From mboxrd@z Thu Jan 1 00:00:00 1970 From: Waiman Long Subject: Re: [PATCH v6 1/3] blk-cgroup: Correctly free percpu iostat_cpu in blkg on error exit Date: Fri, 3 Jun 2022 22:47:48 -0400 Message-ID: <9fe80bd8-7733-066e-d8eb-5e5bab221e45@redhat.com> References: <20220602192020.166940-1-longman@redhat.com> <20220602192020.166940-2-longman@redhat.com> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Return-path: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1654310871; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=Cqh4lNnb8LUprz/k7VVRsZMriLZ9YvGxKq09h6b6YYk=; b=Zf+QEeWfXLxS/vSJlzrKJtdHkrfBSIF/gs4eYGyZhbPk7UBvRmYvtasUKIa0qd6+CgzNqT nVV1UhFOG8ELLrO6lY+WMRalHs8Dimac3iR/jQvs5Z0bujsktF2CZNBWJPHRc2VqvIrnfJ 0x2XX+5fvWMurUnosRDnhkwovJbwCgc= Content-Language: en-US In-Reply-To: List-ID: Content-Type: text/plain; charset="us-ascii"; format="flowed" To: Ming Lei Cc: Tejun Heo , Jens Axboe , cgroups@vger.kernel.org, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org On 6/3/22 22:08, Ming Lei wrote: > On Thu, Jun 02, 2022 at 03:20:18PM -0400, Waiman Long wrote: >> Commit f73316482977 ("blk-cgroup: reimplement basic IO stats using cgroup >> rstat") changes block cgroup IO stats to use the rstat APIs. It added >> a new percpu iostat_cpu field into blkg. The blkg_alloc() was modified >> to allocate the new percpu iostat_cpu but didn't free it when an error >> happened. Fix this by freeing the percpu iostat_cpu on error exit. >> >> Fixes: f73316482977 ("blk-cgroup: reimplement basic IO stats using cgroup rstat") >> Signed-off-by: Waiman Long >> Acked-by: Tejun Heo >> --- >> block/blk-cgroup.c | 7 +++++-- >> 1 file changed, 5 insertions(+), 2 deletions(-) >> >> diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c >> index 40161a3f68d0..acd9b0aa8dc8 100644 >> --- a/block/blk-cgroup.c >> +++ b/block/blk-cgroup.c >> @@ -219,11 +219,11 @@ static struct blkcg_gq *blkg_alloc(struct blkcg *blkcg, struct request_queue *q, >> return NULL; >> >> if (percpu_ref_init(&blkg->refcnt, blkg_release, 0, gfp_mask)) >> - goto err_free; >> + goto err_free_blkg; >> >> blkg->iostat_cpu = alloc_percpu_gfp(struct blkg_iostat_set, gfp_mask); >> if (!blkg->iostat_cpu) >> - goto err_free; >> + goto err_free_blkg; >> >> if (!blk_get_queue(q)) >> goto err_free; >> @@ -259,6 +259,9 @@ static struct blkcg_gq *blkg_alloc(struct blkcg *blkcg, struct request_queue *q, >> return blkg; >> >> err_free: >> + free_percpu(blkg->iostat_cpu); >> + >> +err_free_blkg: >> blkg_free(blkg); > Hi Waiman, > > But blkg_free() frees blkg->iostat_cpu via blkg_free_workfn(), so I am > confused where the leak is in failure path? Yes, you are right. I have overlooked that. So this patch isn't really necessary. Thanks for correcting me. Cheers, Longman