@@ -1822,6 +1822,9 @@ struct btrfs_fs_info {
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;
@@ -2602,6 +2602,7 @@ 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;
@@ -748,6 +748,8 @@ static void reada_start_machine_worker(struct btrfs_work *work)
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 @@ static void __reada_start_machine(struct btrfs_fs_info *fs_info)
* 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 @@ static void reada_start_machine(struct btrfs_fs_info *fs_info)
rmw->fs_info = fs_info;
btrfs_queue_work(fs_info->readahead_workers, &rmw->work);
+ atomic_inc(&fs_info->reada_works_cnt);
}
#ifdef DEBUG
reada create 2 works for each level of tree in recursion. 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 limit max works to BTRFS_MAX_MIRRORS * 2. The works_counter will also used for btrfs_reada_wait() to check is there exist background workers. Changelog v1->v2: Move works_counter from global lobal variable to btrfs_fs_info's member variable, to avoid too small workers when more than one FS mounted, noticed by: Chris Mason <clm@fb.com> Signed-off-by: Zhao Lei <zhaolei@cn.fujitsu.com> --- fs/btrfs/ctree.h | 3 +++ fs/btrfs/disk-io.c | 1 + fs/btrfs/reada.c | 9 ++++++++- 3 files changed, 12 insertions(+), 1 deletion(-)