Re: [PATCH v11 3/6] mm: make alloc_contig_range work at pageblock granularity

From: Zi Yan
Date: Fri Apr 29 2022 - 10:04:10 EST

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On 25 Apr 2022, at 10:31, Zi Yan wrote:

> From: Zi Yan <ziy@xxxxxxxxxx>
>
> alloc_contig_range() worked at MAX_ORDER_NR_PAGES granularity to avoid
> merging pageblocks with different migratetypes. It might unnecessarily
> convert extra pageblocks at the beginning and at the end of the range.
> Change alloc_contig_range() to work at pageblock granularity.
>
> Special handling is needed for free pages and in-use pages across the
> boundaries of the range specified by alloc_contig_range(). Because these
> partially isolated pages causes free page accounting issues. The free
> pages will be split and freed into separate migratetype lists; the
> in-use pages will be migrated then the freed pages will be handled in
> the aforementioned way.
>
> Reported-by: kernel test robot <lkp@xxxxxxxxx>
> Signed-off-by: Zi Yan <ziy@xxxxxxxxxx>
> ---
> include/linux/page-isolation.h | 4 +-
> mm/internal.h | 6 ++
> mm/memory_hotplug.c | 3 +-
> mm/page_alloc.c | 54 ++++++++--
> mm/page_isolation.c | 184 ++++++++++++++++++++++++++++++++-
> 5 files changed, 233 insertions(+), 18 deletions(-)
>
> diff --git a/include/linux/page-isolation.h b/include/linux/page-isolation.h
> index e14eddf6741a..5456b7be38ae 100644
> --- a/include/linux/page-isolation.h
> +++ b/include/linux/page-isolation.h
> @@ -42,7 +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 migratetype, int flags);
> + int migratetype, int flags, gfp_t gfp_flags);
>
> /*
> * Changes MIGRATE_ISOLATE to MIGRATE_MOVABLE.
> @@ -50,7 +50,7 @@ start_isolate_page_range(unsigned long start_pfn, unsigned long end_pfn,
> */
> void
> undo_isolate_page_range(unsigned long start_pfn, unsigned long end_pfn,
> - unsigned migratetype);
> + int migratetype);
>
> /*
> * Test all pages in [start_pfn, end_pfn) are isolated or not.
> diff --git a/mm/internal.h b/mm/internal.h
> index 919fa07e1031..0667abd57634 100644
> --- a/mm/internal.h
> +++ b/mm/internal.h
> @@ -359,6 +359,9 @@ extern void *memmap_alloc(phys_addr_t size, phys_addr_t align,
> phys_addr_t min_addr,
> int nid, bool exact_nid);
>
> +void split_free_page(struct page *free_page,
> + int order, unsigned long split_pfn_offset);
> +
> #if defined CONFIG_COMPACTION || defined CONFIG_CMA
>
> /*
> @@ -422,6 +425,9 @@ isolate_freepages_range(struct compact_control *cc,
> int
> isolate_migratepages_range(struct compact_control *cc,
> unsigned long low_pfn, unsigned long end_pfn);
> +
> +int __alloc_contig_migrate_range(struct compact_control *cc,
> + unsigned long start, unsigned long end);
> #endif
> int find_suitable_fallback(struct free_area *area, unsigned int order,
> int migratetype, bool only_stealable, bool *can_steal);
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index 4c6065e5d274..9f8ae4cb77ee 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -1845,7 +1845,8 @@ int __ref offline_pages(unsigned long start_pfn, unsigned long nr_pages,
> /* set above range as isolated */
> ret = start_isolate_page_range(start_pfn, end_pfn,
> MIGRATE_MOVABLE,
> - MEMORY_OFFLINE | REPORT_FAILURE);
> + MEMORY_OFFLINE | REPORT_FAILURE,
> + GFP_USER | __GFP_MOVABLE | __GFP_RETRY_MAYFAIL);
> if (ret) {
> reason = "failure to isolate range";
> goto failed_removal_pcplists_disabled;
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index ce23ac8ad085..70ddd9a0bcf3 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -1094,6 +1094,43 @@ static inline void __free_one_page(struct page *page,
> page_reporting_notify_free(order);
> }
>
> +/**
> + * split_free_page() -- split a free page at split_pfn_offset
> + * @free_page: the original free page
> + * @order: the order of the page
> + * @split_pfn_offset: split offset within the page
> + *
> + * It is used when the free page crosses two pageblocks with different migratetypes
> + * at split_pfn_offset within the page. The split free page will be put into
> + * separate migratetype lists afterwards. Otherwise, the function achieves
> + * nothing.
> + */
> +void split_free_page(struct page *free_page,
> + int order, unsigned long split_pfn_offset)
> +{
> + struct zone *zone = page_zone(free_page);
> + unsigned long free_page_pfn = page_to_pfn(free_page);
> + unsigned long pfn;
> + unsigned long flags;
> + int free_page_order;
> +
> + spin_lock_irqsave(&zone->lock, flags);
> + del_page_from_free_list(free_page, zone, order);
> + for (pfn = free_page_pfn;
> + pfn < free_page_pfn + (1UL << order);) {
> + int mt = get_pfnblock_migratetype(pfn_to_page(pfn), pfn);
> +
> + free_page_order = ffs(split_pfn_offset) - 1;
> + __free_one_page(pfn_to_page(pfn), pfn, zone, free_page_order,
> + mt, FPI_NONE);
> + pfn += 1UL << free_page_order;
> + split_pfn_offset -= (1UL << free_page_order);
> + /* we have done the first part, now switch to second part */
> + if (split_pfn_offset == 0)
> + split_pfn_offset = (1UL << order) - (pfn - free_page_pfn);
> + }
> + spin_unlock_irqrestore(&zone->lock, flags);
> +}
> /*
> * A bad page could be due to a number of fields. Instead of multiple branches,
> * try and check multiple fields with one check. The caller must do a detailed
> @@ -8919,7 +8956,7 @@ static inline void alloc_contig_dump_pages(struct list_head *page_list)
