Message-ID: <28b77814-efea-d5e5-100b-d96da72254ad@linux.alibaba.com>
Date:   Wed, 8 Feb 2023 01:11:50 +0800
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Subject: Re: [PATCH -v4 4/9] migrate_pages: split unmap_and_move() to _unmap()
 and _move()
To:     Huang Ying <ying.huang@intel.com>,
        Andrew Morton <akpm@linux-foundation.org>
Cc:     linux-mm@kvack.org, linux-kernel@vger.kernel.org,
        Baolin Wang <baolin.wang@linux.alibaba.com>,
        Zi Yan <ziy@nvidia.com>, Yang Shi <shy828301@gmail.com>,
        Oscar Salvador <osalvador@suse.de>,
        Matthew Wilcox <willy@infradead.org>,
        Bharata B Rao <bharata@amd.com>,
        Alistair Popple <apopple@nvidia.com>,
        Minchan Kim <minchan@kernel.org>,
        Mike Kravetz <mike.kravetz@oracle.com>,
        Hyeonggon Yoo <42.hyeyoo@gmail.com>
References: <20230206063313.635011-1-ying.huang@intel.com>
 <20230206063313.635011-5-ying.huang@intel.com>
From:   haoxin <xhao@linux.alibaba.com>
In-Reply-To: <20230206063313.635011-5-ying.huang@intel.com>
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Precedence: bulk


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