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Merge "mm/memory_hotplug: drain per-cpu pages again during memory offline"

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qctecmdr 2020-11-23 19:13:33 -08:00 committed by Gerrit - the friendly Code Review server
commit 48c30d3f71
2 changed files with 22 additions and 0 deletions
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14
mm/memory_hotplug.c
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@ -1603,6 +1603,20 @@ static int __ref __offline_pages(unsigned long start_pfn,
/* check again */
ret = walk_system_ram_range(start_pfn, end_pfn - start_pfn,
NULL, check_pages_isolated_cb);
/*
* per-cpu pages are drained in start_isolate_page_range, but if
* there are still pages that are not free, make sure that we
* drain again, because when we isolated range we might
* have raced with another thread that was adding pages to pcp
* list.
*
* Forward progress should be still guaranteed because
* pages on the pcp list can only belong to MOVABLE_ZONE
* because has_unmovable_pages explicitly checks for
* PageBuddy on freed pages on other zones.
*/
if (ret)
drain_all_pages(zone);
} while (ret);
/* Ok, all of our target is isolated.

8
mm/page_isolation.c
View File

@ -187,6 +187,14 @@ __first_valid_page(unsigned long pfn, unsigned long nr_pages)
* pageblocks we may have modified and return -EBUSY to caller. This
* prevents two threads from simultaneously working on overlapping ranges.
*
* Please note that there is no strong synchronization with the page allocator
* either. Pages might be freed while their page blocks are marked ISOLATED.
* In some cases pages might still end up on pcp lists and that would allow
* for their allocation even when they are in fact isolated already. Depending
* on how strong of a guarantee the caller needs drain_all_pages might be needed
* (e.g. __offline_pages will need to call it after check for isolated range for
* a next retry).
*
* Return: the number of isolated pageblocks on success and -EBUSY if any part
* of range cannot be isolated.
*/