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Wed, 24 Feb 2021 00:27:31 GMT Received: from userv0121.oracle.com (userv0121.oracle.com [156.151.31.72]) by userp3020.oracle.com with ESMTP id 36uc6sesd1-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Wed, 24 Feb 2021 00:27:30 +0000 Received: from abhmp0016.oracle.com (abhmp0016.oracle.com [141.146.116.22]) by userv0121.oracle.com (8.14.4/8.13.8) with ESMTP id 11O0RSGd024704; Wed, 24 Feb 2021 00:27:28 GMT Received: from [192.168.2.112] (/50.38.35.18) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Tue, 23 Feb 2021 16:27:28 -0800 Subject: Re: [PATCH] hugetlb: fix uninitialized subpool pointer From: Mike Kravetz To: Oscar Salvador Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, Gerald Schaefer , Michal Hocko , Muchun Song , Heiko Carstens , Sven Schnelle , Andrew Morton References: <20210223215544.313871-1-mike.kravetz@oracle.com> <20210223224540.GB2740@localhost.localdomain> <53527e9d-d09b-7287-9f79-ebdbf4e9bc7a@oracle.com> Message-ID: <3590f7a0-854d-04eb-6d73-7b3ef2ac49b5@oracle.com> Date: Tue, 23 Feb 2021 16:27:27 -0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.1.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Proofpoint-Virus-Version: vendor=nai engine=6200 definitions=9904 signatures=668683 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 suspectscore=0 mlxscore=0 spamscore=0 mlxlogscore=999 adultscore=0 bulkscore=0 malwarescore=0 phishscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2009150000 definitions=main-2102240001 X-Proofpoint-Virus-Version: vendor=nai engine=6200 definitions=9904 signatures=668683 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 suspectscore=0 spamscore=0 priorityscore=1501 impostorscore=0 bulkscore=0 mlxscore=0 malwarescore=0 clxscore=1015 phishscore=0 mlxlogscore=999 lowpriorityscore=0 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2009150000 definitions=main-2102240000 X-Stat-Signature: 7heu75r3f4y59g76wi8a6p5dxkc1q5yj X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 75CEA20001F2 Received-SPF: none (oracle.com>: No applicable sender policy available) receiver=imf18; identity=mailfrom; envelope-from=""; helo=userp2130.oracle.com; client-ip=156.151.31.86 X-HE-DKIM-Result: pass/pass X-HE-Tag: 1614126455-892313 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000010, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 2/23/21 3:21 PM, Mike Kravetz wrote: > On 2/23/21 2:58 PM, Oscar Salvador wrote: >> On 2021-02-23 23:55, Mike Kravetz wrote: >>> Yes, that is the more common case where the once active hugetlb page >>> will be simply added to the free list via enqueue_huge_page(). This >>> path does not go through prep_new_huge_page. >> >> Right, I see. >> >> Thanks > > You got me thinking ... > When we dynamically allocate gigantic pages via alloc_contig_pages, we > will not use the buddy allocator. Therefore, the usual 'page prepping' > will not take place. Specifically, I could not find anything in that > path which clears page->private of the head page. > Am I missing that somewhere? If not, then we need to clear that as well > in prep_compound_gigantic_page. Or, just clear it in prep_new_huge_page > to handle any change in assumptions about the buddy allocator. > > This is not something introduced with the recent field shuffling, it > looks like something that existed for some time. nm, we do end up calling the same page prepping code (post_alloc_hook) from alloc_contig_range->isolate_freepages_range. Just to make sure, I purpously dirtied page->private of every page as it was being freed. Gigantic page allocation was just fine, and I even ran ltp mm tests with this dirtying in place. -- Mike Kravetz