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Date: Mon, 1 Jun 2026 13:38:31 +0200
From: Christoph Hellwig <hch@lst.de>
To: "Vlastimil Babka (SUSE)" <vbabka@kernel.org>
Cc: Harry Yoo <harry@kernel.org>, Christoph Hellwig <hch@lst.de>,
	Andrew Morton <akpm@linux-foundation.org>,
	Mark Brown <broonie@kernel.org>, Hao Li <hao.li@linux.dev>,
	Christoph Lameter <cl@gentwo.org>,
	David Rientjes <rientjes@google.com>,
	Roman Gushchin <roman.gushchin@linux.dev>,
	Jesper Dangaard Brouer <hawk@kernel.org>,
	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 <aleksander.lobakin@intel.com>,
	Boris Brezillon <boris.brezillon@collabora.com>
Subject: Re: [PATCH] mm/slab: improve kmem_cache_alloc_bulk
Message-ID: <20260601113831.GA25535@lst.de>
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> <58cc76e7-2348-443d-a989-2a06e61178af@kernel.org>
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On Mon, Jun 01, 2026 at 10:16:30AM +0200, Vlastimil Babka (SUSE) wrote:
> > 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?

I don't think it is wrong per se, but it feels like the wrong kind of
API.  I.e. I don't think the MSM caller actually wants this, as they'd
also do a zero-sized kvmalloc.