The loop worker thread only inherit the blkcg of original request,
but does not inherit it's ioprio. So, when a task with the high
ioprio but in root blkcg accesses the loop device, the worker
thread handle this cmd with a normal ioprio. This results in the
request of high ioprio task doesn't be prioritized.
Signed-off-by: Yunlong Xing <yunlong.xing@xxxxxxxxxx>
---
drivers/block/loop.c | 14 +++++++++++++-
1 file changed, 13 insertions(+), 1 deletion(-)
diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index 28a95fd366fe..404ac113c71b 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -442,7 +442,6 @@ static int lo_rw_aio(struct loop_device *lo, struct loop_cmd *cmd,
cmd->iocb.ki_filp = file;
cmd->iocb.ki_complete = lo_rw_aio_complete;
cmd->iocb.ki_flags = IOCB_DIRECT;
- cmd->iocb.ki_ioprio = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_NONE, 0);
if (rw == ITER_SOURCE)
ret = call_write_iter(file, &cmd->iocb, &iter);
@@ -1856,6 +1855,9 @@ static blk_status_t loop_queue_rq(struct blk_mq_hw_ctx *hctx,
break;
}
+ /* get request's ioprio */
+ cmd->iocb.ki_ioprio = rq->ioprio;
+
/* always use the first bio's css */
cmd->blkcg_css = NULL;
cmd->memcg_css = NULL;
@@ -1886,12 +1888,18 @@ static void loop_handle_cmd(struct loop_cmd *cmd)
int ret = 0;
struct mem_cgroup *old_memcg = NULL;
const bool use_aio = cmd->use_aio;
+ int ori_ioprio = 0;
+ int cmd_ioprio = cmd->iocb.ki_ioprio;
if (write && (lo->lo_flags & LO_FLAGS_READ_ONLY)) {
ret = -EIO;
goto failed;
}
+ ori_ioprio = get_current_ioprio();
+ if (ori_ioprio != cmd_ioprio)
+ set_task_ioprio(current, cmd_ioprio);
+
if (cmd_blkcg_css)
kthread_associate_blkcg(cmd_blkcg_css);
if (cmd_memcg_css)
@@ -1913,6 +1921,10 @@ static void loop_handle_cmd(struct loop_cmd *cmd)
set_active_memcg(old_memcg);
css_put(cmd_memcg_css);
}
+
+ if (ori_ioprio != cmd_ioprio)
+ set_task_ioprio(current, ori_ioprio);
+
failed:
/* complete non-aio request */
if (!use_aio || ret) {
--
2.25.1
