From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 9C29F385D78; Mon, 1 Jun 2026 08:16:36 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780301797; cv=none; b=QU1q6BK3LL8J1OBSub1qBODjWfdLNRDMfAIbMIjEc/4eoOkhkWi40M8BG4zYXZfNd44N7QDB6C7qHa7ht/ECeFbmc4Bq9wb9G/EB9f74t9+OnmcRNk/5RiwRYSc/IW+5YbWWOJPH1lMvAwGI6Skr/Usii7bNz1WZf9FbDir/rS8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780301797; c=relaxed/simple; bh=5Iw1lR61ssv5Isf7sRcLJH2Y715/4pxNJP8l8VISprI=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=RmTh/jCDNQH3jWt85gqCwGyh5dG7vYkZ4m9IOFb5oI0a5M3r95NQj+jUKX1SgvTKvveYpts7nWrsNn5YgvLwuYGUkM8HcAxBG7/33fLo+hX+cmhAal84H7Q1koz5qJkqI8aLIujf/2DmkjLFxeBPEpTO4Goyo+tfCGtU+x9TY5M= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=BapgHXqm; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="BapgHXqm" Received: by smtp.kernel.org (Postfix) with ESMTPSA id B4A2A1F00893; Mon, 1 Jun 2026 08:16:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1780301796; bh=7jvZqi8VkeRODB5KZOUNHa6HlOqHzuN+bUrucImc84I=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=BapgHXqmzEjlmgIoOeYSUlyeZ51lqH/ZOhNVuDeecVA6Z2r+IiW/BU4ZCKwAlXtgO DHxzBeLpOvsdHOAmSXVtET9xfot7Tefb/TJDvKr1ooDumPMiEbfuSLJTJ8wbsDGLCg MC1yp+/WAl6sEnceRcUzLtBPKj85SOfRCBtHzq76r5dnmEca8i4cLaN5PyrYUL0qmP 9dLAtNC/cJ5sCQP9BIyz0mfSIxAALpYHIYYnJZ2G+NBfLN8HSuaZUXKwTVlax/x0JR dBYR6a8d2a/nXD3M0+hcCj/ZsKcUHXZyEjsF6Q1DeY10FKa//I0x9xqYF7z/6FTzMi HjcK3n+tskndA== Message-ID: <58cc76e7-2348-443d-a989-2a06e61178af@kernel.org> Date: Mon, 1 Jun 2026 10:16:30 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm/slab: improve kmem_cache_alloc_bulk Content-Language: en-US To: Harry Yoo , Christoph Hellwig Cc: Andrew Morton , Mark Brown , Hao Li , Christoph Lameter , David Rientjes , Roman Gushchin , Jesper Dangaard Brouer , linux-arm-msm@vger.kernel.org, dri-devel@lists.freedesktop.org, freedreno@lists.freedesktop.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, io-uring@vger.kernel.org, kasan-dev@googlegroups.com, bpf@vger.kernel.org, netdev@vger.kernel.org, Alexander Lobakin , Boris Brezillon References: <20260528093437.2519248-1-hch@lst.de> <20260528093437.2519248-2-hch@lst.de> <5f7f90d8-cb32-4ffb-8f1c-0722aafbe869@kernel.org> <20260529135045.GA10647@lst.de> <5f3ba603-a6ad-4cf2-9a54-aebc10273c59@kernel.org> From: "Vlastimil Babka (SUSE)" Autocrypt: addr=vbabka@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 6/1/26 08:39, Harry Yoo wrote: > > > On 5/29/26 10:50 PM, Christoph Hellwig wrote: >> On Fri, May 29, 2026 at 01:54:48PM +0200, Vlastimil Babka (SUSE) wrote: >>> Thanks, I applied it to slab/for-7.2/alloc_bulk and merged to slab/for-next >>> (it's still yankable in case of issues) >>> >>> Did some fixups below (the comment was stale prior to the patch; restored >>> unlikely(), simplified one line). >>> >>> A test merge into yesterday's -next found a conflict in drivers/gpu/drm/ >>> panthor/panthor_mmu.c. Commit 1013bf53650e ("drm/panthor: Split >>> panthor_vm_prepare_map_op_ctx() to prepare for reclaim") moved the changed >>> codeto a new function panthor_vm_op_ctx_prealloc_pts(). >>> But it's solvable so no need for a complicated coordination I think. >> >> Ok, thanks. The two Sashiko complains also look like they had merrits, >> but I won't get to looking into them until Monday. > The review: > https://sashiko.dev/#/patchset/20260528093437.2519248-2-hch%40lst.de > > So there is a user who might call kmem_cache_alloc_bulk() with size = 0 I don't know if it can really happen there, but maybe DRM folks can tell us. > (although the comment says @size must be larger than 0!) and The comment is however new, the caller existed when there was no comment and the return value 0 when asked for 0 was working there. > kmem_cache_alloc_bulk() returning 0 was considered a success in that case. > > Either fixing kmem_cache_alloc_bulk() (and the comment) or fixing the > user sounds fine to me. Would it be wrong if we just returned true for size of 0? Would something else break? > And yeah freeing an object via kfree() allocated via kvmalloc is a bug... Yep.