linux-kernel - Re: [PATCH RFC 0/2] mm/page_alloc: free_pcppages

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Message-ID: <20230821103225.qntnsotdzuthxn2y@techsingularity.net>
Date:   Mon, 21 Aug 2023 11:32:25 +0100
From:   Mel Gorman <mgorman@...hsingularity.net>
To:     Chris Li <chrisl@...nel.org>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Kemeng Shi <shikemeng@...weicloud.com>,
        baolin.wang@...ux.alibaba.com, Michal Hocko <mhocko@...e.com>,
        david@...hat.com, willy@...radead.org, linux-mm@...ck.org,
        Namhyung Kim <namhyung@...gle.com>,
        Greg Thelen <gthelen@...gle.com>, linux-kernel@...r.kernel.org,
        John Sperbeck <jsperbeck@...gle.com>
Subject: Re: [PATCH RFC 0/2] mm/page_alloc: free_pcppages_bulk safeguard

On Thu, Aug 17, 2023 at 11:05:22PM -0700, Chris Li wrote:
> In this patch series I want to safeguard
> the free_pcppage_bulk against change in the
> pcp->count outside of this function. e.g.
> by BPF program inject on the function tracepoint.
> 
> I break up the patches into two seperate patches
> for the safeguard and clean up.
> 
> Hopefully that is easier to review.
> 
> Signed-off-by: Chris Li <chrisl@...nel.org>

This sounds like a maintenance nightmare if internal state can be arbitrary
modified by a BPF program and still expected to work properly in all cases.
Every review would have to take into account "what if a BPF script modifies
state behind our back?"

-- 
Mel Gorman
SUSE Labs