1 files changed, 18 insertions, 7 deletions

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 41b1038f76da..d5987a87bbe5 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -13,6 +13,7 @@
 #include <linux/pagemap.h>
 #include <linux/mempolicy.h>
 #include <linux/cpuset.h>
+#include <linux/mutex.h>
 
 #include <asm/page.h>
 #include <asm/pgtable.h>
@@ -26,6 +27,10 @@ unsigned long max_huge_pages;
 static struct list_head hugepage_freelists[MAX_NUMNODES];
 static unsigned int nr_huge_pages_node[MAX_NUMNODES];
 static unsigned int free_huge_pages_node[MAX_NUMNODES];
+/*
+ * Protects updates to hugepage_freelists, nr_huge_pages, and free_huge_pages
+ */
+static DEFINE_SPINLOCK(hugetlb_lock);
 
 static void clear_huge_page(struct page *page, unsigned long addr)
 {
@@ -50,11 +55,6 @@ static void copy_huge_page(struct page *dst, struct page *src,
         }
 }
 
-/*
- * Protects updates to hugepage_freelists, nr_huge_pages, and free_huge_pages
- */
-static DEFINE_SPINLOCK(hugetlb_lock);
-
 static void enqueue_huge_page(struct page *page)
 {
         int nid = page_to_nid(page);
@@ -508,14 +508,24 @@ int hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma,
         pte_t *ptep;
         pte_t entry;
         int ret;
+        static DEFINE_MUTEX(hugetlb_instantiation_mutex);
 
         ptep = huge_pte_alloc(mm, address);
         if (!ptep)
                 return VM_FAULT_OOM;
 
+        /*
+         * Serialize hugepage allocation and instantiation, so that we don't
+         * get spurious allocation failures if two CPUs race to instantiate
+         * the same page in the page cache.
+         */
+        mutex_lock(&hugetlb_instantiation_mutex);
         entry = *ptep;
-        if (pte_none(entry))
-                return hugetlb_no_page(mm, vma, address, ptep, write_access);
+        if (pte_none(entry)) {
+                ret = hugetlb_no_page(mm, vma, address, ptep, write_access);
+                mutex_unlock(&hugetlb_instantiation_mutex);
+                return ret;
+        }
 
         ret = VM_FAULT_MINOR;
 
@@ -525,6 +535,7 @@ int hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma,
                 if (write_access && !pte_write(entry))
                         ret = hugetlb_cow(mm, vma, address, ptep, entry);
         spin_unlock(&mm->page_table_lock);
+        mutex_unlock(&hugetlb_instantiation_mutex);
 
         return ret;
 }