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SubjectRe: [PATCH v3 00/12] block: always associate blkg and refcount cleanup
Hi Jens,

On Tue, Sep 11, 2018 at 02:41:25PM -0400, Dennis Zhou wrote:
> Hi everyone,
>
> v3: a few minor fixes.
> 0003: Updated the comment to bio_associate_blkg to reflect closest
> association.
> Removed a return branch in __bio_lookup_create.
> 0009: Removed an unnecessary rcu_read_(un)lock pair.
> 0010: Fixed blkg null pointer... blkg->blkcg => blkcg.
>
> This is rebased onto axboe#for-4.20/block 902d53914f64.
>
> From v2 below (updated):
> ------
> This is a followup to the patch series I sent out earlier [1] containing
> the middle two points:
> 1. always associate a bio with a blkg
> 2. remove the extra css ref held by bios and utilize the blkg ref
>
> The major difference with v2 is that error handling on blkg creation
> and association failure is handled more gracefully. Rather than having
> the complex logic to fallback to root, failures walk up the blkg tree.
> This seems more natural and less prone to error with the many possible
> failure scenarios.
>
> Additionally, there are fixes for kbuild errors and some key details
> overlooked by me in the first series that were pointed out in review.
>
> Modified from the first patchset:
> First, both blk-throttle and blk-iolatency rely on blkg association
> to enable their policies. Rather than each policy (and future policies)
> implement this logic independently, this consolidates it such that
> all bios are tagged with a blkg.
>
> Second, with the addition of always having a blkg reference, the blkcg
> can now be referenced through it rather than maintaining an additional
> pointer and reference. So let's clean this up.
>
> [1] https://lore.kernel.org/lkml/20180831015356.69796-1-dennisszhou@gmail.com/T
>
> This patchset contains the following 12 patches:
> 0001-blkcg-fix-ref-count-issue-with-bio_blkcg-using-task_.patch
> 0002-blkcg-update-blkg_lookup_create-to-do-locking.patch
> 0003-blkcg-convert-blkg_lookup_create-to-find-closest-blk.patch
> 0004-blkcg-always-associate-a-bio-with-a-blkg.patch
> 0005-blkcg-consolidate-bio_issue_init-to-be-a-part-of-cor.patch
> 0006-blkcg-associate-a-blkg-for-pages-being-evicted-by-sw.patch
> 0007-blkcg-associate-writeback-bios-with-a-blkg.patch
> 0008-blkcg-remove-bio-bi_css-and-instead-use-bio-bi_blkg.patch
> 0009-blkcg-remove-additional-reference-to-the-css.patch
> 0010-blkcg-cleanup-and-make-blk_get_rl-use-blkg_lookup_cr.patch
> 0011-blkcg-change-blkg-reference-counting-to-use-percpu_r.patch
> 0012-blkcg-rename-blkg_try_get-to-blkg_tryget.patch
>
> This patchset is on top of axboe#for-4.20/block 902d53914f64.
>
> diffstats below:
>
> Dennis Zhou (Facebook) (12):
> blkcg: fix ref count issue with bio_blkcg using task_css
> blkcg: update blkg_lookup_create to do locking
> blkcg: convert blkg_lookup_create to find closest blkg
> blkcg: always associate a bio with a blkg
> blkcg: consolidate bio_issue_init to be a part of core
> blkcg: associate a blkg for pages being evicted by swap
> blkcg: associate writeback bios with a blkg
> blkcg: remove bio->bi_css and instead use bio->bi_blkg
> blkcg: remove additional reference to the css
> blkcg: cleanup and make blk_get_rl use blkg_lookup_create
> blkcg: change blkg reference counting to use percpu_ref
> blkcg: rename blkg_try_get to blkg_tryget
>
> Documentation/admin-guide/cgroup-v2.rst | 8 +-
> block/bfq-cgroup.c | 4 +-
> block/bfq-iosched.c | 2 +-
> block/bio.c | 158 ++++++++++++++++--------
> block/blk-cgroup.c | 123 ++++++++++++------
> block/blk-iolatency.c | 26 +---
> block/blk-throttle.c | 13 +-
> block/bounce.c | 4 +-
> block/cfq-iosched.c | 4 +-
> drivers/block/loop.c | 5 +-
> drivers/md/raid0.c | 2 +-
> fs/buffer.c | 10 +-
> fs/ext4/page-io.c | 2 +-
> include/linux/bio.h | 23 ++--
> include/linux/blk-cgroup.h | 145 +++++++++++++++-------
> include/linux/blk_types.h | 1 -
> include/linux/cgroup.h | 2 +
> include/linux/writeback.h | 5 +-
> kernel/cgroup/cgroup.c | 48 +++++--
> kernel/trace/blktrace.c | 4 +-
> mm/page_io.c | 2 +-
> 21 files changed, 381 insertions(+), 210 deletions(-)
>
> Thanks,
> Dennis

I reran some basic test again for sanity and it seems to be fine on my
end. There are at least acks, and some reviewed-by's on the series. Is
there anything else you think needs to be done before we let this bake
in for-4.20/for-next?

Thanks,
Dennis

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