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Mon, 03 Aug 2020 23:00:59 +0000 Received: from pps.filterd (aserp3030.oracle.com [127.0.0.1]) by aserp3030.oracle.com (8.16.0.42/8.16.0.42) with SMTP id 073Mx5qK012948; Mon, 3 Aug 2020 23:00:58 GMT Received: from userv0122.oracle.com (userv0122.oracle.com [156.151.31.75]) by aserp3030.oracle.com with ESMTP id 32p5grce4b-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Mon, 03 Aug 2020 23:00:58 +0000 Received: from abhmp0011.oracle.com (abhmp0011.oracle.com [141.146.116.17]) by userv0122.oracle.com (8.14.4/8.14.4) with ESMTP id 073N0suD006631; Mon, 3 Aug 2020 23:00:54 GMT Received: from [192.168.2.112] (/50.38.35.18) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Mon, 03 Aug 2020 16:00:54 -0700 Subject: Re: [PATCH] hugetlbfs: remove call to huge_pte_alloc without i_mmap_rwsem To: Matthew Wilcox Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Michal Hocko , Hugh Dickins , Naoya Horiguchi , "Aneesh Kumar K.V" , Andrea Arcangeli , "Kirill A.Shutemov" , Davidlohr Bueso , Prakash Sangappa , Andrew Morton , stable@vger.kernel.org References: <20200803224335.55794-1-mike.kravetz@oracle.com> <20200803225234.GD23808@casper.infradead.org> From: Mike Kravetz Message-ID: <9072d352-7a07-aac7-3439-3f524fc465ed@oracle.com> Date: Mon, 3 Aug 2020 16:00:52 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <20200803225234.GD23808@casper.infradead.org> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9702 signatures=668679 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 malwarescore=0 mlxscore=0 bulkscore=0 phishscore=0 spamscore=0 adultscore=0 suspectscore=0 mlxlogscore=999 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2006250000 definitions=main-2008030158 X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9702 signatures=668679 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 clxscore=1011 priorityscore=1501 impostorscore=0 lowpriorityscore=0 malwarescore=0 spamscore=0 mlxscore=0 suspectscore=0 mlxlogscore=999 phishscore=0 adultscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2006250000 definitions=main-2008030158 X-Rspamd-Queue-Id: 55A7018229837 X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam05 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: On 8/3/20 3:52 PM, Matthew Wilcox wrote: > On Mon, Aug 03, 2020 at 03:43:35PM -0700, Mike Kravetz wrote: >> Commit c0d0381ade79 ("hugetlbfs: use i_mmap_rwsem for more pmd sharing >> synchronization") requires callers of huge_pte_alloc to hold i_mmap_rwsem >> in at least read mode. This is because the explicit locking in >> huge_pmd_share (called by huge_pte_alloc) was removed. When restructuring >> the code, the call to huge_pte_alloc in the else block at the beginning >> of hugetlb_fault was missed. > > Should we have a call to mmap_assert_locked() in huge_pte_alloc(), > at least the generic one? That is the wrong semaphore. However, I was not aware of the checks for a semaphore being held as is done in rwsem_is_locked(). That would have caught this when the original code was changed. Thanks for pointing this out. Let me update the patch and add checks to huge_pmd_share(). -- Mike Kravetz