On Thu, Mar 3, 2022 at 9:06 PM David Hildenbrand <david@xxxxxxxxxx> wrote: > > Hi, > > This probably bounces on the list due to html junk from the gmail app. > > What happened to > > https://lore.kernel.org/linux-mm/20220131162940.210846-10-david@xxxxxxxxxx/ > > Included in the very series mentioned below? > > Was this silently dropped due to folio conversion collisions? :/ I really didn't notice you already proposed this. Maybe folio conversion, maybe mlock cleanup, I can't tell. But anyway this patch needs to get rebased. I will submit v2 to solve the comment, will add your signed-off-by. > > Yang Shi <shy828301@xxxxxxxxx> schrieb am Do. 3. März 2022 um 23:20: >> >> The commit c444eb564fb1 ("mm: thp: make the THP mapcount atomic against >> __split_huge_pmd_locked()") locked the page for PMD split to make >> mapcount stable for reuse_swap_page(), then commit 1c2f67308af4 ("mm: >> thp: fix MADV_REMOVE deadlock on shmem THP") reduce the scope to >> anonymous page only. >> >> However COW has not used mapcount to determine if the page is shared or >> not anymore due to the COW fixes [1] from David Hildenbrand and the >> reuse_swap_page() was removed as well. So PMD split doesn't have to >> lock the page anymore. This patch basically reverted the above two >> commits. >> >> [1] https://lore.kernel.org/linux-mm/20220131162940.210846-1-david@xxxxxxxxxx/ >> >> Cc: David Hildenbrand <david@xxxxxxxxxx> >> Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx> >> Cc: Hugh Dickins <hughd@xxxxxxxxxx> >> Cc: "Kirill A . Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx> >> Signed-off-by: Yang Shi <shy828301@xxxxxxxxx> >> --- >> mm/huge_memory.c | 44 +++++--------------------------------------- >> 1 file changed, 5 insertions(+), 39 deletions(-) >> >> diff --git a/mm/huge_memory.c b/mm/huge_memory.c >> index b49e1a11df2e..daaa698bd273 100644 >> --- a/mm/huge_memory.c >> +++ b/mm/huge_memory.c >> @@ -2134,8 +2134,6 @@ void __split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd, >> { >> spinlock_t *ptl; >> struct mmu_notifier_range range; >> - bool do_unlock_folio = false; >> - pmd_t _pmd; >> >> mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma, vma->vm_mm, >> address & HPAGE_PMD_MASK, >> @@ -2148,48 +2146,16 @@ void __split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd, >> * pmd against. Otherwise we can end up replacing wrong folio. >> */ >> VM_BUG_ON(freeze && !folio); >> - if (folio) { >> - VM_WARN_ON_ONCE(!folio_test_locked(folio)); >> - if (folio != page_folio(pmd_page(*pmd))) >> - goto out; >> - } >> + if (folio && folio != page_folio(pmd_page(*pmd))) >> + goto out; >> >> -repeat: >> - if (pmd_trans_huge(*pmd)) { >> - if (!folio) { >> - folio = page_folio(pmd_page(*pmd)); >> - /* >> - * An anonymous page must be locked, to ensure that a >> - * concurrent reuse_swap_page() sees stable mapcount; >> - * but reuse_swap_page() is not used on shmem or file, >> - * and page lock must not be taken when zap_pmd_range() >> - * calls __split_huge_pmd() while i_mmap_lock is held. >> - */ >> - if (folio_test_anon(folio)) { >> - if (unlikely(!folio_trylock(folio))) { >> - folio_get(folio); >> - _pmd = *pmd; >> - spin_unlock(ptl); >> - folio_lock(folio); >> - spin_lock(ptl); >> - if (unlikely(!pmd_same(*pmd, _pmd))) { >> - folio_unlock(folio); >> - folio_put(folio); >> - folio = NULL; >> - goto repeat; >> - } >> - folio_put(folio); >> - } >> - do_unlock_folio = true; >> - } >> - } >> - } else if (!(pmd_devmap(*pmd) || is_pmd_migration_entry(*pmd))) >> + if (!(pmd_devmap(*pmd) || is_pmd_migration_entry(*pmd))) >> goto out; >> + >> __split_huge_pmd_locked(vma, pmd, range.start, freeze); >> out: >> spin_unlock(ptl); >> - if (do_unlock_folio) >> - folio_unlock(folio); >> + >> /* >> * No need to double call mmu_notifier->invalidate_range() callback. >> * They are 3 cases to consider inside __split_huge_pmd_locked(): >> -- >> 2.26.3 >>
