[PATCH] um: ubd: Submit all data segments atomically

[Richard Weinberger]

On Wed, Nov 18, 2020 at 10:19 PM Gabriel Krisman Bertazi
<krisman at collabora.com> wrote:
>
> Anton Ivanov <anton.ivanov at cambridgegreys.com> writes:
>
> > On 25/10/2020 04:41, Gabriel Krisman Bertazi wrote:
> >> Internally, UBD treats each physical IO segment as a separate command to
> >> be submitted in the execution pipe.  If the pipe returns a transient
> >> error after a few segments have already been written, UBD will tell the
> >> block layer to requeue the request, but there is no way to reclaim the
> >> segments already submitted.  When a new attempt to dispatch the request
> >> is done, those segments already submitted will get duplicated, causing
> >> the WARN_ON below in the best case, and potentially data corruption.
> >> In my system, running a UML instance with 2GB of RAM and a 50M UBD
> >> disk,
>
> >>   [...]
> >> ---[ end trace c6e7444e55386c0f ]---
> >> Cc: Christopher Obbard <chris.obbard at collabora.com>
> >> Reported-by: Martyn Welch <martyn at collabora.com>
> >> Signed-off-by: Gabriel Krisman Bertazi <krisman at collabora.com>
>
> > Acked-By: Anton Ivanov <anton.ivanov at cambridgegreys.com>
>
> Hi,
>
> Is this queued somewhere?  I've been watching the linux-next branch of

I had only one minor comment but apparently the mail got stuck locally. :-(
Just sent my mail again.

-- 
Thanks,
//richard