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-rw-r--r--mm/migrate.c38
1 files changed, 31 insertions, 7 deletions
diff --git a/mm/migrate.c b/mm/migrate.c
index bb940045fe85..2cabbd5fa5bf 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);