Hello, Tahsin.
Generally looks good. Please see below.
> @@ -184,24 +185,48 @@ static struct blkcg_gq *blkg_create(struct blkcg *blkcg,
> + if (unlikely(!wb_congested)) {
> ret = -ENOMEM;
> goto err_put_css;
> + } else if (unlikely(!blkg)) {
> +
blkg_conf_prep() currently calls blkg_lookup_create() while holding
request queue spinlock. This means allocating memory for struct
blkcg_gq has to be made non-blocking. This causes occasional -ENOMEM
failures in call paths like below:
pcpu_alloc+0x68f/0x710
__alloc_percpu_gfp+0xd/0x10
