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

On Thu, May 13, 2021 at 11:47:15AM +0200, Greg Kroah-Hartman wrote:

On Thu, May 13, 2021 at 09:59:41AM +0200, Pavel Machek wrote:

quoted

Hi!

quoted

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.

That's really odd, let me figure out what went wrong there, might be a
quilt thing...

Yup, it's a bug in quilt, the header is just dropped for some reason.
Will dig further, thanks for pointing this out.

greg k-h