On Wed, Sep 21, 2022 at 08:04:49PM +0200, Christoph Hellwig wrote:
> The combinations of an error check with an ERR_PTR return and a lookup
> with a NULL return leads to ugly handling of the return values in the
> callers. Just open coding the check and the lookup is much simpler.
>
> Signed-off-by: Christoph Hellwig <hch@xxxxxx>
> ---
> block/blk-cgroup.c | 36 ++++++++++--------------------------
> 1 file changed, 10 insertions(+), 26 deletions(-)
Reviewed-by: Andreas Herrmann <aherrmann@xxxxxxx>
> diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
> index d1216760d0255..1306112d76486 100644
> --- a/block/blk-cgroup.c
> +++ b/block/blk-cgroup.c
> @@ -602,25 +602,6 @@ u64 __blkg_prfill_u64(struct seq_file *sf, struct blkg_policy_data *pd, u64 v)
> }
> EXPORT_SYMBOL_GPL(__blkg_prfill_u64);
>
> -/* Performs queue bypass and policy enabled checks then looks up blkg. */
> -static struct blkcg_gq *blkg_lookup_check(struct blkcg *blkcg,
> - const struct blkcg_policy *pol,
> - struct request_queue *q)
> -{
> - struct blkcg_gq *blkg;
> -
> - WARN_ON_ONCE(!rcu_read_lock_held());
> - lockdep_assert_held(&q->queue_lock);
> -
> - if (!blkcg_policy_enabled(q, pol))
> - return ERR_PTR(-EOPNOTSUPP);
> -
> - blkg = blkg_lookup(blkcg, q);
> - if (blkg)
> - blkg_update_hint(blkcg, blkg);
> - return blkg;
> -}
> -
> /**
> * blkcg_conf_open_bdev - parse and open bdev for per-blkg config update
> * @inputp: input string pointer
> @@ -697,14 +678,16 @@ int blkg_conf_prep(struct blkcg *blkcg, const struct blkcg_policy *pol,
> rcu_read_lock();
> spin_lock_irq(&q->queue_lock);
>
> - blkg = blkg_lookup_check(blkcg, pol, q);
> - if (IS_ERR(blkg)) {
> - ret = PTR_ERR(blkg);
> + if (!blkcg_policy_enabled(q, pol)) {
> + ret = -EOPNOTSUPP;
> goto fail_unlock;
> }
>
> - if (blkg)
> + blkg = blkg_lookup(blkcg, q);
> + if (blkg) {
> + blkg_update_hint(blkcg, blkg);
> goto success;
> + }
>
> /*
> * Create blkgs walking down from blkcg_root to @blkcg, so that all
> @@ -740,14 +723,15 @@ int blkg_conf_prep(struct blkcg *blkcg, const struct blkcg_policy *pol,
> rcu_read_lock();
> spin_lock_irq(&q->queue_lock);
>
> - blkg = blkg_lookup_check(pos, pol, q);
> - if (IS_ERR(blkg)) {
> - ret = PTR_ERR(blkg);
> + if (!blkcg_policy_enabled(q, pol)) {
> blkg_free(new_blkg);
> + ret = -EOPNOTSUPP;
> goto fail_preloaded;
> }
>
> + blkg = blkg_lookup(pos, q);
> if (blkg) {
> + blkg_update_hint(pos, blkg);
> blkg_free(new_blkg);
> } else {
> blkg = blkg_create(pos, q, new_blkg);
> --
> 2.30.2
>
--
Regards,
Andreas
SUSE Software Solutions Germany GmbH
Frankenstrasse 146, 90461 Nürnberg, Germany
GF: Ivo Totev, Andrew Myers, Andrew McDonald, Martje Boudien Moerman
(HRB 36809, AG Nürnberg)
