linux-kernel - Re: [PATCH v3 2/7] mm/lruvec: add irqsave flags into lruvec struct

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Message-ID: <20191122064645.GA11261@infradead.org>
Date:   Thu, 21 Nov 2019 22:46:45 -0800
From:   Christoph Hellwig <hch@...radead.org>
To:     Alex Shi <alex.shi@...ux.alibaba.com>
Cc:     cgroups@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, akpm@...ux-foundation.org,
        mgorman@...hsingularity.net, tj@...nel.org, hughd@...gle.com,
        khlebnikov@...dex-team.ru, daniel.m.jordan@...cle.com,
        yang.shi@...ux.alibaba.com, willy@...radead.org,
        Vlastimil Babka <vbabka@...e.cz>,
        Dan Williams <dan.j.williams@...el.com>,
        Michal Hocko <mhocko@...e.com>,
        Wei Yang <richard.weiyang@...il.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Arun KS <arunks@...eaurora.org>,
        Rong Chen <rong.a.chen@...el.com>
Subject: Re: [PATCH v3 2/7] mm/lruvec: add irqsave flags into lruvec struct

On Sat, Nov 16, 2019 at 11:15:01AM +0800, Alex Shi wrote:
> We need a irqflags vaiable to save state when do irqsave action, declare
> it here would make code more clear/clean.

This patch is wrong on multiple levels.  Adding a field without the
users is completely pointless.  And as a general pattern we never
add the irqsave flags to sturctures.  They are an intimate part of the
calling conventions, and storing them in a structure will lead to
subtile bugs.