Re: [PATCH v3 2/4] cgroup/cpuset: update some comments about the page allocator

On 7/15/26 7:03 AM, Brendan Jackman wrote:
> These comments describing the page allocator are out of date:
>
> - __alloc_pages() is no longer a public API and has no business being
>    described outside of mm/.
>
> - The `wait` variable is gone.
>
> It may be out of date for other reasons too but this patch is just
> fixing the issues that stood out.
>
> To fix it:
>
> - Instead of referring to a specific function, instead to "the page
>    allocator"
>
> - Completely drop out-of-date details of that function's internal
>    behaviour, since they were irrelevant anyway.
>
> Suggested-by: Zi Yan <[email protected]>
> Link: https://lore.kernel.org/all/[email protected]/
> Reviewed-by: Zi Yan <[email protected]>
> Signed-off-by: Brendan Jackman <[email protected]>
> ---
>   kernel/cgroup/cpuset.c | 13 +++++--------
>   1 file changed, 5 insertions(+), 8 deletions(-)
>
> diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
> index 24ea2d09cdbdb..dfd0f827e3b92 100644
> --- a/kernel/cgroup/cpuset.c
> +++ b/kernel/cgroup/cpuset.c
> @@ -4193,7 +4193,7 @@ static struct cpuset *nearest_hardwall_ancestor(struct cpuset *cs)
>    * nearest enclosing hardwalled ancestor cpuset.
>    *
>    * Scanning up parent cpusets requires callback_lock.  The
> - * __alloc_pages() routine only calls here with __GFP_HARDWALL bit
> + * page allocator only calls here with __GFP_HARDWALL bit
>    * _not_ set if it's a GFP_KERNEL allocation, and all nodes in the
>    * current tasks mems_allowed came up empty on the first pass over
>    * the zonelist.  So only GFP_KERNEL allocations, if all nodes in the
> @@ -4206,11 +4206,8 @@ static struct cpuset *nearest_hardwall_ancestor(struct cpuset *cs)
>    * come before the __GFP_HARDWALL check, otherwise a dying task
>    * would be blocked on the fast path.
>    *
> - * The second pass through get_page_from_freelist() doesn't even call
> - * here for GFP_ATOMIC calls.  For those calls, the __alloc_pages()
> - * variable 'wait' is not set, and the bit ALLOC_CPUSET is not set
> - * in alloc_flags.  That logic and the checks below have the combined
> - * affect that:
> + * The second pass through get_page_from_freelist() doesn't even call here for
> + * GFP_ATOMIC calls.  That, and the checks below have the combined affect that:
>    *	in_interrupt - any node ok (current task context irrelevant)
>    *	GFP_ATOMIC   - any node ok
>    *	tsk_is_oom_victim   - any node ok
> @@ -4327,8 +4324,8 @@ void cpuset_nodes_allowed(struct cgroup *cgroup, nodemask_t *mask)
>    * should not be possible for the following code to return an
>    * offline node.  But if it did, that would be ok, as this routine
>    * is not returning the node where the allocation must be, only
> - * the node where the search should start.  The zonelist passed to
> - * __alloc_pages() will include all nodes.  If the slab allocator
> + * the node where the search should start.  The zonelist used by
> + * the allocator will include all nodes.  If the slab allocator
>    * is passed an offline node, it will fall back to the local node.
>    * See kmem_cache_alloc_node().
>    */
Acked-by: Waiman Long <[email protected]>