On 1/28/25 15:34, Nilay Shroff wrote:
The nr_hw_queue update could potentially race with disk addtion/removal
while registering/unregistering hctx sysfs files. The __blk_mq_update_
nr_hw_queues() runs with q->tag_list_lock held and so to avoid it racing
with disk addition/removal we should acquire q->tag_list_lock while
registering/unregistering hctx sysfs files.
With this patch, blk_mq_sysfs_register() (called during disk addition)
and blk_mq_sysfs_unregister() (called during disk removal) now runs
with q->tag_list_lock held so that it avoids racing with __blk_mq_update
_nr_hw_queues().
Signed-off-by: Nilay Shroff <nilay@xxxxxxxxxxxxx>
---
block/blk-mq-sysfs.c | 17 +++++++++--------
1 file changed, 9 insertions(+), 8 deletions(-)
diff --git a/block/blk-mq-sysfs.c b/block/blk-mq-sysfs.c
index 6113328abd70..3feeeccf8a99 100644
--- a/block/blk-mq-sysfs.c
+++ b/block/blk-mq-sysfs.c
@@ -225,25 +225,25 @@ int blk_mq_sysfs_register(struct gendisk *disk)
ret = kobject_add(q->mq_kobj, &disk_to_dev(disk)->kobj, "mq");
if (ret < 0)
- goto out;
+ return ret;
kobject_uevent(q->mq_kobj, KOBJ_ADD);
+ mutex_lock(&q->tag_set->tag_list_lock);
Maybe a comment here to indicate that it prevents a race?
queue_for_each_hw_ctx(q, hctx, i) {
ret = blk_mq_register_hctx(hctx);
if (ret)
- goto unreg;
+ goto out_unreg;
}
+ mutex_unlock(&q->tag_set->tag_list_lock);
+ return 0;
-
-out:
- return ret;
-
-unreg:
+out_unreg:
queue_for_each_hw_ctx(q, hctx, j) {
if (j < i)
blk_mq_unregister_hctx(hctx);
}
+ mutex_unlock(&q->tag_set->tag_list_lock);
kobject_uevent(q->mq_kobj, KOBJ_REMOVE);
kobject_del(q->mq_kobj);
@@ -256,9 +256,10 @@ void blk_mq_sysfs_unregister(struct gendisk *disk)
struct blk_mq_hw_ctx *hctx;
unsigned long i;
-
+ mutex_lock(&q->tag_set->tag_list_lock);
Similar here.
queue_for_each_hw_ctx(q, hctx, i)
blk_mq_unregister_hctx(hctx);
+ mutex_unlock(&q->tag_set->tag_list_lock);
kobject_uevent(q->mq_kobj, KOBJ_REMOVE);
kobject_del(q->mq_kobj);
Otherwise looks good.
Reviewed-by: Hannes Reinecke <hare@xxxxxxx>
Cheers,
Hannes
--
Dr. Hannes Reinecke Kernel Storage Architect
hare@xxxxxxx +49 911 74053 688
SUSE Software Solutions GmbH, Frankenstr. 146, 90461 Nürnberg
HRB 36809 (AG Nürnberg), GF: I. Totev, A. McDonald, W. Knoblich
