Re: [PATCH v2] F2FS customized migrate_page callback

[Chao Yu <chao@kernel.org>]

On 2016/9/20 5:03, Weichao Guo wrote:
> This patch improves the migration of dirty pages and allows migrating atomic
> written pages that F2FS uses in Page Cache. Instead of the fallback releasing
> page path, it provides better performance for memory compaction, CMA and other
> users of memory page migrating. For dirty pages, there is no need to write back
> first when migrating. For an atomic written page before committing, we can
> migrate the page and update the related 'inmem_pages' list at the same time.
> 
> Signed-off-by: Weichao Guo <guoweichao@huawei.com>
> ---
>  fs/f2fs/checkpoint.c |  3 +++
>  fs/f2fs/data.c       | 56 ++++++++++++++++++++++++++++++++++++++++++++++++++++
>  fs/f2fs/f2fs.h       |  4 ++++
>  fs/f2fs/node.c       |  3 +++
>  4 files changed, 66 insertions(+)
> 
> diff --git a/fs/f2fs/checkpoint.c b/fs/f2fs/checkpoint.c
> index df56a43..a366521 100644
> --- a/fs/f2fs/checkpoint.c
> +++ b/fs/f2fs/checkpoint.c
> @@ -388,6 +388,9 @@ const struct address_space_operations f2fs_meta_aops = {
>  	.set_page_dirty	= f2fs_set_meta_page_dirty,
>  	.invalidatepage = f2fs_invalidate_page,
>  	.releasepage	= f2fs_release_page,
> +#ifdef CONFIG_MIGRATION
> +	.migratepage    = f2fs_migrate_page,
> +#endif
>  };
>  
>  static void __add_ino_entry(struct f2fs_sb_info *sbi, nid_t ino, int type)
> diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
> index 528c3c0..eb0d63f 100644
> --- a/fs/f2fs/data.c
> +++ b/fs/f2fs/data.c
> @@ -1882,6 +1882,59 @@ static sector_t f2fs_bmap(struct address_space *mapping, sector_t block)
>  	return generic_block_bmap(mapping, block, get_data_block_bmap);
>  }
>  
> +#ifdef CONFIG_MIGRATION
> +
> +#include <linux/migrate.h>
> +
> +int f2fs_migrate_page(struct address_space *mapping,
> +		struct page *newpage, struct page *page, enum migrate_mode mode)
> +{
> +	int rc, extra_count;
> +	struct f2fs_inode_info *fi = F2FS_I(mapping->host);
> +	bool atomic_written = IS_ATOMIC_WRITTEN_PAGE(page);
> +
> +	BUG_ON(PageWriteback(page));
> +
> +	/* migrating an atomic written page is safe with the inmem_lock hold */
> +	if (atomic_written && !mutex_trylock(&fi->inmem_lock))
> +		return -EAGAIN;
> +
> +	/*
> +	 * A reference is expected if PagePrivate set when move mapping,
> +	 * however F2FS breaks this for maintaining dirty page counts when
> +	 * truncating pages. So here adjusting the 'extra_count' make it work.
> +	 */
> +	extra_count = (atomic_written ? 1 : 0) - page_has_private(page);
> +	rc = migrate_page_move_mapping(mapping, newpage,
> +				page, NULL, mode, extra_count);
> +	if (rc != MIGRATEPAGE_SUCCESS) {
> +		if (atomic_written)
> +			mutex_unlock(&fi->inmem_lock);
> +		return rc;
> +	}
> +
> +	if (atomic_written) {
> +		struct inmem_pages *cur;
> +		list_for_each_entry(cur, &fi->inmem_pages, list)
> +			if (cur->page == page) {
> +				cur->page = newpage;
> +				break;
> +			}
> +		mutex_unlock(&fi->inmem_lock);
> +		put_page(page);
> +		get_page(newpage);

Should we also do put_page(oldpage) & get_page(newpage) for non-atomic-written page?

Thanks,

> +	}
> +
> +	if (PagePrivate(page))
> +		SetPagePrivate(newpage);
> +	set_page_private(newpage, page_private(page));
> +
> +	migrate_page_copy(newpage, page);
> +
> +	return MIGRATEPAGE_SUCCESS;
> +}
> +#endif
> +
>  const struct address_space_operations f2fs_dblock_aops = {
>  	.readpage	= f2fs_read_data_page,
>  	.readpages	= f2fs_read_data_pages,
> @@ -1894,4 +1947,7 @@ const struct address_space_operations f2fs_dblock_aops = {
>  	.releasepage	= f2fs_release_page,
>  	.direct_IO	= f2fs_direct_IO,
>  	.bmap		= f2fs_bmap,
> +#ifdef CONFIG_MIGRATION
> +	.migratepage    = f2fs_migrate_page,
> +#endif
>  };
> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> index 5d2aa6a..b951482 100644
> --- a/fs/f2fs/f2fs.h
> +++ b/fs/f2fs/f2fs.h
> @@ -2126,6 +2126,10 @@ int f2fs_fiemap(struct inode *inode, struct fiemap_extent_info *, u64, u64);
>  void f2fs_set_page_dirty_nobuffers(struct page *);
>  void f2fs_invalidate_page(struct page *, unsigned int, unsigned int);
>  int f2fs_release_page(struct page *, gfp_t);
> +#ifdef CONFIG_MIGRATION
> +int f2fs_migrate_page(struct address_space *mapping,
> +	struct page *newpage, struct page *page, enum migrate_mode mode);
> +#endif
>  
>  /*
>   * gc.c
> diff --git a/fs/f2fs/node.c b/fs/f2fs/node.c
> index 2322a8e..55c22a9 100644
> --- a/fs/f2fs/node.c
> +++ b/fs/f2fs/node.c
> @@ -1670,6 +1670,9 @@ const struct address_space_operations f2fs_node_aops = {
>  	.set_page_dirty	= f2fs_set_node_page_dirty,
>  	.invalidatepage	= f2fs_invalidate_page,
>  	.releasepage	= f2fs_release_page,
> +#ifdef CONFIG_MIGRATION
> +	.migratepage    = f2fs_migrate_page,
> +#endif
>  };
>  
>  static struct free_nid *__lookup_free_nid_list(struct f2fs_nm_info *nm_i,
> 

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