From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 646D4E95A91 for ; Mon, 9 Oct 2023 11:20:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1346197AbjJILUk (ORCPT ); Mon, 9 Oct 2023 07:20:40 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46594 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1345822AbjJILUi (ORCPT ); Mon, 9 Oct 2023 07:20:38 -0400 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1CFF999 for ; Mon, 9 Oct 2023 04:20:37 -0700 (PDT) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 339EFC433C7; Mon, 9 Oct 2023 11:20:35 +0000 (UTC) Date: Mon, 9 Oct 2023 12:20:32 +0100 From: Catalin Marinas To: Vlastimil Babka Cc: linux-mm@kvack.org, Andrew Morton , linux-kernel@vger.kernel.org, Mark Rutland , Peter Collingbourne , Petr Tesarik Subject: Re: [RESEND PATCH] mm: slab: Do not create kmalloc caches smaller than arch_slab_minalign() Message-ID: References: <20231006163934.3273940-1-catalin.marinas@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Oct 09, 2023 at 10:22:52AM +0200, Vlastimil Babka wrote: > 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 > > Reported-by: Mark Rutland > > Cc: Andrew Morton > > Cc: Vlastimil Babka > > Cc: Peter Collingbourne > > Cc: # 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. Thanks. > > 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 :) Yeah, max() would do since they are all a power of two. Do you want me to repost? -- Catalin