Re: [PULL REQUEST] md bug fixes and minor improvements

[Dan Williams <dan.j.williams@intel.com>]

On Fri, 2008-08-01 at 19:22 +0200, Jens Axboe wrote:
> It is a bit asymmetrical, largely due to the fact that the ->unplug_fn()
> itself grabs the lock. The below patch should fix it, since Neil has
> added a proper queue lock to the md queues. If someone can confirm that
> this fixes it, I'll queue up a patch with proper descriptions.
> 
> > I guess Jens is gone too..
> 
> I'm back, just been busy this week :-)
> 
> diff --git a/drivers/md/bitmap.c b/drivers/md/bitmap.c
> index 621a272..f19b52f 100644
> --- a/drivers/md/bitmap.c
> +++ b/drivers/md/bitmap.c
> @@ -1234,7 +1234,9 @@ int bitmap_startwrite(struct bitmap *bitmap, sector_t offset, unsigned long sect
>  		case 0:
>  			bitmap_file_set_bit(bitmap, offset);
>  			bitmap_count_page(bitmap,offset, 1);
> +			spin_lock_irq(&bitmap->mddev->queue->queue_lock);
>  			blk_plug_device(bitmap->mddev->queue);
> +			spin_unlock_irq(&bitmap->mddev->queue->queue_lock);
>  			/* fall through */
>  		case 1:
>  			*bmc = 2;
> 

We also need to protect the blk_plug_device call a few lines down (and
an obvious compile fix).

diff --git a/drivers/md/bitmap.c b/drivers/md/bitmap.c
index 621a272..c1b07e7 100644
--- a/drivers/md/bitmap.c
+++ b/drivers/md/bitmap.c
@@ -1224,7 +1224,9 @@ int bitmap_startwrite(struct bitmap *bitmap, sector_t offset, unsigned long sect
 			prepare_to_wait(&bitmap->overflow_wait, &__wait,
 					TASK_UNINTERRUPTIBLE);
 			spin_unlock_irq(&bitmap->lock);
+			spin_lock_irq(bitmap->mddev->queue->queue_lock);
 			blk_unplug(bitmap->mddev->queue);
+			spin_unlock_irq(bitmap->mddev->queue->queue_lock);
 			schedule();
 			finish_wait(&bitmap->overflow_wait, &__wait);
 			continue;
@@ -1234,7 +1236,9 @@ int bitmap_startwrite(struct bitmap *bitmap, sector_t offset, unsigned long sect
 		case 0:
 			bitmap_file_set_bit(bitmap, offset);
 			bitmap_count_page(bitmap,offset, 1);
+			spin_lock_irq(bitmap->mddev->queue->queue_lock);
 			blk_plug_device(bitmap->mddev->queue);
+			spin_unlock_irq(bitmap->mddev->queue->queue_lock);
 			/* fall through */
 		case 1:
 			*bmc = 2;