Btrfs: skip states when they does not contain bits to clear
Liu Bo [Thu, 16 Feb 2012 10:34:37 +0000 (18:34 +0800)]
Clearing a range's bits is different with setting them, since we don't
need to touch them when states do not contain bits we want.

Signed-off-by: Liu Bo <liubo2009@cn.fujitsu.com>

fs/btrfs/extent_io.c

index 8d6f55f..fe14285 100644 (file)
@@ -513,6 +513,15 @@ hit_next:
        WARN_ON(state->end < start);
        last_end = state->end;
 
+       if (state->end < end && !need_resched())
+               next_node = rb_next(&state->rb_node);
+       else
+               next_node = NULL;
+
+       /* the state doesn't have the wanted bits, go ahead */
+       if (!(state->state & bits))
+               goto next;
+
        /*
         *     | ---- desired range ---- |
         *  | state | or
@@ -565,12 +574,8 @@ hit_next:
                goto out;
        }
 
-       if (state->end < end && prealloc && !need_resched())
-               next_node = rb_next(&state->rb_node);
-       else
-               next_node = NULL;
-
        set |= clear_state_bit(tree, state, &bits, wake);
+next:
        if (last_end == (u64)-1)
                goto out;
        start = last_end + 1;