mm: split free page with properly free memory accounting and without race

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@linux-foundation.org/
Link: https://lkml.kernel.org/r/20220526231531.2404977-2-zi.yan@sent.com
Fixes: b2c9e2fbba32 ("mm: make alloc_contig_range work at pageblock granularity")
Signed-off-by: Zi Yan <ziy@nvidia.com>
Reported-by: Doug Berger <opendmb@gmail.com>
Link: https://lore.kernel.org/linux-mm/c3932a6f-77fe-29f7-0c29-fe6b1c67ab7b@gmail.com/
Cc: David Hildenbrand <david@redhat.com>
Cc: Qian Cai <quic_qiancai@quicinc.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Eric Ren <renzhengeek@gmail.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: Michael Walle <michael@walle.cc>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/mm/internal.h b/mm/internal.h
index 64e61b0..c0f8fbe 100644 (file)
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -374,8 +374,8 @@ 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);
+int split_free_page(struct page *free_page,
+                       unsigned int order, unsigned long split_pfn_offset);
 
 #if defined CONFIG_COMPACTION || defined CONFIG_CMA
 

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index bc93a82..6f6e464 100644 (file)
--- a/mm/page_alloc.c
+++ b/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_page,
                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,

diff --git a/mm/page_isolation.c b/mm/page_isolation.c
index fbd820b..6021f84 100644 (file)
--- a/mm/page_isolation.c
+++ b/mm/page_isolation.c
@@ -371,9 +371,13 @@ static int isolate_single_pageblock(unsigned long boundary_pfn, int flags,
                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;
                }
                /*