btrfs: reada: limit max works count

Reada creates 2 works for each level of tree recursively.

In case of a tree having many levels, the number of created works
is 2^level_of_tree.
Actually we don't need so many works in parallel, this patch limits
max works to BTRFS_MAX_MIRRORS * 2.

The per-fs works_counter will be also used for btrfs_reada_wait() to
check is there are background workers.

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

1 files changed, 1 insertions, 0 deletions

diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 498156ede32c..5e3ec1fc0ac3 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -2603,6 +2603,7 @@ int open_ctree(struct super_block *sb,
         atomic_set(&fs_info->nr_async_bios, 0);
         atomic_set(&fs_info->defrag_running, 0);
         atomic_set(&fs_info->qgroup_op_seq, 0);
+        atomic_set(&fs_info->reada_works_cnt, 0);
         atomic64_set(&fs_info->tree_mod_seq, 0);
         fs_info->sb = sb;
         fs_info->max_inline = BTRFS_DEFAULT_MAX_INLINE;