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Date: Wed, 27 May 2026 14:20:13 +0200
From: Christoph Hellwig <hch@lst.de>
To: "Vlastimil Babka (SUSE)" <vbabka@kernel.org>
Cc: Christoph Hellwig <hch@lst.de>, Harry Yoo <harry@kernel.org>,
	Andrew Morton <akpm@linux-foundation.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
Subject: Re: [PATCH] mm/slab: improve kmem_cache_alloc_bulk
Message-ID: <20260527122013.GA6765@lst.de>
References: <20260527070239.2252948-1-hch@lst.de> <20260527070239.2252948-2-hch@lst.de> <f7f35169-f77d-4678-8797-a2ad00d89e6c@kernel.org>
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On Wed, May 27, 2026 at 11:38:21AM +0200, Vlastimil Babka (SUSE) wrote:
> On 5/27/26 09:02, 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 <hch@lst.de>
> 
> Would 0 / -ENOMEM be more like what people would expect? I guess both that
> and bool are better than the current API.

I find an errno return where the API could not return anything but the
specific error code a bit odd.  But even that would be a lot better
than the current version.