linux-kernel - Re: powerpc/mm: Don't report hugepage tables as memory leaks when using kmemleak

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Message-Id: <42QjK73m02z9s8J@ozlabs.org>
Date:   Thu,  4 Oct 2018 16:14:35 +1000 (AEST)
From:   Michael Ellerman <patch-notifications@...erman.id.au>
To:     Christophe Leroy <christophe.leroy@....fr>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>
Cc:     linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: Re: powerpc/mm: Don't report hugepage tables as memory leaks when using kmemleak

On Mon, 2018-08-13 at 13:19:52 UTC, Christophe Leroy wrote:
> When a process allocates a hugepage, the following leak is
> reported by kmemleak. This is a false positive which is
> due to the pointer to the table being stored in the PGD
> as physical memory address and not virtual memory pointer.
> 
> unreferenced object 0xc30f8200 (size 512):
>   comm "mmap", pid 374, jiffies 4872494 (age 627.630s)
>   hex dump (first 32 bytes):
>     00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
>     00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
>   backtrace:
>     [<e32b68da>] huge_pte_alloc+0xdc/0x1f8
>     [<9e0df1e1>] hugetlb_fault+0x560/0x8f8
>     [<7938ec6c>] follow_hugetlb_page+0x14c/0x44c
>     [<afbdb405>] __get_user_pages+0x1c4/0x3dc
>     [<b8fd7cd9>] __mm_populate+0xac/0x140
>     [<3215421e>] vm_mmap_pgoff+0xb4/0xb8
>     [<c148db69>] ksys_mmap_pgoff+0xcc/0x1fc
>     [<4fcd760f>] ret_from_syscall+0x0/0x38
> 
> See commit a984506c542e2 ("powerpc/mm: Don't report PUDs as
> memory leaks when using kmemleak") for detailed explanation.
> 
> To fix that, this patch tells kmemleak to ignore the allocated
> hugepage table.
> 
> Signed-off-by: Christophe Leroy <christophe.leroy@....fr>

Applied to powerpc next, thanks.

https://git.kernel.org/powerpc/c/803d690e68f0c5230183f1a42c7d50

cheers