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SubjectRe: [RFC PATCH 5/5] mm, memory_hotplug: be more verbose for memory offline failures
On Thu 08-11-18 12:46:47, Anshuman Khandual wrote:
>
>
> On 11/07/2018 03:48 PM, Michal Hocko wrote:
[...]
> > @@ -1411,8 +1409,14 @@ do_migrate_range(unsigned long start_pfn, unsigned long end_pfn)
> > /* Allocate a new page from the nearest neighbor node */
> > ret = migrate_pages(&source, new_node_page, NULL, 0,
> > MIGRATE_SYNC, MR_MEMORY_HOTPLUG);
> > - if (ret)
> > + if (ret) {
> > + list_for_each_entry(page, &source, lru) {
> > + pr_warn("migrating pfn %lx failed ",
> > + page_to_pfn(page), ret);
>
> Seems like pr_warn() needs to have %d in here to print 'ret'.

Dohh. Rebase hickup. You are right ret:%d got lost on the way.

> Though
> dumping return code from migrate_pages() makes sense, wondering if
> it is required for each and every page which failed to migrate here
> or just one instance is enough.

Does it matter enough to special case one printk?

> > + dump_page(page, NULL);
> > + }
>
> s/NULL/failed to migrate/ for dump_page().

Yes, makes sense.

>
> > putback_movable_pages(&source);
> > + }
> > }
> > out:
> > return ret;
> > diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> > index a919ba5cb3c8..23267767bf98 100644
> > --- a/mm/page_alloc.c
> > +++ b/mm/page_alloc.c
> > @@ -7845,6 +7845,7 @@ bool has_unmovable_pages(struct zone *zone, struct page *page, int count,
> > return false;
> > unmovable:
> > WARN_ON_ONCE(zone_idx(zone) == ZONE_MOVABLE);
> > + dump_page(pfn_to_page(pfn+iter), "has_unmovable_pages");
>
> s/has_unmovable_pages/is unmovable/

OK

> If we eally care about the function name, then dump_page() should be
> followed by dump_stack() like the case in some other instances.
>
> > return true;
>
> This will be dumped from HugeTLB and CMA allocation paths as well through
> alloc_contig_range(). But it should be okay as those occurrences should be
> rare and dumping page state then will also help.

yes

Thanks and here is the incremental fix:

diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index bf214beccda3..820397e18e59 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -1411,9 +1411,9 @@ do_migrate_range(unsigned long start_pfn, unsigned long end_pfn)
MIGRATE_SYNC, MR_MEMORY_HOTPLUG);
if (ret) {
list_for_each_entry(page, &source, lru) {
- pr_warn("migrating pfn %lx failed ",
+ pr_warn("migrating pfn %lx failed ret:%d ",
page_to_pfn(page), ret);
- dump_page(page, NULL);
+ dump_page(page, "migration failure");
}
putback_movable_pages(&source);
}
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 23267767bf98..ec2c7916dc2d 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -7845,7 +7845,7 @@ bool has_unmovable_pages(struct zone *zone, struct page *page, int count,
return false;
unmovable:
WARN_ON_ONCE(zone_idx(zone) == ZONE_MOVABLE);
- dump_page(pfn_to_page(pfn+iter), "has_unmovable_pages");
+ dump_page(pfn_to_page(pfn+iter), "unmovable page");
return true;
}

--
Michal Hocko
SUSE Labs
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