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Wed, 30 Oct 2019 21:04:28 GMT Received: from userv0121.oracle.com (userv0121.oracle.com [156.151.31.72]) by userp3030.oracle.com with ESMTP id 2vxwhwtage-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Wed, 30 Oct 2019 21:04:24 +0000 Received: from abhmp0010.oracle.com (abhmp0010.oracle.com [141.146.116.16]) by userv0121.oracle.com (8.14.4/8.13.8) with ESMTP id x9UL3Iov013454; Wed, 30 Oct 2019 21:03:19 GMT Received: from ca-dmjordan1.us.oracle.com (/10.211.9.48) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Wed, 30 Oct 2019 14:03:18 -0700 Date: Wed, 30 Oct 2019 17:03:14 -0400 From: Daniel Jordan To: Roman Gushchin Cc: linux-mm@kvack.org, Michal Hocko , Johannes Weiner , linux-kernel@vger.kernel.org, kernel-team@fb.com, Vladimir Davydov , Shakeel Butt Subject: Re: [PATCH] mm: slab: make page_cgroup_ino() to recognize non-compound slab pages properly Message-ID: <20191030210314.2el7wysojucqypoq@ca-dmjordan1.us.oracle.com> References: <20191025232710.4081957-1-guro@fb.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20191025232710.4081957-1-guro@fb.com> User-Agent: NeoMutt/20180716 X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9426 signatures=668685 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 suspectscore=0 malwarescore=0 phishscore=0 bulkscore=0 spamscore=0 mlxscore=0 mlxlogscore=729 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1908290000 definitions=main-1910300183 X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9426 signatures=668685 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1011 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=816 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1908290000 definitions=main-1910300184 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: Hi Roman, On Fri, Oct 25, 2019 at 04:27:10PM -0700, Roman Gushchin wrote: > page_cgroup_ino() doesn't return a valid memcg pointer for non-compund > slab pages, because it depends on PgHead AND PgSlab flags to be set > to determine the memory cgroup from the kmem_cache. > It's correct for compound pages, but not for generic small pages. Those > don't have PgHead set, so it ends up returning zero. > > Fix this by replacing the condition to PageSlab() && !PageTail(). You may also want to update the comment above memcg_from_slab_page(): * So this function assumes that the page can pass PageHead() and PageSlab() * checks.