From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pg1-f199.google.com (mail-pg1-f199.google.com [209.85.215.199]) by kanga.kvack.org (Postfix) with ESMTP id E4A6A6B2A6E for ; Thu, 23 Aug 2018 09:51:56 -0400 (EDT) Received: by mail-pg1-f199.google.com with SMTP id q12-v6so2938079pgp.6 for ; Thu, 23 Aug 2018 06:51:56 -0700 (PDT) Received: from mx1.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id 1-v6si4410509plw.99.2018.08.23.06.51.55 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 23 Aug 2018 06:51:55 -0700 (PDT) Date: Thu, 23 Aug 2018 15:51:51 +0200 From: Michal Hocko Subject: Re: [PATCH] xen/gntdev: fix up blockable calls to mn_invl_range_start Message-ID: <20180823135151.GM29735@dhcp22.suse.cz> References: <20180823120707.10998-1-mhocko@kernel.org> <07c7ead4-334d-9b25-f588-25e9b46bbea0@i-love.sakura.ne.jp> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <07c7ead4-334d-9b25-f588-25e9b46bbea0@i-love.sakura.ne.jp> Sender: owner-linux-mm@kvack.org List-ID: To: Tetsuo Handa Cc: Andrew Morton , linux-mm@kvack.org, xen-devel@lists.xenproject.org, LKML , Boris Ostrovsky , Juergen Gross On Thu 23-08-18 22:44:07, Tetsuo Handa wrote: > On 2018/08/23 21:07, Michal Hocko wrote: > > diff --git a/drivers/xen/gntdev.c b/drivers/xen/gntdev.c > > index 57390c7666e5..e7d8bb1bee2a 100644 > > --- a/drivers/xen/gntdev.c > > +++ b/drivers/xen/gntdev.c > > @@ -519,21 +519,20 @@ static int mn_invl_range_start(struct mmu_notifier *mn, > > struct gntdev_grant_map *map; > > int ret = 0; > > > > - /* TODO do we really need a mutex here? */ > > if (blockable) > > mutex_lock(&priv->lock); > > else if (!mutex_trylock(&priv->lock)) > > return -EAGAIN; > > > > list_for_each_entry(map, &priv->maps, next) { > > - if (in_range(map, start, end)) { > > + if (!blockable && in_range(map, start, end)) { > > This still looks strange. Prior to 93065ac753e4, in_range() test was > inside unmap_if_in_range(). But this patch removes in_range() test > if blockable == true. That is, unmap_if_in_range() will unconditionally > unmap if blockable == true, which seems to be an unexpected change. You are right. I completely forgot I've removed in_range there. Does this look any better? diff --git a/drivers/xen/gntdev.c b/drivers/xen/gntdev.c index e7d8bb1bee2a..30f81004ea63 100644 --- a/drivers/xen/gntdev.c +++ b/drivers/xen/gntdev.c @@ -525,14 +525,20 @@ static int mn_invl_range_start(struct mmu_notifier *mn, return -EAGAIN; list_for_each_entry(map, &priv->maps, next) { - if (!blockable && in_range(map, start, end)) { + if (in_range(map, start, end)) { + if (blockable) + continue; + ret = -EAGAIN; goto out_unlock; } unmap_if_in_range(map, start, end); } list_for_each_entry(map, &priv->freeable_maps, next) { - if (!blockable && in_range(map, start, end)) { + if (in_range(map, start, end)) { + if (blockable) + continue; + ret = -EAGAIN; goto out_unlock; } -- Michal Hocko SUSE Labs