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-rw-r--r--mm/hugetlb.c13
1 files changed, 11 insertions, 2 deletions
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 450493d25572..2ef66a2a148d 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -2293,6 +2293,9 @@ retry_avoidcopy:
outside_reserve = 1;
page_cache_get(old_page);
+
+ /* Drop page_table_lock as buddy allocator may be called */
+ spin_unlock(&mm->page_table_lock);
new_page = alloc_huge_page(vma, address, outside_reserve);
if (IS_ERR(new_page)) {
@@ -2310,19 +2313,25 @@ retry_avoidcopy:
if (unmap_ref_private(mm, vma, old_page, address)) {
BUG_ON(page_count(old_page) != 1);
BUG_ON(huge_pte_none(pte));
+ spin_lock(&mm->page_table_lock);
goto retry_avoidcopy;
}
WARN_ON_ONCE(1);
}
+ /* Caller expects lock to be held */
+ spin_lock(&mm->page_table_lock);
return -PTR_ERR(new_page);
}
- spin_unlock(&mm->page_table_lock);
copy_huge_page(new_page, old_page, address, vma);
__SetPageUptodate(new_page);
- spin_lock(&mm->page_table_lock);
+ /*
+ * Retake the page_table_lock to check for racing updates
+ * before the page tables are altered
+ */
+ spin_lock(&mm->page_table_lock);
ptep = huge_pte_offset(mm, address & huge_page_mask(h));
if (likely(pte_same(huge_ptep_get(ptep), pte))) {
/* Break COW */