blk-iocost: fix lockdep warning on blkcg->lock

blkcg->lock depends on q->queue_lock which may depend on another driver
lock required in irq context, one example is dm-thin:

	Chain exists of:
	  &pool->lock#3 --> &q->queue_lock --> &blkcg->lock

	 Possible interrupt unsafe locking scenario:

	       CPU0                    CPU1
	       ----                    ----
	  lock(&blkcg->lock);
	                               local_irq_disable();
	                               lock(&pool->lock#3);
	                               lock(&q->queue_lock);
	  <Interrupt>
	    lock(&pool->lock#3);

Fix the issue by using spin_lock_irq(&blkcg->lock) in ioc_weight_write().

Cc: Tejun Heo <tj@kernel.org>
Reported-by: Bruno Goncalves <bgoncalv@redhat.com>
Link: https://lore.kernel.org/linux-block/CA+QYu4rzz6079ighEanS3Qq_Dmnczcf45ZoJoHKVLVATTo1e4Q@mail.gmail.com/T/#u
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Acked-by: Tejun Heo <tj@kernel.org>
Link: https://lore.kernel.org/r/20210803070608.1766400-1-ming.lei@redhat.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/block/blk-iocost.c b/block/blk-iocost.c
index 5fac375..0e56557 100644 (file)
--- a/block/blk-iocost.c
+++ b/block/blk-iocost.c
@@ -3061,19 +3061,19 @@ static ssize_t ioc_weight_write(struct kernfs_open_file *of, char *buf,
                if (v < CGROUP_WEIGHT_MIN || v > CGROUP_WEIGHT_MAX)
                        return -EINVAL;
 
-               spin_lock(&blkcg->lock);
+               spin_lock_irq(&blkcg->lock);
                iocc->dfl_weight = v * WEIGHT_ONE;
                hlist_for_each_entry(blkg, &blkcg->blkg_list, blkcg_node) {
                        struct ioc_gq *iocg = blkg_to_iocg(blkg);
 
                        if (iocg) {
-                               spin_lock_irq(&iocg->ioc->lock);
+                               spin_lock(&iocg->ioc->lock);
                                ioc_now(iocg->ioc, &now);
                                weight_updated(iocg, &now);
-                               spin_unlock_irq(&iocg->ioc->lock);
+                               spin_unlock(&iocg->ioc->lock);
                        }
                }
-               spin_unlock(&blkcg->lock);
+               spin_unlock_irq(&blkcg->lock);
 
                return nbytes;
        }