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 44B613C3BF3; Fri, 29 May 2026 11:54:53 +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=1780055695; cv=none; b=RCHQAIG80pyoqi0oWQmB1fd4Nzb6sjBjcQnES6onov1gmepc2zopST4xwrDl7M9LVokaI8AFfQfmqImTC6P8sVzyKxaFtzxiM4oD9TuOSdGourwEfZ/53GJyXTxlsGnL0opGBQbzth/fZO6E9rconb3PDQF0EaSsUb8mKWfpdHA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780055695; c=relaxed/simple; bh=CploV4r1XHi0hyyHrOSw/drP95odjiL6JuuR/nNDCpc=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=FAku3iLN1Z4Y4uHRBqm8sIZJNZyi9YYm0r0Vdod70qKhvgVNn//U+a+x5FgdrhTI59B8u3rSDAbJt2k1uQJY6WhxpfucJvH+ZNRiaf4V5nNW3yXJcx/mcqNCG8zd4ccVVxW+pxnE6AQCsBUJj/WYwmk2lcEKymmyd3qCmYZz4Ig= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=L8VZz9V7; 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="L8VZz9V7" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 298511F00893; Fri, 29 May 2026 11:54:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1780055693; bh=wDOsRW9HSX03yxtZDtOoclJqvTh9mPV1pfPcH0+q2no=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=L8VZz9V7K1eN2jdYePACCXZ60MYUhFC1fOihSN+0H+7dhVQgUxdGJ9EQdJmCDTbwW G+lY0xHDWzx6pTWX1lLWl/0EpNCsU5b9yHlXtO5sbBEMs7G5VmlF0dXcZ9v/DGu76f /viJGQXlwamh7rHUkI0iAX99Shho8pimXeoM0y7KNHlU+cpwDo6MSIljUf43lop+B4 Y/IKFYrX4MCpwS9OMGK+k+HTotpqSCbAaZXWldCVwdTAjK0G+boxDWKQ2C5xXoy/Dg Frr8k2GRRRiGohLe6GdGc+rFcv3VqLP0ZveFBiJjWHREuNVs5EyBZwfujpGuPitREW 03hx7I5WrTEiQ== Message-ID: <5f7f90d8-cb32-4ffb-8f1c-0722aafbe869@kernel.org> Date: Fri, 29 May 2026 13:54:48 +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: Christoph Hellwig , Harry Yoo , Andrew Morton , Mark Brown Cc: 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> From: "Vlastimil Babka (SUSE)" Autocrypt: addr=vbabka@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 5/28/26 11:34, Christoph Hellwig wrote: > The kmem_cache_alloc_bulk return value is weird. It returns the number > of allocated objects, but that must always be 0 or the requested number > based on the implementations and the handling in the callers, but that > assumption is not actually documented anywhere, which confuses automated > review tools. > > Fix this by returning a bool if the allocation succeeded and adding a > kerneldoc comment explaining the API. > > Signed-off-by: Christoph Hellwig > Reviewed-by: Alexander Lobakin # skbuff > --- > drivers/gpu/drm/msm/msm_iommu.c | 6 +-- > drivers/gpu/drm/panthor/panthor_mmu.c | 13 +++--- > include/linux/slab.h | 6 ++- > io_uring/io_uring.c | 23 ++++------- > lib/test_meminit.c | 23 +++++------ > mm/kasan/kasan_test_c.c | 5 +-- > mm/kfence/kfence_test.c | 9 ++-- > mm/slub.c | 59 +++++++++++++++------------ > net/bpf/test_run.c | 7 ++-- > net/core/skbuff.c | 24 ++++++----- > tools/include/linux/slab.h | 2 +- > tools/testing/shared/linux.c | 19 ++++----- > 12 files changed, 97 insertions(+), 99 deletions(-) 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. diff --git a/mm/slub.c b/mm/slub.c index 6caf6f3ceeed..711df528c9a6 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -7372,10 +7372,7 @@ bool kmem_cache_alloc_bulk_noprof(struct kmem_cache *s, gfp_t flags, } out: - /* - * memcg and kmem_cache debug support and memory initialization. - * Done outside of the IRQ disabled fastpath loop. - */ + /* memcg and kmem_cache debug support and memory initialization */ return likely(slab_post_alloc_hook(s, NULL, flags, size, p, slab_want_init_on_alloc(flags, s), s->object_size)); } diff --git a/net/bpf/test_run.c b/net/bpf/test_run.c index 99ab9ddb05e3..dbf0d8eae8d8 100644 --- a/net/bpf/test_run.c +++ b/net/bpf/test_run.c @@ -246,8 +246,8 @@ static int xdp_recv_frames(struct xdp_frame **frames, int nframes, int i; LIST_HEAD(list); - if (!kmem_cache_alloc_bulk(net_hotdata.skbuff_cache, gfp, nframes, - (void **)skbs)) { + if (unlikely(!kmem_cache_alloc_bulk(net_hotdata.skbuff_cache, gfp, + nframes, (void **)skbs))) { for (i = 0; i < nframes; i++) xdp_return_frame(frames[i]); return -ENOMEM; diff --git a/tools/testing/shared/linux.c b/tools/testing/shared/linux.c index e9c3bc9b3272..e0a0693df08f 100644 --- a/tools/testing/shared/linux.c +++ b/tools/testing/shared/linux.c @@ -301,7 +301,7 @@ int kmem_cache_refill_sheaf(struct kmem_cache *s, gfp_t gfp, if (!kmem_cache_alloc_bulk(s, gfp, size - sheaf->size, &sheaf->objects[sheaf->size])) return -ENOMEM; - sheaf->size += (size - sheaf->size); + sheaf->size = size; return 0; }