On Mon, Jun 20, 2022 at 04:29:11PM +0800, Muchun Song wrote: > > > Although it works, I think PageVmemmapSelfHosted() check for the 1st pfn's > > > vmemmap page is not always reliable. Since we reused PG_owner_priv_1 > > > as PG_vmemmap_self_hosted, the test is noly reliable for vmemmap page's > > > vmemmap page. Other non-vmemmap page can be flagged with PG_owner_priv_1. > > > So this check can be false-positive. Maybe the following code snippet is > > > the solution. > > > > How could that happen for pages used for backing a vmemmap? > > > > It cannot happen for memmap_on_memory case. Howwver, it can happen for other > cases. E.g. the 1st pfn (of boot memory block) whose vmemmap page may be flagged > as PG_owner_priv_1 (if PG_swapcache is set). Then, the check is false-positive. If this can really happen, which I am not that sure tbh, maybe a way out would be to just define a new page-type as we did in previous versions of memmap_on_memory. In that way we would not for flags, but for its type. But as I said, I am not entirely sure about the potential fallout of what you mention. -- Oscar Salvador SUSE Labs
