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SubjectRe: [PATCH v1 3/4] mm/memory_hotplug: Make __remove_section() never fail
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On Tue, 2019-04-09 at 12:01 +0200, David Hildenbrand wrote:
> Let's just warn in case a section is not valid instead of failing to
> remove somewhere in the middle of the process, returning an error
> that
> will be mostly ignored by callers.
>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: Oscar Salvador <osalvador@suse.de>
> Cc: Michal Hocko <mhocko@suse.com>
> Cc: David Hildenbrand <david@redhat.com>
> Cc: Pavel Tatashin <pasha.tatashin@soleen.com>
> Cc: Qian Cai <cai@lca.pw>
> Cc: Wei Yang <richard.weiyang@gmail.com>
> Cc: Arun KS <arunks@codeaurora.org>
> Cc: Mathieu Malaterre <malat@debian.org>
> Signed-off-by: David Hildenbrand <david@redhat.com>

Just a nit:

I think this could be combined with patch#2.
The only reason to fail in here is 1) !valid_section 2)
!present_section.
As I stated in patch#2, one cannot be without the other, so makes sense
to rip present_section check from unregister_mem_section() as well.
Then, you could combine both changelogs explaining the whole thing, and
why we do not need the present_section check either.

But the change looks good to me:

Reviewed-by: Oscar Salvador <osalvador@suse.de>

> ---
> 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 b0cb05748f99..17a60281c36f 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -517,15 +517,15 @@ static void __remove_zone(struct zone *zone,
> unsigned long start_pfn)
> pgdat_resize_unlock(zone->zone_pgdat, &flags);
> }
>
> -static int __remove_section(struct zone *zone, struct mem_section
> *ms,
> - unsigned long map_offset, struct vmem_altmap
> *altmap)
> +static void __remove_section(struct zone *zone, struct mem_section
> *ms,
> + unsigned long map_offset,
> + struct vmem_altmap *altmap)
> {
> unsigned long start_pfn;
> int scn_nr;
> - int ret = -EINVAL;
>
> - if (!valid_section(ms))
> - return ret;
> + if (WARN_ON_ONCE(!valid_section(ms)))
> + return;
>
> unregister_memory_section(ms);
>
> @@ -534,7 +534,6 @@ static int __remove_section(struct zone *zone,
> struct mem_section *ms,
> __remove_zone(zone, start_pfn);
>
> sparse_remove_one_section(zone, ms, map_offset, altmap);
> - return 0;
> }
>
> /**
> @@ -554,7 +553,7 @@ int __remove_pages(struct zone *zone, unsigned
> long phys_start_pfn,
> {
> unsigned long i;
> unsigned long map_offset = 0;
> - int sections_to_remove, ret = 0;
> + int sections_to_remove;
>
> /* In the ZONE_DEVICE case device driver owns the memory
> region */
> if (is_dev_zone(zone)) {
> @@ -575,16 +574,13 @@ int __remove_pages(struct zone *zone, unsigned
> long phys_start_pfn,
> unsigned long pfn = phys_start_pfn +
> i*PAGES_PER_SECTION;
>
> cond_resched();
> - ret = __remove_section(zone, __pfn_to_section(pfn),
> map_offset,
> - altmap);
> + __remove_section(zone, __pfn_to_section(pfn),
> map_offset,
> + altmap);
> map_offset = 0;
> - if (ret)
> - break;
> }
>
> set_zone_contiguous(zone);
> -
> - return ret;
> + return 0;
> }
> #endif /* CONFIG_MEMORY_HOTREMOVE */
>
--
Oscar Salvador
SUSE L3

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