Re: [PATCH 1/3] sched_ext: Rename scx_cmask.nr_bits to nr_cids

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Low] Incomplete refactoring of `nr_bits` to `nr_cids` causes a compilation error in `cmask_copy_from_kernel()`.
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commit 7049bf95e9f693c1107678499b063bd2c1a25e08
Author: Tejun Heo <tj@kernel.org>

sched_ext: Rename scx_cmask.nr_bits to nr_cids
    
struct scx_cmask is a base-windowed bitmap over cid space. Each bit
represents one cid, so the count of active bits is the count of cids. The
sibling struct scx_cid_shard already uses nr_cids. Rename as a prep so the
following patches that grow the cmask API can use the consistent name.

> diff --git a/kernel/sched/ext_types.h b/kernel/sched/ext_types.h
> index ebb8cdf906123..c6c4e3db73111 100644
> --- a/kernel/sched/ext_types.h
> +++ b/kernel/sched/ext_types.h
[ ... ]
> @@ -82,21 +82,21 @@ struct scx_cid_topo {
>   */
>  struct scx_cmask {
>  	u32 base;
> -	u32 nr_bits;
> +	u32 nr_cids;
>  	DECLARE_FLEX_ARRAY(u64, bits);
>  };

Will this rename cause a build failure for BPF programs using
cmask_copy_from_kernel() from tools/sched_ext/include/scx/cid.bpf.h?

It appears cmask_copy_from_kernel() still references the old nr_bits
member:

static __always_inline void cmask_copy_from_kernel(struct scx_cmask __arena *dst,
						   const struct scx_cmask *src)
{
	u32 base = 0, nr_bits = 0, nr_words, wi;
...
	if (bpf_probe_read_kernel(&nr_bits, sizeof(nr_bits), &src->nr_bits)) {
		scx_bpf_error("probe-read cmask->nr_bits failed");
		return;
	}

	if (nr_bits > dst->nr_bits) {
		scx_bpf_error("src cmask nr_bits=%u exceeds dst nr_bits=%u",
			      nr_bits, dst->nr_bits);
		return;
	}
...

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Sashiko AI review · https://sashiko.dev/#/patchset/20260517181022.1184056-1-tj@kernel.org?part=1