From: Michal Hocko <mhocko@xxxxxxxx>
Memory migration might fail during offlining and we keep retrying in
that case. This is currently obfuscate by goto retry loop. The code
is hard to follow and as a result it is even suboptimal becase each
retry round scans the full range from start_pfn even though we have
successfully scanned/migrated [start_pfn, pfn] range already. This
is all only because check_pages_isolated failure has to rescan the full
range again.
De-obfuscate the migration retry loop by promoting it to a real for
loop. In fact remove the goto altogether by making it a proper double
loop (yeah, gotos are nasty in this specific case). In the end we
will get a slightly more optimal code which is better readable.
Signed-off-by: Michal Hocko <mhocko@xxxxxxxx>
---
mm/memory_hotplug.c | 60 +++++++++++++++++++++++----------------------
1 file changed, 31 insertions(+), 29 deletions(-)
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 6263c8cd4491..9cd161db3061 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -1591,38 +1591,40 @@ static int __ref __offline_pages(unsigned long start_pfn,
goto failed_removal_isolated;
}
- pfn = start_pfn;
-repeat:
- /* start memory hot removal */
- ret = -EINTR;
- if (signal_pending(current)) {
- reason = "signal backoff";
- goto failed_removal_isolated;
- }
+ do {
+ for (pfn = start_pfn; pfn;)
+ {
+ /* start memory hot removal */
+ ret = -EINTR;
+ if (signal_pending(current)) {
+ reason = "signal backoff";
+ goto failed_removal_isolated;
+ }
- cond_resched();
- lru_add_drain_all();
- drain_all_pages(zone);
+ cond_resched();
+ lru_add_drain_all();
+ drain_all_pages(zone);
- pfn = scan_movable_pages(start_pfn, end_pfn);
- if (pfn) { /* We have movable pages */
- ret = do_migrate_range(pfn, end_pfn);
- goto repeat;
- }
+ pfn = scan_movable_pages(pfn, end_pfn);
+ if (pfn) {
+ /* TODO fatal migration failures should bail out */
+ do_migrate_range(pfn, end_pfn);
+ }
+ }
+
+ /*
+ * dissolve free hugepages in the memory block before doing offlining
+ * actually in order to make hugetlbfs's object counting consistent.
+ */
+ ret = dissolve_free_huge_pages(start_pfn, end_pfn);
+ if (ret) {
+ reason = "failure to dissolve huge pages";
+ goto failed_removal_isolated;
+ }
+ /* check again */
+ offlined_pages = check_pages_isolated(start_pfn, end_pfn);
+ } while (offlined_pages < 0);
- /*
- * dissolve free hugepages in the memory block before doing offlining
- * actually in order to make hugetlbfs's object counting consistent.
- */
- ret = dissolve_free_huge_pages(start_pfn, end_pfn);
- if (ret) {
- reason = "failure to dissolve huge pages";
- goto failed_removal_isolated;
- }
- /* check again */
- offlined_pages = check_pages_isolated(start_pfn, end_pfn);
- if (offlined_pages < 0)
- goto repeat;
pr_info("Offlined Pages %ld\n", offlined_pages);
/* Ok, all of our target is isolated.
We cannot do rollback at this point. */
--
2.19.1
