Re: [PATCH] f2fs: adjust readahead block number during recovery

[Chao Yu <chao@kernel.org>]

Jaegeuk, any comments on this patch?

Thanks,

On 2022/1/29 16:21, Chao Yu wrote:
> In a fragmented image, entries in dnode block list may locate in
> incontiguous physical block address space, however, in recovery flow,
> we will always readahead BIO_MAX_VECS size blocks, so in such case,
> current readahead policy is low efficient, let's adjust readahead
> window size dynamically based on consecutiveness of dnode blocks.
> 
> Signed-off-by: Chao Yu <chao@kernel.org>
> ---
>   fs/f2fs/checkpoint.c |  8 ++++++--
>   fs/f2fs/f2fs.h       |  6 +++++-
>   fs/f2fs/recovery.c   | 27 ++++++++++++++++++++++++---
>   3 files changed, 35 insertions(+), 6 deletions(-)
> 
> diff --git a/fs/f2fs/checkpoint.c b/fs/f2fs/checkpoint.c
> index 57a2d9164bee..203a1577942d 100644
> --- a/fs/f2fs/checkpoint.c
> +++ b/fs/f2fs/checkpoint.c
> @@ -282,18 +282,22 @@ int f2fs_ra_meta_pages(struct f2fs_sb_info *sbi, block_t start, int nrpages,
>   	return blkno - start;
>   }
>   
> -void f2fs_ra_meta_pages_cond(struct f2fs_sb_info *sbi, pgoff_t index)
> +void f2fs_ra_meta_pages_cond(struct f2fs_sb_info *sbi, pgoff_t index,
> +							unsigned int ra_blocks)
>   {
>   	struct page *page;
>   	bool readahead = false;
>   
> +	if (ra_blocks == RECOVERY_MIN_RA_BLOCKS)
> +		return;
> +
>   	page = find_get_page(META_MAPPING(sbi), index);
>   	if (!page || !PageUptodate(page))
>   		readahead = true;
>   	f2fs_put_page(page, 0);
>   
>   	if (readahead)
> -		f2fs_ra_meta_pages(sbi, index, BIO_MAX_VECS, META_POR, true);
> +		f2fs_ra_meta_pages(sbi, index, ra_blocks, META_POR, true);
>   }
>   
>   static int __f2fs_write_meta_page(struct page *page,
> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> index 5af415208488..1fa6b3f98a71 100644
> --- a/fs/f2fs/f2fs.h
> +++ b/fs/f2fs/f2fs.h
> @@ -590,6 +590,9 @@ enum {
>   /* number of extent info in extent cache we try to shrink */
>   #define EXTENT_CACHE_SHRINK_NUMBER	128
>   
> +#define RECOVERY_MAX_RA_BLOCKS		BIO_MAX_VECS
> +#define RECOVERY_MIN_RA_BLOCKS		1
> +
>   struct rb_entry {
>   	struct rb_node rb_node;		/* rb node located in rb-tree */
>   	union {
> @@ -3655,7 +3658,8 @@ bool f2fs_is_valid_blkaddr(struct f2fs_sb_info *sbi,
>   					block_t blkaddr, int type);
>   int f2fs_ra_meta_pages(struct f2fs_sb_info *sbi, block_t start, int nrpages,
>   			int type, bool sync);
> -void f2fs_ra_meta_pages_cond(struct f2fs_sb_info *sbi, pgoff_t index);
> +void f2fs_ra_meta_pages_cond(struct f2fs_sb_info *sbi, pgoff_t index,
> +							unsigned int ra_blocks);
>   long f2fs_sync_meta_pages(struct f2fs_sb_info *sbi, enum page_type type,
>   			long nr_to_write, enum iostat_type io_type);
>   void f2fs_add_ino_entry(struct f2fs_sb_info *sbi, nid_t ino, int type);
