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a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1730759265; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=rdldSJbzGGB8VsbtXnsJM+dYQ2GkhY29L4a6wrfkKT4=; b=g+K8Rfkv0q/NDboUNiSx/wBoyw/QTUF83YOhQ/z1FsUx/kJRGnaFjIbdg9IgBjCc7xnG1r IxPKoEYGrRCW62Slms1K6Dlgn+KF+NMTZw4YDugSxObPGP5g9Cx/M9sKvtfe4VjSO6Qj+y brVlWBYWBf2CdmhB0CLg7H0E5BAfsOs= Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by nyc.source.kernel.org (Postfix) with ESMTP id 849FEA419B9; Mon, 4 Nov 2024 22:26:47 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id A17B9C4CECE; Mon, 4 Nov 2024 22:28:39 +0000 (UTC) Date: Mon, 4 Nov 2024 22:28:37 +0000 From: Catalin Marinas To: Vlastimil Babka Cc: Matthew Wilcox , Koichiro Den , Peter Collingbourne , cl@linux.com, penberg@kernel.org, rientjes@google.com, iamjoonsoo.kim@lge.com, akpm@linux-foundation.org, roman.gushchin@linux.dev, 42.hyeyoo@gmail.com, kees@kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: Re: [PATCH] mm/slab: fix warning caused by duplicate kmem_cache creation in kmem_buckets_create Message-ID: References: <20241104150837.2756047-1-koichiro.den@gmail.com> <8202821f-05bc-41f8-9de3-bf78899a7c7b@suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspam-User: X-Rspamd-Queue-Id: D92481C0010 X-Rspamd-Server: rspam01 X-Stat-Signature: of561b1eomr9s1eeithrrit1y37oa9o4 X-HE-Tag: 1730759261-14888 X-HE-Meta: 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 ROBFrIkG 8bvPqohJGkvp/XZOBkezyMZnpVlrVy4lios9b05FCOZo75nTwcBsoFJXOlJoUsPmz/CZ2zZUwCVxkiKdknZymVvCsshSUl++m+4A8PIoxxMR205VSQLSiStECDMiwmHnXwsqAi9tPDJfimbxCqQ8PQ1tvyJM1Cuyq50YvcXrdVKXmOVZyBnnDO77y3S+q/YYMAhRO9RtEGiC9m6tml4ja3MijaGeRnr1fTM3n0C6BT3dJpDauSde7y1w3zSZylS6ld4/K/7885R+Jcx/EmvcagX3KH0lEY/3cP0ndkFyFbxaanyHGbnJGsCIsc2mDe+pUl8+FekB8Fiz1gOUxzVNOgZpM8vML6Ks/iO0KhDI1FgV2Bi/nMJJUj0XLbDqw6SAkFBZ7Hut4dE2EERMAfKyRV7PVgqkc9/pm3hiWfzWAnayRAv3QJex04y5rfL4xHQJqrJ8TCxifv80cEV789lFB8s4CVA== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, Nov 04, 2024 at 10:22:37PM +0000, Catalin Marinas wrote: > On Mon, Nov 04, 2024 at 07:16:20PM +0100, Vlastimil Babka wrote: > > On 11/4/24 19:00, Matthew Wilcox wrote: > > > On Tue, Nov 05, 2024 at 12:08:37AM +0900, Koichiro Den wrote: > > >> Commit b035f5a6d852 ("mm: slab: reduce the kmalloc() minimum alignment > > >> if DMA bouncing possible") reduced ARCH_KMALLOC_MINALIGN to 8 on arm64. > > >> However, with KASAN_HW_TAGS enabled, arch_slab_minalign() becomes 16. > > >> This causes kmalloc_caches[*][8] to be aliased to kmalloc_caches[*][16], > > >> resulting in kmem_buckets_create() attempting to create a kmem_cache for > > >> size 16 twice. This duplication triggers warnings on boot: > > > > > > Wouldn't this be easier? > > > > They wanted it to depend on actual HW capability / kernel parameter, see > > d949a8155d13 ("mm: make minimum slab alignment a runtime property") > > > > Also Catalin's commit referenced above was part of the series that made the > > alignment more dynamic for other cases IIRC. So I doubt we can simply reduce > > it back to a build-time constant. > > I principle, I wouldn't reduce it back to constant though the 8 vs 16 > difference is not significant. It matter if one enables KASAN_HW_TAGS > and wants to run it on hardware without MTE, getting the *-8 caches > back. > > That said, I haven't managed to trigger this warning yet. Do I need > other config options than KASAN_HW_TAGS and DEBUG_VM? Ah, I was missing SLAB_BUCKETS. I'll have a look tomorrow. -- Catalin