blk-iocost: move wbt_enable/disable_default() out of spinlock

There are following smatch warning:

block/blk-wbt.c:843 wbt_init() warn: sleeping in atomic context
ioc_qos_write() <- disables preempt
-> wbt_enable_default()
   -> wbt_init()

wbt_init() will be called from wbt_enable_default() if wbt is not
initialized, currently this is only possible in blk_register_queue(), hence
wbt_init() will never be called from iocost and this warning is false
positive.

However, we might support rq_qos destruction dynamically in the future,
and it's better to prevent that, hence move wbt_enable_default() outside
'ioc->lock'. This is safe because queue is still freezed.

Reported-by: Dan Carpenter <error27@gmail.com>
Link: https://lore.kernel.org/lkml/Y+Ja5SRs886CEz7a@kadam/
Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20230527010644.647900-5-yukuai1@huaweicloud.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/block/blk-iocost.c b/block/blk-iocost.c
index 6084a95..9dfcf54 100644 (file)
--- a/block/blk-iocost.c
+++ b/block/blk-iocost.c
@@ -3301,11 +3301,9 @@ static ssize_t ioc_qos_write(struct kernfs_open_file *of, char *input,
                blk_stat_enable_accounting(disk->queue);
                blk_queue_flag_set(QUEUE_FLAG_RQ_ALLOC_TIME, disk->queue);
                ioc->enabled = true;
-               wbt_disable_default(disk);
        } else {
                blk_queue_flag_clear(QUEUE_FLAG_RQ_ALLOC_TIME, disk->queue);
                ioc->enabled = false;
-               wbt_enable_default(disk);
        }
 
        if (user) {
@@ -3318,6 +3316,11 @@ static ssize_t ioc_qos_write(struct kernfs_open_file *of, char *input,
        ioc_refresh_params(ioc, true);
        spin_unlock_irq(&ioc->lock);
 
+       if (enable)
+               wbt_disable_default(disk);
+       else
+               wbt_enable_default(disk);
+
        blk_mq_unquiesce_queue(disk->queue);
        blk_mq_unfreeze_queue(disk->queue);