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

[Ryo Tsuruta]

Hi Vivek,

Vivek Goyal <vgoyal at redhat.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The patch attached with your mail is obsolete and it may potentially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