> #endif
>
> /* [start, end) must belong to a single zone. */
> -static int __alloc_contig_migrate_range(struct compact_control *cc,
> +int __alloc_contig_migrate_range(struct compact_control *cc,
> unsigned long start, unsigned long end)
> {
> /* This function is based on compact_zone() from compaction.c. */
> @@ -9002,7 +9039,7 @@ int alloc_contig_range(unsigned long start, unsigned long end,
> unsigned migratetype, gfp_t gfp_mask)
> {
> unsigned long outer_start, outer_end;
> - unsigned int order;
> + int order;
> int ret = 0;
>
> struct compact_control cc = {
> @@ -9021,14 +9058,11 @@ int alloc_contig_range(unsigned long start, unsigned long end,
> * What we do here is we mark all pageblocks in range as
> * MIGRATE_ISOLATE. Because pageblock and max order pages may
> * have different sizes, and due to the way page allocator
> - * work, we align the range to biggest of the two pages so
> - * that page allocator won't try to merge buddies from
> - * different pageblocks and change MIGRATE_ISOLATE to some
> - * other migration type.
> + * work, start_isolate_page_range() has special handlings for this.
> *
> * Once the pageblocks are marked as MIGRATE_ISOLATE, we
> * migrate the pages from an unaligned range (ie. pages that
> - * we are interested in). This will put all the pages in
> + * we are interested in). This will put all the pages in
> * range back to page allocator as MIGRATE_ISOLATE.
> *
> * When this is done, we take the pages in range from page
> @@ -9042,9 +9076,9 @@ int alloc_contig_range(unsigned long start, unsigned long end,
> */
>
> ret = start_isolate_page_range(pfn_max_align_down(start),
> - pfn_max_align_up(end), migratetype, 0);
> + pfn_max_align_up(end), migratetype, 0, gfp_mask);
> if (ret)
> - return ret;
> + goto done;
>
> drain_all_pages(cc.zone);
>
> @@ -9064,7 +9098,7 @@ int alloc_contig_range(unsigned long start, unsigned long end,
> ret = 0;
>
> /*
> - * Pages from [start, end) are within a MAX_ORDER_NR_PAGES
> + * Pages from [start, end) are within a pageblock_nr_pages
> * aligned blocks that are marked as MIGRATE_ISOLATE. What's
> * more, all pages in [start, end) are free in page allocator.
> * What we are going to do is to allocate all pages from
> diff --git a/mm/page_isolation.c b/mm/page_isolation.c
> index c2f7a8bb634d..94b3467e5ba2 100644
> --- a/mm/page_isolation.c
> +++ b/mm/page_isolation.c
> @@ -203,7 +203,7 @@ static int set_migratetype_isolate(struct page *page, int migratetype, int isol_
> return -EBUSY;
> }
>
> -static void unset_migratetype_isolate(struct page *page, unsigned migratetype)
> +static void unset_migratetype_isolate(struct page *page, int migratetype)
> {
> struct zone *zone;
> unsigned long flags, nr_pages;
> @@ -279,6 +279,157 @@ __first_valid_page(unsigned long pfn, unsigned long nr_pages)
> return NULL;
> }
>
> +/**
> + * isolate_single_pageblock() -- tries to isolate a pageblock that might be
> + * within a free or in-use page.
> + * @boundary_pfn: pageblock-aligned pfn that a page might cross
> + * @gfp_flags: GFP flags used for migrating pages
> + * @isolate_before: isolate the pageblock before the boundary_pfn
> + *
> + * Free and in-use pages can be as big as MAX_ORDER-1 and contain more than one
> + * pageblock. When not all pageblocks within a page are isolated at the same
> + * time, free page accounting can go wrong. For example, in the case of
> + * MAX_ORDER-1 = pageblock_order + 1, a MAX_ORDER-1 page has two pagelbocks.
> + * [ MAX_ORDER-1 ]
> + * [ pageblock0 | pageblock1 ]
> + * When either pageblock is isolated, if it is a free page, the page is not
> + * split into separate migratetype lists, which is supposed to; if it is an
> + * in-use page and freed later, __free_one_page() does not split the free page
> + * either. The function handles this by splitting the free page or migrating
> + * the in-use page then splitting the free page.
> + */
> +static int isolate_single_pageblock(unsigned long boundary_pfn, gfp_t gfp_flags,
> + bool isolate_before)
> +{
> + unsigned char saved_mt;
> + unsigned long start_pfn;
> + unsigned long isolate_pageblock;
> + unsigned long pfn;
> + struct zone *zone;
> +
> + VM_BUG_ON(!IS_ALIGNED(boundary_pfn, pageblock_nr_pages));
> +
> + if (isolate_before)
> + isolate_pageblock = boundary_pfn - pageblock_nr_pages;
> + else
> + isolate_pageblock = boundary_pfn;
> +
> + /*
> + * scan at the beginning of MAX_ORDER_NR_PAGES aligned range to avoid
> + * only isolating a subset of pageblocks from a bigger than pageblock
> + * free or in-use page. Also make sure all to-be-isolated pageblocks
> + * are within the same zone.
> + */
> + zone = page_zone(pfn_to_page(isolate_pageblock));
> + start_pfn = max(ALIGN_DOWN(isolate_pageblock, MAX_ORDER_NR_PAGES),
> + zone->zone_start_pfn);
> +
> + saved_mt = get_pageblock_migratetype(pfn_to_page(isolate_pageblock));
> + set_pageblock_migratetype(pfn_to_page(isolate_pageblock), MIGRATE_ISOLATE);
> +
> + /*
> + * Bail out early when the to-be-isolated pageblock does not form
> + * a free or in-use page across boundary_pfn:
> + *
> + * 1. isolate before boundary_pfn: the page after is not online
> + * 2. isolate after boundary_pfn: the page before is not online
> + *
> + * This also ensures correctness. Without it, when isolate after
> + * boundary_pfn and [start_pfn, boundary_pfn) are not online,
