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Wed, 17 Aug 2022 23:40:47 +0000 Received: from MN2PR12MB4192.namprd12.prod.outlook.com ([fe80::462:7fe:f04f:d0d5]) by MN2PR12MB4192.namprd12.prod.outlook.com ([fe80::462:7fe:f04f:d0d5%6]) with mapi id 15.20.5525.019; Wed, 17 Aug 2022 23:40:47 +0000 Date: Wed, 17 Aug 2022 20:40:40 -0300 From: Jason Gunthorpe To: Alistair Popple Cc: John Hubbard , linux-mm@kvack.org, akpm@linux-foundation.org, linux-kernel@vger.kernel.org, "Sierra Guiza, Alejandro (Alex)" , Chaitanya Kulkarni , Dan Williams , Felix Kuehling , Logan Gunthorpe , Miaohe Lin , Muchun Song , Ralph Campbell , David Hildenbrand , Matthew Wilcox Subject: Re: [PATCH v4 2/2] mm/gup.c: Refactor check_and_migrate_movable_pages() Message-ID: References: <487960bf67c7273ff5606c76f73bb51271bc7b90.1660269441.git-series.apopple@nvidia.com> <6b61e9bf7c65f78524db32ba3e65a7eb6b8a76a0.1660269441.git-series.apopple@nvidia.com> <87edxgvixy.fsf@nvdebian.thelocal> <87wnb7tycb.fsf@nvdebian.thelocal> <87k076tpd1.fsf@nvdebian.thelocal> Content-Type: text/plain; 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dkim=pass header.d=Nvidia.com header.s=selector2 header.b=SvDvgkOG; spf=pass (imf21.hostedemail.com: domain of jgg@nvidia.com designates 40.107.92.42 as permitted sender) smtp.mailfrom=jgg@nvidia.com; arc=pass ("microsoft.com:s=arcselector9901:i=1"); dmarc=pass (policy=reject) header.from=nvidia.com X-Rspam-User: X-Rspamd-Server: rspam04 X-HE-Tag: 1660779649-627880 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 Thu, Aug 18, 2022 at 09:24:28AM +1000, Alistair Popple wrote: > collected = collect_longterm_unpinnable_pages(&movable_page_list, > nr_pages, pages); > if (collected == 0) > return 0; > > ret = migrate_longterm_unpinnable_pages(&movable_page_list, nr_pages, > pages); > if (ret) > return ret; > > return -EAGAIN; > > Which IMHO looks at lot more normal and sane than what I had. That isn't "success oriented flow" :) > > But why return 0 from the helper function in the first place? > > To stick with the paradigm of 0 == success. Ie. But it doesn't mean success if we squashed it to EAGAIN here. -EAGAIN == retry 0 == success, real success everything else == -ERRNO, failure Stick with one convection in all the functions in this file in this grouping. Jason