Merge: blk-cgroup: fix possible deadlock while configuring policy

MR: https://gitlab.com/redhat/centos-stream/src/kernel/centos-stream-9/-/merge_requests/7643

blk-cgroup: fix possible deadlock while configuring policy

JIRA: https://issues.redhat.com/browse/RHEL-129939

Signed-off-by: Ming Lei <ming.lei@redhat.com>

Approved-by: Jeff Moyer <jmoyer@redhat.com>
Approved-by: Ewan D. Milne <emilne@redhat.com>
Approved-by: CKI KWF Bot <cki-ci-bot+kwf-gitlab-com@redhat.com>

Merged-by: CKI GitLab Kmaint Pipeline Bot <26919896-cki-kmaint-pipeline-bot@users.noreply.gitlab.com>

Author: CKI KWF Bot

block/blk-cgroup.c

@@ -883,14 +883,8 @@ int blkg_conf_prep(struct blkcg *blkcg, const struct blkcg_policy *pol,
 	disk = ctx->bdev->bd_disk;
 	q = disk->queue;
 
-	/*
-	 * blkcg_deactivate_policy() requires queue to be frozen, we can grab
-	 * q_usage_counter to prevent concurrent with blkcg_deactivate_policy().
-	 */
-	ret = blk_queue_enter(q, 0);
-	if (ret)
-		goto fail;
-
+	/* Prevent concurrent with blkcg_deactivate_policy() */
+	mutex_lock(&q->blkcg_mutex);
 	spin_lock_irq(&q->queue_lock);
 
 	if (!blkcg_policy_enabled(q, pol)) {
@@ -920,16 +914,16 @@ int blkg_conf_prep(struct blkcg *blkcg, const struct blkcg_policy *pol,
 		/* Drop locks to do new blkg allocation with GFP_KERNEL. */
 		spin_unlock_irq(&q->queue_lock);
 
-		new_blkg = blkg_alloc(pos, disk, GFP_KERNEL);
+		new_blkg = blkg_alloc(pos, disk, GFP_NOIO);
 		if (unlikely(!new_blkg)) {
 			ret = -ENOMEM;
-			goto fail_exit_queue;
+			goto fail_exit;
 		}
 
 		if (radix_tree_preload(GFP_KERNEL)) {
 			blkg_free(new_blkg);
 			ret = -ENOMEM;
-			goto fail_exit_queue;
+			goto fail_exit;
 		}
 
 		spin_lock_irq(&q->queue_lock);
@@ -957,17 +951,16 @@ int blkg_conf_prep(struct blkcg *blkcg, const struct blkcg_policy *pol,
 			goto success;
 	}
 success:
-	blk_queue_exit(q);
+	mutex_unlock(&q->blkcg_mutex);
 	ctx->blkg = blkg;
 	return 0;
 
 fail_preloaded:
 	radix_tree_preload_end();
 fail_unlock:
 	spin_unlock_irq(&q->queue_lock);
-fail_exit_queue:
-	blk_queue_exit(q);
-fail:
+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