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SubjectRe: [PATCH 5.10 050/530] md: md_open returns -EBUSY when entering racing area
Hi!

> commit 6a4db2a60306eb65bfb14ccc9fde035b74a4b4e7 upstream.
>
> commit d3374825ce57 ("md: make devices disappear when they are no longer
> needed.") introduced protection between mddev creating & removing. The
> md_open shouldn't create mddev when all_mddevs list doesn't contain
> mddev. With currently code logic, there will be very easy to trigger
> soft lockup in non-preempt env.
>
> This patch changes md_open returning from -ERESTARTSYS to -EBUSY, which
> will break the infinitely retry when md_open enter racing area.
>
> This patch is partly fix soft lockup issue, full fix needs mddev_find
> is split into two functions: mddev_find & mddev_find_or_alloc. And
> md_open should call new mddev_find (it only does searching job).
>
> For more detail, please refer with Christoph's "split mddev_find" patch
> in later commits.

Something went wrong here; changelog is truncated, in particular it
does not contain required sign-offs.

Best regards,
Pavel

> +++ b/drivers/md/md.c
> @@ -7857,8 +7857,7 @@ static int md_open(struct block_device *
> /* Wait until bdev->bd_disk is definitely gone */
> if (work_pending(&mddev->del_work))
> flush_workqueue(md_misc_wq);
> - /* Then retry the open from the top */
> - return -ERESTARTSYS;
> + return -EBUSY;
> }
> BUG_ON(mddev != bdev->bd_disk->private_data);


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