[PATCH v4 10/12] blk-iolatency: fix incorrect lock order for rq_qos_mutex and freeze queue
From: Yu Kuai <hidden>
Date: 2025-12-01 08:34:38
Subsystem:
block layer, control group - block io controller (blkio), the rest · Maintainers:
Jens Axboe, Tejun Heo, Josef Bacik, Linus Torvalds
Currently blk-iolatency will hold rq_qos_mutex first and then call rq_qos_add() to freeze queue. Fix this problem by converting to use blkg_conf_open_bdev_frozen() from iolatency_set_limit(), and convert to use rq_qos_add_frozen(). Signed-off-by: Yu Kuai <redacted> --- block/blk-iolatency.c | 15 +++++++++------ 1 file changed, 9 insertions(+), 6 deletions(-)
diff --git a/block/blk-iolatency.c b/block/blk-iolatency.c
index 45bd18f68541..1558afbf517b 100644
--- a/block/blk-iolatency.c
+++ b/block/blk-iolatency.c@@ -764,8 +764,8 @@ static int blk_iolatency_init(struct gendisk *disk) if (!blkiolat) return -ENOMEM; - ret = rq_qos_add(&blkiolat->rqos, disk, RQ_QOS_LATENCY, - &blkcg_iolatency_ops); + ret = rq_qos_add_frozen(&blkiolat->rqos, disk, RQ_QOS_LATENCY, + &blkcg_iolatency_ops); if (ret) goto err_free; ret = blkcg_activate_policy(disk, &blkcg_policy_iolatency);
@@ -831,16 +831,19 @@ static ssize_t iolatency_set_limit(struct kernfs_open_file *of, char *buf, struct blkcg_gq *blkg; struct blkg_conf_ctx ctx; struct iolatency_grp *iolat; + unsigned long memflags; char *p, *tok; u64 lat_val = 0; u64 oldval; - int ret; + int ret = 0; blkg_conf_init(&ctx, buf); - ret = blkg_conf_open_bdev(&ctx); - if (ret) + memflags = blkg_conf_open_bdev_frozen(&ctx); + if (IS_ERR_VALUE(memflags)) { + ret = memflags; goto out; + } /* * blk_iolatency_init() may fail after rq_qos_add() succeeds which can
@@ -890,7 +893,7 @@ static ssize_t iolatency_set_limit(struct kernfs_open_file *of, char *buf, iolatency_clear_scaling(blkg); ret = 0; out: - blkg_conf_exit(&ctx); + blkg_conf_exit_frozen(&ctx, memflags); return ret ?: nbytes; }
--
2.51.0