[PATCH v4 3/7] mm: page_isolation: check specified range for unmovable pages
From: Zi Yan
Date: Wed Jan 19 2022 - 14:07:14 EST
From: Zi Yan <ziy@xxxxxxxxxx>
Enable set_migratetype_isolate() to check specified sub-range for
unmovable pages during isolation. Page isolation is done
at max(MAX_ORDER_NR_PAEGS, pageblock_nr_pages) granularity, but not all
pages within that granularity are intended to be isolated. For example,
alloc_contig_range(), which uses page isolation, allows ranges without
alignment. This commit makes unmovable page check only look for
interesting pages, so that page isolation can succeed for any
non-overlapping ranges.
Signed-off-by: Zi Yan <ziy@xxxxxxxxxx>
---
include/linux/page-isolation.h | 1 +
mm/memory_hotplug.c | 12 +++++++-
mm/page_alloc.c | 2 +-
mm/page_isolation.c | 53 +++++++++++++++++++++-------------
4 files changed, 46 insertions(+), 22 deletions(-)
diff --git a/include/linux/page-isolation.h b/include/linux/page-isolation.h
index e14eddf6741a..a4d2687ed4e6 100644
--- a/include/linux/page-isolation.h
+++ b/include/linux/page-isolation.h
@@ -42,6 +42,7 @@ int move_freepages_block(struct zone *zone, struct page *page,
*/
int
start_isolate_page_range(unsigned long start_pfn, unsigned long end_pfn,
+ unsigned long isolate_start, unsigned long isolate_end,
unsigned migratetype, int flags);
/*
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 0139b77c51d5..5db84c3fa882 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -1901,8 +1901,18 @@ int __ref offline_pages(unsigned long start_pfn, unsigned long nr_pages,
zone_pcp_disable(zone);
lru_cache_disable();
- /* set above range as isolated */
+ /*
+ * set above range as isolated
+ *
+ * start_pfn and end_pfn are the same as isolate_start and isolate_end,
+ * because start_pfn and end_pfn are already PAGES_PER_SECTION
+ * (>= MAX_ORDER_NR_PAGES) aligned; if start_pfn is
+ * pageblock_nr_pages aligned in memmap_on_memory case, there is no
+ * need to isolate pages before start_pfn, since they are used by
+ * memmap thus not user visible.
+ */
ret = start_isolate_page_range(start_pfn, end_pfn,
+ start_pfn, end_pfn,
MIGRATE_MOVABLE,
MEMORY_OFFLINE | REPORT_FAILURE);
if (ret) {
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 1d812268c2a9..812cf557b20f 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -9016,7 +9016,7 @@ int alloc_contig_range(unsigned long start, unsigned long end,
* put back to page allocator so that buddy can use them.
*/
- ret = start_isolate_page_range(pfn_max_align_down(start),
+ ret = start_isolate_page_range(start, end, pfn_max_align_down(start),
pfn_max_align_up(end), migratetype, 0);
if (ret)
return ret;
diff --git a/mm/page_isolation.c b/mm/page_isolation.c
index 6c841274bf46..d17ad9a7d4bf 100644
--- a/mm/page_isolation.c
+++ b/mm/page_isolation.c
@@ -16,7 +16,8 @@
#include <trace/events/page_isolation.h>
/*
- * This function checks whether pageblock includes unmovable pages or not.
+ * This function checks whether pageblock within [start_pfn, end_pfn) includes
+ * unmovable pages or not.
