linux-kernel - Re: [PATCH v2] blk-cgroup: remove entries in blkg

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Date:   Wed, 11 Apr 2018 13:55:25 -0600
From:   Bart Van Assche <bart.vanassche@....com>
To:     Alexandru Moise <00moses.alexander00@...il.com>
Cc:     "tj@...nel.org" <tj@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-block@...r.kernel.org" <linux-block@...r.kernel.org>,
        "nborisov@...e.com" <nborisov@...e.com>,
        "axboe@...nel.dk" <axboe@...nel.dk>, "shli@...com" <shli@...com>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "joseph.qi@...ux.alibaba.com" <joseph.qi@...ux.alibaba.com>,
        "arnd@...db.de" <arnd@...db.de>
Subject: Re: [PATCH v2] blk-cgroup: remove entries in blkg_tree before queue
 release

On 04/11/18 13:00, Alexandru Moise wrote:
> But the root cause of it is in blkcg_init_queue() when blkg_create() returns
> an ERR ptr, because it tries to insert into a populated index into blkcg->blkg_tree,
> the entry that we fail to remove at __blk_release_queue().

Hello Alex,

Had you considered something like the untested patch below?

Thanks,

Bart.


diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index 1c16694ae145..f2ced19e74b8 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -1191,14 +1191,17 @@ int blkcg_init_queue(struct request_queue *q)
  	if (preloaded)
  		radix_tree_preload_end();

-	if (IS_ERR(blkg))
-		return PTR_ERR(blkg);
+	if (IS_ERR(blkg)) {
+		ret = PTR_ERR(blkg);
+		goto destroy_all;
+	}

  	q->root_blkg = blkg;
  	q->root_rl.blkg = blkg;

  	ret = blk_throtl_init(q);
  	if (ret) {
+destroy_all:
  		spin_lock_irq(q->queue_lock);
  		blkg_destroy_all(q);
  		spin_unlock_irq(q->queue_lock);