On Thu, Jul 29, 2021 at 02:53:50PM -0700, Andrew Morton wrote: > From: Shakeel Butt <shakeelb@xxxxxxxxxx> > 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@xxxxxxxxxx > Fixes: 6a486c0ad4dc ("mm, sl[ou]b: improve memory accounting") > Signed-off-by: Shakeel Butt <shakeelb@xxxxxxxxxx> > Acked-by: Michal Hocko <mhocko@xxxxxxxx> > Acked-by: Roman Gushchin <guro@xxxxxx> > Reviewed-by: Muchun Song <songmuchun@xxxxxxxxxxxxx> > Cc: Christoph Lameter <cl@xxxxxxxxx> > Cc: Pekka Enberg <penberg@xxxxxxxxxx> > Cc: David Rientjes <rientjes@xxxxxxxxxx> > Cc: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx> > Cc: Vlastimil Babka <vbabka@xxxxxxx> > Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> > --- > > 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