> + * __first_valid_page() will return unexpected NULL in the for loop
> + * below.
> + */
> + if (isolate_before) {
> + if (!pfn_to_online_page(boundary_pfn))
> + return 0;
> + } else {
> + if (!pfn_to_online_page(boundary_pfn - 1))
> + return 0;
> + }
> +
> + for (pfn = start_pfn; pfn < boundary_pfn;) {
> + struct page *page = __first_valid_page(pfn, boundary_pfn - pfn);
> +
> + VM_BUG_ON(!page);
> + pfn = page_to_pfn(page);
> + /*
> + * start_pfn is MAX_ORDER_NR_PAGES aligned, if there is any
> + * free pages in [start_pfn, boundary_pfn), its head page will
> + * always be in the range.
> + */
> + if (PageBuddy(page)) {
> + int order = buddy_order(page);
> +
> + if (pfn + (1UL << order) > boundary_pfn)
> + split_free_page(page, order, boundary_pfn - pfn);
> + pfn += (1UL << order);
> + continue;
> + }
> + /*
> + * migrate compound pages then let the free page handling code
> + * above do the rest. If migration is not enabled, just fail.
> + */
> + if (PageHuge(page) || PageTransCompound(page)) {
> +#if defined CONFIG_COMPACTION || defined CONFIG_CMA
> + unsigned long nr_pages = compound_nr(page);
> + int order = compound_order(page);
> + struct page *head = compound_head(page);
> + unsigned long head_pfn = page_to_pfn(head);
> + int ret;
> + struct compact_control cc = {
> + .nr_migratepages = 0,
> + .order = -1,
> + .zone = page_zone(pfn_to_page(head_pfn)),
> + .mode = MIGRATE_SYNC,
> + .ignore_skip_hint = true,
> + .no_set_skip_hint = true,
> + .gfp_mask = gfp_flags,
> + .alloc_contig = true,
> + };
> + INIT_LIST_HEAD(&cc.migratepages);
> +
> + if (head_pfn + nr_pages < boundary_pfn) {
> + pfn += nr_pages;
> + continue;
> + }
> +
> + ret = __alloc_contig_migrate_range(&cc, head_pfn,
> + head_pfn + nr_pages);
> +
> + if (ret)
> + goto failed;
> + /*
> + * reset pfn, let the free page handling code above
> + * split the free page to the right migratetype list.
> + *
> + * head_pfn is not used here as a hugetlb page order
> + * can be bigger than MAX_ORDER-1, but after it is
> + * freed, the free page order is not. Use pfn within
> + * the range to find the head of the free page and
> + * reset order to 0 if a hugetlb page with
> + * >MAX_ORDER-1 order is encountered.
> + */
> + if (order > MAX_ORDER-1)
> + order = 0;
> + while (!PageBuddy(pfn_to_page(pfn))) {
> + order++;
> + pfn &= ~0UL << order;
> + }
> + continue;
> +#else
> + goto failed;
> +#endif
> + }
> +
> + pfn++;
> + }
> + return 0;
> +failed:
> + /* restore the original migratetype */
> + set_pageblock_migratetype(pfn_to_page(isolate_pageblock), saved_mt);
> + return -EBUSY;
> +}
> +
> /**
> * start_isolate_page_range() - make page-allocation-type of range of pages to
> * be MIGRATE_ISOLATE.
> @@ -293,6 +444,8 @@ __first_valid_page(unsigned long pfn, unsigned long nr_pages)
> * and PageOffline() pages.
> * REPORT_FAILURE - report details about the failure to
> * isolate the range
> + * @gfp_flags: GFP flags used for migrating pages that sit across the
> + * range boundaries.
> *
> * Making page-allocation-type to be MIGRATE_ISOLATE means free pages in
> * the range will never be allocated. Any free pages and pages freed in the
> @@ -301,6 +454,10 @@ __first_valid_page(unsigned long pfn, unsigned long nr_pages)
> * pages in the range finally, the caller have to free all pages in the range.
> * test_page_isolated() can be used for test it.
> *
> + * The function first tries to isolate the pageblocks at the beginning and end
> + * of the range, since there might be pages across the range boundaries.
> + * Afterwards, it isolates the rest of the range.
> + *
> * There is no high level synchronization mechanism that prevents two threads
> * from trying to isolate overlapping ranges. If this happens, one thread
> * will notice pageblocks in the overlapping range already set to isolate.
> @@ -321,21 +478,38 @@ __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 migratetype, int flags)
> + int migratetype, int flags, gfp_t gfp_flags)
> {
> unsigned long pfn;
> struct page *page;
> + int ret;
>
> 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;
> + /* isolate [start_pfn, start_pfn + pageblock_nr_pages) pageblock */
> + ret = isolate_single_pageblock(start_pfn, gfp_flags, false);
> + if (ret)
> + return ret;
> +
> + /* isolate [end_pfn - pageblock_nr_pages, end_pfn) pageblock */
> + ret = isolate_single_pageblock(end_pfn, gfp_flags, true);
> + if (ret) {
> + unset_migratetype_isolate(pfn_to_page(start_pfn), migratetype);
> + return ret;
> + }
> +
> + /* skip isolated pageblocks at the beginning and end */
> + for (pfn = start_pfn + pageblock_nr_pages;
> + pfn < end_pfn - pageblock_nr_pages;
> pfn += pageblock_nr_pages) {
> page = __first_valid_page(pfn, pageblock_nr_pages);
> if (page && set_migratetype_isolate(page, migratetype, flags,
> start_pfn, end_pfn)) {
> undo_isolate_page_range(start_pfn, pfn, migratetype);
> + unset_migratetype_isolate(
> + pfn_to_page(end_pfn - pageblock_nr_pages),
> + migratetype);
> return -EBUSY;
> }
> }
> @@ -346,7 +520,7 @@ int start_isolate_page_range(unsigned long start_pfn, unsigned long end_pfn,
> * Make isolated pages available again.
> */
> void undo_isolate_page_range(unsigned long start_pfn, unsigned long end_pfn,
> - unsigned migratetype)
> + int migratetype)
> {
> unsigned long pfn;
> struct page *page;
> --
> 2.35.1

