERY_FROZEN, &mddev->recovery)) {

		did_freeze = 1;

		set_bit(MD_RECOVERY_FROZEN, &mddev->recovery);

		md_wakeup_thread(mddev->thread);

	}

	if (mddev->sync_thread) {

		set_bit(MD_RECOVERY_INTR, &mddev->recovery);

		/* Thread might be blocked waiting for metadata update

		 * which will now never happen */

		wake_up_process(mddev->sync_thread->tsk);

	}

	mddev_unlock(mddev);

	wait_event(resync_wait, mddev->sync_thread == NULL);

	mddev_lock_nointr(mddev);



	mutex_lock(&mddev->open_mutex);

	if (atomic_read(&mddev->openers) > !!bdev) {

	if (atomic_read(&mddev->openers) > !!bdev ||

	    mddev->sync_thread ||

	    (bdev && !test_bit(MD_STILL_CLOSED, &mddev->flags))) {

		printk("md: %s still in use.\n",mdname(mddev));

		if (did_freeze) {

			clear_bit(MD_RECOVERY_FROZEN, &mddev->recovery);

			md_wakeup_thread(mddev->thread);

		}

		err = -EBUSY;

		goto out;

	}

	if (bdev && !test_bit(MD_STILL_CLOSED, &mddev->flags)) {

		/* Someone opened the device since we flushed it

		 * so page cache could be dirty and it is too late

		 * to flush.  So abort

		 */

		mutex_unlock(&mddev->open_mutex);

		return -EBUSY;

	}

	if (mddev->pers) {

		__md_stop_writes(mddev);
@@ -5380,20 +5395,34 @@ static int do_md_stop(struct mddev * mddev, int mode, 
{

	struct gendisk *disk = mddev->gendisk;

	struct md_rdev *rdev;

	int did_freeze = 0;



	if (!test_bit(MD_RECOVERY_FROZEN, &mddev->recovery)) {

		did_freeze = 1;

		set_bit(MD_RECOVERY_FROZEN, &mddev->recovery);

		md_wakeup_thread(mddev->thread);

	}

	if (mddev->sync_thread) {

		set_bit(MD_RECOVERY_INTR, &mddev->recovery);

		/* Thread might be blocked waiting for metadata update

		 * which will now never happen */

		wake_up_process(mddev->sync_thread->tsk);

	}

	mddev_unlock(mddev);

	wait_event(resync_wait, mddev->sync_thread == NULL);

	mddev_lock_nointr(mddev);



	mutex_lock(&mddev->open_mutex);

	if (atomic_read(&mddev->openers) > !!bdev ||

	    mddev->sysfs_active) {

	    mddev->sysfs_active ||

	    mddev->sync_thread ||

	    (bdev && !test_bit(MD_STILL_CLOSED, &mddev->flags))) {

		printk("md: %s still in use.\n",mdname(mddev));

		mutex_unlock(&mddev->open_mutex);

		return -EBUSY;

		if (did_freeze) {

			clear_bit(MD_RECOVERY_FROZEN, &mddev->recovery);

			md_wakeup_thread(mddev->thread);

		}

	if (bdev && !test_bit(MD_STILL_CLOSED, &mddev->flags)) {

		/* Someone opened the device since we flushed it

		 * so page cache could be dirty and it is too late

		 * to flush.  So abort

		 */

		mutex_unlock(&mddev->open_mutex);

		return -EBUSY;

	}

	if (mddev->pers) {
@@ -7931,6 +7960,7 @@ void md_reap_sync_thread(struct mddev *mddev) 


	/* resync has finished, collect result */

	md_unregister_thread(&mddev->sync_thread);

	wake_up(&resync_wait);

	if (!test_bit(MD_RECOVERY_INTR, &mddev->recovery) &&

	    !test_bit(MD_RECOVERY_REQUESTED, &mddev->recovery)) {

		/* success...*/

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