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 | 14 +++++++++++++-
1 file changed, 13 insertions(+), 1 deletion(-)
diff --git a/block/blk-mq-sysfs.c b/block/blk-mq-sysfs.c
index 6113328abd70..2b9df2b73bf6 100644
--- a/block/blk-mq-sysfs.c
+++ b/block/blk-mq-sysfs.c
@@ -229,22 +229,31 @@ int blk_mq_sysfs_register(struct gendisk *disk)
kobject_uevent(q->mq_kobj, KOBJ_ADD);
+ mutex_lock(&q->tag_set->tag_list_lock);
+
queue_for_each_hw_ctx(q, hctx, i) {
ret = blk_mq_register_hctx(hctx);
- if (ret)
+ if (ret) {
+ mutex_unlock(&q->tag_set->tag_list_lock);
goto unreg;
+ }
}
+ mutex_unlock(&q->tag_set->tag_list_lock);
out:
return ret;
unreg:
+ mutex_lock(&q->tag_set->tag_list_lock);
+
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);
return ret;
@@ -256,10 +265,13 @@ 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);
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);
}
--
2.47.1
