2022-09-20 13:21:28

by zhaoyang.huang

Subject: [RFC PATCH] mm: track bad page via kmemleak

From: Zhaoyang Huang <[email protected]>

Bad pages will failed go back to allocator and leaved as orphan pages, track
them down via kmemleak.

Signed-off-by: Zhaoyang Huang <[email protected]>
---
mm/page_alloc.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index e5486d4..24f682e 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1408,7 +1408,7 @@ static __always_inline bool free_pages_prepare(struct page *page,
__memcg_kmem_uncharge_page(page, order);
reset_page_owner(page, order);
page_table_check_free(page, order);
- return false;
+ goto err;
}

/*
@@ -1442,7 +1442,7 @@ static __always_inline bool free_pages_prepare(struct page *page,
if (check_free)
bad += check_free_page(page);
if (bad)
- return false;
+ goto err;

page_cpupid_reset_last(page);
page->flags &= ~PAGE_FLAGS_CHECK_AT_PREP;
@@ -1486,6 +1486,10 @@ static __always_inline bool free_pages_prepare(struct page *page,
debug_pagealloc_unmap_pages(page, 1 << order);

return true;
+err:
+ kmemleak_alloc(page_address(page), PAGE_SIZE << order, 1, GFP_KERNEL);
+ return false;
+
}

#ifdef CONFIG_DEBUG_VM
--
1.9.1

2022-10-28 12:22:37

by Catalin Marinas

Subject: Re: [RFC PATCH] mm: track bad page via kmemleak

(sorry, I missed this last month when it was posted)

On Tue, Sep 20, 2022 at 09:11:08PM +0800, zhaoyang.huang wrote:
> From: Zhaoyang Huang <[email protected]>
>
> Bad pages will failed go back to allocator and leaved as orphan pages, track
> them down via kmemleak.
>
> Signed-off-by: Zhaoyang Huang <[email protected]>
> ---
> mm/page_alloc.c | 8 ++++++--
> 1 file changed, 6 insertions(+), 2 deletions(-)
>
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index e5486d4..24f682e 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -1408,7 +1408,7 @@ static __always_inline bool free_pages_prepare(struct page *page,
> __memcg_kmem_uncharge_page(page, order);
> reset_page_owner(page, order);
> page_table_check_free(page, order);
> - return false;
> + goto err;
> }
>
> /*
> @@ -1442,7 +1442,7 @@ static __always_inline bool free_pages_prepare(struct page *page,
> if (check_free)
> bad += check_free_page(page);
> if (bad)
> - return false;
> + goto err;
>
> page_cpupid_reset_last(page);
> page->flags &= ~PAGE_FLAGS_CHECK_AT_PREP;
> @@ -1486,6 +1486,10 @@ static __always_inline bool free_pages_prepare(struct page *page,
> debug_pagealloc_unmap_pages(page, 1 << order);
>
> return true;
> +err:
> + kmemleak_alloc(page_address(page), PAGE_SIZE << order, 1, GFP_KERNEL);
> + return false;
> +
> }

What's the aim of this tracking? First of all, that's a HWPoison page
and it should note be touched, so the min_count should be -1 otherwise
kmemleak will try to read it for references to other objects.

Now, if all you need is a list of the bad pages, I don't think that's
kmemleak's job. Maybe add them to a list and expose it somewhere else
via debugfs.

--
Catalin