Re: [PATCH -v4 4/9] migrate_pages: split unmap_and_move() to _unmap() and _move()

[haoxin <xhao@linux.alibaba.com>]

在 2023/2/8 上午1:11, haoxin 写道:
>
> 在 2023/2/6 下午2:33, Huang Ying 写道:
>> This is a preparation patch to batch the folio unmapping and moving.
>>
>> In this patch, unmap_and_move() is split to migrate_folio_unmap() and
>> migrate_folio_move().  So, we can batch _unmap() and _move() in
>> different loops later.  To pass some information between unmap and
>> move, the original unused dst->mapping and dst->private are used.
>>
>> Signed-off-by: "Huang, Ying" <ying.huang@intel.com>
>> Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
>> Cc: Zi Yan <ziy@nvidia.com>
>> Cc: Yang Shi <shy828301@gmail.com>
>> Cc: Oscar Salvador <osalvador@suse.de>
>> Cc: Matthew Wilcox <willy@infradead.org>
>> Cc: Bharata B Rao <bharata@amd.com>
>> Cc: Alistair Popple <apopple@nvidia.com>
>> Cc: haoxin <xhao@linux.alibaba.com>
>> Cc: Minchan Kim <minchan@kernel.org>
>> Cc: Mike Kravetz <mike.kravetz@oracle.com>
>> Cc: Hyeonggon Yoo <42.hyeyoo@gmail.com>
>> ---
>>   include/linux/migrate.h |   1 +
>>   mm/migrate.c            | 170 ++++++++++++++++++++++++++++++----------
>>   2 files changed, 130 insertions(+), 41 deletions(-)
>>
>> diff --git a/include/linux/migrate.h b/include/linux/migrate.h
>> index 3ef77f52a4f0..7376074f2e1e 100644
>> --- a/include/linux/migrate.h
>> +++ b/include/linux/migrate.h
>> @@ -18,6 +18,7 @@ struct migration_target_control;
>>    * - zero on page migration success;
>>    */
>>   #define MIGRATEPAGE_SUCCESS        0
>> +#define MIGRATEPAGE_UNMAP        1
>>     /**
>>    * struct movable_operations - Driver page migration
>> diff --git a/mm/migrate.c b/mm/migrate.c
>> index 9a667039c34c..0428449149f4 100644
>> --- a/mm/migrate.c
>> +++ b/mm/migrate.c
>> @@ -1009,11 +1009,53 @@ static int move_to_new_folio(struct folio 
>> *dst, struct folio *src,
>>       return rc;
>>   }
>>   -static int __unmap_and_move(struct folio *src, struct folio *dst,
>> +/*
>> + * To record some information during migration, we uses
> uses / use
>>   some unused
>> + * fields (mapping and private) of struct folio of the newly allocated
>> + * destination folio.  This is safe because nobody is using them
>> + * except us.
>> + */
>> +static void __migrate_folio_record(struct folio *dst,
>> +                   unsigned long page_was_mapped,
>> +                   struct anon_vma *anon_vma)
>> +{
>> +    dst->mapping = (void *)anon_vma;
>> +    dst->private = (void *)page_was_mapped;
>> +}
>> +
>> +static void __migrate_folio_extract(struct folio *dst,
>> +                   int *page_was_mappedp,
>> +                   struct anon_vma **anon_vmap)
>> +{
>> +    *anon_vmap = (void *)dst->mapping;
>> +    *page_was_mappedp = (unsigned long)dst->private;
>> +    dst->mapping = NULL;
>> +    dst->private = NULL;
>> +}
>> +
>> +/* Cleanup src folio upon migration success */
>> +static void migrate_folio_done(struct folio *src,
>> +                   enum migrate_reason reason)
>> +{
>> +    /*
>> +     * Compaction can migrate also non-LRU pages which are
>> +     * not accounted to NR_ISOLATED_*. They can be recognized
>> +     * as __PageMovable
>> +     */
>> +    if (likely(!__folio_test_movable(src)))
>> +        mod_node_page_state(folio_pgdat(src), NR_ISOLATED_ANON +
>> +                    folio_is_file_lru(src), -folio_nr_pages(src));
>> +
>> +    if (reason != MR_MEMORY_FAILURE)
>> +        /* We release the page in page_handle_poison. */
>> +        folio_put(src);
>> +}
>> +
>> +static int __migrate_folio_unmap(struct folio *src, struct folio *dst,
>>                   int force, enum migrate_mode mode)
>>   {
>>       int rc = -EAGAIN;
>> -    bool page_was_mapped = false;
>> +    int page_was_mapped = 0;
>>       struct anon_vma *anon_vma = NULL;
