Re: [PATCH v6 00/19] The new cgroup slab memory controller

[Qian Cai]

> On Jun 21, 2020, at 7:34 PM, Roman Gushchin <guro@xxxxxx> 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 canât 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