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Violators will be prosecuted; (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256/256) Tue, 4 Jun 2019 09:30:34 +0100 Received: from b03ledav001.gho.boulder.ibm.com (b03ledav001.gho.boulder.ibm.com [9.17.130.232]) by b03cxnp08028.gho.boulder.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id x548UXQM32637338 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 4 Jun 2019 08:30:33 GMT Received: from b03ledav001.gho.boulder.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 86C816E04C; Tue, 4 Jun 2019 08:30:33 +0000 (GMT) Received: from b03ledav001.gho.boulder.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 9BC076E04E; Tue, 4 Jun 2019 08:30:30 +0000 (GMT) Received: from [9.124.35.234] (unknown [9.124.35.234]) by b03ledav001.gho.boulder.ibm.com (Postfix) with ESMTP; Tue, 4 Jun 2019 08:30:30 +0000 (GMT) Subject: Re: [PATCH] mm/gup: remove unnecessary check against CMA in __gup_longterm_locked() To: Pingfan Liu , linux-mm@kvack.org Cc: Andrew Morton , Ira Weiny , Dan Williams , Thomas Gleixner , Mike Rapoport , John Hubbard , Keith Busch , linux-kernel@vger.kernel.org References: <1559633160-14809-1-git-send-email-kernelfans@gmail.com> From: "Aneesh Kumar K.V" Date: Tue, 4 Jun 2019 14:00:29 +0530 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.7.0 MIME-Version: 1.0 In-Reply-To: <1559633160-14809-1-git-send-email-kernelfans@gmail.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 x-cbid: 19060408-0020-0000-0000-00000EF3EFEC X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00011212; HX=3.00000242; KW=3.00000007; PH=3.00000004; SC=3.00000286; SDB=6.01213022; UDB=6.00637519; IPR=6.00994090; MB=3.00027177; MTD=3.00000008; XFM=3.00000015; UTC=2019-06-04 08:30:37 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 19060408-0021-0000-0000-000066163871 Message-Id: X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2019-06-04_06:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=915 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1906040057 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 6/4/19 12:56 PM, Pingfan Liu wrote: > The PF_MEMALLOC_NOCMA is set by memalloc_nocma_save(), which is finally > cast to ~_GFP_MOVABLE. So __get_user_pages_locked() will get pages from > non CMA area and pin them. There is no need to > check_and_migrate_cma_pages(). That is not completely correct. We can fault in that pages outside get_user_pages_longterm at which point those pages can get allocated from CMA region. memalloc_nocma_save() as added as an optimization to avoid unnecessary page migration. -aneesh