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-rw-r--r--include/linux/mm.h1
-rw-r--r--mm/ksm.c2
-rw-r--r--mm/memory.c20
3 files changed, 20 insertions, 3 deletions
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 6124f1db50fe..e7c3f9a0111a 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1651,6 +1651,7 @@ static inline struct page *follow_page(struct vm_area_struct *vma,
#define FOLL_SPLIT 0x80 /* don't return transhuge pages, split them */
#define FOLL_HWPOISON 0x100 /* check page is hwpoisoned */
#define FOLL_NUMA 0x200 /* force NUMA hinting page fault */
+#define FOLL_MIGRATION 0x400 /* wait for page to replace migration entry */
typedef int (*pte_fn_t)(pte_t *pte, pgtable_t token, unsigned long addr,
void *data);
diff --git a/mm/ksm.c b/mm/ksm.c
index 0320327b8a6c..d61cba6fa1dc 100644
--- a/mm/ksm.c
+++ b/mm/ksm.c
@@ -364,7 +364,7 @@ static int break_ksm(struct vm_area_struct *vma, unsigned long addr)
do {
cond_resched();
- page = follow_page(vma, addr, FOLL_GET);
+ page = follow_page(vma, addr, FOLL_GET | FOLL_MIGRATION);
if (IS_ERR_OR_NULL(page))
break;
if (PageKsm(page))
diff --git a/mm/memory.c b/mm/memory.c
index 5d2ef1217d0c..ec8ba011fa7d 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -1548,8 +1548,24 @@ split_fallthrough:
ptep = pte_offset_map_lock(mm, pmd, address, &ptl);
pte = *ptep;
- if (!pte_present(pte))
- goto no_page;
+ if (!pte_present(pte)) {
+ swp_entry_t entry;
+ /*
+ * KSM's break_ksm() relies upon recognizing a ksm page
+ * even while it is being migrated, so for that case we
+ * need migration_entry_wait().
+ */
+ if (likely(!(flags & FOLL_MIGRATION)))
+ goto no_page;
+ if (pte_none(pte) || pte_file(pte))
+ goto no_page;
+ entry = pte_to_swp_entry(pte);
+ if (!is_migration_entry(entry))
+ goto no_page;
+ pte_unmap_unlock(ptep, ptl);
+ migration_entry_wait(mm, pmd, address);
+ goto split_fallthrough;
+ }
if ((flags & FOLL_NUMA) && pte_numa(pte))
goto no_page;
if ((flags & FOLL_WRITE) && !pte_write(pte))