Re: [PATCH v4 13/35] mm, slub: do initial checks in ___slab_alloc() with irqs enabled

[Vlastimil Babka]

On 8/5/21 5:19 PM, Vlastimil Babka wrote:
> As another step of shortening irq disabled sections in ___slab_alloc(), delay
> disabling irqs until we pass the initial checks if there is a cached percpu
> slab and it's suitable for our allocation.
> 
> Now we have to recheck c->page after actually disabling irqs as an allocation
> in irq handler might have replaced it.

Please add an extra paragraph that related to the fixup below (which I
assume will be squashed as usual):

Because we call pfmemalloc_match() as one of the checks, we might hit
VM_BUG_ON_PAGE(!PageSlab(page)) in PageSlabPfmemalloc in case we get
interrupted and the page is freed. Thus introduce a
pfmemalloc_match_unsafe() variant that lacks the PageSlab check.

> Signed-off-by: Vlastimil Babka <vbabka@xxxxxxx>
> Acked-by: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>

And the fixup:
----8<----