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Subject[PATCH RESEND v6 02/16] mm/gup: Fix __get_user_pages() on fault retry of hugetlb
Date
When follow_hugetlb_page() returns with *locked==0, it means we've got
a VM_FAULT_RETRY within the fauling process and we've released the
mmap_sem. When that happens, we should stop and bail out.

Signed-off-by: Peter Xu <peterx@redhat.com>
---
mm/gup.c | 10 ++++++++++
1 file changed, 10 insertions(+)

diff --git a/mm/gup.c b/mm/gup.c
index 1b4411bd0042..76cb420c0fb7 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -849,6 +849,16 @@ static long __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
i = follow_hugetlb_page(mm, vma, pages, vmas,
&start, &nr_pages, i,
gup_flags, locked);
+ if (locked && *locked == 0) {
+ /*
+ * We've got a VM_FAULT_RETRY
+ * and we've lost mmap_sem.
+ * We must stop here.
+ */
+ BUG_ON(gup_flags & FOLL_NOWAIT);
+ BUG_ON(ret != 0);
+ goto out;
+ }
continue;
}
}
--
2.24.1
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