diff options
Diffstat (limited to 'mm/migrate.c')
| -rw-r--r-- | mm/migrate.c | 38 |
1 files changed, 31 insertions, 7 deletions
diff --git a/mm/migrate.c b/mm/migrate.c index bb940045fe8..2cabbd5fa5b 100644 --- a/mm/migrate.c +++ b/mm/migrate.c @@ -1722,6 +1722,7 @@ int migrate_misplaced_transhuge_page(struct mm_struct *mm, struct page *new_page = NULL; struct mem_cgroup *memcg = NULL; int page_lru = page_is_file_cache(page); + pmd_t orig_entry; /* * Rate-limit the amount of data that is being migrated to a node. @@ -1756,7 +1757,8 @@ int migrate_misplaced_transhuge_page(struct mm_struct *mm, /* Recheck the target PMD */ ptl = pmd_lock(mm, pmd); - if (unlikely(!pmd_same(*pmd, entry))) { + if (unlikely(!pmd_same(*pmd, entry) || page_count(page) != 2)) { +fail_putback: spin_unlock(ptl); /* Reverse changes made by migrate_page_copy() */ @@ -1786,16 +1788,34 @@ int migrate_misplaced_transhuge_page(struct mm_struct *mm, */ mem_cgroup_prepare_migration(page, new_page, &memcg); + orig_entry = *pmd; entry = mk_pmd(new_page, vma->vm_page_prot); - entry = pmd_mknonnuma(entry); - entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma); entry = pmd_mkhuge(entry); + entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma); + /* + * Clear the old entry under pagetable lock and establish the new PTE. + * Any parallel GUP will either observe the old page blocking on the + * page lock, block on the page table lock or observe the new page. + * The SetPageUptodate on the new page and page_add_new_anon_rmap + * guarantee the copy is visible before the pagetable update. + */ + flush_cache_range(vma, haddr, haddr + HPAGE_PMD_SIZE); + page_add_new_anon_rmap(new_page, vma, haddr); pmdp_clear_flush(vma, haddr, pmd); set_pmd_at(mm, haddr, pmd, entry); - page_add_new_anon_rmap(new_page, vma, haddr); update_mmu_cache_pmd(vma, address, &entry); + + if (page_count(page) != 2) { + set_pmd_at(mm, haddr, pmd, orig_entry); + flush_tlb_range(vma, haddr, haddr + HPAGE_PMD_SIZE); + update_mmu_cache_pmd(vma, address, &entry); + page_remove_rmap(new_page); + goto fail_putback; + } + page_remove_rmap(page); + /* * Finish the charge transaction under the page table lock to * prevent split_huge_page() from dividing up the charge @@ -1820,9 +1840,13 @@ int migrate_misplaced_transhuge_page(struct mm_struct *mm, out_fail: count_vm_events(PGMIGRATE_FAIL, HPAGE_PMD_NR); out_dropref: - entry = pmd_mknonnuma(entry); - set_pmd_at(mm, haddr, pmd, entry); - update_mmu_cache_pmd(vma, address, &entry); + ptl = pmd_lock(mm, pmd); + if (pmd_same(*pmd, entry)) { + entry = pmd_mknonnuma(entry); + set_pmd_at(mm, haddr, pmd, entry); + update_mmu_cache_pmd(vma, address, &entry); + } + spin_unlock(ptl); unlock_page(page); put_page(page); |