Re: [PATCH] mm, slab, slub: clear the slab_cache field when freeing page

[David Rientjes]

On Thu, 10 Dec 2020, Vlastimil Babka wrote:

> The page allocator expects that page->mapping is NULL for a page being freed.
> SLAB and SLUB use the slab_cache field which is in union with mapping, but
> before freeing the page, the field is referenced with the "mapping" name when
> set to NULL.
> 
> It's IMHO more correct (albeit functionally the same) to use the slab_cache
> name as that's the field we use in SL*B, and document why we clear it in a
> comment (we don't clear fields such as s_mem or freelist, as page allocator
> doesn't care about those). While using the 'mapping' name would automagically
> keep the code correct if the unions in struct page changed, such changes should
> be done consciously and needed changes evaluated - the comment should help with
> that.
> 
> Signed-off-by: Vlastimil Babka <vbabka@xxxxxxx>

Acked-by: David Rientjes <rientjes@xxxxxxxxxx>