On Tue, Dec 04, 2018 at 01:35:52PM -0500, Dennis Zhou wrote:
> Previously, blkg association was handled by controller specific code in
> blk-throttle and blk-iolatency. However, because a blkg represents a
> relationship between a blkcg and a request_queue, it makes sense to keep
> the blkg->q and bio->bi_disk->queue consistent.
>
> This patch moves association into the bio_set_dev macro(). This should
> cover the majority of cases where the device is set/changed keeping the
> two pointers consistent. Fallback code is added to
> blkcg_bio_issue_check() to catch any missing paths.
>
> Signed-off-by: Dennis Zhou <dennis@xxxxxxxxxx>
> ---
> block/bio.c | 1 +
> block/blk-iolatency.c | 4 +---
> block/blk-throttle.c | 1 -
> include/linux/bio.h | 2 ++
> include/linux/blk-cgroup.h | 11 +++--------
> 5 files changed, 7 insertions(+), 12 deletions(-)
>
> diff --git a/block/bio.c b/block/bio.c
> index 41ebb3f8e2fc..1e852ab904aa 100644
> --- a/block/bio.c
> +++ b/block/bio.c
> @@ -2074,6 +2074,7 @@ void bio_associate_blkg(struct bio *bio)
>
> rcu_read_unlock();
> }
> +EXPORT_SYMBOL_GPL(bio_associate_blkg);
>
> /**
> * bio_disassociate_task - undo bio_associate_current()
> diff --git a/block/blk-iolatency.c b/block/blk-iolatency.c
> index cdbd10564e66..e6b47c255521 100644
> --- a/block/blk-iolatency.c
> +++ b/block/blk-iolatency.c
> @@ -472,14 +472,12 @@ static void check_scale_change(struct iolatency_grp *iolat)
> static void blkcg_iolatency_throttle(struct rq_qos *rqos, struct bio *bio)
> {
> struct blk_iolatency *blkiolat = BLKIOLATENCY(rqos);
> - struct blkcg_gq *blkg;
> + struct blkcg_gq *blkg = bio->bi_blkg;
> bool issue_as_root = bio_issue_as_root_blkg(bio);
>
> if (!blk_iolatency_enabled(blkiolat))
> return;
>
> - bio_associate_blkg(bio);
> - blkg = bio->bi_blkg;
> bio_issue_init(&bio->bi_issue, bio_sectors(bio));
>
> while (blkg && blkg->parent) {
> diff --git a/block/blk-throttle.c b/block/blk-throttle.c
> index 228c3a007ebc..1c6529df2002 100644
> --- a/block/blk-throttle.c
> +++ b/block/blk-throttle.c
> @@ -2118,7 +2118,6 @@ static inline void throtl_update_latency_buckets(struct throtl_data *td)
> static void blk_throtl_assoc_bio(struct bio *bio)
> {
> #ifdef CONFIG_BLK_DEV_THROTTLING_LOW
> - bio_associate_blkg(bio);
> bio_issue_init(&bio->bi_issue, bio_sectors(bio));
> #endif
> }
> diff --git a/include/linux/bio.h b/include/linux/bio.h
> index 62715a5a4f32..6ee2ea8b378a 100644
> --- a/include/linux/bio.h
> +++ b/include/linux/bio.h
> @@ -491,12 +491,14 @@ do { \
> bio_clear_flag(bio, BIO_THROTTLED);\
> (bio)->bi_disk = (bdev)->bd_disk; \
> (bio)->bi_partno = (bdev)->bd_partno; \
> + bio_associate_blkg(bio); \
> } while (0)
>
> #define bio_copy_dev(dst, src) \
> do { \
> (dst)->bi_disk = (src)->bi_disk; \
> (dst)->bi_partno = (src)->bi_partno; \
> + bio_clone_blkcg_association(dst, src); \
> } while (0)
>
> #define bio_dev(bio) \
> diff --git a/include/linux/blk-cgroup.h b/include/linux/blk-cgroup.h
> index c08e96e521ed..3c87ae71156f 100644
> --- a/include/linux/blk-cgroup.h
> +++ b/include/linux/blk-cgroup.h
> @@ -802,21 +802,17 @@ static inline bool blk_throtl_bio(struct request_queue *q, struct blkcg_gq *blkg
> static inline bool blkcg_bio_issue_check(struct request_queue *q,
> struct bio *bio)
> {
> - struct blkcg *blkcg;
> struct blkcg_gq *blkg;
> bool throtl = false;
>
> - rcu_read_lock();
> + if (!bio->bi_blkg)
> + bio_associate_blkg(bio);
>
Should we maybe WARN_ON_ONCE() here since this really shouldn't happen?
Otherwise you can add
Reviewed-by: Josef Bacik <josef@xxxxxxxxxxxxxx>
Thanks,
Josef
