linux-kernel - Re: [Resend RFC PATCH] mm: introduce __GFP_TRACKLEAK to track in-kernel allocation

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Message-ID: <YxhrtC/Z6H5MqUgq@arm.com>
Date:   Wed, 7 Sep 2022 11:00:20 +0100
From:   Catalin Marinas <catalin.marinas@....com>
To:     "zhaoyang.huang" <zhaoyang.huang@...soc.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Zhaoyang Huang <huangzhaoyang@...il.com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, ke.wang@...soc.com
Subject: Re: [Resend RFC PATCH] mm: introduce __GFP_TRACKLEAK to track
 in-kernel allocation

On Fri, Sep 02, 2022 at 06:59:07PM +0800, zhaoyang.huang wrote:
> From: Zhaoyang Huang <zhaoyang.huang@...soc.com>
> 
> Kthread and drivers could fetch memory via alloc_pages directly which make them
> hard to debug when leaking. Solve this by introducing __GFP_TRACELEAK and reuse
> kmemleak mechanism which unified most of kernel cosuming pages into kmemleak.

This may be helpful for debugging individual drivers but they could as
well call kmemleak_alloc/free() directly and not bother with new GFP and
page flags.

I wonder whether we could go the other way around. Add a
__GFP_NOLEAKTRACE (we have SLAB_NOLEAKTRACE for example) and pass it in
the places where we don't want pages to be scanned/tracked: page cache
pages (too many and they don't store pointers to other kernel objects),
sl*b, CMA etc. allocations (basically in all places where you have
kmemleak_alloc() calls, otherwise the pointers overlap and confuse
kmemleak).

-- 
Catalin