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.
Signed-off-by: Zhao Lei <zhaolei@xxxxxxxxxxxxxx>
---
fs/btrfs/reada.c | 11 ++++++++++-
1 file changed, 10 insertions(+), 1 deletion(-)
diff --git a/fs/btrfs/reada.c b/fs/btrfs/reada.c
index 53ee7b1..7b150b2 100644
--- a/fs/btrfs/reada.c
+++ b/fs/btrfs/reada.c
@@ -103,6 +103,9 @@ static void __reada_start_machine(struct btrfs_fs_info *fs_info);
static int reada_add_block(struct reada_control *rc, u64 logical,
struct btrfs_key *top, u64 generation);
+/* To limit max reada works */
+static atomic_t works_cnt = ATOMIC_INIT(0);
+
/* recurses */
/* in case of err, eb might be NULL */
static void __readahead_hook(struct btrfs_fs_info *fs_info,
@@ -759,6 +762,8 @@ 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(&works_cnt);
}
static void __reada_start_machine(struct btrfs_fs_info *fs_info)
@@ -790,8 +795,11 @@ 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(&works_cnt) > BTRFS_MAX_MIRRORS * 2)
+ break;
+ }
}
static void reada_start_machine(struct btrfs_fs_info *fs_info)
@@ -808,6 +816,7 @@ 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(&works_cnt);
}
#ifdef DEBUG
--
1.8.5.1
--
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