3 files changed, 35 insertions, 1 deletions

diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
index 6b4890fa57e7..feaf0c7fb7d8 100644
--- a/include/linux/hugetlb.h
+++ b/include/linux/hugetlb.h
@@ -358,6 +358,17 @@ static inline int hstate_index(struct hstate *h)
         return h - hstates;
 }
 
+pgoff_t __basepage_index(struct page *page);
+
+/* Return page->index in PAGE_SIZE units */
+static inline pgoff_t basepage_index(struct page *page)
+{
+        if (!PageCompound(page))
+                return page->index;
+
+        return __basepage_index(page);
+}
+
 #else   /* CONFIG_HUGETLB_PAGE */
 struct hstate {};
 #define alloc_huge_page_node(h, nid) NULL
@@ -378,6 +389,11 @@ static inline unsigned int pages_per_huge_page(struct hstate *h)
 }
 #define hstate_index_to_shift(index) 0
 #define hstate_index(h) 0
+
+static inline pgoff_t basepage_index(struct page *page)
+{
+        return page->index;
+}
 #endif  /* CONFIG_HUGETLB_PAGE */
 
 #endif /* _LINUX_HUGETLB_H */
diff --git a/kernel/futex.c b/kernel/futex.c
index b26dcfc02c94..49dacfb45745 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -61,6 +61,7 @@
 #include <linux/nsproxy.h>
 #include <linux/ptrace.h>
 #include <linux/sched/rt.h>
+#include <linux/hugetlb.h>
 
 #include <asm/futex.h>
 
@@ -365,7 +366,7 @@ again:
         } else {
                 key->both.offset |= FUT_OFF_INODE; /* inode-based key */
                 key->shared.inode = page_head->mapping->host;
-                key->shared.pgoff = page_head->index;
+                key->shared.pgoff = basepage_index(page);
         }
 
         get_futex_key_refs(key);
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index e2bfbf73a551..5cf99bf8cce2 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -690,6 +690,23 @@ int PageHuge(struct page *page)
 }
 EXPORT_SYMBOL_GPL(PageHuge);
 
+pgoff_t __basepage_index(struct page *page)
+{
+        struct page *page_head = compound_head(page);
+        pgoff_t index = page_index(page_head);
+        unsigned long compound_idx;
+
+        if (!PageHuge(page_head))
+                return page_index(page);
+
+        if (compound_order(page_head) >= MAX_ORDER)
+                compound_idx = page_to_pfn(page) - page_to_pfn(page_head);
+        else
+                compound_idx = page - page_head;
+
+        return (index << compound_order(page_head)) + compound_idx;
+}
+
 static struct page *alloc_fresh_huge_page_node(struct hstate *h, int nid)
 {
         struct page *page;