[PATCH v3 2/4] mm/page_isolation: remove migratetype from move_freepages_block_isolate()

Zi Yan
2025-05-07T21:11:36Z

Since migratetype is no longer overwritten during pageblock isolation,
moving pageblocks to and from MIGRATE_ISOLATE no longer needs migratetype.

Add MIGRATETYPE_NO_ISO_MASK to allow read before-isolation migratetype
when a pageblock is isolated. It is used by move_freepages_block_isolate().

Add pageblock_isolate_and_move_free_pages() and
pageblock_unisolate_and_move_free_pages() to be explicit about the page
isolation operations. Both share the common code in
__move_freepages_block_isolate(), which is renamed from
move_freepages_block_isolate().

Signed-off-by: Zi Yan <ziy@nvidia.com>
---
include/linux/mmzone.h | 4 ++-
include/linux/page-isolation.h | 4 +--
mm/page_alloc.c | 49 +++++++++++++++++++++++++++-------
mm/page_isolation.c | 21 +++++++--------
4 files changed, 55 insertions(+), 23 deletions(-)

diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index 9ec022a0b826..b88b98fb8a54 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -107,8 +107,10 @@ static inline bool migratetype_is_mergeable(int mt)
extern int page_group_by_mobility_disabled;

#ifdef CONFIG_MEMORY_ISOLATION
-#define MIGRATETYPE_MASK ((BIT(PB_migratetype_bits) - 1) | PB_migrate_isolate_bit)
+#define MIGRATETYPE_NO_ISO_MASK (BIT(PB_migratetype_bits) - 1)
+#define MIGRATETYPE_MASK (MIGRATETYPE_NO_ISO_MASK | PB_migrate_isolate_bit)
#else
+#define MIGRATETYPE_NO_ISO_MASK MIGRATETYPE_MASK
#define MIGRATETYPE_MASK (BIT(PB_migratetype_bits) - 1)
#endif

diff --git a/include/linux/page-isolation.h b/include/linux/page-isolation.h
index 51797dc39cbc..28c56f423e34 100644
--- a/include/linux/page-isolation.h
+++ b/include/linux/page-isolation.h
@@ -27,8 +27,8 @@ static inline bool is_migrate_isolate(int migratetype)

void set_pageblock_migratetype(struct page *page, int migratetype);

-bool move_freepages_block_isolate(struct zone *zone, struct page *page,
- int migratetype);
+bool pageblock_isolate_and_move_free_pages(struct zone *zone, struct page *page);
+bool pageblock_unisolate_and_move_free_pages(struct zone *zone, struct page *page);

int start_isolate_page_range(unsigned long start_pfn, unsigned long end_pfn,
int migratetype, int flags);
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index acf68ef041d8..186d69c9f049 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1948,11 +1948,17 @@ static unsigned long find_large_buddy(unsigned long start_pfn)
return start_pfn;
}

+static inline void toggle_pageblock_isolate(struct page *page, bool isolate)
+{
+ set_pfnblock_flags_mask(page, (isolate << PB_migrate_isolate),
+ page_to_pfn(page), PB_migrate_isolate_bit);
+}
+
/**
- * move_freepages_block_isolate - move free pages in block for page isolation
+ * __move_freepages_block_isolate - move free pages in block for page isolation
* @zone: the zone
* @page: the pageblock page
- * @migratetype: migratetype to set on the pageblock
+ * @isolate: to isolate the given pageblock or unisolate it
*
* This is similar to move_freepages_block(), but handles the special
* case encountered in page isolation, where the block of interest
@@ -1967,10 +1973,15 @@ static unsigned long find_large_buddy(unsigned long start_pfn)
*
* Returns %true if pages could be moved, %false otherwise.
*/
-bool move_freepages_block_isolate(struct zone *zone, struct page *page,
- int migratetype)
+static bool __move_freepages_block_isolate(struct zone *zone,
+ struct page *page, bool isolate)
{
unsigned long start_pfn, pfn;
+ int from_mt;
+ int to_mt;
+
+ if (isolate == get_pageblock_isolate(page))
+ return false;

if (!prep_move_freepages_block(zone, page, &start_pfn, NULL, NULL))
return false;
@@ -1987,7 +1998,7 @@ bool move_freepages_block_isolate(struct zone *zone, struct page *page,

del_page_from_free_list(buddy, zone, order,
get_pfnblock_migratetype(buddy, pfn));
- set_pageblock_migratetype(page, migratetype);
+ toggle_pageblock_isolate(page, isolate);
split_large_buddy(zone, buddy, pfn, order, FPI_NONE);
return true;
}
@@ -1998,16 +2009,36 @@ bool move_freepages_block_isolate(struct zone *zone, struct page *page,

