btrfs: don't do extra find_extent_buffer() in do_walk_down()

We do find_extent_buffer(), and then if we don't find the eb in cache we
call btrfs_find_create_tree_block(), which calls find_extent_buffer()
first and then allocates the extent buffer.

The reason we're doing this is because if we don't find the extent
buffer in cache we set reada = 1.  However this doesn't matter, because
lower down we only trigger reada if !btrfs_buffer_uptodate(eb), which is
what the case would be if we didn't find the extent buffer in cache and
had to allocate it.

Clean this up to simply call btrfs_find_create_tree_block(), and then
use the fact that we're having to read the extent buffer off of disk to
go ahead and kick off readahead.

Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index d720c03e4c62d561b49d111adeb0a00e4dcef73f..3e31dc7538779066c541a4d82c85cda3381ebaa4 100644 (file)
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -5433,7 +5433,6 @@ static noinline int do_walk_down(struct btrfs_trans_handle *trans,
        struct btrfs_key key;
        struct extent_buffer *next;
        int level = wc->level;
-       int reada = 0;
        int ret = 0;
        bool need_account = false;
 
@@ -5459,14 +5458,11 @@ static noinline int do_walk_down(struct btrfs_trans_handle *trans,
        btrfs_node_key_to_cpu(path->nodes[level], &check.first_key,
                              path->slots[level]);
 
-       next = find_extent_buffer(fs_info, bytenr);
-       if (!next) {
-               next = btrfs_find_create_tree_block(fs_info, bytenr,
-                               btrfs_root_id(root), level - 1);
-               if (IS_ERR(next))
-                       return PTR_ERR(next);
-               reada = 1;
-       }
+       next = btrfs_find_create_tree_block(fs_info, bytenr, btrfs_root_id(root),
+                                           level - 1);
+       if (IS_ERR(next))
+               return PTR_ERR(next);
+
        btrfs_tree_lock(next);
 
        ret = btrfs_lookup_extent_info(trans, fs_info, bytenr, level - 1, 1,
@@ -5517,7 +5513,7 @@ static noinline int do_walk_down(struct btrfs_trans_handle *trans,
        }
 
        if (!next) {
-               if (reada && level == 1)
+               if (level == 1)
                        reada_walk_down(trans, root, wc, path);
                next = read_tree_block(fs_info, bytenr, &check);
                if (IS_ERR(next)) {