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-rw-r--r--mm/ksm.c67
1 files changed, 58 insertions, 9 deletions
diff --git a/mm/ksm.c b/mm/ksm.c
index e2b0afd0a031..4d5a681923bb 100644
--- a/mm/ksm.c
+++ b/mm/ksm.c
@@ -412,6 +412,29 @@ out:
up_read(&mm->mmap_sem);
}
+static struct page *page_trans_compound_anon(struct page *page)
+{
+ if (PageTransCompound(page)) {
+ struct page *head;
+ head = compound_head(page);
+ /*
+ * head may be a dangling pointer.
+ * __split_huge_page_refcount clears PageTail
+ * before overwriting first_page, so if
+ * PageTail is still there it means the head
+ * pointer isn't dangling.
+ */
+ if (head != page) {
+ smp_rmb();
+ if (!PageTransCompound(page))
+ return NULL;
+ }
+ if (PageAnon(head))
+ return head;
+ }
+ return NULL;
+}
+
static struct page *get_mergeable_page(struct rmap_item *rmap_item)
{
struct mm_struct *mm = rmap_item->mm;
@@ -431,7 +454,7 @@ static struct page *get_mergeable_page(struct rmap_item *rmap_item)
page = follow_page(vma, addr, FOLL_GET);
if (IS_ERR_OR_NULL(page))
goto out;
- if (PageAnon(page) && !PageTransCompound(page)) {
+ if (PageAnon(page) || page_trans_compound_anon(page)) {
flush_anon_page(vma, page, addr);
flush_dcache_page(page);
} else {
@@ -709,6 +732,7 @@ static int write_protect_page(struct vm_area_struct *vma, struct page *page,
if (addr == -EFAULT)
goto out;
+ BUG_ON(PageTransCompound(page));
ptep = page_check_address(page, mm, addr, &ptl, 0);
if (!ptep)
goto out;
@@ -784,6 +808,7 @@ static int replace_page(struct vm_area_struct *vma, struct page *page,
goto out;
pmd = pmd_offset(pud, addr);
+ BUG_ON(pmd_trans_huge(*pmd));
if (!pmd_present(*pmd))
goto out;
@@ -811,6 +836,33 @@ out:
return err;
}
+static int page_trans_compound_anon_split(struct page *page)
+{
+ int ret = 0;
+ struct page *transhuge_head = page_trans_compound_anon(page);
+ if (transhuge_head) {
+ /* Get the reference on the head to split it. */
+ if (get_page_unless_zero(transhuge_head)) {
+ /*
+ * Recheck we got the reference while the head
+ * was still anonymous.
+ */
+ if (PageAnon(transhuge_head))
+ ret = split_huge_page(transhuge_head);
+ else
+ /*
+ * Retry later if split_huge_page run
+ * from under us.
+ */
+ ret = 1;
+ put_page(transhuge_head);
+ } else
+ /* Retry later if split_huge_page run from under us. */
+ ret = 1;
+ }
+ return ret;
+}
+
/*
* try_to_merge_one_page - take two pages and merge them into one
* @vma: the vma that holds the pte pointing to page
@@ -831,6 +883,9 @@ static int try_to_merge_one_page(struct vm_area_struct *vma,
if (!(vma->vm_flags & VM_MERGEABLE))
goto out;
+ if (PageTransCompound(page) && page_trans_compound_anon_split(page))
+ goto out;
+ BUG_ON(PageTransCompound(page));
if (!PageAnon(page))
goto out;
@@ -1285,14 +1340,8 @@ next_mm:
cond_resched();
continue;
}
- if (PageTransCompound(*page)) {
- put_page(*page);
- ksm_scan.address &= HPAGE_PMD_MASK;
- ksm_scan.address += HPAGE_PMD_SIZE;
- cond_resched();
- continue;
- }
- if (PageAnon(*page)) {
+ if (PageAnon(*page) ||
+ page_trans_compound_anon(*page)) {
flush_anon_page(vma, *page, ksm_scan.address);
flush_dcache_page(*page);
rmap_item = get_next_rmap_item(slot,