On 9 Feb 2024, at 15:46, Vlastimil Babka wrote: > On 2/9/24 20:40, Zi Yan wrote: >> On 9 Feb 2024, at 14:36, Zi Yan wrote: >> >>> On 9 Feb 2024, at 11:37, Vlastimil Babka wrote: >>> >>>> On 2/2/24 17:15, Zi Yan wrote: >>>> >>>> ... >>>> >>>>> /* >>>>> @@ -1835,9 +1857,17 @@ static struct folio *compaction_alloc(struct folio *src, unsigned long data) >>>>> static void compaction_free(struct folio *dst, unsigned long data) >>>>> { >>>>> struct compact_control *cc = (struct compact_control *)data; >>>>> + int order = folio_order(dst); >>>>> + struct page *page = &dst->page; >>>>> + >>>>> + folio_set_count(dst, 0); >>>> >>>> We can't change refcount to 0 like this, after it was already set to 1 and >>>> somebody else might have done get_page_unless_zero(). You need to either >>>> put_page_testzero() and if it's false, consider the page lost, or leave it >>>> refcounted and adjust the code to handle both refcounted and non-refcounted >>>> pages on the lists (the first option is simpler and shouldn't be too bad). >>> Got it. Will fix it with the first option. Thanks. >> >> Do you think we should have a WARN or WARN_ONCE if we lose a page here? > > No, no WARN, it all happens legitimately. It's only our compaction losing > the page - whoever would do the get_page_unless_zero() to inspect that page > would then have to put_page() which will free it back to page allocator. Got it. Thanks for the explanation. -- Best Regards, Yan, Zi
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