From: Tahsin Erdogan <tahsin@google.com>
To: Tejun Heo <tj@kernel.org>
Cc: Jens Axboe <axboe@kernel.dk>,
linux-block@vger.kernel.org, David Rientjes <rientjes@google.com>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] blkcg: allocate struct blkcg_gq outside request queue spinlock
Date: Tue, 28 Feb 2017 15:51:27 -0800 [thread overview]
Message-ID: <CAAeU0aMMmWagAKc_nUoZj77EYiuiyhdtPZ35C4Yk6BPG-_=kxg@mail.gmail.com> (raw)
In-Reply-To: <20170228224728.GJ15287@htj.duckdns.org>
On Tue, Feb 28, 2017 at 2:47 PM, Tejun Heo <tj@kernel.org> wrote:
>> + if (!blkcg_policy_enabled(q, pol)) {
>> + ret = -EOPNOTSUPP;
>> + goto fail;
>
> Pulling this out of the queue_lock doesn't seem safe to me. This
> function may end up calling into callbacks of disabled policies this
> way.
I will move this to within the lock. To make things safe, I am also
thinking of rechecking both blkcg_policy_enabled() and
blk_queue_bypass() after reacquiring the locks in each iteration.
>> + parent = blkcg_parent(blkcg);
>> + while (parent && !__blkg_lookup(parent, q, false)) {
>> + pos = parent;
>> + parent = blkcg_parent(parent);
>> + }
>
> Hmm... how about adding @new_blkg to blkg_lookup_create() and calling
> it with non-NULL @new_blkg until it succeeds? Wouldn't that be
> simpler?
>
>> +
>> + new_blkg = blkg_alloc(pos, q, GFP_KERNEL);
The challenge with that approach is creating a new_blkg with the right
blkcg before passing to blkg_lookup_create(). blkg_lookup_create()
walks down the hierarchy and will try to fill the first missing entry
and the preallocated new_blkg must have been created with the right
blkcg (feel free to send a code fragment if you think I am
misunderstanding the suggestion).
next prev parent reply other threads:[~2017-02-28 23:51 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-02-28 2:49 [PATCH] blkcg: allocate struct blkcg_gq outside request queue spinlock Tahsin Erdogan
2017-02-28 22:47 ` Tejun Heo
2017-02-28 23:51 ` Tahsin Erdogan [this message]
2017-03-01 16:55 ` Tejun Heo
2017-03-01 23:43 ` [PATCH v2] " Tahsin Erdogan
2017-03-01 23:49 ` Tahsin Erdogan
2017-03-02 19:32 ` Tejun Heo
2017-03-02 22:33 ` Tahsin Erdogan
2017-03-03 19:23 ` Tejun Heo
2017-03-04 1:40 ` [PATCH v3] " Tahsin Erdogan
2017-03-04 19:23 ` Tejun Heo
2017-03-05 14:12 ` [PATCH v4] " Tahsin Erdogan
2017-03-05 14:24 ` Tahsin Erdogan
2017-03-06 20:03 ` Tejun Heo
2017-03-09 8:05 ` [PATCH v5] " Tahsin Erdogan
2017-03-09 18:27 ` Tejun Heo
2017-03-11 22:42 ` Jens Axboe
2017-03-11 22:52 ` Jens Axboe
2017-03-12 4:35 ` Tahsin Erdogan
2017-03-13 14:32 ` Jens Axboe
2017-03-13 16:17 ` Tahsin Erdogan
2017-03-24 21:56 ` [PATCH] " Tahsin Erdogan
2017-03-24 22:04 ` Jens Axboe
2017-03-28 21:53 ` Tejun Heo
2017-03-28 21:59 ` [PATCH v5] " Jens Axboe
2017-03-28 22:01 ` Tahsin Erdogan
2017-03-09 5:25 ` [lkp-robot] [blkcg] ad63af3cb7: BUG:sleeping_function_called_from_invalid_context_at_mm/slab.h kernel test robot
2017-03-09 7:59 ` Tahsin Erdogan
2017-03-26 10:54 [PATCH] blkcg: allocate struct blkcg_gq outside request queue spinlock Julia Lawall
2017-03-27 18:29 ` Tahsin Erdogan
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to='CAAeU0aMMmWagAKc_nUoZj77EYiuiyhdtPZ35C4Yk6BPG-_=kxg@mail.gmail.com' \
--to=tahsin@google.com \
--cc=axboe@kernel.dk \
--cc=linux-block@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=rientjes@google.com \
--cc=tj@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).