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/ctree.h b/fs/btrfs/ctree.h
index e557e05..e43d987 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -1822,6 +1822,9 @@
spinlock_t reada_lock;
struct radix_tree_root reada_tree;
+ /* readahead works cnt */
+ atomic_t reada_works_cnt;
+
/* Extent buffer radix tree */
spinlock_t buffer_lock;
struct radix_tree_root buffer_radix;
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 498156e..5e3ec1f 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -2603,6 +2603,7 @@
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;
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
