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Date: Wed, 25 May 2022 13:53:04 -0400
From: Zi Yan <ziy@...dia.com>
To: Doug Berger <opendmb@...il.com>
Cc: David Hildenbrand <david@...hat.com>, linux-mm@...ck.org,
linux-kernel@...r.kernel.org,
virtualization@...ts.linux-foundation.org,
Vlastimil Babka <vbabka@...e.cz>,
Mel Gorman <mgorman@...hsingularity.net>,
Eric Ren <renzhengeek@...il.com>,
Mike Rapoport <rppt@...nel.org>,
Oscar Salvador <osalvador@...e.de>,
Christophe Leroy <christophe.leroy@...roup.eu>,
Andrew Morton <akpm@...ux-foundation.org>,
kernel test robot <lkp@...el.com>,
Qian Cai <quic_qiancai@...cinc.com>
Subject: Re: [PATCH v11 3/6] mm: make alloc_contig_range work at pageblock granularity
On 25 May 2022, at 13:41, Doug Berger wrote:
> I am seeing some free memory accounting problems with linux-next that I have bisected to this commit (i.e. b2c9e2fbba32 ("mm: make alloc_contig_range work at pageblock granularity").
>
> On an arm64 SMP platform with 4GB total memory and the default 16MB default CMA pool, I am seeing the following after boot with a sysrq Show Memory (e.g. 'echo m > /proc/sysrq-trigger'):
>
> [ 16.015906] sysrq: Show Memory
> [ 16.019039] Mem-Info:
> [ 16.021348] active_anon:14604 inactive_anon:919 isolated_anon:0
> [ 16.021348] active_file:0 inactive_file:0 isolated_file:0
> [ 16.021348] unevictable:0 dirty:0 writeback:0
> [ 16.021348] slab_reclaimable:3662 slab_unreclaimable:3333
> [ 16.021348] mapped:928 shmem:15146 pagetables:63 bounce:0
> [ 16.021348] kernel_misc_reclaimable:0
> [ 16.021348] free:976766 free_pcp:991 free_cma:7017
> [ 16.056937] Node 0 active_anon:58416kB inactive_anon:3676kB active_file:0kB inactive_file:0kB unevictable:0kB isolated(anon):0kB isolated(file):0kB mapped:3712kB dirty:0kB writeback:0kB shmem:60584kB writeback_tmp:0kB kernel_stack:1200kB pagetables:252kB all_unreclaimable? no
> [ 16.081526] DMA free:3041036kB boost:0kB min:6036kB low:9044kB high:12052kB reserved_highatomic:0KB active_anon:0kB inactive_anon:0kB active_file:0kB inactive_file:0kB unevictable:0kB writepending:0kB present:3145728kB managed:3029992kB mlocked:0kB bounce:0kB free_pcp:636kB local_pcp:0kB free_cma:28068kB
> [ 16.108650] lowmem_reserve[]: 0 0 944 944
> [ 16.112746] Normal free:866028kB boost:0kB min:1936kB low:2900kB high:3864kB reserved_highatomic:0KB active_anon:58416kB inactive_anon:3676kB active_file:0kB inactive_file:0kB unevictable:0kB writepending:0kB present:1048576kB managed:967352kB mlocked:0kB bounce:0kB free_pcp:3328kB local_pcp:864kB free_cma:0kB
> [ 16.140393] lowmem_reserve[]: 0 0 0 0
> [ 16.144133] DMA: 7*4kB (UMC) 4*8kB (M) 3*16kB (M) 3*32kB (MC) 5*64kB (M) 4*128kB (MC) 5*256kB (UMC) 7*512kB (UM) 5*1024kB (UM) 9*2048kB (UMC) 732*4096kB (MC) = 3027724kB
> [ 16.159609] Normal: 149*4kB (UM) 95*8kB (UME) 26*16kB (UME) 8*32kB (ME) 2*64kB (UE) 1*128kB (M) 2*256kB (ME) 2*512kB (ME) 2*1024kB (UM) 0*2048kB 210*4096kB (M) = 866028kB
> [ 16.175165] Node 0 hugepages_total=0 hugepages_free=0 hugepages_surp=0 hugepages_size=1048576kB
> [ 16.183937] Node 0 hugepages_total=0 hugepages_free=0 hugepages_surp=0 hugepages_size=32768kB
> [ 16.192533] Node 0 hugepages_total=0 hugepages_free=0 hugepages_surp=0 hugepages_size=2048kB
> [ 16.201040] Node 0 hugepages_total=0 hugepages_free=0 hugepages_surp=0 hugepages_size=64kB
> [ 16.209374] 15146 total pagecache pages
> [ 16.213246] 0 pages in swap cache
> [ 16.216595] Swap cache stats: add 0, delete 0, find 0/0
> [ 16.221867] Free swap = 0kB
> [ 16.224780] Total swap = 0kB
> [ 16.227693] 1048576 pages RAM
> [ 16.230694] 0 pages HighMem/MovableOnly
> [ 16.234564] 49240 pages reserved
> [ 16.237825] 4096 pages cma reserved
>
> Some anomolies in the above are:
> free_cma:7017 with only 4096 pages cma reserved
> DMA free:3041036kB with only managed:3029992kB
>
> I'm not sure what is going on here, but I am suspicious of split_free_page() since del_page_from_free_list doesn't affect migrate_type accounting, but __free_one_page() can.
> Also PageBuddy(page) is being checked without zone->lock in isolate_single_pageblock().
>
> Please investigate this as well.
Can you try this patch https://lore.kernel.org/linux-mm/20220524194756.1698351-1-zi.yan@sent.com/
and see if it fixes the issue?
Thanks.
>
> Thanks!
> Doug
>
> On 4/29/2022 6:54 AM, Zi Yan wrote:
>> On 25 Apr 2022, at 10:31, Zi Yan wrote:
>>
>>> From: Zi Yan <ziy@...dia.com>
>>>
>>> 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@...el.com>
>>> Signed-off-by: Zi Yan <ziy@...dia.com>
>>> ---
>>> 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++;
--
Best Regards,
Yan, Zi
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