>>       bool is_lru = !__PageMovable(&src->page);
>>   @@ -1089,8 +1131,8 @@ static int __unmap_and_move(struct folio 
>> *src, struct folio *dst,
>>           goto out_unlock;
>>         if (unlikely(!is_lru)) {
>> -        rc = move_to_new_folio(dst, src, mode);
>> -        goto out_unlock_both;
>> +        __migrate_folio_record(dst, page_was_mapped, anon_vma);
>> +        return MIGRATEPAGE_UNMAP;
>>       }
>>         /*
>> @@ -1115,11 +1157,42 @@ static int __unmap_and_move(struct folio 
>> *src, struct folio *dst,
>>           VM_BUG_ON_FOLIO(folio_test_anon(src) &&
>>                      !folio_test_ksm(src) && !anon_vma, src);
>>           try_to_migrate(src, 0);
>> -        page_was_mapped = true;
>> +        page_was_mapped = 1;
>>       }
>>   -    if (!folio_mapped(src))
>> -        rc = move_to_new_folio(dst, src, mode);
>> +    if (!folio_mapped(src)) {
>> +        __migrate_folio_record(dst, page_was_mapped, anon_vma);
>> +        return MIGRATEPAGE_UNMAP;
>> +    }
>> +
>> +    if (page_was_mapped)
>> +        remove_migration_ptes(src, src, false);
>> +
>> +out_unlock_both:
>> +    folio_unlock(dst);
>> +out_unlock:
>> +    /* Drop an anon_vma reference if we took one */
>> +    if (anon_vma)
>> +        put_anon_vma(anon_vma);
>> +    folio_unlock(src);
>> +out:
>> +
>> +    return rc;
>> +}
>> +
>> +static int __migrate_folio_move(struct folio *src, struct folio *dst,
>> +                enum migrate_mode mode)
>> +{
>> +    int rc;
>> +    int page_was_mapped = 0;
>> +    struct anon_vma *anon_vma = NULL;
>> +    bool is_lru = !__PageMovable(&src->page);
>> +
>> +    __migrate_folio_extract(dst, &page_was_mapped, &anon_vma);
>> +
>> +    rc = move_to_new_folio(dst, src, mode);
>> +    if (unlikely(!is_lru))
>> +        goto out_unlock_both;
>>         /*
>>        * When successful, push dst to LRU immediately: so that if it
>> @@ -1142,12 +1215,10 @@ static int __unmap_and_move(struct folio 
>> *src, struct folio *dst,
>>     out_unlock_both:
>>       folio_unlock(dst);
>> -out_unlock:
>>       /* Drop an anon_vma reference if we took one */
>>       if (anon_vma)
>>           put_anon_vma(anon_vma);
>>       folio_unlock(src);
>> -out:
>>       /*
>>        * If migration is successful, decrease refcount of dst,
>>        * which will not free the page because new page owner increased
>> @@ -1159,19 +1230,15 @@ static int __unmap_and_move(struct folio 
>> *src, struct folio *dst,
>>       return rc;
>>   }
>>   -/*
>> - * Obtain the lock on folio, remove all ptes and migrate the folio
>> - * to the newly allocated folio in dst.
>> - */
>> -static int unmap_and_move(new_page_t get_new_page,
>> -                   free_page_t put_new_page,
>> -                   unsigned long private, struct folio *src,
>> -                   int force, enum migrate_mode mode,
>> -                   enum migrate_reason reason,
>> -                   struct list_head *ret)
>> +/* Obtain the lock on page, remove all ptes. */
>> +static int migrate_folio_unmap(new_page_t get_new_page, free_page_t 
>> put_new_page,
>> +                   unsigned long private, struct folio *src,
>> +                   struct folio **dstp, int force,
>> +                   enum migrate_mode mode, enum migrate_reason reason,
>> +                   struct list_head *ret)
>>   {
>>       struct folio *dst;
>> -    int rc = MIGRATEPAGE_SUCCESS;
>> +    int rc = MIGRATEPAGE_UNMAP;
>>       struct page *newpage = NULL;
>>         if (!thp_migration_supported() && folio_test_transhuge(src))
>> @@ -1182,20 +1249,50 @@ static int unmap_and_move(new_page_t 
>> get_new_page,
>>           folio_clear_active(src);
>>           folio_clear_unevictable(src);
>>           /* free_pages_prepare() will clear PG_isolated. */
>> -        goto out;
>> +        list_del(&src->lru);
