[dm-devel] block: flush queued bios when the process blocks
Mike Snitzer
snitzer at redhat.com
Tue Oct 6 18:50:16 UTC 2015
On Tue, Oct 06 2015 at 2:17pm -0400,
Mikulas Patocka <mpatocka at redhat.com> wrote:
>
>
> On Mon, 5 Oct 2015, Mike Snitzer wrote:
>
> > FYI, I've put rebased versions of your 2 patches in my wip branch, see:
> > http://git.kernel.org/cgit/linux/kernel/git/snitzer/linux.git/log/?h=wip
>
> I found a bug in the first patch
> (http://git.kernel.org/cgit/linux/kernel/git/snitzer/linux.git/commit/?h=wip&id=2e90df2e9cf482f45be4230152535fdab525fbd8)
>
> There is this piece of code:
>
> spin_lock(&bs->rescue_lock);
> bio_list_add(&bs->rescue_list, bio);
> spin_unlock(&bs->rescue_lock);
> queue_work(bs->rescue_workqueue, &bs->rescue_work);
>
> It is possible that after spin_unlock and before queue_work the bio is
> finished by previous workqueue invocation. When the bio is finished, it is
> possible that the block device is unloaded and queue_work accesses freed
> memory.
>
> Change the code so that queue_work is executed inside the spinlock:
> spin_lock(&bs->rescue_lock);
> bio_list_add(&bs->rescue_list, bio);
> queue_work(bs->rescue_workqueue, &bs->rescue_work);
> spin_unlock(&bs->rescue_lock);
OK, but that should get pulled out to a separate stable@ fix that patch
you reference builds on.
I've adjusted my 'wip' branch accordingly (with placeholder commit that
needs revised header, etc).
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