linux-kernel - Re: [PATCH] move_pages.2: not return ENOENT if the page are already on the target nodes

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Message-Id: <BE1B9B9B-17C2-4093-A332-183DF3B6F2A3@lca.pw>
Date:   Fri, 6 Dec 2019 13:00:18 -0500
From:   Qian Cai <cai@....pw>
To:     Yang Shi <yang.shi@...ux.alibaba.com>
Cc:     Michal Hocko <mhocko@...nel.org>,
        John Hubbard <jhubbard@...dia.com>, mtk.manpages@...il.com,
        cl@...ux.com, akpm@...ux-foundation.org, linux-man@...r.kernel.org,
        linux-api@...r.kernel.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] move_pages.2: not return ENOENT if the page are already on the target nodes



> On Dec 6, 2019, at 12:31 PM, Yang Shi <yang.shi@...ux.alibaba.com> wrote:
> 
> It looks since commit e78bbfa82624 ("mm: stop returning -ENOENT from sys_move_pages() if nothing got migrated") too, which reset err to 0 unconditionally. It seems it is on purpose by that commit the syscall caller should check status for the details according to the commit log.

I don’t read it on purpose. “There is no point in returning -ENOENT from sys_move_pages() if all pages
were already on the right node”, so this is only taking about the pages in the desired node. Anyway, but now it is probably the best time to think outside the box redesigning this syscalls and nuke this whole mess.