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Message-ID: <YakMQA1A75ZADeHi@arm.com>
Date: Thu, 2 Dec 2021 18:11:12 +0000
From: Catalin Marinas <catalin.marinas@....com>
To: Calvin Zhang <calvinzhang.cool@...il.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
Christoph Hellwig <hch@....de>,
Marek Szyprowski <m.szyprowski@...sung.com>,
Robin Murphy <robin.murphy@....com>,
Rob Herring <robh+dt@...nel.org>,
Frank Rowand <frowand.list@...il.com>,
devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-mm@...ck.org, iommu@...ts.linux-foundation.org
Subject: Re: [PATCH] mm: kmemleak: Ignore kmemleak scanning on CMA regions
On Sun, Nov 28, 2021 at 09:50:53AM +0800, Calvin Zhang wrote:
> On Sat, Nov 27, 2021 at 04:07:18PM -0800, Andrew Morton wrote:
> >On Fri, 26 Nov 2021 10:47:11 +0800 Calvin Zhang <calvinzhang.cool@...il.com> wrote:
> >> Just like this:
> >> commit 620951e27457 ("mm/cma: make kmemleak ignore CMA regions").
> >>
> >> Add kmemleak_ignore_phys() for CMA created from of reserved node.
[...]
> >The 620951e27457 changelog says "Without this, the kernel crashes...".
> >Does your patch also fix a crash? If so under what circumstances and
> >should we backport this fix into -stable kernels?
>
> No crash occurred. 620951e27457 avoids crashes caused by accessing
> highmem and it was fixed later. Now kmemleak_alloc_phys() and
> kmemleak_ignore_phys() skip highmem. This patch is based on the
> point that CMA regions don't contain pointers to other kmemleak
> objects, and ignores CMA regions from reserved memory as what
> 620951e27457 did.
Note that kmemleak_ignore() only works if there was a prior
kmemleak_alloc() on that address range. With the previous commit we get
this via the memblock_alloc_range() but I fail to see one on the
rmem_cma_setup() path.
--
Catalin
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