Commit ac05f256 authored by NeilBrown's avatar NeilBrown
Browse files

md: don't start resync thread directly from md thread. 



The main 'md' thread is needed for processing writes, so if it blocks
write requests could be delayed.

Starting a new thread requires some GFP_KERNEL allocations and so can
wait for writes to complete.  This can deadlock.

So instead, ask a workqueue to start the sync thread.
There is no particular rush for this to happen, so any work queue
will do.

MD_RECOVERY_RUNNING is used to ensure only one thread is started.

Reported-by: default avatarBillStuff <billstuff2001@sbcglobal.net>
Signed-off-by: default avatarNeilBrown <neilb@suse.de>
parent 8b1afc3d

drivers/md/md.c

+36 −23
Original line number Diff line number Diff line
@@ -7767,6 +7767,33 @@ no_add: 
	return spares;

}



static void md_start_sync(struct work_struct *ws)

{

	struct mddev *mddev = container_of(ws, struct mddev, del_work);



	mddev->sync_thread = md_register_thread(md_do_sync,

						mddev,

						"resync");

	if (!mddev->sync_thread) {

		printk(KERN_ERR "%s: could not start resync"

		       " thread...\n",

		       mdname(mddev));

		/* leave the spares where they are, it shouldn't hurt */

		clear_bit(MD_RECOVERY_SYNC, &mddev->recovery);

		clear_bit(MD_RECOVERY_RESHAPE, &mddev->recovery);

		clear_bit(MD_RECOVERY_REQUESTED, &mddev->recovery);

		clear_bit(MD_RECOVERY_CHECK, &mddev->recovery);

		clear_bit(MD_RECOVERY_RUNNING, &mddev->recovery);

		if (test_and_clear_bit(MD_RECOVERY_RECOVER,

				       &mddev->recovery))

			if (mddev->sysfs_action)

				sysfs_notify_dirent_safe(mddev->sysfs_action);

	} else

		md_wakeup_thread(mddev->sync_thread);

	sysfs_notify_dirent_safe(mddev->sysfs_action);

	md_new_event(mddev);

}



/*

 * This routine is regularly called by all per-raid-array threads to

 * deal with generic issues like resync and super-block update.
@@ -7883,7 +7910,7 @@ void md_check_recovery(struct mddev *mddev) 


		if (!test_and_clear_bit(MD_RECOVERY_NEEDED, &mddev->recovery) ||

		    test_bit(MD_RECOVERY_FROZEN, &mddev->recovery))

			goto unlock;

			goto not_running;

		/* no recovery is running.

		 * remove any failed drives, then

		 * add spares if possible.
@@ -7895,7 +7922,7 @@ void md_check_recovery(struct mddev *mddev) 
			if (mddev->pers->check_reshape == NULL ||

			    mddev->pers->check_reshape(mddev) != 0)

				/* Cannot proceed */

				goto unlock;

				goto not_running;

			set_bit(MD_RECOVERY_RESHAPE, &mddev->recovery);

			clear_bit(MD_RECOVERY_RECOVER, &mddev->recovery);

		} else if ((spares = remove_and_add_spares(mddev, NULL))) {
@@ -7908,7 +7935,7 @@ void md_check_recovery(struct mddev *mddev) 
			clear_bit(MD_RECOVERY_RECOVER, &mddev->recovery);

		} else if (!test_bit(MD_RECOVERY_SYNC, &mddev->recovery))

			/* nothing to be done ... */

			goto unlock;

			goto not_running;



		if (mddev->pers->sync_request) {

			if (spares) {
@@ -7918,27 +7945,11 @@ void md_check_recovery(struct mddev *mddev) 
				 */

				bitmap_write_all(mddev->bitmap);

			}

			mddev->sync_thread = md_register_thread(md_do_sync,

								mddev,

								"resync");

			if (!mddev->sync_thread) {

				printk(KERN_ERR "%s: could not start resync"

					" thread...\n", 

					mdname(mddev));

				/* leave the spares where they are, it shouldn't hurt */

				clear_bit(MD_RECOVERY_RUNNING, &mddev->recovery);

				clear_bit(MD_RECOVERY_SYNC, &mddev->recovery);

				clear_bit(MD_RECOVERY_RESHAPE, &mddev->recovery);

				clear_bit(MD_RECOVERY_REQUESTED, &mddev->recovery);

				clear_bit(MD_RECOVERY_CHECK, &mddev->recovery);

			} else

				md_wakeup_thread(mddev->sync_thread);

			sysfs_notify_dirent_safe(mddev->sysfs_action);

			md_new_event(mddev);

			INIT_WORK(&mddev->del_work, md_start_sync);

			queue_work(md_misc_wq, &mddev->del_work);

			goto unlock;

		}

	unlock:

		wake_up(&mddev->sb_wait);



	not_running:

		if (!mddev->sync_thread) {

			clear_bit(MD_RECOVERY_RUNNING, &mddev->recovery);

			if (test_and_clear_bit(MD_RECOVERY_RECOVER,
@@ -7946,6 +7957,8 @@ void md_check_recovery(struct mddev *mddev) 
				if (mddev->sysfs_action)

					sysfs_notify_dirent_safe(mddev->sysfs_action);

		}

	unlock:

		wake_up(&mddev->sb_wait);

		mddev_unlock(mddev);

	}

}

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