linux-kernel - Re: [Intel-gfx] [PATCH 3/4] drm/ttm: Don't leak a resource on eviction error

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Message-ID: <ZJVOTzorVVTvvF2z@ashyti-mobl2.lan>
Date:   Fri, 23 Jun 2023 09:48:31 +0200
From:   Andi Shyti <andi.shyti@...ux.intel.com>
To:     Thomas Hellström 
        <thomas.hellstrom@...ux.intel.com>
Cc:     Christian König <christian.koenig@....com>,
        Andi Shyti <andi.shyti@...ux.intel.com>,
        intel-xe@...ts.freedesktop.org,
        Andrey Grodzovsky <andrey.grodzovsky@....com>,
        Christian König 
        <ckoenig.leichtzumerken@...il.com>,
        intel-gfx@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        stable@...r.kernel.org, Huang Rui <ray.huang@....com>,
        dri-devel@...ts.freedesktop.org
Subject: Re: [Intel-gfx] [PATCH 3/4] drm/ttm: Don't leak a resource on
 eviction error

Hi Christian and Thomas,

> > > > > diff --git a/drivers/gpu/drm/ttm/ttm_bo.c
> > > > > b/drivers/gpu/drm/ttm/ttm_bo.c
> > > > > index 615d30c4262d..89530f2a027f 100644
> > > > > --- a/drivers/gpu/drm/ttm/ttm_bo.c
> > > > > +++ b/drivers/gpu/drm/ttm/ttm_bo.c
> > > > > @@ -462,14 +462,14 @@ static int ttm_bo_evict(struct
> > > > > ttm_buffer_object *bo,
> > > > >       ret = ttm_bo_handle_move_mem(bo, evict_mem, true, ctx, &hop);
> > > > >       if (ret == -EMULTIHOP) {
> > > > >           ret = ttm_bo_bounce_temp_buffer(bo, &evict_mem, ctx, &hop);
> > > > > -        if (ret) {
> > > > > -            if (ret != -ERESTARTSYS && ret != -EINTR)
> > > > > -                pr_err("Buffer eviction failed\n");
> > > > > -            ttm_resource_free(bo, &evict_mem);
> > > > > -            goto out;
> > > > > -        }
> > > > > -        /* try and move to final place now. */
> > > > > -        goto bounce;
> > > > > +        if (!ret)
> > > > > +            /* try and move to final place now. */
> > > > > +            goto bounce;
> > > > As we are at this, can't we replace this with a while()? Goto's
> > > > used instead of a while loop are a fist in the eye...
> > > 
> > > I'm completely OK with that. this patch already did away with one of
> > > them. Let's hear Christian's opinion first, though.
> > 
> > I'm not a fan of that goto either, but could we somehow avoid the
> > while(1) ? E.g. something like do { } while (!ret) after handling the
> > multihop?
> 
> I think the construct that makes it most obvious what's happening, although
> it needs two tests for -EMULTIHOP is something like
> 
> do {
> ....
>    if (ret != -EMULTIHOP)
>       break;
>    ....
> } while (ret ==-EMULTIHOP);

even better :)

Thank you!
Andi