sysctl: use bitmap library functions

[linux-flexiantxendom0-3.2.10.git] / kernel / futex.c

diff --git a/kernel/futex.c b/kernel/futex.c
index 4b1c4b6..72efa1e 100644 (file)
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -314,17 +314,29 @@ again:
 #endif
 
        lock_page(page_head);
+
+       /*
+        * If page_head->mapping is NULL, then it cannot be a PageAnon
+        * page; but it might be the ZERO_PAGE or in the gate area or
+        * in a special mapping (all cases which we are happy to fail);
+        * or it may have been a good file page when get_user_pages_fast
+        * found it, but truncated or holepunched or subjected to
+        * invalidate_complete_page2 before we got the page lock (also
+        * cases which we are happy to fail).  And we hold a reference,
+        * so refcount care in invalidate_complete_page's remove_mapping
+        * prevents drop_caches from setting mapping to NULL beneath us.
+        *
+        * The case we do have to guard against is when memory pressure made
+        * shmem_writepage move it from filecache to swapcache beneath us:
+        * an unlikely race, but we do need to retry for page_head->mapping.
+        */
        if (!page_head->mapping) {
+               int shmem_swizzled = PageSwapCache(page_head);
                unlock_page(page_head);
                put_page(page_head);
-               /*
-               * ZERO_PAGE pages don't have a mapping. Avoid a busy loop
-               * trying to find one. RW mapping would have COW'd (and thus
-               * have a mapping) so this page is RO and won't ever change.
-               */
-               if ((page_head == ZERO_PAGE(address)))
-                       return -EFAULT;
-               goto again;
+               if (shmem_swizzled)
+                       goto again;
+               return -EFAULT;
        }
 
        /*
@@ -2616,7 +2628,7 @@ void exit_robust_list(struct task_struct *curr)
 long do_futex(u32 __user *uaddr, int op, u32 val, ktime_t *timeout,
                u32 __user *uaddr2, u32 val2, u32 val3)
 {
-       int ret = -ENOSYS, cmd = op & FUTEX_CMD_MASK;
+       int cmd = op & FUTEX_CMD_MASK;
        unsigned int flags = 0;
 
        if (!(op & FUTEX_PRIVATE_FLAG))
@@ -2642,43 +2654,31 @@ long do_futex(u32 __user *uaddr, int op, u32 val, ktime_t *timeout,
        case FUTEX_WAIT:
                val3 = FUTEX_BITSET_MATCH_ANY;
        case FUTEX_WAIT_BITSET:
-               ret = futex_wait(uaddr, flags, val, timeout, val3);
-               break;
+               return futex_wait(uaddr, flags, val, timeout, val3);
        case FUTEX_WAKE:
                val3 = FUTEX_BITSET_MATCH_ANY;
        case FUTEX_WAKE_BITSET:
-               ret = futex_wake(uaddr, flags, val, val3);
-               break;
+               return futex_wake(uaddr, flags, val, val3);
        case FUTEX_REQUEUE:
-               ret = futex_requeue(uaddr, flags, uaddr2, val, val2, NULL, 0);
-               break;
+               return futex_requeue(uaddr, flags, uaddr2, val, val2, NULL, 0);
        case FUTEX_CMP_REQUEUE:
-               ret = futex_requeue(uaddr, flags, uaddr2, val, val2, &val3, 0);
-               break;
+               return futex_requeue(uaddr, flags, uaddr2, val, val2, &val3, 0);
        case FUTEX_WAKE_OP:
-               ret = futex_wake_op(uaddr, flags, uaddr2, val, val2, val3);
-               break;
+               return futex_wake_op(uaddr, flags, uaddr2, val, val2, val3);
        case FUTEX_LOCK_PI:
-               ret = futex_lock_pi(uaddr, flags, val, timeout, 0);
-               break;
+               return futex_lock_pi(uaddr, flags, val, timeout, 0);
        case FUTEX_UNLOCK_PI:
-               ret = futex_unlock_pi(uaddr, flags);
-               break;
+               return futex_unlock_pi(uaddr, flags);
        case FUTEX_TRYLOCK_PI:
-               ret = futex_lock_pi(uaddr, flags, 0, timeout, 1);
-               break;
+               return futex_lock_pi(uaddr, flags, 0, timeout, 1);
        case FUTEX_WAIT_REQUEUE_PI:
                val3 = FUTEX_BITSET_MATCH_ANY;
-               ret = futex_wait_requeue_pi(uaddr, flags, val, timeout, val3,
-                                           uaddr2);
-               break;
+               return futex_wait_requeue_pi(uaddr, flags, val, timeout, val3,
+                                            uaddr2);
        case FUTEX_CMP_REQUEUE_PI:
-               ret = futex_requeue(uaddr, flags, uaddr2, val, val2, &val3, 1);
-               break;
-       default:
-               ret = -ENOSYS;
+               return futex_requeue(uaddr, flags, uaddr2, val, val2, &val3, 1);
        }
-       return ret;
+       return -ENOSYS;
 }