Messages in this thread | | | From | Linus Torvalds <> | Date | Wed, 30 Mar 2022 15:27:04 -0700 | Subject | Re: [PATCH] mm: page_alloc: validate buddy before check its migratetype. |
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On Wed, Mar 30, 2022 at 3:12 PM Zi Yan <zi.yan@sent.com> wrote: > > Whenever a buddy page is found, page_is_buddy() should be called to > check its validity. Add the missing check during pageblock merge check.
Applied.
> buddy_pfn = __find_buddy_pfn(pfn, order); > buddy = page + (buddy_pfn - pfn); > + > + if (!page_is_buddy(page, buddy, order)) > + goto done_merging;
I wonder if that sequence shouldn't be made some helper function.
Also, looking around, I will note that unset_migratetype_isolate() in mm/page_isolation.c is missing that "page_is_buddy()" check.
I _think_ it's probably ok because we checked
if (PageBuddy(page)) {
on the (original, non-puddy) page, and then we only use the buddy page pointer for that
if (!is_migrate_isolate_page(buddy)) {
and it's been like that for a _loong_ time.
But honestly, it feels like we would be better off with always having the page_is_buddy() check anyway.
Or is there some reason why we don't want it here?
Linus
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