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SubjectRe: [PATCH v1 4/4] mm/memory_hotplug: online_pages cannot be 0 in online_pages()
On Fri 09-08-19 14:57:01, David Hildenbrand wrote:
> walk_system_ram_range() will fail with -EINVAL in case
> online_pages_range() was never called (== no resource applicable in the
> range). Otherwise, we will always call online_pages_range() with
> nr_pages > 0 and, therefore, have online_pages > 0.

I have no idea why those checks where there TBH. Tried to dig out
commits which added them but didn't help.

> Remove that special handling.
>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: Oscar Salvador <osalvador@suse.de>
> Cc: Michal Hocko <mhocko@suse.com>
> Cc: Pavel Tatashin <pasha.tatashin@soleen.com>
> Cc: Dan Williams <dan.j.williams@intel.com>
> Signed-off-by: David Hildenbrand <david@redhat.com>

Acked-by: Michal Hocko <mhocko@suse.com>

> ---
> mm/memory_hotplug.c | 22 +++++++++-------------
> 1 file changed, 9 insertions(+), 13 deletions(-)
>
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index 87f85597a19e..07e72fe17495 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -854,6 +854,7 @@ int __ref online_pages(unsigned long pfn, unsigned long nr_pages, int online_typ
> ret = walk_system_ram_range(pfn, nr_pages, &onlined_pages,
> online_pages_range);
> if (ret) {
> + /* not a single memory resource was applicable */
> if (need_zonelists_rebuild)
> zone_pcp_reset(zone);
> goto failed_addition;
> @@ -867,27 +868,22 @@ int __ref online_pages(unsigned long pfn, unsigned long nr_pages, int online_typ
>
> shuffle_zone(zone);
>
> - if (onlined_pages) {
> - node_states_set_node(nid, &arg);
> - if (need_zonelists_rebuild)
> - build_all_zonelists(NULL);
> - else
> - zone_pcp_update(zone);
> - }
> + node_states_set_node(nid, &arg);
> + if (need_zonelists_rebuild)
> + build_all_zonelists(NULL);
> + else
> + zone_pcp_update(zone);
>
> init_per_zone_wmark_min();
>
> - if (onlined_pages) {
> - kswapd_run(nid);
> - kcompactd_run(nid);
> - }
> + kswapd_run(nid);
> + kcompactd_run(nid);
>
> vm_total_pages = nr_free_pagecache_pages();
>
> writeback_set_ratelimit();
>
> - if (onlined_pages)
> - memory_notify(MEM_ONLINE, &arg);
> + memory_notify(MEM_ONLINE, &arg);
> mem_hotplug_done();
> return 0;
>
> --
> 2.21.0

--
Michal Hocko
SUSE Labs

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