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

[haoxin <xhao@xxxxxxxxxxxxxxxxx>]

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@xxxxxxxxx>
> > Reviewed-by: Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx>
> > Cc: Zi Yan <ziy@xxxxxxxxxx>
> > Cc: Yang Shi <shy828301@xxxxxxxxx>
> > Cc: Oscar Salvador <osalvador@xxxxxxx>
> > Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
> > Cc: Bharata B Rao <bharata@xxxxxxx>
> > Cc: Alistair Popple <apopple@xxxxxxxxxx>
> > Cc: haoxin <xhao@xxxxxxxxxxxxxxxxx>
> > Cc: Minchan Kim <minchan@xxxxxxxxxx>
> > Cc: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
> > Cc: Hyeonggon Yoo <42.hyeyoo@xxxxxxxxx>
> > ---
> >   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@xxxxxxxxxxxxxxxxx>

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