linux-kernel - Re: [PATCH -next] bootmem: remove the vmemmap pages from kmemleak in free_bootmem

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Message-Id: <8EC06FE1-3963-4F22-83DF-48B3EFAA62CA@linux.dev>
Date:   Fri, 19 Aug 2022 11:31:30 +0800
From:   Muchun Song <muchun.song@...ux.dev>
To:     Liu Shixin <liushixin2@...wei.com>
Cc:     Muchun Song <songmuchun@...edance.com>,
        Matthew Wilcox <willy@...radead.org>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Oscar Salvador <osalvador@...e.de>,
        Andrew Morton <akpm@...ux-foundation.org>,
        linux-kernel@...r.kernel.org, Linux MM <linux-mm@...ck.org>
Subject: Re: [PATCH -next] bootmem: remove the vmemmap pages from kmemleak in
 free_bootmem_page



> On Aug 18, 2022, at 21:21, Liu Shixin <liushixin2@...wei.com> wrote:
> 
> The vmemmap pages is marked by kmemleak when allocated from memblock.
> Remove it from kmemleak when free the page. Otherwise, when we reuse the
> page, kmemleak may report such an error and then stop working.
> 
> kmemleak: Cannot insert 0xffff98fb6eab3d40 into the object search tree (overlaps existing)
> kmemleak: Kernel memory leak detector disabled
> kmemleak: Object 0xffff98fb6be00000 (size 335544320):
> kmemleak:   comm "swapper", pid 0, jiffies 4294892296
> kmemleak:   min_count = 0
> kmemleak:   count = 0
> kmemleak:   flags = 0x1
> kmemleak:   checksum = 0
> kmemleak:   backtrace:
> 
> Fixes: f41f2ed43ca5 ("mm: hugetlb: free the vmemmap pages associated with each HugeTLB page")
> Signed-off-by: Liu Shixin <liushixin2@...wei.com>
> ---
> include/linux/bootmem_info.h | 6 ++++--
> 1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/include/linux/bootmem_info.h b/include/linux/bootmem_info.h
> index cc35d010fa94..899bc56948f7 100644
> --- a/include/linux/bootmem_info.h
> +++ b/include/linux/bootmem_info.h
> @@ -3,6 +3,7 @@
> #define __LINUX_BOOTMEM_INFO_H
> 
> #include <linux/mm.h>
> +#include <linux/kmemleak.h>
> 
> /*
>  * Types for free bootmem stored in page->lru.next. These have to be in
> @@ -38,9 +39,10 @@ static inline void free_bootmem_page(struct page *page)
> 	 */
> 	VM_BUG_ON_PAGE(page_ref_count(page) != 2, page);

I am wondering if we should fix put_page_bootmem() instead of
free_bootmem_page() since there are some users of put_page_bootmem()
to free a page allocated from memblock which also can be reused
afterwards.

Thanks.

> 
> -	if (magic == SECTION_INFO || magic == MIX_SECTION_INFO)
> +	if (magic == SECTION_INFO || magic == MIX_SECTION_INFO) {
> +		kmemleak_free_part(page_to_virt(page), PAGE_SIZE);
> 		put_page_bootmem(page);
> -	else
> +	} else
> 		VM_BUG_ON_PAGE(1, page);
> }
> #else
> -- 
> 2.25.1
> 
>