> diff --git a/fs/f2fs/recovery.c b/fs/f2fs/recovery.c
> index f69b685fb2b2..0b88d0ce284a 100644
> --- a/fs/f2fs/recovery.c
> +++ b/fs/f2fs/recovery.c
> @@ -346,6 +346,19 @@ static int recover_inode(struct inode *inode, struct page *page)
>   	return 0;
>   }
>   
> +static unsigned int adjust_por_ra_blocks(struct f2fs_sb_info *sbi,
> +				unsigned int ra_blocks, unsigned int blkaddr,
> +				unsigned int next_blkaddr)
> +{
> +	if (blkaddr + 1 == next_blkaddr)
> +		ra_blocks = min_t(unsigned int, RECOVERY_MIN_RA_BLOCKS,
> +							ra_blocks * 2);
> +	else if (next_blkaddr % sbi->blocks_per_seg)
> +		ra_blocks = max_t(unsigned int, RECOVERY_MAX_RA_BLOCKS,
> +							ra_blocks / 2);
> +	return ra_blocks;
> +}
> +
>   static int find_fsync_dnodes(struct f2fs_sb_info *sbi, struct list_head *head,
>   				bool check_only)
>   {
> @@ -353,6 +366,7 @@ static int find_fsync_dnodes(struct f2fs_sb_info *sbi, struct list_head *head,
>   	struct page *page = NULL;
>   	block_t blkaddr;
>   	unsigned int loop_cnt = 0;
> +	unsigned int ra_blocks = RECOVERY_MAX_RA_BLOCKS;
>   	unsigned int free_blocks = MAIN_SEGS(sbi) * sbi->blocks_per_seg -
>   						valid_user_blocks(sbi);
>   	int err = 0;
> @@ -427,11 +441,14 @@ static int find_fsync_dnodes(struct f2fs_sb_info *sbi, struct list_head *head,
>   			break;
>   		}
>   
> +		ra_blocks = adjust_por_ra_blocks(sbi, ra_blocks, blkaddr,
> +						next_blkaddr_of_node(page));
> +
>   		/* check next segment */
>   		blkaddr = next_blkaddr_of_node(page);
>   		f2fs_put_page(page, 1);
>   
> -		f2fs_ra_meta_pages_cond(sbi, blkaddr);
> +		f2fs_ra_meta_pages_cond(sbi, blkaddr, ra_blocks);
>   	}
>   	return err;
>   }
> @@ -707,6 +724,7 @@ static int recover_data(struct f2fs_sb_info *sbi, struct list_head *inode_list,
>   	struct page *page = NULL;
>   	int err = 0;
>   	block_t blkaddr;
> +	unsigned int ra_blocks = RECOVERY_MAX_RA_BLOCKS;
>   
>   	/* get node pages in the current segment */
>   	curseg = CURSEG_I(sbi, CURSEG_WARM_NODE);
> @@ -718,8 +736,6 @@ static int recover_data(struct f2fs_sb_info *sbi, struct list_head *inode_list,
>   		if (!f2fs_is_valid_blkaddr(sbi, blkaddr, META_POR))
>   			break;
>   
> -		f2fs_ra_meta_pages_cond(sbi, blkaddr);
> -
>   		page = f2fs_get_tmp_page(sbi, blkaddr);
>   		if (IS_ERR(page)) {
>   			err = PTR_ERR(page);
> @@ -762,9 +778,14 @@ static int recover_data(struct f2fs_sb_info *sbi, struct list_head *inode_list,
>   		if (entry->blkaddr == blkaddr)
>   			list_move_tail(&entry->list, tmp_inode_list);
>   next:
> +		ra_blocks = adjust_por_ra_blocks(sbi, ra_blocks, blkaddr,
> +						next_blkaddr_of_node(page));
> +
>   		/* check next segment */
>   		blkaddr = next_blkaddr_of_node(page);
>   		f2fs_put_page(page, 1);
> +
> +		f2fs_ra_meta_pages_cond(sbi, blkaddr, ra_blocks);
>   	}
>   	if (!err)
>   		f2fs_allocate_new_segments(sbi);