Qian hit a bug caused by this series https://lore.kernel.org/linux-mm/20220426201855.GA1014@qian/
and the fix is:

diff --git a/mm/page_isolation.c b/mm/page_isolation.c
index 75e454f5cf45..b3f074d1682e 100644
--- a/mm/page_isolation.c
+++ b/mm/page_isolation.c
@@ -367,58 +367,67 @@ static int isolate_single_pageblock(unsigned long boundary_pfn, gfp_t gfp_flags,
}
/*
* migrate compound pages then let the free page handling code
- * above do the rest. If migration is not enabled, just fail.
+ * above do the rest. If migration is not possible, just fail.
*/
- if (PageHuge(page) || PageTransCompound(page)) {
-#if defined CONFIG_COMPACTION || defined CONFIG_CMA
+ if (PageCompound(page)) {
unsigned long nr_pages = compound_nr(page);
- int order = compound_order(page);
struct page *head = compound_head(page);
unsigned long head_pfn = page_to_pfn(head);
- int ret;
- struct compact_control cc = {
- .nr_migratepages = 0,
- .order = -1,
- .zone = page_zone(pfn_to_page(head_pfn)),
- .mode = MIGRATE_SYNC,
- .ignore_skip_hint = true,
- .no_set_skip_hint = true,
- .gfp_mask = gfp_flags,
- .alloc_contig = true,
- };
- INIT_LIST_HEAD(&cc.migratepages);