*
* PageLRU check without isolation or lru_lock could race so that
* MIGRATE_MOVABLE block might include unmovable pages. And __PageMovable
@@ -29,11 +30,14 @@
*
*/
static struct page *has_unmovable_pages(struct zone *zone, struct page *page,
- int migratetype, int flags)
+ int migratetype, int flags,
+ unsigned long start_pfn, unsigned long end_pfn)
{
- unsigned long iter = 0;
- unsigned long pfn = page_to_pfn(page);
- unsigned long offset = pfn % pageblock_nr_pages;
+ unsigned long first_pfn = max(page_to_pfn(page), start_pfn);
+ unsigned long pfn = first_pfn;
+ unsigned long last_pfn = min(ALIGN(pfn + 1, pageblock_nr_pages), end_pfn);
+
+ page = pfn_to_page(pfn);
if (is_migrate_cma_page(page)) {
/*
@@ -47,8 +51,8 @@ static struct page *has_unmovable_pages(struct zone *zone, struct page *page,
return page;
}
- for (; iter < pageblock_nr_pages - offset; iter++) {
- page = pfn_to_page(pfn + iter);
+ for (pfn = first_pfn; pfn < last_pfn; pfn++) {
+ page = pfn_to_page(pfn);
/*
* Both, bootmem allocations and memory holes are marked
@@ -85,7 +89,7 @@ static struct page *has_unmovable_pages(struct zone *zone, struct page *page,
}
skip_pages = compound_nr(head) - (page - head);
- iter += skip_pages - 1;
+ pfn += skip_pages - 1;
continue;
}
@@ -97,7 +101,7 @@ static struct page *has_unmovable_pages(struct zone *zone, struct page *page,
*/
if (!page_ref_count(page)) {
if (PageBuddy(page))
- iter += (1 << buddy_order(page)) - 1;
+ pfn += (1 << buddy_order(page)) - 1;
continue;
}
@@ -134,7 +138,13 @@ static struct page *has_unmovable_pages(struct zone *zone, struct page *page,
return NULL;
}
-static int set_migratetype_isolate(struct page *page, int migratetype, int isol_flags)
+/*
+ * This function set pageblock migratetype to isolate if no unmovable page is
+ * present in [start_pfn, end_pfn). The pageblock must be within
+ * [start_pfn, end_pfn).
+ */
+static int set_migratetype_isolate(struct page *page, int migratetype, int isol_flags,
+ unsigned long start_pfn, unsigned long end_pfn)
{
struct zone *zone = page_zone(page);
struct page *unmovable;
@@ -156,7 +166,7 @@ static int set_migratetype_isolate(struct page *page, int migratetype, int isol_
* FIXME: Now, memory hotplug doesn't call shrink_slab() by itself.
* We just check MOVABLE pages.
*/
- unmovable = has_unmovable_pages(zone, page, migratetype, isol_flags);
+ unmovable = has_unmovable_pages(zone, page, migratetype, isol_flags, start_pfn, end_pfn);
if (!unmovable) {
unsigned long nr_pages;
int mt = get_pageblock_migratetype(page);
@@ -265,8 +275,12 @@ __first_valid_page(unsigned long pfn, unsigned long nr_pages)
/**
* start_isolate_page_range() - make page-allocation-type of range of pages to
* be MIGRATE_ISOLATE.
- * @start_pfn: The lower PFN of the range to be isolated.
- * @end_pfn: The upper PFN of the range to be isolated.
+ * @start_pfn: The lower PFN of the range to be checked for
+ * possibility of isolation.
+ * @end_pfn: The upper PFN of the range to be checked for
+ * possibility of isolation.
+ * @isolate_start: The lower PFN of the range to be isolated.
+ * @isolate_end: The upper PFN of the range to be isolated.
* start_pfn/end_pfn must be aligned to pageblock_order.
* @migratetype: Migrate type to set in error recovery.
* @flags: The following flags are allowed (they can be combined in
@@ -304,20 +318,19 @@ __first_valid_page(unsigned long pfn, unsigned long nr_pages)
* Return: 0 on success and -EBUSY if any part of range cannot be isolated.
*/
int start_isolate_page_range(unsigned long start_pfn, unsigned long end_pfn,
+ unsigned long isolate_start, unsigned long isolate_end,
unsigned migratetype, int flags)
{
unsigned long pfn;
struct page *page;
- BUG_ON(!IS_ALIGNED(start_pfn, pageblock_nr_pages));
- BUG_ON(!IS_ALIGNED(end_pfn, pageblock_nr_pages));
-
- for (pfn = start_pfn;
- pfn < end_pfn;
+ for (pfn = isolate_start;
+ pfn < isolate_end;
pfn += pageblock_nr_pages) {
page = __first_valid_page(pfn, pageblock_nr_pages);
- if (page && set_migratetype_isolate(page, migratetype, flags)) {
- undo_isolate_page_range(start_pfn, pfn, migratetype);
+ if (page && set_migratetype_isolate(page, migratetype, flags,
+ start_pfn, end_pfn)) {
+ undo_isolate_page_range(isolate_start, pfn, migratetype);
return -EBUSY;
}
}
--
2.34.1