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Date: Sun, 21 Jun 2020 19:53:23 -0400 From: Qian Cai <cai@....pw> To: Roman Gushchin <guro@...com> Cc: Andrew Morton <akpm@...ux-foundation.org>, Christoph Lameter <cl@...ux.com>, Johannes Weiner <hannes@...xchg.org>, Michal Hocko <mhocko@...nel.org>, Shakeel Butt <shakeelb@...gle.com>, linux-mm@...ck.org, Vlastimil Babka <vbabka@...e.cz>, kernel-team@...com, linux-kernel@...r.kernel.org, catalin.marinas@....com Subject: Re: [PATCH v6 00/19] The new cgroup slab memory controller > On Jun 21, 2020, at 7:34 PM, Roman Gushchin <guro@...com> wrote: > > My wild guess is that kmemleak is getting confused by modifying the lowest > bit of page->mem_cgroup/obhj_cgroups pointer: > > struct page { > ... > union { > struct mem_cgroup *mem_cgroup; > struct obj_cgroup **obj_cgroups; > }; > ... > } > > We're using the lowest bit to distinguish between a "normal" mem_cgroup > pointer and a vector of obj_cgroup pointers. > > This pointer to obj_cgroup vector is saved only here, so if we're modifying > the address, I guess it's what makes kmemleak think that there is a leak. > > Or do you have a real leak? The point is that we can’t have a patchset in the current form to totally render kmemleak useless with so many even false positives. Anyway, this is rather easy to reproduce where I am able to reproduce on multiple bare-metal machines by just booting it. # echo scan > /sys/kernel/debug/kmemleak # cat /sys/kernel/debug/kmemleak
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