if (head_pfn + nr_pages < boundary_pfn) {
- pfn += nr_pages;
+ pfn = head_pfn + nr_pages;
continue;
}
-
- ret = __alloc_contig_migrate_range(&cc, head_pfn,
- head_pfn + nr_pages);
-
- if (ret)
- goto failed;
+#if defined CONFIG_COMPACTION || defined CONFIG_CMA
/*
- * reset pfn, let the free page handling code above
- * split the free page to the right migratetype list.
- *
- * head_pfn is not used here as a hugetlb page order
- * can be bigger than MAX_ORDER-1, but after it is
- * freed, the free page order is not. Use pfn within
- * the range to find the head of the free page and
- * reset order to 0 if a hugetlb page with
- * >MAX_ORDER-1 order is encountered.
+ * hugetlb, lru compound (THP), and movable compound pages
+ * can be migrated. Otherwise, fail the isolation.
*/
- if (order > MAX_ORDER-1)
+ if (PageHuge(page) || PageLRU(page) || __PageMovable(page)) {
+ int order;
+ unsigned long outer_pfn;
+ int ret;
+ struct compact_control cc = {
+ .nr_migratepages = 0,
+ .order = -1,
+ .zone = page_zone(pfn_to_page(head_pfn)),
+ .mode = MIGRATE_SYNC,
+ .ignore_skip_hint = true,
+ .no_set_skip_hint = true,
+ .gfp_mask = gfp_flags,
+ .alloc_contig = true,
+ };
+ INIT_LIST_HEAD(&cc.migratepages);
+
+ ret = __alloc_contig_migrate_range(&cc, head_pfn,
+ head_pfn + nr_pages);
+
+ if (ret)
+ goto failed;
+ /*
+ * reset pfn to the head of the free page, so
+ * that the free page handling code above can split
+ * the free page to the right migratetype list.
+ *
+ * head_pfn is not used here as a hugetlb page order
+ * can be bigger than MAX_ORDER-1, but after it is
+ * freed, the free page order is not. Use pfn within
+ * the range to find the head of the free page.
+ */
order = 0;
- while (!PageBuddy(pfn_to_page(pfn))) {
- order++;
- pfn &= ~0UL << order;
- }
- continue;
-#else
- goto failed;
+ outer_pfn = pfn;
+ while (!PageBuddy(pfn_to_page(outer_pfn))) {
+ if (++order >= MAX_ORDER) {
+ outer_pfn = pfn;
+ break;
+ }
+ outer_pfn &= ~0UL << order;
+ }
+ pfn = outer_pfn;
+ continue;
+ } else
#endif
+ goto failed;
}

pfn++;
--
2.35.1

The fixed-up patch is below for easy review purpose:

From fce466e89e50bcb0ebb56d7809db1b8bbea47628 Mon Sep 17 00:00:00 2001
From: Zi Yan <ziy@xxxxxxxxxx>
Date: Tue, 26 Apr 2022 23:00:33 -0400
Subject: [PATCH] mm: make alloc_contig_range work at pageblock granularity

alloc_contig_range() worked at MAX_ORDER_NR_PAGES granularity to avoid
merging pageblocks with different migratetypes. It might unnecessarily
convert extra pageblocks at the beginning and at the end of the range.
Change alloc_contig_range() to work at pageblock granularity.

Special handling is needed for free pages and in-use pages across the
boundaries of the range specified by alloc_contig_range(). Because these
partially isolated pages causes free page accounting issues. The free
pages will be split and freed into separate migratetype lists; the in-use
pages will be migrated then the freed pages will be handled in the
aforementioned way.

Signed-off-by: Zi Yan <ziy@xxxxxxxxxx>
---
include/linux/page-isolation.h | 4 +-
mm/internal.h | 6 +
mm/memory_hotplug.c | 3 +-
mm/page_alloc.c | 54 +++++++--
mm/page_isolation.c | 193 ++++++++++++++++++++++++++++++++-
5 files changed, 242 insertions(+), 18 deletions(-)

diff --git a/include/linux/page-isolation.h b/include/linux/page-isolation.h
index e14eddf6741a..5456b7be38ae 100644
--- a/include/linux/page-isolation.h
+++ b/include/linux/page-isolation.h
@@ -42,7 +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 migratetype, int flags);
+ int migratetype, int flags, gfp_t gfp_flags);

/*
* Changes MIGRATE_ISOLATE to MIGRATE_MOVABLE.
@@ -50,7 +50,7 @@ start_isolate_page_range(unsigned long start_pfn, unsigned long end_pfn,
*/
void
undo_isolate_page_range(unsigned long start_pfn, unsigned long end_pfn,
- unsigned migratetype);
+ int migratetype);

/*
* Test all pages in [start_pfn, end_pfn) are isolated or not.
diff --git a/mm/internal.h b/mm/internal.h
index 919fa07e1031..0667abd57634 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -359,6 +359,9 @@ extern void *memmap_alloc(phys_addr_t size, phys_addr_t align,
phys_addr_t min_addr,
int nid, bool exact_nid);

+void split_free_page(struct page *free_page,
+ int order, unsigned long split_pfn_offset);
+
#if defined CONFIG_COMPACTION || defined CONFIG_CMA

