The patch titled
Subject: mm/hotplug: fix offline undo_isolate_page_range()
has been added to the -mm tree. Its filename is
mm-hotplug-fix-offline-undo_isolate_page_range.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-hotplug-fix-offline-undo_isolate_page_range.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-hotplug-fix-offline-undo_isolate_page_range.patch
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------------------------------------------------------
From: Qian Cai <cai@xxxxxx>
Subject: mm/hotplug: fix offline undo_isolate_page_range()
f1dd2cd13c4b ("mm, memory_hotplug: do not associate hotadded memory to
zones until online") introduced move_pfn_range_to_zone() which calls
memmap_init_zone() during onlining a memory block. memmap_init_zone()
will reset pagetype flags and makes migrate type to be MOVABLE.
However, in __offline_pages(), it also call undo_isolate_page_range()
after offline_isolated_pages() to do the same thing. Due to 2ce13640b3f4
("mm: __first_valid_page skip over offline pages") changed
__first_valid_page() to skip offline pages, undo_isolate_page_range() here
just waste CPU cycles looping around the offlining PFN range while doing
nothing, because __first_valid_page() will return NULL as
offline_isolated_pages() has already marked all memory sections within the
pfn range as offline via offline_mem_sections().
Also, after calling the "useless" undo_isolate_page_range() here, it
reaches the point of no returning by notifying MEM_OFFLINE. Those pages
will be marked as MIGRATE_MOVABLE again once onlining. The only thing
left to do is to decrease the number of isolated pageblocks zone counter
which would make some paths of the page allocation slower that the above
commit introduced. A memory block is usually at most 1GiB in size, so an
"int" should be enough to represent the number of pageblocks in a block.
Fix an incorrect comment along the way.
Link: http://lkml.kernel.org/r/20190313143133.46200-1-cai@xxxxxx
Fixes: 2ce13640b3f4 ("mm: __first_valid_page skip over offline pages")
Signed-off-by: Qian Cai <cai@xxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxxxx>
Cc: Oscar Salvador <osalvador@xxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
--- a/mm/memory_hotplug.c~mm-hotplug-fix-offline-undo_isolate_page_range
+++ a/mm/memory_hotplug.c
@@ -1580,7 +1580,7 @@ static int __ref __offline_pages(unsigne
{
unsigned long pfn, nr_pages;
long offlined_pages;
- int ret, node;
+ int ret, node, count;
unsigned long flags;
unsigned long valid_start, valid_end;
struct zone *zone;
@@ -1606,10 +1606,11 @@ static int __ref __offline_pages(unsigne
ret = start_isolate_page_range(start_pfn, end_pfn,
MIGRATE_MOVABLE,
SKIP_HWPOISON | REPORT_FAILURE);
- if (ret) {
+ if (ret < 0) {
reason = "failure to isolate range";
goto failed_removal;
}
+ count = ret;
arg.start_pfn = start_pfn;
arg.nr_pages = nr_pages;
@@ -1661,8 +1662,16 @@ static int __ref __offline_pages(unsigne
/* Ok, all of our target is isolated.
We cannot do rollback at this point. */
offline_isolated_pages(start_pfn, end_pfn);
- /* reset pagetype flags and makes migrate type to be MOVABLE */
- undo_isolate_page_range(start_pfn, end_pfn, MIGRATE_MOVABLE);
+
+ /*
+ * Onlining will reset pagetype flags and makes migrate type
+ * MOVABLE, so just need to decrease the number of isolated
+ * pageblocks zone counter here.
+ */
+ spin_lock_irqsave(&zone->lock, flags);
+ zone->nr_isolate_pageblock -= count;
+ spin_unlock_irqrestore(&zone->lock, flags);
+
/* removal success */
adjust_managed_page_count(pfn_to_page(start_pfn), -offlined_pages);
zone->present_pages -= offlined_pages;
--- a/mm/page_alloc.c~mm-hotplug-fix-offline-undo_isolate_page_range
+++ a/mm/page_alloc.c
@@ -8233,7 +8233,7 @@ int alloc_contig_range(unsigned long sta
ret = start_isolate_page_range(pfn_max_align_down(start),
pfn_max_align_up(end), migratetype, 0);
- if (ret)
+ if (ret < 0)
return ret;
/*
--- a/mm/page_isolation.c~mm-hotplug-fix-offline-undo_isolate_page_range
+++ a/mm/page_isolation.c
@@ -172,7 +172,8 @@ __first_valid_page(unsigned long pfn, un
* future will not be allocated again.
*
* start_pfn/end_pfn must be aligned to pageblock_order.
- * Return 0 on success and -EBUSY if any part of range cannot be isolated.
+ * Return the number of isolated pageblocks on success and -EBUSY if any part of
+ * range cannot be isolated.
*
* There is no high level synchronization mechanism that prevents two threads
* from trying to isolate overlapping ranges. If this happens, one thread
@@ -188,6 +189,7 @@ int start_isolate_page_range(unsigned lo
unsigned long pfn;
unsigned long undo_pfn;
struct page *page;
+ int count = 0;
BUG_ON(!IS_ALIGNED(start_pfn, pageblock_nr_pages));
BUG_ON(!IS_ALIGNED(end_pfn, pageblock_nr_pages));
@@ -196,13 +198,15 @@ int start_isolate_page_range(unsigned lo
pfn < end_pfn;
pfn += pageblock_nr_pages) {
page = __first_valid_page(pfn, pageblock_nr_pages);
- if (page &&
- set_migratetype_isolate(page, migratetype, flags)) {
- undo_pfn = pfn;
- goto undo;
+ if (page) {
+ if (set_migratetype_isolate(page, migratetype, flags)) {
+ undo_pfn = pfn;
+ goto undo;
+ }
+ count++;
}
}
- return 0;
+ return count;
undo:
for (pfn = start_pfn;
pfn < undo_pfn;
--- a/mm/sparse.c~mm-hotplug-fix-offline-undo_isolate_page_range
+++ a/mm/sparse.c
@@ -567,7 +567,7 @@ void online_mem_sections(unsigned long s
}
#ifdef CONFIG_MEMORY_HOTREMOVE
-/* Mark all memory sections within the pfn range as online */
+/* Mark all memory sections within the pfn range as offline */
void offline_mem_sections(unsigned long start_pfn, unsigned long end_pfn)
{
unsigned long pfn;
_
Patches currently in -mm which might be from cai@xxxxxx are
kasan-fix-variable-tag-set-but-not-used-warning.patch
mm-debug-add-a-cast-to-u64-for-atomic64_read.patch
kmemleak-skip-scanning-holes-in-the-bss-section.patch
kmemleak-skip-scanning-holes-in-the-bss-section-v2.patch
mm-hotplug-fix-offline-undo_isolate_page_range.patch
