From mboxrd@z Thu Jan 1 00:00:00 1970 From: Yang Shi Subject: Re: [PATCH] move_pages.2: not return ENOENT if the page are already on the target nodes Date: Thu, 2 Jan 2020 14:15:12 -0800 Message-ID: References: <1575596090-115377-1-git-send-email-yang.shi@linux.alibaba.com> <0dc96e40-5f2b-a2fe-6e5f-b6f3d5e9ebde@nvidia.com> <95170ea5-5b62-9168-fcd9-93b43330a1b4@linux.alibaba.com> <092adc11-7039-9343-7067-0e0199c9dc13@gmail.com> <51dd767a-221f-882d-c7f6-45bd0c217a67@nvidia.com> <20191218101711.GB21485@dhcp22.suse.cz> <0059a598-5726-2488-cd37-b4b7f9b3353e@linux.alibaba.com> <87lfqtcfyo.fsf@x220.int.ebiederm.org> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <87lfqtcfyo.fsf@x220.int.ebiederm.org> Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org To: "Eric W. Biederman" Cc: Michal Hocko , John Hubbard , "Michael Kerrisk (man-pages)" , cl@linux.com, cai@lca.pw, akpm@linux-foundation.org, linux-man@vger.kernel.org, linux-api@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org List-Id: linux-api@vger.kernel.org On 12/30/19 7:49 PM, Eric W. Biederman wrote: > Yang Shi writes: > >> On 12/18/19 2:17 AM, Michal Hocko wrote: >>> On Tue 17-12-19 23:36:09, John Hubbard wrote: >>> [...] >>>> diff --git a/man2/move_pages.2 b/man2/move_pages.2 >>>> index 2d96468fa..1bf1053f2 100644 >>>> --- a/man2/move_pages.2 >>>> +++ b/man2/move_pages.2 >>>> @@ -191,12 +191,6 @@ was specified or an attempt was made to migrate pages of a kernel thread. >>>> .B ENODEV >>>> One of the target nodes is not online. >>>> .TP >>>> -.B ENOENT >>>> -No pages were found that require moving. >>>> -All pages are either already >>>> -on the target node, not present, had an invalid address or could not be >>>> -moved because they were mapped by multiple processes. >>>> -.TP >>>> .B EPERM >>>> The caller specified >>>> .B MPOL_MF_MOVE_ALL >>>> >>>> ...But I'm not sure if we should change the implementation, instead, so >>>> that it *can* return ENOENT. That's the main question to resolve before >>>> creating any more patches, I think. >>> I would start by dropping any note about ENOENT first. I am not really >>> sure there is a reasonable usecase for it but maybe somebody comes up >>> with something and only then we should consider it. >>> >>> Feel free to add >>> Acked-by: Michal Hocko >>> >>> ideally with a kernel commit which removed the ENOENT. >> A quick audit doesn't show kernel code or comment notes about ENOENT >> wrongly. The status could be set as ENOENT if the page is not present >> (follow_page() returns NULL), and man page does match what kernel >> does. > Doesn't the function one layer up then consume the ENOENT? No, it doesn't. The return value would be reset unconditionally by store_status(). This is what the man page patch tries to correct. > > Eric