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Diffstat (limited to 'mm/huge_memory.c')
-rw-r--r--mm/huge_memory.c18
1 files changed, 17 insertions, 1 deletions
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 530e6427f823..6c6f5ccfcda1 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1269,6 +1269,16 @@ out_unlock:
return ret;
}
+/*
+ * FOLL_FORCE can write to even unwritable pmd's, but only
+ * after we've gone through a COW cycle and they are dirty.
+ */
+static inline bool can_follow_write_pmd(pmd_t pmd, unsigned int flags)
+{
+ return pmd_write(pmd) ||
+ ((flags & FOLL_FORCE) && (flags & FOLL_COW) && pmd_dirty(pmd));
+}
+
struct page *follow_trans_huge_pmd(struct vm_area_struct *vma,
unsigned long addr,
pmd_t *pmd,
@@ -1279,7 +1289,7 @@ struct page *follow_trans_huge_pmd(struct vm_area_struct *vma,
assert_spin_locked(pmd_lockptr(mm, pmd));
- if (flags & FOLL_WRITE && !pmd_write(*pmd))
+ if (flags & FOLL_WRITE && !can_follow_write_pmd(*pmd, flags))
goto out;
/* Avoid dumping huge zero page */
@@ -1353,8 +1363,11 @@ int do_huge_pmd_numa_page(struct mm_struct *mm, struct vm_area_struct *vma,
*/
if (unlikely(pmd_trans_migrating(*pmdp))) {
page = pmd_page(*pmdp);
+ if (!get_page_unless_zero(page))
+ goto out_unlock;
spin_unlock(ptl);
wait_on_page_locked(page);
+ put_page(page);
goto out;
}
@@ -1386,8 +1399,11 @@ int do_huge_pmd_numa_page(struct mm_struct *mm, struct vm_area_struct *vma,
/* Migration could have started since the pmd_trans_migrating check */
if (!page_locked) {
+ if (!get_page_unless_zero(page))
+ goto out_unlock;
spin_unlock(ptl);
wait_on_page_locked(page);
+ put_page(page);
page_nid = -1;
goto out;
}