/*
@@ -422,6 +425,9 @@ isolate_freepages_range(struct compact_control *cc,
int
isolate_migratepages_range(struct compact_control *cc,
unsigned long low_pfn, unsigned long end_pfn);
+
+int __alloc_contig_migrate_range(struct compact_control *cc,
+ unsigned long start, unsigned long end);
#endif
int find_suitable_fallback(struct free_area *area, unsigned int order,
int migratetype, bool only_stealable, bool *can_steal);
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 4c6065e5d274..9f8ae4cb77ee 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -1845,7 +1845,8 @@ int __ref offline_pages(unsigned long start_pfn, unsigned long nr_pages,
/* set above range as isolated */
ret = start_isolate_page_range(start_pfn, end_pfn,
MIGRATE_MOVABLE,
- MEMORY_OFFLINE | REPORT_FAILURE);
+ MEMORY_OFFLINE | REPORT_FAILURE,
+ GFP_USER | __GFP_MOVABLE | __GFP_RETRY_MAYFAIL);
if (ret) {
reason = "failure to isolate range";
goto failed_removal_pcplists_disabled;
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 93dbe05a6029..6a0d1746c095 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1094,6 +1094,43 @@ static inline void __free_one_page(struct page *page,
page_reporting_notify_free(order);
}

+/**
+ * split_free_page() -- split a free page at split_pfn_offset
+ * @free_page: the original free page
+ * @order: the order of the page
+ * @split_pfn_offset: split offset within the page
+ *
+ * It is used when the free page crosses two pageblocks with different migratetypes
+ * at split_pfn_offset within the page. The split free page will be put into
+ * separate migratetype lists afterwards. Otherwise, the function achieves
+ * nothing.
+ */
+void split_free_page(struct page *free_page,
+ int order, unsigned long split_pfn_offset)
+{
+ struct zone *zone = page_zone(free_page);
+ unsigned long free_page_pfn = page_to_pfn(free_page);
+ unsigned long pfn;
+ unsigned long flags;
+ int free_page_order;
+
+ spin_lock_irqsave(&zone->lock, flags);
+ del_page_from_free_list(free_page, zone, order);
+ for (pfn = free_page_pfn;
+ pfn < free_page_pfn + (1UL << order);) {
+ int mt = get_pfnblock_migratetype(pfn_to_page(pfn), pfn);
+
+ free_page_order = ffs(split_pfn_offset) - 1;
+ __free_one_page(pfn_to_page(pfn), pfn, zone, free_page_order,
+ mt, FPI_NONE);
+ pfn += 1UL << free_page_order;
+ split_pfn_offset -= (1UL << free_page_order);
+ /* we have done the first part, now switch to second part */
+ if (split_pfn_offset == 0)
+ split_pfn_offset = (1UL << order) - (pfn - free_page_pfn);
+ }
+ spin_unlock_irqrestore(&zone->lock, flags);
+}
/*
* A bad page could be due to a number of fields. Instead of multiple branches,
* try and check multiple fields with one check. The caller must do a detailed
@@ -8919,7 +8956,7 @@ static inline void alloc_contig_dump_pages(struct list_head *page_list)
#endif

/* [start, end) must belong to a single zone. */
-static int __alloc_contig_migrate_range(struct compact_control *cc,
+int __alloc_contig_migrate_range(struct compact_control *cc,
unsigned long start, unsigned long end)
{
/* This function is based on compact_zone() from compaction.c. */
@@ -9002,7 +9039,7 @@ int alloc_contig_range(unsigned long start, unsigned long end,
unsigned migratetype, gfp_t gfp_mask)
{
unsigned long outer_start, outer_end;
- unsigned int order;
+ int order;
int ret = 0;

struct compact_control cc = {
@@ -9021,14 +9058,11 @@ int alloc_contig_range(unsigned long start, unsigned long end,
* What we do here is we mark all pageblocks in range as
* MIGRATE_ISOLATE. Because pageblock and max order pages may
* have different sizes, and due to the way page allocator
- * work, we align the range to biggest of the two pages so
- * that page allocator won't try to merge buddies from
- * different pageblocks and change MIGRATE_ISOLATE to some
- * other migration type.
+ * work, start_isolate_page_range() has special handlings for this.
*
* Once the pageblocks are marked as MIGRATE_ISOLATE, we
* migrate the pages from an unaligned range (ie. pages that
- * we are interested in). This will put all the pages in
+ * we are interested in). This will put all the pages in
* range back to page allocator as MIGRATE_ISOLATE.
*
* When this is done, we take the pages in range from page
@@ -9042,9 +9076,9 @@ int alloc_contig_range(unsigned long start, unsigned long end,
*/

ret = start_isolate_page_range(pfn_max_align_down(start),
- pfn_max_align_up(end), migratetype, 0);
+ pfn_max_align_up(end), migratetype, 0, gfp_mask);
if (ret)
- return ret;
+ goto done;

drain_all_pages(cc.zone);

@@ -9064,7 +9098,7 @@ int alloc_contig_range(unsigned long start, unsigned long end,
ret = 0;