>> +        migrate_folio_done(src, reason);
>> +        return MIGRATEPAGE_SUCCESS;
>>       }
>>         newpage = get_new_page(&src->page, private);
>>       if (!newpage)
>>           return -ENOMEM;
>>       dst = page_folio(newpage);
>> +    *dstp = dst;
>>         dst->private = NULL;
>> -    rc = __unmap_and_move(src, dst, force, mode);
>> +    rc = __migrate_folio_unmap(src, dst, force, mode);
>> +    if (rc == MIGRATEPAGE_UNMAP)
>> +        return rc;
>> +
>> +    /*
>> +     * A page that has not been migrated will have kept its
>> +     * references and be restored.
>> +     */
>> +    /* restore the folio to right list. */
>> +    if (rc != -EAGAIN)
>> +        list_move_tail(&src->lru, ret);
>> +
>> +    if (put_new_page)
>> +        put_new_page(&dst->page, private);
>> +    else
>> +        folio_put(dst);
>> +
>> +    return rc;
>> +}
>> +
>> +/* Migrate the folio to the newly allocated folio in dst. */
>> +static int migrate_folio_move(free_page_t put_new_page, unsigned 
>> long private,
>> +                  struct folio *src, struct folio *dst,
>> +                  enum migrate_mode mode, enum migrate_reason reason,
>> +                  struct list_head *ret)
>> +{
>> +    int rc;
>> +
>> +    rc = __migrate_folio_move(src, dst, mode);
>>       if (rc == MIGRATEPAGE_SUCCESS)
>>           set_page_owner_migrate_reason(&dst->page, reason);
>>   -out:
>>       if (rc != -EAGAIN) {
>>           /*
>>            * A folio that has been migrated has all references
>> @@ -1211,20 +1308,7 @@ static int unmap_and_move(new_page_t 
>> get_new_page,
>>        * we want to retry.
>>        */
>>       if (rc == MIGRATEPAGE_SUCCESS) {
>> -        /*
>> -         * Compaction can migrate also non-LRU folios which are
>> -         * not accounted to NR_ISOLATED_*. They can be recognized
>> -         * as __folio_test_movable
>> -         */
>> -        if (likely(!__folio_test_movable(src)))
>> -            mod_node_page_state(folio_pgdat(src), NR_ISOLATED_ANON +
>> -                    folio_is_file_lru(src), -folio_nr_pages(src));
>> -
>> -        if (reason != MR_MEMORY_FAILURE)
>> -            /*
>> -             * We release the folio in page_handle_poison.
>> -             */
>> -            folio_put(src);
>> +        migrate_folio_done(src, reason);
>>       } else {
>>           if (rc != -EAGAIN)
>>               list_add_tail(&src->lru, ret);
>> @@ -1516,7 +1600,7 @@ static int migrate_pages_batch(struct list_head 
>> *from, new_page_t get_new_page,
>>       int pass = 0;
>>       bool is_large = false;
>>       bool is_thp = false;
>> -    struct folio *folio, *folio2;
>> +    struct folio *folio, *folio2, *dst = NULL;
>>       int rc, nr_pages;
>>       LIST_HEAD(split_folios);
>>       bool nosplit = (reason == MR_NUMA_MISPLACED);
>> @@ -1543,9 +1627,13 @@ static int migrate_pages_batch(struct 
>> list_head *from, new_page_t get_new_page,
>>                 cond_resched();
>>   -            rc = unmap_and_move(get_new_page, put_new_page,
>> -                        private, folio, pass > 2, mode,
>> -                        reason, ret_folios);
>> +            rc = migrate_folio_unmap(get_new_page, put_new_page, 
>> private,
>> +                         folio, &dst, pass > 2, mode,
>> +                         reason, ret_folios);
>> +            if (rc == MIGRATEPAGE_UNMAP)
>> +                rc = migrate_folio_move(put_new_page, private,
>> +                            folio, dst, mode,
>> +                            reason, ret_folios);
> How to deal with the whole  pages are ummaped success,  but only part  
> pages are moved success ?

Please ignore this, i get answer from patch 5.

Reviewed-by: Xin Hao <xhao@linux.alibaba.com>

>>               /*
>>                * The rules are:
>>                *    Success: folio will be freed