del_page_from_free_list(page, zone, order,
get_pfnblock_migratetype(page, pfn));
- set_pageblock_migratetype(page, migratetype);
+ toggle_pageblock_isolate(page, isolate);
split_large_buddy(zone, page, pfn, order, FPI_NONE);
return true;
}
move:
- __move_freepages_block(zone, start_pfn,
- get_pfnblock_migratetype(page, start_pfn),
- migratetype);
+ /* use MIGRATETYPE_NO_ISO_MASK to get the non-isolate migratetype */
+ if (isolate) {
+ from_mt = get_pfnblock_flags_mask(page, page_to_pfn(page),
+ MIGRATETYPE_NO_ISO_MASK);
+ to_mt = MIGRATE_ISOLATE;
+ } else {
+ from_mt = MIGRATE_ISOLATE;
+ to_mt = get_pfnblock_flags_mask(page, page_to_pfn(page),
+ MIGRATETYPE_NO_ISO_MASK);
+ }
+
+ __move_freepages_block(zone, start_pfn, from_mt, to_mt);
return true;
}
+
+bool pageblock_isolate_and_move_free_pages(struct zone *zone, struct page *page)
+{
+ return __move_freepages_block_isolate(zone, page, true);
+}
+
+bool pageblock_unisolate_and_move_free_pages(struct zone *zone, struct page *page)
+{
+ return __move_freepages_block_isolate(zone, page, false);
+}
+
#endif /* CONFIG_MEMORY_ISOLATION */

static void change_pageblock_range(struct page *pageblock_page,
diff --git a/mm/page_isolation.c b/mm/page_isolation.c
index b2fc5266e3d2..08f627a5032f 100644
--- a/mm/page_isolation.c
+++ b/mm/page_isolation.c
@@ -188,7 +188,7 @@ static int set_migratetype_isolate(struct page *page, int migratetype, int isol_
unmovable = has_unmovable_pages(check_unmovable_start, check_unmovable_end,
migratetype, isol_flags);
if (!unmovable) {
- if (!move_freepages_block_isolate(zone, page, MIGRATE_ISOLATE)) {
+ if (!pageblock_isolate_and_move_free_pages(zone, page)) {
spin_unlock_irqrestore(&zone->lock, flags);
return -EBUSY;
}
@@ -209,7 +209,7 @@ static int set_migratetype_isolate(struct page *page, int migratetype, int isol_
return -EBUSY;
}

-static void unset_migratetype_isolate(struct page *page, int migratetype)
+static void unset_migratetype_isolate(struct page *page)
{
struct zone *zone;
unsigned long flags;
@@ -262,10 +262,10 @@ static void unset_migratetype_isolate(struct page *page, int migratetype)
* Isolating this block already succeeded, so this
* should not fail on zone boundaries.
*/
- WARN_ON_ONCE(!move_freepages_block_isolate(zone, page, migratetype));
+ WARN_ON_ONCE(!pageblock_unisolate_and_move_free_pages(zone, page));
} else {
- set_pageblock_migratetype(page, migratetype);
- __putback_isolated_page(page, order, migratetype);
+ clear_pageblock_isolate(page);
+ __putback_isolated_page(page, order, get_pageblock_migratetype(page));
}
zone->nr_isolate_pageblock--;
out:
@@ -383,7 +383,7 @@ static int isolate_single_pageblock(unsigned long boundary_pfn, int flags,
if (PageBuddy(page)) {
int order = buddy_order(page);

- /* move_freepages_block_isolate() handled this */
+ /* pageblock_isolate_and_move_free_pages() handled this */
VM_WARN_ON_ONCE(pfn + (1 << order) > boundary_pfn);

pfn += 1UL << order;
@@ -433,7 +433,7 @@ static int isolate_single_pageblock(unsigned long boundary_pfn, int flags,
failed:
/* restore the original migratetype */
if (!skip_isolation)
- unset_migratetype_isolate(pfn_to_page(isolate_pageblock), migratetype);
+ unset_migratetype_isolate(pfn_to_page(isolate_pageblock));
return -EBUSY;
}

@@ -504,7 +504,7 @@ int start_isolate_page_range(unsigned long start_pfn, unsigned long end_pfn,
ret = isolate_single_pageblock(isolate_end, flags, true,
skip_isolation, migratetype);
if (ret) {
- unset_migratetype_isolate(pfn_to_page(isolate_start), migratetype);
+ unset_migratetype_isolate(pfn_to_page(isolate_start));
return ret;
}

@@ -517,8 +517,7 @@ int start_isolate_page_range(unsigned long start_pfn, unsigned long end_pfn,
start_pfn, end_pfn)) {
undo_isolate_page_range(isolate_start, pfn, migratetype);
unset_migratetype_isolate(
- pfn_to_page(isolate_end - pageblock_nr_pages),
- migratetype);
+ pfn_to_page(isolate_end - pageblock_nr_pages));
return -EBUSY;
}
}
@@ -548,7 +547,7 @@ void undo_isolate_page_range(unsigned long start_pfn, unsigned long end_pfn,
page = __first_valid_page(pfn, pageblock_nr_pages);
if (!page || !is_migrate_isolate_page(page))
continue;
- unset_migratetype_isolate(page, migratetype);
+ unset_migratetype_isolate(page);
}
}
/*
--
2.47.2