From: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
When processing a hugetlb fault for no page present, check the vma to
determine if faults are to be handled via userfaultfd. If so, drop the
hugetlb_fault_mutex and call handle_userfault().
Signed-off-by: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
Acked-by: Hillf Danton <hillf.zj@xxxxxxxxxxxxxxx>
Signed-off-by: Andrea Arcangeli <aarcange@xxxxxxxxxx>
---
mm/hugetlb.c | 33 +++++++++++++++++++++++++++++++++
1 file changed, 33 insertions(+)
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 9ea7588..621ea74 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -32,6 +32,7 @@
#include <linux/hugetlb.h>
#include <linux/hugetlb_cgroup.h>
#include <linux/node.h>
+#include <linux/userfaultfd_k.h>
#include "internal.h"
int hugepages_treat_as_movable;
@@ -3661,6 +3662,38 @@ static int hugetlb_no_page(struct mm_struct *mm, struct vm_area_struct *vma,
size = i_size_read(mapping->host) >> huge_page_shift(h);
if (idx >= size)
goto out;
+
+ /*
+ * Check for page in userfault range
+ */
+ if (userfaultfd_missing(vma)) {
+ u32 hash;
+ struct vm_fault vmf = {
+ .vma = vma,
+ .address = address,
+ .flags = flags,
+ /*
+ * Hard to debug if it ends up being
+ * used by a callee that assumes
+ * something about the other
+ * uninitialized fields... same as in
+ * memory.c
+ */
+ };
+
+ /*
+ * hugetlb_fault_mutex must be dropped before
+ * handling userfault. Reacquire after handling
+ * fault to make calling code simpler.
+ */
+ hash = hugetlb_fault_mutex_hash(h, mm, vma, mapping,
+ idx, address);
+ mutex_unlock(&hugetlb_fault_mutex_table[hash]);
+ ret = handle_userfault(&vmf, VM_UFFD_MISSING);
+ mutex_lock(&hugetlb_fault_mutex_table[hash]);
+ goto out;
+ }
+
page = alloc_huge_page(vma, address, 0);
if (IS_ERR(page)) {
ret = PTR_ERR(page);
--
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