[PATCH v5 2/6] mm: page_isolation: check specified range for unmovable pages

Zi Yan
2022-02-11T16:51:09Z

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@nvidia.com>
---
include/linux/page-isolation.h | 12 +++++++++
mm/page_alloc.c | 15 +----------
mm/page_isolation.c | 46 +++++++++++++++++++++-------------
3 files changed, 41 insertions(+), 32 deletions(-)

diff --git a/include/linux/page-isolation.h b/include/linux/page-isolation.h
index e14eddf6741a..4ef7be6def83 100644
--- a/include/linux/page-isolation.h
+++ b/include/linux/page-isolation.h
@@ -15,6 +15,18 @@ static inline bool is_migrate_isolate(int migratetype)
{
return migratetype == MIGRATE_ISOLATE;
}
+static inline unsigned long pfn_max_align_down(unsigned long pfn)
+{
+ return ALIGN_DOWN(pfn, max_t(unsigned long, MAX_ORDER_NR_PAGES,
+ pageblock_nr_pages));
+}
+
+static inline unsigned long pfn_max_align_up(unsigned long pfn)
+{
+ return ALIGN(pfn, max_t(unsigned long, MAX_ORDER_NR_PAGES,
+ pageblock_nr_pages));
+}
+
#else
static inline bool has_isolate_pageblock(struct zone *zone)
{
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index e2c6a67fc386..62ef78f3d771 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -8963,18 +8963,6 @@ void *__init alloc_large_system_hash(const char *tablename,
}

#ifdef CONFIG_CONTIG_ALLOC
-static unsigned long pfn_max_align_down(unsigned long pfn)
-{
- return pfn & ~(max_t(unsigned long, MAX_ORDER_NR_PAGES,
- pageblock_nr_pages) - 1);
-}
-
-static unsigned long pfn_max_align_up(unsigned long pfn)
-{
- return ALIGN(pfn, max_t(unsigned long, MAX_ORDER_NR_PAGES,
- pageblock_nr_pages));
-}
-
#if defined(CONFIG_DYNAMIC_DEBUG) || \
(defined(CONFIG_DYNAMIC_DEBUG_CORE) && defined(DYNAMIC_DEBUG_MODULE))
/* Usage: See admin-guide/dynamic-debug-howto.rst */
@@ -9119,8 +9107,7 @@ 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),
- pfn_max_align_up(end), migratetype, 0);
+ ret = start_isolate_page_range(start, end, migratetype, 0);
if (ret)
return ret;

diff --git a/mm/page_isolation.c b/mm/page_isolation.c
index b34f1310aeaa..64d093ab83ec 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);
@@ -267,7 +277,6 @@ __first_valid_page(unsigned long pfn, unsigned long nr_pages)
* 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/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
* a bit mask)
@@ -309,15 +318,16 @@ int start_isolate_page_range(unsigned long start_pfn, unsigned long end_pfn,
unsigned long pfn;
struct page *page;

- BUG_ON(!IS_ALIGNED(start_pfn, pageblock_nr_pages));
- BUG_ON(!IS_ALIGNED(end_pfn, pageblock_nr_pages));
+ unsigned long isolate_start = pfn_max_align_down(start_pfn);
+ unsigned long isolate_end = pfn_max_align_up(end_pfn);

- 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