/*
- * Pages from [start, end) are within a MAX_ORDER_NR_PAGES
+ * Pages from [start, end) are within a pageblock_nr_pages
* aligned blocks that are marked as MIGRATE_ISOLATE. What's
* more, all pages in [start, end) are free in page allocator.
* What we are going to do is to allocate all pages from
diff --git a/mm/page_isolation.c b/mm/page_isolation.c
index c2f7a8bb634d..8a0f16d2e4c3 100644
--- a/mm/page_isolation.c
+++ b/mm/page_isolation.c
@@ -203,7 +203,7 @@ static int set_migratetype_isolate(struct page *page, int migratetype, int isol_
return -EBUSY;
}

-static void unset_migratetype_isolate(struct page *page, unsigned migratetype)
+static void unset_migratetype_isolate(struct page *page, int migratetype)
{
struct zone *zone;
unsigned long flags, nr_pages;
@@ -279,6 +279,166 @@ __first_valid_page(unsigned long pfn, unsigned long nr_pages)
return NULL;
}

+/**
+ * isolate_single_pageblock() -- tries to isolate a pageblock that might be
+ * within a free or in-use page.
+ * @boundary_pfn: pageblock-aligned pfn that a page might cross
+ * @gfp_flags: GFP flags used for migrating pages
+ * @isolate_before: isolate the pageblock before the boundary_pfn
+ *
+ * Free and in-use pages can be as big as MAX_ORDER-1 and contain more than one
+ * pageblock. When not all pageblocks within a page are isolated at the same
+ * time, free page accounting can go wrong. For example, in the case of
+ * MAX_ORDER-1 = pageblock_order + 1, a MAX_ORDER-1 page has two pagelbocks.
+ * [ MAX_ORDER-1 ]
+ * [ pageblock0 | pageblock1 ]
+ * When either pageblock is isolated, if it is a free page, the page is not
+ * split into separate migratetype lists, which is supposed to; if it is an
+ * in-use page and freed later, __free_one_page() does not split the free page
+ * either. The function handles this by splitting the free page or migrating
+ * the in-use page then splitting the free page.
+ */
+static int isolate_single_pageblock(unsigned long boundary_pfn, gfp_t gfp_flags,
+ bool isolate_before)
+{
+ unsigned char saved_mt;
+ unsigned long start_pfn;
+ unsigned long isolate_pageblock;
+ unsigned long pfn;
+ struct zone *zone;
+
+ VM_BUG_ON(!IS_ALIGNED(boundary_pfn, pageblock_nr_pages));
+
+ if (isolate_before)
+ isolate_pageblock = boundary_pfn - pageblock_nr_pages;
+ else
+ isolate_pageblock = boundary_pfn;
+
+ /*
+ * scan at the beginning of MAX_ORDER_NR_PAGES aligned range to avoid
+ * only isolating a subset of pageblocks from a bigger than pageblock
+ * free or in-use page. Also make sure all to-be-isolated pageblocks
+ * are within the same zone.
+ */
+ zone = page_zone(pfn_to_page(isolate_pageblock));
+ start_pfn = max(ALIGN_DOWN(isolate_pageblock, MAX_ORDER_NR_PAGES),
+ zone->zone_start_pfn);
+
+ saved_mt = get_pageblock_migratetype(pfn_to_page(isolate_pageblock));
+ set_pageblock_migratetype(pfn_to_page(isolate_pageblock), MIGRATE_ISOLATE);
+
+ /*
+ * Bail out early when the to-be-isolated pageblock does not form
+ * a free or in-use page across boundary_pfn:
+ *
+ * 1. isolate before boundary_pfn: the page after is not online
+ * 2. isolate after boundary_pfn: the page before is not online
+ *
+ * This also ensures correctness. Without it, when isolate after
+ * boundary_pfn and [start_pfn, boundary_pfn) are not online,
+ * __first_valid_page() will return unexpected NULL in the for loop
+ * below.
+ */
+ if (isolate_before) {
+ if (!pfn_to_online_page(boundary_pfn))
+ return 0;
+ } else {
+ if (!pfn_to_online_page(boundary_pfn - 1))
+ return 0;
+ }
+
+ for (pfn = start_pfn; pfn < boundary_pfn;) {
+ struct page *page = __first_valid_page(pfn, boundary_pfn - pfn);
+
+ VM_BUG_ON(!page);
+ pfn = page_to_pfn(page);
+ /*
+ * start_pfn is MAX_ORDER_NR_PAGES aligned, if there is any
+ * free pages in [start_pfn, boundary_pfn), its head page will
+ * always be in the range.
+ */
+ if (PageBuddy(page)) {
+ int order = buddy_order(page);
+
+ if (pfn + (1UL << order) > boundary_pfn)
+ split_free_page(page, order, boundary_pfn - pfn);
+ pfn += (1UL << order);
+ continue;
+ }
+ /*
+ * migrate compound pages then let the free page handling code
+ * above do the rest. If migration is not possible, just fail.
+ */
+ if (PageCompound(page)) {
+ unsigned long nr_pages = compound_nr(page);
+ struct page *head = compound_head(page);
+ unsigned long head_pfn = page_to_pfn(head);
+
+ if (head_pfn + nr_pages < boundary_pfn) {
+ pfn = head_pfn + nr_pages;
+ continue;
+ }
+#if defined CONFIG_COMPACTION || defined CONFIG_CMA
+ /*
+ * hugetlb, lru compound (THP), and movable compound pages
+ * can be migrated. Otherwise, fail the isolation.
+ */
+ if (PageHuge(page) || PageLRU(page) || __PageMovable(page)) {
+ int order;
+ unsigned long outer_pfn;
+ int ret;
+ struct compact_control cc = {
+ .nr_migratepages = 0,
+ .order = -1,
+ .zone = page_zone(pfn_to_page(head_pfn)),
+ .mode = MIGRATE_SYNC,
+ .ignore_skip_hint = true,
+ .no_set_skip_hint = true,
+ .gfp_mask = gfp_flags,
+ .alloc_contig = true,
+ };
+ INIT_LIST_HEAD(&cc.migratepages);
+
+ ret = __alloc_contig_migrate_range(&cc, head_pfn,
+ head_pfn + nr_pages);
+
+ if (ret)
+ goto failed;
+ /*
+ * reset pfn to the head of the free page, so
+ * that the free page handling code above can split
+ * the free page to the right migratetype list.
+ *
+ * head_pfn is not used here as a hugetlb page order
+ * can be bigger than MAX_ORDER-1, but after it is
+ * freed, the free page order is not. Use pfn within
+ * the range to find the head of the free page.
+ */
+ order = 0;
+ outer_pfn = pfn;
+ while (!PageBuddy(pfn_to_page(outer_pfn))) {
+ if (++order >= MAX_ORDER) {
+ outer_pfn = pfn;
+ break;
+ }
+ outer_pfn &= ~0UL << order;
+ }
+ pfn = outer_pfn;
+ continue;
+ } else
+#endif
+ goto failed;
+ }
+
+ pfn++;
+ }
+ return 0;
+failed:
+ /* restore the original migratetype */
+ set_pageblock_migratetype(pfn_to_page(isolate_pageblock), saved_mt);
+ return -EBUSY;
+}
+
/**
* start_isolate_page_range() - make page-allocation-type of range of pages to
* be MIGRATE_ISOLATE.
@@ -293,6 +453,8 @@ __first_valid_page(unsigned long pfn, unsigned long nr_pages)
* and PageOffline() pages.
* REPORT_FAILURE - report details about the failure to
* isolate the range
+ * @gfp_flags: GFP flags used for migrating pages that sit across the
+ * range boundaries.
*
* Making page-allocation-type to be MIGRATE_ISOLATE means free pages in
* the range will never be allocated. Any free pages and pages freed in the
@@ -301,6 +463,10 @@ __first_valid_page(unsigned long pfn, unsigned long nr_pages)
* pages in the range finally, the caller have to free all pages in the range.
* test_page_isolated() can be used for test it.
*
+ * The function first tries to isolate the pageblocks at the beginning and end
+ * of the range, since there might be pages across the range boundaries.
+ * Afterwards, it isolates the rest of the range.
+ *
* There is no high level synchronization mechanism that prevents two threads
* from trying to isolate overlapping ranges. If this happens, one thread
* will notice pageblocks in the overlapping range already set to isolate.
@@ -321,21 +487,38 @@ __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 migratetype, int flags)
+ int migratetype, int flags, gfp_t gfp_flags)
{
unsigned long pfn;
struct page *page;
+ int ret;

