On 7/17/23 08:35, Yu Zhao wrote: > On Sun, Jul 16, 2023 at 6:00 PM Yin, Fengwei <fengwei.yin@xxxxxxxxx> wrote: >> >> On 7/15/2023 2:06 PM, Yu Zhao wrote: >>> There is a problem here that I didn't have the time to elaborate: we >>> can't mlock() a folio that is within the range but not fully mapped >>> because this folio can be on the deferred split queue. When the split >>> happens, those unmapped folios (not mapped by this vma but are mapped >>> into other vmas) will be stranded on the unevictable lru. >> >> This should be fine unless I missed something. During large folio split, >> the unmap_folio() will be migrate(anon)/unmap(file) folio. Folio will be >> munlocked in unmap_folio(). So the head/tail pages will be evictable always. > > It's close but not entirely accurate: munlock can fail on isolated folios. Yes. The munlock just clear PG_mlocked bit but with PG_unevictable left. Could this also happen against normal 4K page? I mean when user try to munlock a normal 4K page and this 4K page is isolated. So it become unevictable page? Regards Yin, Fengwei
