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>
diff --git a/fs/btrfs/reada.c b/fs/btrfs/reada.c
index 9157d78..e97bc8e 100644
--- a/fs/btrfs/reada.c
+++ b/fs/btrfs/reada.c
@@ -748,6 +748,8 @@
set_task_ioprio(current, BTRFS_IOPRIO_READA);
__reada_start_machine(fs_info);
set_task_ioprio(current, old_ioprio);
+
+ atomic_dec(&fs_info->reada_works_cnt);
}
static void __reada_start_machine(struct btrfs_fs_info *fs_info)
@@ -779,8 +781,12 @@
* enqueue to workers to finish it. This will distribute the load to
* the cores.
*/
- for (i = 0; i < 2; ++i)
+ for (i = 0; i < 2; ++i) {
reada_start_machine(fs_info);
+ if (atomic_read(&fs_info->reada_works_cnt) >
+ BTRFS_MAX_MIRRORS * 2)
+ break;
+ }
}
static void reada_start_machine(struct btrfs_fs_info *fs_info)
@@ -797,6 +803,7 @@
rmw->fs_info = fs_info;
btrfs_queue_work(fs_info->readahead_workers, &rmw->work);
+ atomic_inc(&fs_info->reada_works_cnt);
}
#ifdef DEBUG