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Commit 5792a285 authored by NeilBrown's avatar NeilBrown Committed by Linus Torvalds
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[PATCH] md: avoid a deadlock when removing a device from an md array via sysfs 



A device can be removed from an md array via e.g.
  echo remove > /sys/block/md3/md/dev-sde/state

This will try to remove the 'dev-sde' subtree which will deadlock
since
  commit e7b0d26a

With this patch we run the kobject_del via schedule_work so as to
avoid the deadlock.

Cc: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: default avatarNeil Brown <neilb@suse.de>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 456a09dc

drivers/md/md.c

+15 −1
Original line number Original line Diff line number Diff line
@@ -1378,6 +1378,12 @@ static int bind_rdev_to_array(mdk_rdev_t * rdev, mddev_t * mddev) 
	return err;

	return err;

}

}





static void delayed_delete(struct work_struct *ws)

{

	mdk_rdev_t *rdev = container_of(ws, mdk_rdev_t, del_work);

	kobject_del(&rdev->kobj);

}



static void unbind_rdev_from_array(mdk_rdev_t * rdev)

static void unbind_rdev_from_array(mdk_rdev_t * rdev)

{

{

	char b[BDEVNAME_SIZE];

	char b[BDEVNAME_SIZE];
@@ -1390,7 +1396,12 @@ static void unbind_rdev_from_array(mdk_rdev_t * rdev) 
	printk(KERN_INFO "md: unbind<%s>\n", bdevname(rdev->bdev,b));

	printk(KERN_INFO "md: unbind<%s>\n", bdevname(rdev->bdev,b));

	rdev->mddev = NULL;

	rdev->mddev = NULL;

	sysfs_remove_link(&rdev->kobj, "block");

	sysfs_remove_link(&rdev->kobj, "block");

	kobject_del(&rdev->kobj);



	/* We need to delay this, otherwise we can deadlock when

	 * writing to 'remove' to "dev/state"

	 */

	INIT_WORK(&rdev->del_work, delayed_delete);

	schedule_work(&rdev->del_work);

}

}





/*

/*
@@ -3389,6 +3400,9 @@ static int do_md_stop(mddev_t * mddev, int mode) 
				sysfs_remove_link(&mddev->kobj, nm);

				sysfs_remove_link(&mddev->kobj, nm);

			}

			}





		/* make sure all delayed_delete calls have finished */

		flush_scheduled_work();



		export_array(mddev);

		export_array(mddev);





		mddev->array_size = 0;

		mddev->array_size = 0;

include/linux/raid/md_k.h

+1 −0
Original line number Original line Diff line number Diff line
@@ -104,6 +104,7 @@ struct mdk_rdev_s 
					   * for reporting to userspace and storing

					   * for reporting to userspace and storing

					   * in superblock.

					   * in superblock.

					   */

					   */

	struct work_struct del_work;	/* used for delayed sysfs removal */

};

};





struct mddev_s

struct mddev_s