Messages in this thread | | | Date | Mon, 9 Oct 2023 10:22:52 +0200 | Subject | Re: [RESEND PATCH] mm: slab: Do not create kmalloc caches smaller than arch_slab_minalign() | From | Vlastimil Babka <> |
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On 10/6/23 18:39, Catalin Marinas wrote: > Commit b035f5a6d852 ("mm: slab: reduce the kmalloc() minimum alignment > if DMA bouncing possible") allows architectures with non-coherent DMA to > define a small ARCH_KMALLOC_MINALIGN (e.g. sizeof(unsigned long long)) > and this has been enabled on arm64. With KASAN_HW_TAGS enabled, however, > ARCH_SLAB_MINALIGN becomes 16 on arm64 (arch_slab_minalign() dynamically > selects it since commit d949a8155d13 ("mm: make minimum slab alignment a > runtime property")). This can lead to a situation where kmalloc-8 caches > are attempted to be created with a kmem_caches.size aligned to 16. When > the cache is mergeable, it can lead to kernel warnings like: > > sysfs: cannot create duplicate filename '/kernel/slab/:d-0000016' > CPU: 0 PID: 1 Comm: swapper/0 Not tainted 6.6.0-rc1-00001-gda98843cd306-dirty #5 > Hardware name: QEMU QEMU Virtual Machine, BIOS 0.0.0 02/06/2015 > Call trace: > dump_backtrace+0x90/0xe8 > show_stack+0x18/0x24 > dump_stack_lvl+0x48/0x60 > dump_stack+0x18/0x24 > sysfs_warn_dup+0x64/0x80 > sysfs_create_dir_ns+0xe8/0x108 > kobject_add_internal+0x98/0x264 > kobject_init_and_add+0x8c/0xd8 > sysfs_slab_add+0x12c/0x248 > slab_sysfs_init+0x98/0x14c > do_one_initcall+0x6c/0x1b0 > kernel_init_freeable+0x1c0/0x288 > kernel_init+0x24/0x1e0 > ret_from_fork+0x10/0x20 > kobject: kobject_add_internal failed for :d-0000016 with -EEXIST, don't try to register things with the same name in the same directory. > SLUB: Unable to add boot slab dma-kmalloc-8 to sysfs > > Limit the __kmalloc_minalign() return value (used to create the > kmalloc-* caches) to arch_slab_minalign() so that kmalloc-8 caches are > skipped when KASAN_HW_TAGS is enabled (both config and runtime). > > Fixes: b035f5a6d852 ("mm: slab: reduce the kmalloc() minimum alignment if DMA bouncing possible") > Signed-off-by: Catalin Marinas <catalin.marinas@arm.com> > Reported-by: Mark Rutland <mark.rutland@arm.com> > Cc: Andrew Morton <akpm@linux-foundation.org> > Cc: Vlastimil Babka <vbabka@suse.cz> > Cc: Peter Collingbourne <pcc@google.com> > Cc: <stable@vger.kernel.org> # 6.5.x > --- > > The previous post was messed up by my git send-email configuration, so > sending it again. Also cc'ing Vlastimil since he reviewed the previous > slab changes for ARCH_KMALLOC_MINALIGN. Thanks.
It also touches only slab files so I can take it via slab tree.
> mm/slab_common.c | 7 +++++-- > 1 file changed, 5 insertions(+), 2 deletions(-) > > diff --git a/mm/slab_common.c b/mm/slab_common.c > index cd71f9581e67..8b45922ed295 100644 > --- a/mm/slab_common.c > +++ b/mm/slab_common.c > @@ -895,10 +895,13 @@ void __init setup_kmalloc_cache_index_table(void) > > static unsigned int __kmalloc_minalign(void) > { > + unsigned int minalign = dma_get_cache_alignment(); > + > if (IS_ENABLED(CONFIG_DMA_BOUNCE_UNALIGNED_KMALLOC) && > is_swiotlb_allocated()) > - return ARCH_KMALLOC_MINALIGN; > - return dma_get_cache_alignment(); > + minalign = ARCH_KMALLOC_MINALIGN; > + > + return ALIGN(minalign, arch_slab_minalign());
Could it be max() instead of ALIGN()? It would be more obvious, at least to me :)
> } > > void __init
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