1 files changed, 48 insertions, 14 deletions

diff --git a/kernel/futex.c b/kernel/futex.c
index 3019b92e6917..b766d28accd6 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -233,7 +233,7 @@ get_futex_key(u32 __user *uaddr, int fshared, union futex_key *key)
 {
         unsigned long address = (unsigned long)uaddr;
         struct mm_struct *mm = current->mm;
-        struct page *page;
+        struct page *page, *page_head;
         int err;
 
         /*
@@ -265,11 +265,46 @@ again:
         if (err < 0)
                 return err;
 
-        page = compound_head(page);
-        lock_page(page);
-        if (!page->mapping) {
-                unlock_page(page);
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
+        page_head = page;
+        if (unlikely(PageTail(page))) {
                 put_page(page);
+                /* serialize against __split_huge_page_splitting() */
+                local_irq_disable();
+                if (likely(__get_user_pages_fast(address, 1, 1, &page) == 1)) {
+                        page_head = compound_head(page);
+                        /*
+                         * page_head is valid pointer but we must pin
+                         * it before taking the PG_lock and/or
+                         * PG_compound_lock. The moment we re-enable
+                         * irqs __split_huge_page_splitting() can
+                         * return and the head page can be freed from
+                         * under us. We can't take the PG_lock and/or
+                         * PG_compound_lock on a page that could be
+                         * freed from under us.
+                         */
+                        if (page != page_head) {
+                                get_page(page_head);
+                                put_page(page);
+                        }
+                        local_irq_enable();
+                } else {
+                        local_irq_enable();
+                        goto again;
+                }
+        }
+#else
+        page_head = compound_head(page);
+        if (page != page_head) {
+                get_page(page_head);
+                put_page(page);
+        }
+#endif
+
+        lock_page(page_head);
+        if (!page_head->mapping) {
+                unlock_page(page_head);
+                put_page(page_head);
                 goto again;
         }
 
@@ -280,20 +315,20 @@ again:
          * it's a read-only handle, it's expected that futexes attach to
          * the object not the particular process.
          */
-        if (PageAnon(page)) {
+        if (PageAnon(page_head)) {
                 key->both.offset |= FUT_OFF_MMSHARED; /* ref taken on mm */
                 key->private.mm = mm;
                 key->private.address = address;
         } else {
                 key->both.offset |= FUT_OFF_INODE; /* inode-based key */
-                key->shared.inode = page->mapping->host;
-                key->shared.pgoff = page->index;
+                key->shared.inode = page_head->mapping->host;
+                key->shared.pgoff = page_head->index;
         }
 
         get_futex_key_refs(key);
 
-        unlock_page(page);
-        put_page(page);
+        unlock_page(page_head);
+        put_page(page_head);
         return 0;
 }
 
@@ -791,10 +826,9 @@ static int wake_futex_pi(u32 __user *uaddr, u32 uval, struct futex_q *this)
         new_owner = rt_mutex_next_owner(&pi_state->pi_mutex);
 
         /*
-         * This happens when we have stolen the lock and the original
-         * pending owner did not enqueue itself back on the rt_mutex.
-         * Thats not a tragedy. We know that way, that a lock waiter
-         * is on the fly. We make the futex_q waiter the pending owner.
+         * It is possible that the next waiter (the one that brought
+         * this owner to the kernel) timed out and is no longer
+         * waiting on the lock.
          */
         if (!new_owner)
                 new_owner = this->task;