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Thu, 23 Aug 2018 14:05:36 +0000 Received: from aserv0121.oracle.com (aserv0121.oracle.com [141.146.126.235]) by userv0021.oracle.com (8.14.4/8.14.4) with ESMTP id w7NE5T4b030387 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Thu, 23 Aug 2018 14:05:30 GMT Received: from abhmp0010.oracle.com (abhmp0010.oracle.com [141.146.116.16]) by aserv0121.oracle.com (8.14.4/8.13.8) with ESMTP id w7NE5TRY021205; Thu, 23 Aug 2018 14:05:29 GMT Received: from dhcp-burlington7-2nd-B-east-10-152-55-162.usdhcp.oraclecorp.com (/10.152.32.65) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Thu, 23 Aug 2018 07:05:29 -0700 Subject: Re: [PATCH] xen/gntdev: fix up blockable calls to mn_invl_range_start To: Michal Hocko , Tetsuo Handa Cc: Andrew Morton , linux-mm@kvack.org, xen-devel@lists.xenproject.org, LKML , Juergen Gross References: <20180823120707.10998-1-mhocko@kernel.org> <07c7ead4-334d-9b25-f588-25e9b46bbea0@i-love.sakura.ne.jp> <20180823135151.GM29735@dhcp22.suse.cz> From: Boris Ostrovsky Openpgp: preference=signencrypt Autocrypt: addr=boris.ostrovsky@oracle.com; 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Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <20180823135151.GM29735@dhcp22.suse.cz> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Content-Language: en-US X-Proofpoint-Virus-Version: vendor=nai engine=5900 definitions=8993 signatures=668707 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 suspectscore=0 malwarescore=0 phishscore=0 bulkscore=0 spamscore=0 mlxscore=0 mlxlogscore=967 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1807170000 definitions=main-1808230150 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 08/23/2018 09:51 AM, Michal Hocko wrote: > 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); (I obviously missed that too with my R-b). This will never get anything done either. How about     if (in_range()) {         if (!blockable) {             ret = -EGAIN;             goto out_unlock;         }         unmap_range(); // new name since unmap_if_in_range() doesn't perform any checks now     } -boris > } > 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; > }