On 6/1/26 13:38, Christoph Hellwig wrote: > 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.
If p->count is 0 then indeed there's a zero-sized kvmalloc so p->pages == ZERO_SIZE_PTR but then nothing breaks because nothing tries to dereference it? msm_iommu_pagetable_prealloc_cleanup() has a "if (p->count > 0)" branch so it seems it's considered possible. But then the rest of the functions also seems working fine, i.e. kmem_cache_free_bulk() of zero size does nothing, kvfree() of ZERO_SIZE_PTR does nothing. It seems to me kmem_cache_alloc_bulk() returning true for size == 0 fits naturally in this world and is less likely to result in a gotcha?
