[PATCH] block/cgroup: Drop stale -EBUSY retry from blkg_conf_prep()

[PATCH] block/cgroup: Drop stale -EBUSY retry from blkg_conf_prep()

[Yang Xiuwei]

Since commit 8f4236d9008b ("block: remove QUEUE_FLAG_BYPASS and
->bypass") nothing in the blkcg blkg lookup/creation path
returns -EBUSY anymore. blkg_conf_prep() nevertheless still
retries at fail_exit with msleep(10) and restart_syscall()
— logic added in 2012 when blk_queue_bypass() could
cause blkg lookup/creation to fail with -EBUSY while the queue was
temporarily bypassed during elevator changes.

Signed-off-by: Yang Xiuwei <yangxiuwei@kylinos.cn>
---
 block/blk-cgroup.c | 10 ----------
 1 file changed, 10 deletions(-)

diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index 3093c1c03902..259f2240e7df 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -919,16 +919,6 @@ int blkg_conf_prep(struct blkcg *blkcg, const struct blkcg_policy *pol,
 	spin_unlock_irq(&q->queue_lock);
 fail_exit:
 	mutex_unlock(&q->blkcg_mutex);
-	/*
-	 * If queue was bypassing, we should retry.  Do so after a
-	 * short msleep().  It isn't strictly necessary but queue
-	 * can be bypassing for some time and it's always nice to
-	 * avoid busy looping.
-	 */
-	if (ret == -EBUSY) {
-		msleep(10);
-		ret = restart_syscall();
-	}
 	return ret;
 }
 EXPORT_SYMBOL_GPL(blkg_conf_prep);
-- 
2.25.1

Re: [PATCH] block/cgroup: Drop stale -EBUSY retry from blkg_conf_prep()

[Tao Cui]

在 2026/6/22 16:56, Yang Xiuwei 写道:
> Since commit 8f4236d9008b ("block: remove QUEUE_FLAG_BYPASS and
> ->bypass") nothing in the blkcg blkg lookup/creation path
> returns -EBUSY anymore...

Correct. I traced every error path in blkg_conf_prep() (and blkg_create()
underneath it): the only possible values are -EINVAL, -EOPNOTSUPP, -ENOMEM,
-ENODEV and -EEXIST (from radix_tree_insert). The -EBUSY source was indeed
the blk_queue_bypass() check removed by 8f4236d9008b, so the retry branch
has been dead since 2018. Clean removal with no behavioral change.

Reviewed-by: Tao Cui <cuitao@kylinos.cn>