Re: [PATCH] f2fs: implement cgroup writeback supprot

[Chao Yu]

On 2018/1/5 14:28, Yufen Yu wrote:
> Cgroup writeback requires explicit support from the filesystem.
> f2fs's data and node writeback IOs go through __write_data_page,
> which sets fio for submiting IOs. So, we add io_wbc for fio,
> associate bios with blkcg by invoking wbc_init_bio() and
> account IOs issuing by wbc_account_io().
> In addtion, f2fs_fill_super() is updated to set SB_I_CGROUPWB.
> 
> Meta writeback IOs is left alone by this patch and will always be
> attributed to the root cgroup.
> 
> The results show that f2fs can throttle writeback nicely for
> data writing and file creating.
> 
> Signed-off-by: Yufen Yu <yuyufen@xxxxxxxxxx>
> ---
>  fs/f2fs/data.c  | 11 +++++++++--
>  fs/f2fs/f2fs.h  |  1 +
>  fs/f2fs/node.c  |  1 +
>  fs/f2fs/super.c |  1 +
>  4 files changed, 12 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
> index 516fa0d..402df03 100644
> --- a/fs/f2fs/data.c
> +++ b/fs/f2fs/data.c
> @@ -169,6 +169,7 @@ static bool __same_bdev(struct f2fs_sb_info *sbi,
>   * Low-level block read/write IO operations.
>   */
>  static struct bio *__bio_alloc(struct f2fs_sb_info *sbi, block_t blk_addr,
> +				struct writeback_control *wbc,
>  				int npages, bool is_read)
>  {
>  	struct bio *bio;
> @@ -178,6 +179,8 @@ static struct bio *__bio_alloc(struct f2fs_sb_info *sbi, block_t blk_addr,
>  	f2fs_target_device(sbi, blk_addr, bio);
>  	bio->bi_end_io = is_read ? f2fs_read_end_io : f2fs_write_end_io;
>  	bio->bi_private = is_read ? NULL : sbi;
> +	if (wbc)
> +		wbc_init_bio(wbc, bio);
>  
>  	return bio;
>  }
> @@ -373,7 +376,8 @@ int f2fs_submit_page_bio(struct f2fs_io_info *fio)
>  	f2fs_trace_ios(fio, 0);
>  
>  	/* Allocate a new bio */
> -	bio = __bio_alloc(fio->sbi, fio->new_blkaddr, 1, is_read_io(fio->op));
> +	bio = __bio_alloc(fio->sbi, fio->new_blkaddr, fio->io_wbc,
> +				1, is_read_io(fio->op));
>  
>  	if (bio_add_page(bio, page, PAGE_SIZE, 0) < PAGE_SIZE) {
>  		bio_put(bio);
> @@ -435,7 +439,7 @@ int f2fs_submit_page_write(struct f2fs_io_info *fio)
>  			dec_page_count(sbi, WB_DATA_TYPE(bio_page));
>  			goto out_fail;
>  		}
> -		io->bio = __bio_alloc(sbi, fio->new_blkaddr,
> +		io->bio = __bio_alloc(sbi, fio->new_blkaddr, fio->io_wbc,
>  						BIO_MAX_PAGES, false);
>  		io->fio = *fio;
>  	}
> @@ -443,6 +447,8 @@ int f2fs_submit_page_write(struct f2fs_io_info *fio)
>  	if (bio_add_page(io->bio, bio_page, PAGE_SIZE, 0) < PAGE_SIZE) {
>  		__submit_merged_bio(io);
>  		goto alloc_new;
> +	} else if (fio->io_wbc) {
> +		wbc_account_io(fio->io_wbc, bio_page, PAGE_SIZE);
>  	}

if (bio_add_page()) {
	__submit_merged_bio();
	goto alloc_new;
}

if (fio->io_wbc)
	wbc_account_io(fio->io_wbc, bio_page, PAGE_SIZE);

Other part looks good to me.

Reviewed-by: Chao Yu <yuchao0@xxxxxxxxxx>

Thanks,

>  
>  	io->last_block_in_bio = fio->new_blkaddr;
> @@ -1508,6 +1514,7 @@ static int __write_data_page(struct page *page, bool *submitted,
>  		.submitted = false,
>  		.need_lock = LOCK_RETRY,
>  		.io_type = io_type,
> +		.io_wbc = wbc,
>  	};
>  
>  	trace_f2fs_writepage(page, DATA);
> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> index 6abf26c..4887dde 100644
> --- a/fs/f2fs/f2fs.h
> +++ b/fs/f2fs/f2fs.h
> @@ -957,6 +957,7 @@ struct f2fs_io_info {
>  	int need_lock;		/* indicate we need to lock cp_rwsem */
>  	bool in_list;		/* indicate fio is in io_list */
>  	enum iostat_type io_type;	/* io type */
> +	struct writeback_control *io_wbc; /* writeback control */
>  };
>  
>  #define is_read_io(rw) ((rw) == READ)
> diff --git a/fs/f2fs/node.c b/fs/f2fs/node.c
> index d332275..e4f8bb0 100644
> --- a/fs/f2fs/node.c
> +++ b/fs/f2fs/node.c
> @@ -1336,6 +1336,7 @@ static int __write_node_page(struct page *page, bool atomic, bool *submitted,
>  		.encrypted_page = NULL,
>  		.submitted = false,
>  		.io_type = io_type,
> +		.io_wbc = wbc,
>  	};
>  
>  	trace_f2fs_writepage(page, NODE);
> diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
> index 708155d..deeba98 100644
> --- a/fs/f2fs/super.c
> +++ b/fs/f2fs/super.c
> @@ -2475,6 +2475,7 @@ static int f2fs_fill_super(struct super_block *sb, void *data, int silent)
>  	sb->s_flags = (sb->s_flags & ~SB_POSIXACL) |
>  		(test_opt(sbi, POSIX_ACL) ? SB_POSIXACL : 0);
>  	memcpy(&sb->s_uuid, raw_super->uuid, sizeof(raw_super->uuid));
> +	sb->s_iflags |= SB_I_CGROUPWB;
>  
>  	/* init f2fs-specific super block info */
>  	sbi->valid_super_block = valid_super_block;
>