f2fs: implement cgroup writeback support

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.

Reviewed-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Yufen Yu <yuyufen@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/data.c

@@ -170,6 +170,7 @@ 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;
@@ -179,6 +180,8 @@ 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;
 }
@@ -374,7 +377,8 @@ 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);
@@ -436,7 +440,7 @@ alloc_new:
 			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;
 	}
@@ -446,6 +450,9 @@ alloc_new:
 		goto alloc_new;
 	}
 
+	if (fio->io_wbc)
+		wbc_account_io(fio->io_wbc, bio_page, PAGE_SIZE);
+
 	io->last_block_in_bio = fio->new_blkaddr;
 	f2fs_trace_ios(fio, 0);
 
@@ -1529,6 +1536,7 @@ 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);

fs/f2fs/f2fs.h

@@ -961,6 +961,7 @@ 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)

fs/f2fs/node.c

@@ -1335,6 +1335,7 @@ 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);

fs/f2fs/super.c

@@ -2518,6 +2518,7 @@ try_onemore:
 	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;