btrfs: reada: Move is_need_to_readahead contition earlier

Move is_need_to_readahead contition earlier to avoid useless loop
to get relative data for readahead.

Signed-off-by: Zhao Lei <zhaolei@cn.fujitsu.com>
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/fs/btrfs/reada.c b/fs/btrfs/reada.c
index f0cf5f3b865ae4d16c8f61b0662684b0838d53e6..b2f768a3174a625fc50dd4227b1cb20631ee6056 100644 (file)
--- a/fs/btrfs/reada.c
+++ b/fs/btrfs/reada.c
@@ -660,7 +660,6 @@ static int reada_start_machine_dev(struct btrfs_fs_info *fs_info,
        u64 logical;
        int ret;
        int i;
-       int need_kick = 0;
 
        spin_lock(&fs_info->reada_lock);
        if (dev->reada_curr_zone == NULL) {
@@ -696,6 +695,15 @@ static int reada_start_machine_dev(struct btrfs_fs_info *fs_info,
 
        spin_unlock(&fs_info->reada_lock);
 
+       spin_lock(&re->lock);
+       if (re->scheduled_for || list_empty(&re->extctl)) {
+               spin_unlock(&re->lock);
+               reada_extent_put(fs_info, re);
+               return 0;
+       }
+       re->scheduled_for = dev;
+       spin_unlock(&re->lock);
+
        /*
         * find mirror num
         */
@@ -707,18 +715,8 @@ static int reada_start_machine_dev(struct btrfs_fs_info *fs_info,
        }
        logical = re->logical;
 
-       spin_lock(&re->lock);
-       if (!re->scheduled_for && !list_empty(&re->extctl)) {
-               re->scheduled_for = dev;
-               need_kick = 1;
-       }
-       spin_unlock(&re->lock);
-
        reada_extent_put(fs_info, re);
 
-       if (!need_kick)
-               return 0;
-
        atomic_inc(&dev->reada_in_flight);
        ret = reada_tree_block_flagged(fs_info->extent_root, logical,
                        mirror_num, &eb);