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;
+ /* isolate [start_pfn, start_pfn + pageblock_nr_pages) pageblock */
+ ret = isolate_single_pageblock(start_pfn, gfp_flags, false);
+ if (ret)
+ return ret;
+
+ /* isolate [end_pfn - pageblock_nr_pages, end_pfn) pageblock */
+ ret = isolate_single_pageblock(end_pfn, gfp_flags, true);
+ if (ret) {
+ unset_migratetype_isolate(pfn_to_page(start_pfn), migratetype);
+ return ret;
+ }
+
+ /* skip isolated pageblocks at the beginning and end */
+ for (pfn = start_pfn + pageblock_nr_pages;
+ pfn < end_pfn - pageblock_nr_pages;
pfn += pageblock_nr_pages) {
page = __first_valid_page(pfn, pageblock_nr_pages);
if (page && set_migratetype_isolate(page, migratetype, flags,
start_pfn, end_pfn)) {
undo_isolate_page_range(start_pfn, pfn, migratetype);
+ unset_migratetype_isolate(
+ pfn_to_page(end_pfn - pageblock_nr_pages),
+ migratetype);
return -EBUSY;
}
}
@@ -346,7 +529,7 @@ int start_isolate_page_range(unsigned long start_pfn, unsigned long end_pfn,
* Make isolated pages available again.
*/
void undo_isolate_page_range(unsigned long start_pfn, unsigned long end_pfn,
- unsigned migratetype)
+ int migratetype)
{
unsigned long pfn;
struct page *page;
--
2.35.1

--
Best Regards,
Yan, Zi

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