Re: [PATCH bpf-next v4 1/2] mm/bpf: Add bpf_proactive_reclaim kfuncs

> diff --git a/mm/bpf_memcontrol.c b/mm/bpf_memcontrol.c
> index 716df49d7647..dc51868b3acf 100644
> --- a/mm/bpf_memcontrol.c
> +++ b/mm/bpf_memcontrol.c

[ ... ]

> @@ -159,6 +160,120 @@ __bpf_kfunc void bpf_mem_cgroup_flush_stats(struct mem_cgroup *memcg)
>  	mem_cgroup_flush_stats(memcg);
>  }
>
> +/*
> + * Shared implementation of the proactive reclaim kfuncs: performs one
> + * reclaim pass on @memcg with @nr_pages as the goal, allowing swap, and
> + * @swappiness as the anon/file balance override (NULL to follow the
> + * cgroup's own swappiness setting). Returns the reclaimed amount in
> + * bytes, keeping the byte-based unit of the kfuncs' @size argument.
> + */
> +static unsigned long
> +bpf_proactive_reclaim_pages(struct mem_cgroup *memcg, unsigned long nr_pages,
> +			    int *swappiness)

This isn't a bug, but would it be worth trimming the comment above
bpf_proactive_reclaim_pages() and de-duplicating the identical 'Return:'
paragraph that now appears in both kfunc kernel-docs, so the byte/page
unit conversion is documented in exactly one place?

> +{
> +	unsigned long nr_reclaimed;
> +
> +	if (!nr_pages || unlikely(bpf_in_reclaim_context()))
> +		return 0;
> +
> +	nr_reclaimed = try_to_free_mem_cgroup_pages(memcg, nr_pages, GFP_KERNEL,
> +						    MEMCG_RECLAIM_MAY_SWAP |
> +						    MEMCG_RECLAIM_PROACTIVE,
> +						    swappiness);
> +
> +	return nr_reclaimed * PAGE_SIZE;
> +}
> +
> +/**
> + * bpf_proactive_reclaim - proactively reclaim memory from a memory
> + *                         cgroup
> + * @memcg: the target memory cgroup to reclaim from
> + * @size:  the amount of memory to reclaim, in bytes
> + *
> + * Trigger one proactive reclaim pass on @memcg, similar to a write to
> + * the memory.reclaim cgroup file: pages are reclaimed according to the
> + * cgroup's own swappiness setting and swap is allowed. Note that,
> + * unlike memory.reclaim, this does not retry until @size is reached;
> + * callers can invoke it again if needed.
> + *
> + * The reclaim runs with GFP_KERNEL, so this function must not be called
> + * from a context that holds a filesystem lock (e.g. an LSM hook invoked
> + * with inode_lock held): the reclaim path may enter filesystem shrinkers
> + * and deadlock trying to reacquire the lock. Contexts that set
> + * PF_MEMALLOC_NOFS/NOIO are handled by the gfp context inheritance.
> + *
> + * Return:
> + *   The amount of memory actually reclaimed, in bytes (rounded to full
> + *   pages), or 0 if @size is smaller than a page or the calling task is
> + *   already in a reclaim/freeing context (PF_MEMALLOC).
> + */
> +__bpf_kfunc unsigned long bpf_proactive_reclaim(struct mem_cgroup *memcg,
> +						unsigned long size)
> +{
> +	return bpf_proactive_reclaim_pages(memcg, size / PAGE_SIZE, NULL);
> +}
> +
> +/**
> + * bpf_proactive_reclaim_swappiness - proactively reclaim memory from a
> + *                                    memory cgroup with an explicit
> + *                                    swappiness
> + * @memcg:      the target memory cgroup to reclaim from
> + * @size:       the amount of memory to reclaim, in bytes
> + * @swappiness: swappiness override for this reclaim pass
> + *
> + * Same as bpf_proactive_reclaim(), except that the anon/file reclaim
> + * balance is controlled by @swappiness instead of the cgroup's
> + * swappiness setting. Valid values are [MIN_SWAPPINESS, MAX_SWAPPINESS]
> + * and SWAPPINESS_ANON_ONLY, which restricts reclaim to anon folios.
> + *
> + * Return:
> + *   The amount of memory actually reclaimed, in bytes (rounded to full
> + *   pages), (unsigned long)-1 if @swappiness is out of range, or 0 if
> + *   @size is smaller than a page or the calling task is already in a
> + *   reclaim/freeing context (PF_MEMALLOC).
> + */
> +__bpf_kfunc unsigned long
> +bpf_proactive_reclaim_swappiness(struct mem_cgroup *memcg, unsigned long size,
> +				 int swappiness)
> +{
> +	if (swappiness < MIN_SWAPPINESS || swappiness > SWAPPINESS_ANON_ONLY)
> +		return (unsigned long)-1;
> +
> +	return bpf_proactive_reclaim_pages(memcg, size / PAGE_SIZE,
> +					   &swappiness);
> +}

[ ... ]


---
AI reviewed your patch. Please fix the bug or email reply why it's not a bug.
See: https://github.com/kernel-patches/vmtest/blob/master/ci/claude/README.md

CI run summary: https://github.com/kernel-patches/bpf/actions/runs/32339450346