[dm-devel] [PATCH] md: fix bug due to nested suspend

[Mikulas Patocka]

On Wed, 16 Dec 2015, NeilBrown wrote:

> On Thu, Nov 26 2015, Mikulas Patocka wrote:
> 
> > The patch c7bfced9a6716ff66c9d61f934bb60af08d4688c committed to 4.4-rc 
> > causes crash in LVM test shell/lvchange-raid.sh. The kernel crashes with 
> > this BUG, the reason is that we attempt to suspend a device that is 
> > already suspended. See also 
> > https://bugzilla.redhat.com/show_bug.cgi?id=1283491
> >
> > This patch fixes the bug by introducing functions mddev_nested_suspend and
> > mddev_nested_resume that can be called when the device is already
> > suspended. The number of calls to mddev_nested_suspend is kept in the
> > variable mddev->suspended.
> 
> Hi,
>  thanks for the report and patch.
> 
> I think I would rather just make mddev_suspend() always nest.
> It is always called under ->reconfig_mutex or some similar guarentee of
> being single-threaded in dm-raid, so we don't need an atomic_t.
> 
> Just
>   mddev_suspend()
> 	if (mddev->suspended++)
>         	return;
>         ...do the suspend.
> 
> and
>   mddev_resume()
>        if (--mddev->suspended)
>        		return;
>        ... to the resume
> 
> Does that seem reasonable to you?

Yes, it seems OK.

Mikulas