linux-kernel - Re: [PATCH v1] Revert "mm: kmemleak: alloc gray object for reserved region with direct map"

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Date:   Wed, 25 Jan 2023 15:02:15 -0600
From:   Rob Herring <robh@...nel.org>
To:     "Isaac J. Manjarres" <isaacmanjarres@...gle.com>
Cc:     Catalin Marinas <catalin.marinas@....com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Frank Rowand <frowand.list@...il.com>, linux-mm@...ck.org,
        Saravana Kannan <saravanak@...gle.com>, stable@....kernel.org,
        Calvin Zhang <calvinzhang.cool@...il.com>,
        kernel-team@...roid.com, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1] Revert "mm: kmemleak: alloc gray object for reserved
 region with direct map"

On Tue, Jan 24, 2023 at 03:02:54PM -0800, Isaac J. Manjarres wrote:
> This reverts commit 972fa3a7c17c9d60212e32ecc0205dc585b1e769.
> 
> Kmemleak operates by periodically scanning memory regions for pointers
> to allocated memory blocks to determine if they are leaked or not.
> However, reserved memory regions can be used for DMA transactions
> between a device and a CPU, and thus, wouldn't contain pointers to
> allocated memory blocks, making them inappropriate for kmemleak to
> scan. Thus, revert this commit.

Both commits talk about the same type of memory as CMA is used for DMA. 
Neither commit tells me what are the implications of kmemleak scanning 
or not scanning the region? Are there false positives?

> Cc: stable@...r.kernel.org # 5.17+
> Cc: Calvin Zhang <calvinzhang.cool@...il.com>
> Signed-off-by: Isaac J. Manjarres <isaacmanjarres@...gle.com>
> ---
>  drivers/of/fdt.c | 6 +-----
>  1 file changed, 1 insertion(+), 5 deletions(-)