On Tue, Nov 24, 2020 at 03:56:22PM -0500, Andrea Arcangeli wrote: > Hello, > > On Tue, Nov 24, 2020 at 01:32:05PM +0000, Mel Gorman wrote: > > I would hope that is not the case because they are not meant to overlap. > > However, if the beginning of the pageblock was not the start of a zone > > then the pages would be valid but the pfn would still be outside the > > zone boundary. If it was reserved, the struct page is valid but not > > suitable for set_pfnblock_flags_mask. However, it is a concern in > > general because the potential is there that pages are isolated from the > > wrong zone. > > I guess we have more than one issue to correct in that function > because the same BUG_ON reproduced again even with the tentative patch > I posted earlier. > > So my guess is that the problematic reserved page isn't pointed by the > min_pfn, but it must have been pointed by the "highest" variable > calculated below? > > if (pfn >= highest) > highest = pageblock_start_pfn(pfn); > > When I looked at where "highest" comes from, it lacks > pageblock_pfn_to_page check (which was added around v5.7 to min_pfn). > > Is that the real bug, which may be fixed by something like this? (untested) > It's plausible as it is a potential source of leaking but as you note in another mail, it's surprising to me that valid struct pages, even if within memory holes and reserved would have broken node/zone information in the page flags. -- Mel Gorman SUSE Labs
