[PATCH] block: increase BLKCG_MAX_POLS

[PATCH] block: increase BLKCG_MAX_POLS

[Oleksandr Natalenko]

After mq-deadline learnt to deal with cgroups, the BLKCG_MAX_POLS value
became too small for all the elevators to be registered properly. The
following issue is seen:

```
calling  bfq_init+0x0/0x8b @ 1
blkcg_policy_register: BLKCG_MAX_POLS too small
initcall bfq_init+0x0/0x8b returned -28 after 507 usecs
```

and BFQ is non-functional.

Increase BLKCG_MAX_POLS to allow space for everyone

Link: https://lore.kernel.org/lkml/8988303.mDXGIdCtx8@natalenko.name/
Signed-off-by: Oleksandr Natalenko <oleksandr@natalenko.name>
---
 include/linux/blkdev.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 3177181c4326..d3afea47ade6 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -57,7 +57,7 @@ struct blk_keyslot_manager;
  * Maximum number of blkcg policies allowed to be registered concurrently.
  * Defined here to simplify include dependency.
  */
-#define BLKCG_MAX_POLS		5
+#define BLKCG_MAX_POLS		6
 
 typedef void (rq_end_io_fn)(struct request *, blk_status_t);
 
-- 
2.32.0

Re: [PATCH] block: increase BLKCG_MAX_POLS

[Jens Axboe]

On 7/17/21 6:33 AM, Oleksandr Natalenko wrote:
> After mq-deadline learnt to deal with cgroups, the BLKCG_MAX_POLS value
> became too small for all the elevators to be registered properly. The
> following issue is seen:
> 
> ```
> calling  bfq_init+0x0/0x8b @ 1
> blkcg_policy_register: BLKCG_MAX_POLS too small
> initcall bfq_init+0x0/0x8b returned -28 after 507 usecs
> ```
> 
> and BFQ is non-functional.
> 
> Increase BLKCG_MAX_POLS to allow space for everyone

LGTM, just needs a:

Fixes: 08a9ad8bf607 ("block/mq-deadline: Add cgroup support")

in there too, I'll add it.

-- 
Jens Axboe