The patch titled
Subject: mm: split free page with properly free memory accounting and without race
has been added to the -mm mm-unstable branch. Its filename is
mm-split-free-page-with-properly-free-memory-accounting-and-without-race.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-split-free-page-with-properly-free-memory-accounting-and-without-race.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Zi Yan <ziy@xxxxxxxxxx>
Subject: mm: split free page with properly free memory accounting and without race
Date: Thu, 26 May 2022 19:15:31 -0400
In isolate_single_pageblock(), free pages are checked without holding zone
lock, but they can go away in split_free_page() when zone lock is held.
Check the free page and its order again in split_free_page() when zone lock
is held. Recheck the page if the free page is gone under zone lock.
In addition, in split_free_page(), the free page was deleted from the page
list without changing free page accounting. Add the missing free page
accounting code.
Fix the type of order parameter in split_free_page().
Link: https://lore.kernel.org/lkml/20220525103621.987185e2ca0079f7b97b856d@xxxxxxxxxxxxxxxxxxxx/
Link: https://lkml.kernel.org/r/20220526231531.2404977-2-zi.yan@xxxxxxxx
Fixes: b2c9e2fbba32 ("mm: make alloc_contig_range work at pageblock granularity")
Signed-off-by: Zi Yan <ziy@xxxxxxxxxx>
Reported-by: Doug Berger <opendmb@xxxxxxxxx>
Link: https://lore.kernel.org/linux-mm/c3932a6f-77fe-29f7-0c29-fe6b1c67ab7b@xxxxxxxxx/
Cc: David Hildenbrand <david@xxxxxxxxxx>
Cc: Qian Cai <quic_qiancai@xxxxxxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Cc: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
Cc: Eric Ren <renzhengeek@xxxxxxxxx>
Cc: Mike Rapoport <rppt@xxxxxxxxxx>
Cc: Oscar Salvador <osalvador@xxxxxxx>
Cc: Christophe Leroy <christophe.leroy@xxxxxxxxxx>
Cc: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>
Cc: Michael Walle <michael@xxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/internal.h | 4 ++--
mm/page_alloc.c | 24 ++++++++++++++++++++----
mm/page_isolation.c | 10 +++++++---
3 files changed, 29 insertions(+), 9 deletions(-)
--- a/mm/internal.h~mm-split-free-page-with-properly-free-memory-accounting-and-without-race
+++ a/mm/internal.h
@@ -374,8 +374,8 @@ extern void *memmap_alloc(phys_addr_t si
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);
+int split_free_page(struct page *free_page,
+ unsigned int order, unsigned long split_pfn_offset);
#if defined CONFIG_COMPACTION || defined CONFIG_CMA
--- a/mm/page_alloc.c~mm-split-free-page-with-properly-free-memory-accounting-and-without-race
+++ a/mm/page_alloc.c
@@ -1100,30 +1100,44 @@ done_merging:
* @order: the order of the page
* @split_pfn_offset: split offset within the page
*
+ * Return -ENOENT if the free page is changed, otherwise 0
+ *
* 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)
+int split_free_page(struct page *free_page,
+ unsigned 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;
+ int mt;
+ int ret = 0;
if (split_pfn_offset == 0)
- return;
+ return ret;
spin_lock_irqsave(&zone->lock, flags);
+
+ if (!PageBuddy(free_page) || buddy_order(free_page) != order) {
+ ret = -ENOENT;
+ goto out;
+ }
+
+ mt = get_pageblock_migratetype(free_page);
+ if (likely(!is_migrate_isolate(mt)))
+ __mod_zone_freepage_state(zone, -(1UL << order), mt);
+
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 = min_t(int,
+ free_page_order = min_t(unsigned int,
pfn ? __ffs(pfn) : order,
__fls(split_pfn_offset));
__free_one_page(pfn_to_page(pfn), pfn, zone, free_page_order,
@@ -1134,7 +1148,9 @@ void split_free_page(struct page *free_p
if (split_pfn_offset == 0)
split_pfn_offset = (1UL << order) - (pfn - free_page_pfn);
}
+out:
spin_unlock_irqrestore(&zone->lock, flags);
+ return ret;
}
/*
* A bad page could be due to a number of fields. Instead of multiple branches,
--- a/mm/page_isolation.c~mm-split-free-page-with-properly-free-memory-accounting-and-without-race
+++ a/mm/page_isolation.c
@@ -371,9 +371,13 @@ static int isolate_single_pageblock(unsi
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);
+ if (pfn + (1UL << order) > boundary_pfn) {
+ /* free page changed before split, check it again */
+ if (split_free_page(page, order, boundary_pfn - pfn))
+ continue;
+ }
+
+ pfn += 1UL << order;
continue;
}
/*
_
Patches currently in -mm which might be from ziy@xxxxxxxxxx are
mm-page-isolation-skip-isolated-pageblock-in-start_isolate_page_range.patch
mm-split-free-page-with-properly-free-memory-accounting-and-without-race.patch
