From: Nathan Chancellor <nathan@kernel.org>
To: linux-kernel@vger.kernel.org
Cc: akpm@linux-foundation.org, cl@linux.com, guro@fb.com,
iamjoonsoo.kim@lge.com, linux-mm@kvack.org, mhocko@suse.com,
mm-commits@vger.kernel.org, penberg@kernel.org,
rientjes@google.com, shakeelb@google.com,
songmuchun@bytedance.com, torvalds@linux-foundation.org,
vbabka@suse.cz
Subject: Re: [patch 6/7] slub: fix unreclaimable slab stat for bulk free
Date: Sat, 31 Jul 2021 15:18:06 -0700 [thread overview]
Message-ID: <YQXMHnWRsmfzKK00@archlinux-ax161> (raw)
In-Reply-To: <20210729215350.SZC9InNuL%akpm@linux-foundation.org>
On Thu, Jul 29, 2021 at 02:53:50PM -0700, Andrew Morton wrote:
> From: Shakeel Butt <shakeelb@google.com>
> Subject: slub: fix unreclaimable slab stat for bulk free
>
> SLUB uses page allocator for higher order allocations and update
> unreclaimable slab stat for such allocations. At the moment, the bulk
> free for SLUB does not share code with normal free code path for these
> type of allocations and have missed the stat update. So, fix the stat
> update by common code. The user visible impact of the bug is the
> potential of inconsistent unreclaimable slab stat visible through meminfo
> and vmstat.
>
> Link: https://lkml.kernel.org/r/20210728155354.3440560-1-shakeelb@google.com
> Fixes: 6a486c0ad4dc ("mm, sl[ou]b: improve memory accounting")
> Signed-off-by: Shakeel Butt <shakeelb@google.com>
> Acked-by: Michal Hocko <mhocko@suse.com>
> Acked-by: Roman Gushchin <guro@fb.com>
> Reviewed-by: Muchun Song <songmuchun@bytedance.com>
> Cc: Christoph Lameter <cl@linux.com>
> Cc: Pekka Enberg <penberg@kernel.org>
> Cc: David Rientjes <rientjes@google.com>
> Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
> Cc: Vlastimil Babka <vbabka@suse.cz>
> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
> ---
>
> mm/slub.c | 22 ++++++++++++----------
> 1 file changed, 12 insertions(+), 10 deletions(-)
>
> --- a/mm/slub.c~slub-fix-unreclaimable-slab-stat-for-bulk-free
> +++ a/mm/slub.c
> @@ -3236,6 +3236,16 @@ struct detached_freelist {
> struct kmem_cache *s;
> };
>
> +static inline void free_nonslab_page(struct page *page)
> +{
> + unsigned int order = compound_order(page);
> +
> + VM_BUG_ON_PAGE(!PageCompound(page), page);
> + kfree_hook(page_address(page));
> + mod_lruvec_page_state(page, NR_SLAB_UNRECLAIMABLE_B, -(PAGE_SIZE << order));
> + __free_pages(page, order);
> +}
> +
> /*
> * This function progressively scans the array with free objects (with
> * a limited look ahead) and extract objects belonging to the same
> @@ -3272,9 +3282,7 @@ int build_detached_freelist(struct kmem_
> if (!s) {
> /* Handle kalloc'ed objects */
> if (unlikely(!PageSlab(page))) {
> - BUG_ON(!PageCompound(page));
> - kfree_hook(object);
> - __free_pages(page, compound_order(page));
> + free_nonslab_page(page);
> p[size] = NULL; /* mark object processed */
> return size;
> }
> @@ -4250,13 +4258,7 @@ void kfree(const void *x)
>
> page = virt_to_head_page(x);
> if (unlikely(!PageSlab(page))) {
> - unsigned int order = compound_order(page);
> -
> - BUG_ON(!PageCompound(page));
> - kfree_hook(object);
> - mod_lruvec_page_state(page, NR_SLAB_UNRECLAIMABLE_B,
> - -(PAGE_SIZE << order));
> - __free_pages(page, order);
> + free_nonslab_page(page);
> return;
> }
> slab_free(page->slab_cache, page, object, NULL, 1, _RET_IP_);
> _
This patch, now in mainline as commit f227f0faf63b ("slub: fix
unreclaimable slab stat for bulk free") causes the KASAN KUnit test
kmalloc_pagealloc_invalid_free to no longer fail:
[ 0.000000] Linux version 5.14.0-rc3-00066-gf227f0faf63b (nathan@archlinux-ax161) (x86_64-linux-gcc (GCC) 11.2.0, GNU ld (GNU Binutils) 2.37) #1 SMP Sat Jul 31 15:08:11 MST 2021
...
[ 5.717678] # kmalloc_pagealloc_invalid_free: EXPECTATION FAILED at lib/test_kasan.c:203
[ 5.717678] KASAN failure expected in "kfree(ptr + 1)", but none occurred
[ 5.718909] not ok 6 - kmalloc_pagealloc_invalid_free
...
[ 9.481520] not ok 1 - kasan
The previous commit is fine:
[ 0.000000] Linux version 5.14.0-rc3-00065-gb5916c025432 (nathan@archlinux-ax161) (x86_64-linux-gcc (GCC) 11.2.0, GNU ld (GNU Binutils) 2.37) #1 SMP Sat Jul 31 15:05:09 MST 2021
...
[ 9.347598] ok 1 - kasan
I am by no means a KASAN or mm/ expert, I noticed this when trying to
test KASAN with clang for ClangBuiltLinux's CI, so it does not appear to
be compiler dependent. It is reproducible for me in QEMU with
x86_64_defconfig + CONFIG_KASAN=y + CONFIG_KUNIT=y +
CONFIG_KASAN_KUNIT_TEST=y.
Please let me know if there is any other information I can provide or
testing I can do.
Cheers,
Nathan
next prev parent reply other threads:[~2021-07-31 22:18 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-29 21:52 incoming Andrew Morton
2021-07-29 21:53 ` [patch 1/7] lib/test_string.c: move string selftest in the Runtime Testing menu Andrew Morton
2021-07-29 21:53 ` [patch 2/7] ocfs2: fix zero out valid data Andrew Morton
2021-07-29 21:53 ` [patch 3/7] ocfs2: issue zeroout to EOF blocks Andrew Morton
2021-07-29 21:53 ` [patch 4/7] mm: memcontrol: fix blocking rstat function called from atomic cgroup1 thresholding code Andrew Morton
2021-07-29 21:53 ` [patch 5/7] mm/migrate: fix NR_ISOLATED corruption on 64-bit Andrew Morton
2021-07-29 21:53 ` [patch 6/7] slub: fix unreclaimable slab stat for bulk free Andrew Morton
2021-07-31 22:18 ` Nathan Chancellor [this message]
2021-08-01 5:32 ` Shakeel Butt
2021-07-29 21:53 ` [patch 7/7] mm/memcg: fix NULL pointer dereference in memcg_slab_free_hook() Andrew Morton
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