From: Bart Van Assche <Bart.VanAssche@wdc.com>
To: "tj@kernel.org" <tj@kernel.org>
Cc: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"linux-block@vger.kernel.org" <linux-block@vger.kernel.org>,
"nborisov@suse.com" <nborisov@suse.com>,
"axboe@kernel.dk" <axboe@kernel.dk>, "shli@fb.com" <shli@fb.com>,
"gregkh@linuxfoundation.org" <gregkh@linuxfoundation.org>,
"00moses.alexander00@gmail.com" <00moses.alexander00@gmail.com>,
"joseph.qi@linux.alibaba.com" <joseph.qi@linux.alibaba.com>,
"arnd@arndb.de" <arnd@arndb.de>
Subject: Re: [PATCH v2] blk-cgroup: remove entries in blkg_tree before queue release
Date: Wed, 11 Apr 2018 20:23:05 +0000 [thread overview]
Message-ID: <f9527dc23ae63e4a58e3fabda0320c8bce7714ae.camel@wdc.com> (raw)
In-Reply-To: <20180411200245.GQ793541@devbig577.frc2.facebook.com>
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WARNING: multiple messages have this Message-ID (diff)
From: Bart Van Assche <Bart.VanAssche@wdc.com>
To: "tj@kernel.org" <tj@kernel.org>
Cc: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"linux-block@vger.kernel.org" <linux-block@vger.kernel.org>,
"nborisov@suse.com" <nborisov@suse.com>,
"axboe@kernel.dk" <axboe@kernel.dk>, "shli@fb.com" <shli@fb.com>,
"gregkh@linuxfoundation.org" <gregkh@linuxfoundation.org>,
"00moses.alexander00@gmail.com" <00moses.alexander00@gmail.com>,
"joseph.qi@linux.alibaba.com" <joseph.qi@linux.alibaba.com>,
"arnd@arndb.de" <arnd@arndb.de>
Subject: Re: [PATCH v2] blk-cgroup: remove entries in blkg_tree before queue release
Date: Wed, 11 Apr 2018 20:23:05 +0000 [thread overview]
Message-ID: <f9527dc23ae63e4a58e3fabda0320c8bce7714ae.camel@wdc.com> (raw)
In-Reply-To: <20180411200245.GQ793541@devbig577.frc2.facebook.com>
On Wed, 2018-04-11 at 13:02 -0700, tj@kernel.org wrote:
> On Wed, Apr 11, 2018 at 08:00:29PM +0000, Bart Van Assche wrote:
> > On Wed, 2018-04-11 at 12:57 -0700, tj@kernel.org wrote:
> > > On Wed, Apr 11, 2018 at 01:55:25PM -0600, Bart Van Assche wrote:
> > > > 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?
> > >
> > > But queue init shouldn't fail here, right?
> >
> > Hello Tejun,
> >
> > Your question is not entirely clear to me. Are you referring to the atomic
> > allocations in blkg_create() or are you perhaps referring to something else?
>
> Hmm.. maybe I'm confused but I thought that the fact that
> blkcg_init_queue() fails itself is already a bug, which happens
> because a previously destroyed queue left behind blkgs.
Hello Tejun,
I had missed the start of this thread so I was not aware of which problem Alex
was trying to solve. In the description of v1 of this patch I read that Alex
thinks that he ran into a scenario in which blk_queue_alloc_node() assigns a
q->id that is still in use by another request queue? That's weird. The following
code still occurs in __blk_release_queue():
ida_simple_remove(&blk_queue_ida, q->id);
It's not clear to me how that remove call could happen *before* q->id is removed
from the blkcg radix tree.
Bart.
next prev parent reply other threads:[~2018-04-11 20:23 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-04-07 10:21 [PATCH v2] blk-cgroup: remove entries in blkg_tree before queue release Alexandru Moise
2018-04-09 22:09 ` Tejun Heo
2018-04-11 10:12 ` Alexandru Moise
2018-04-11 14:20 ` Tejun Heo
2018-04-11 14:28 ` Alexandru Moise
2018-04-11 14:46 ` Tejun Heo
2018-04-11 14:51 ` Tejun Heo
2018-04-11 14:56 ` Tejun Heo
2018-04-11 16:42 ` Bart Van Assche
2018-04-11 16:42 ` Bart Van Assche
2018-04-11 17:00 ` tj
2018-04-11 17:06 ` Bart Van Assche
2018-04-11 17:06 ` Bart Van Assche
2018-04-11 17:15 ` tj
2018-04-11 17:26 ` Bart Van Assche
2018-04-11 17:26 ` Bart Van Assche
2018-04-11 17:30 ` tj
2018-04-11 15:54 ` Bart Van Assche
2018-04-11 15:54 ` Bart Van Assche
2018-04-11 19:00 ` Alexandru Moise
2018-04-11 19:55 ` Bart Van Assche
2018-04-11 19:57 ` tj
2018-04-11 20:00 ` Bart Van Assche
2018-04-11 20:00 ` Bart Van Assche
2018-04-11 20:02 ` tj
2018-04-11 20:23 ` Bart Van Assche [this message]
2018-04-11 20:23 ` Bart Van Assche
2018-04-11 21:23 ` Alexandru Moise
2018-04-11 21:28 ` Bart Van Assche
2018-04-11 21:28 ` Bart Van Assche
2018-04-11 22:58 ` Alexandru Moise
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