futex: split out futex value validation code

Refactor the code to validate the expected futex value in order to
reuse it with the requeue_pi code.

Signed-off-by: Darren Hart <dvhltc@us.ibm.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

1 files changed, 72 insertions, 44 deletions

diff --git a/kernel/futex.c b/kernel/futex.c
index e76942e2a79f..dbe857aa4381 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -1398,42 +1398,29 @@ static void futex_wait_queue_me(struct futex_hash_bucket *hb, struct futex_q *q,
         __set_current_state(TASK_RUNNING);
 }
 
-static int futex_wait(u32 __user *uaddr, int fshared,
-                      u32 val, ktime_t *abs_time, u32 bitset, int clockrt)
+/**
+ * futex_wait_setup() - Prepare to wait on a futex
+ * @uaddr:      the futex userspace address
+ * @val:        the expected value
+ * @fshared:    whether the futex is shared (1) or not (0)
+ * @q:          the associated futex_q
+ * @hb:         storage for hash_bucket pointer to be returned to caller
+ *
+ * Setup the futex_q and locate the hash_bucket.  Get the futex value and
+ * compare it with the expected value.  Handle atomic faults internally.
+ * Return with the hb lock held and a q.key reference on success, and unlocked
+ * with no q.key reference on failure.
+ *
+ * Returns:
+ *  0 - uaddr contains val and hb has been locked
+ * <1 - -EFAULT or -EWOULDBLOCK (uaddr does not contain val) and hb is unlcoked
+ */
+static int futex_wait_setup(u32 __user *uaddr, u32 val, int fshared,
+                           struct futex_q *q, struct futex_hash_bucket **hb)
 {
-        struct hrtimer_sleeper timeout, *to = NULL;
-        DECLARE_WAITQUEUE(wait, current);
-        struct restart_block *restart;
-        struct futex_hash_bucket *hb;
-        struct futex_q q;
         u32 uval;
         int ret;
 
-        if (!bitset)
-                return -EINVAL;
-
-        q.pi_state = NULL;
-        q.bitset = bitset;
-
-        if (abs_time) {
-                to = &timeout;
-
-                hrtimer_init_on_stack(&to->timer, clockrt ? CLOCK_REALTIME :
-                                      CLOCK_MONOTONIC, HRTIMER_MODE_ABS);
-                hrtimer_init_sleeper(to, current);
-                hrtimer_set_expires_range_ns(&to->timer, *abs_time,
-                                             current->timer_slack_ns);
-        }
-
-retry:
-        q.key = FUTEX_KEY_INIT;
-        ret = get_futex_key(uaddr, fshared, &q.key);
-        if (unlikely(ret != 0))
-                goto out;
-
-retry_private:
-        hb = queue_lock(&q);
-
         /*
          * Access the page AFTER the hash-bucket is locked.
          * Order is important:
@@ -1450,33 +1437,74 @@ retry_private:
          * A consequence is that futex_wait() can return zero and absorb
          * a wakeup when *uaddr != val on entry to the syscall.  This is
          * rare, but normal.
-         *
-         * For shared futexes, we hold the mmap semaphore, so the mapping
-         * cannot have changed since we looked it up in get_futex_key.
          */
+retry:
+        q->key = FUTEX_KEY_INIT;
+        ret = get_futex_key(uaddr, fshared, &q->key);
+        if (unlikely(ret != 0))
+                goto out;
+
+retry_private:
+        *hb = queue_lock(q);
+
         ret = get_futex_value_locked(&uval, uaddr);
 
-        if (unlikely(ret)) {
-                queue_unlock(&q, hb);
+        if (ret) {
+                queue_unlock(q, *hb);
 
                 ret = get_user(uval, uaddr);
                 if (ret)
-                        goto out_put_key;
+                        goto out;
 
                 if (!fshared)
                         goto retry_private;
 
-                put_futex_key(fshared, &q.key);
+                put_futex_key(fshared, &q->key);
                 goto retry;
         }
-        ret = -EWOULDBLOCK;
 
-        /* Only actually queue if *uaddr contained val.  */
-        if (unlikely(uval != val)) {
-                queue_unlock(&q, hb);
-                goto out_put_key;
+        if (uval != val) {
+                queue_unlock(q, *hb);
+                ret = -EWOULDBLOCK;
         }
 
+out:
+        if (ret)
+                put_futex_key(fshared, &q->key);
+        return ret;
+}
+
+static int futex_wait(u32 __user *uaddr, int fshared,
+                      u32 val, ktime_t *abs_time, u32 bitset, int clockrt)
+{
+        struct hrtimer_sleeper timeout, *to = NULL;
+        DECLARE_WAITQUEUE(wait, current);
+        struct restart_block *restart;
+        struct futex_hash_bucket *hb;
+        struct futex_q q;
+        int ret;
+
+        if (!bitset)
+                return -EINVAL;
+
+        q.pi_state = NULL;
+        q.bitset = bitset;
+
+        if (abs_time) {
+                to = &timeout;
+
+                hrtimer_init_on_stack(&to->timer, clockrt ? CLOCK_REALTIME :
+                                      CLOCK_MONOTONIC, HRTIMER_MODE_ABS);
+                hrtimer_init_sleeper(to, current);
+                hrtimer_set_expires_range_ns(&to->timer, *abs_time,
+                                             current->timer_slack_ns);
+        }
+
+        /* Prepare to wait on uaddr. */
+        ret = futex_wait_setup(uaddr, val, fshared, &q, &hb);
+        if (ret)
+                goto out;
+
         /* queue_me and wait for wakeup, timeout, or a signal. */
         futex_wait_queue_me(hb, &q, to, &wait);