linux-kernel - Re: [PATCH 18/24] blkio_cgroup patches from Ryo to track async bios.

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Message-Id: <20090818.204212.59676649.ryov@valinux.co.jp>
Date:	Tue, 18 Aug 2009 20:42:12 +0900 (JST)
From:	Ryo Tsuruta <ryov@...inux.co.jp>
To:	vgoyal@...hat.com
Cc:	linux-kernel@...r.kernel.org,
	containers@...ts.linux-foundation.org, dm-devel@...hat.com,
	jens.axboe@...cle.com, balbir@...ux.vnet.ibm.com,
	righi.andrea@...il.com, nauman@...gle.com, dpshah@...gle.com,
	lizf@...fujitsu.com, mikew@...gle.com, fchecconi@...il.com,
	paolo.valente@...more.it, fernando@....ntt.co.jp,
	s-uchida@...jp.nec.com, taka@...inux.co.jp,
	guijianfeng@...fujitsu.com, jmoyer@...hat.com,
	dhaval@...ux.vnet.ibm.com, m-ikeda@...jp.nec.com, agk@...hat.com,
	akpm@...ux-foundation.org, peterz@...radead.org,
	jmarchan@...hat.com
Subject: Re: [PATCH 18/24] blkio_cgroup patches from Ryo to track async
 bios.

Hi Vivek,

Vivek Goyal <vgoyal@...hat.com> wrote:
> o blkio_cgroup patches from Ryo to track async bios.
> 
> o Fernando is also working on another IO tracking mechanism. We are not
>   particular about any IO tracking mechanism. This patchset can make use
>   of any mechanism which makes it to upstream. For the time being making
>   use of Ryo's posting.

The patch attached with your mail is obsolete and it may potentially
cause a deadlock when lock_page_cgroup() is called under radix_tree->lock.
http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=e767e0561d7fd2333df1921f1ab4176211f9036b

The latest blkio-cgroup fixes the above issue and reduces IO tracking
overhead since lock_page_cgroup() is no longer used. I would recommend
to update to the latest version.

And I have a suggestion, how about moving get_cgroup_from_page() to
biotrack.c, I think this function would be useful for people who
want to make use of the IO tracking mechanism.

Please let me know your opinion.

Thanks,
Ryo Tsuruta
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