Re: [PATCH v3 16/22] btrfs-progs: convert: Introduce function to migrate reserved ranges

[Liu Bo <bo.li.liu@oracle.com>]

On Fri, Jan 29, 2016 at 01:03:26PM +0800, Qu Wenruo wrote:
> Introduce new function, migrate_reserved_ranges() to migrate used fs
> data in btrfs reserved space.
> 
> Unlike old implement, which will need to relocate all the complicated
> csum and reference relocation, previous patches already ensure such
> reserved ranges won't be allocated.
> So here we only need copy these data out and create new
> extent/csum/reference.
> 
> Signed-off-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
> Signed-off-by: David Sterba <dsterba@suse.com>
> ---
>  btrfs-convert.c | 124 +++++++++++++++++++++++++++++++++++++++++++++++++++++++-
>  1 file changed, 122 insertions(+), 2 deletions(-)
> 
> diff --git a/btrfs-convert.c b/btrfs-convert.c
> index 16e2309..f6126db 100644
> --- a/btrfs-convert.c
> +++ b/btrfs-convert.c
> @@ -1679,6 +1679,123 @@ static int create_image_file_range_v2(struct btrfs_trans_handle *trans,
>  	return ret;
>  }
>  
> +
> +/*
> + * Relocate old fs data in one reserved ranges
> + *
> + * Since all old fs data in reserved range is not covered by any chunk nor
> + * data extent, we don't need to handle any reference but add new
> + * extent/reference, which makes codes more clear
> + */
> +static int migrate_one_reserved_range(struct btrfs_trans_handle *trans,
> +				      struct btrfs_root *root,
> +				      struct cache_tree *used,
> +				      struct btrfs_inode_item *inode, int fd,
> +				      u64 ino, u64 start, u64 len, int datacsum)
> +{
> +	u64 cur_off = start;
> +	u64 cur_len = len;
> +	struct cache_extent *cache;
> +	struct btrfs_key key;
> +	struct extent_buffer *eb;
> +	int ret = 0;
> +
> +	while (cur_off < start + len) {
> +		cache = lookup_cache_extent(used, cur_off, cur_len);
> +		if (!cache)
> +			break;
> +		cur_off = max(cache->start, cur_off);
> +		cur_len = min(cache->start + cache->size, start + len) -
> +			  cur_off;
> +		BUG_ON(cur_len < root->sectorsize);
> +
> +		/* reserve extent for the data */
> +		ret = btrfs_reserve_extent(trans, root, cur_len, 0, 0, (u64)-1,
> +					   &key, 1);
> +		if (ret < 0)
> +			break;
> +
> +		eb = malloc(sizeof(*eb) + cur_len);
> +		if (!eb) {
> +			ret = -ENOMEM;
> +			break;
> +		}
> +
> +		ret = pread(fd, eb->data, cur_len, cur_off);
> +		if (ret < cur_len) {
> +			ret = (ret < 0 ? ret : -EIO);
> +			free(eb);
> +			break;
> +		}
> +		eb->start = key.objectid;
> +		eb->len = key.offset;
> +
> +		/* Write the data */
> +		ret = write_and_map_eb(trans, root, eb);
> +		free(eb);
> +		if (ret < 0)
> +			break;

With write_data_to_disk(), we don't have to create eb for write.

Thanks,

-liubo
> +
> +		/* Now handle extent item and file extent things */
> +		ret = btrfs_record_file_extent(trans, root, ino, inode, cur_off,
> +					       key.objectid, key.offset);
> +		if (ret < 0)
> +			break;
> +		/* Finally, insert csum items */
> +		if (datacsum)
> +			ret = csum_disk_extent(trans, root, key.objectid,
> +					       key.offset);
> +
> +		cur_off += key.offset;
> +		cur_len = start + len - cur_off;
> +	}
> +	return ret;
> +}
> +
> +/*
> + * Relocate the used ext2 data in reserved ranges
> + * [0,1M)
> + * [btrfs_sb_offset(1), +BTRFS_STRIPE_LEN)
> + * [btrfs_sb_offset(2), +BTRFS_STRIPE_LEN)
> + */
> +static int migrate_reserved_ranges(struct btrfs_trans_handle *trans,
> +				   struct btrfs_root *root,
> +				   struct cache_tree *used,
> +				   struct btrfs_inode_item *inode, int fd,
> +				   u64 ino, u64 total_bytes, int datacsum)
> +{
> +	u64 cur_off;
> +	u64 cur_len;
> +	int ret = 0;
> +
> +	/* 0 ~ 1M */
> +	cur_off = 0;
> +	cur_len = 1024 * 1024;
> +	ret = migrate_one_reserved_range(trans, root, used, inode, fd, ino,
> +					 cur_off, cur_len, datacsum);
> +	if (ret < 0)
> +		return ret;
> +
> +	/* second sb(fisrt sb is included in 0~1M) */
> +	cur_off = btrfs_sb_offset(1);
> +	cur_len = min(total_bytes, cur_off + BTRFS_STRIPE_LEN) - cur_off;
> +	if (cur_off < total_bytes)
> +		return ret;
> +	ret = migrate_one_reserved_range(trans, root, used, inode, fd, ino,
> +					 cur_off, cur_len, datacsum);
> +	if (ret < 0)
> +		return ret;
> +
> +	/* Last sb */
> +	cur_off = btrfs_sb_offset(2);
> +	cur_len = min(total_bytes, cur_off + BTRFS_STRIPE_LEN) - cur_off;
> +	if (cur_off < total_bytes)
> +		return ret;
> +	ret = migrate_one_reserved_range(trans, root, used, inode, fd, ino,
> +					 cur_off, cur_len, datacsum);
> +	return ret;
> +}
> +
>  static int wipe_reserved_ranges(struct cache_tree *tree, u64 min_stripe_size,
>  				int ensure_size);
>  
> @@ -1687,11 +1804,10 @@ static int wipe_reserved_ranges(struct cache_tree *tree, u64 min_stripe_size,
>   *
>   * This is completely fs independent as we have cctx->used, only
>   * need to create file extents point to all the posistions.
> - * TODO: Add handler for reserved ranges in next patch
>   */
>  static int create_image_v2(struct btrfs_root *root,
>  			   struct btrfs_mkfs_config *cfg,
> -			   struct btrfs_convert_context *cctx,
> +			   struct btrfs_convert_context *cctx, int fd,
>  			   u64 size, char *name, int datacsum)
>  {
>  	struct btrfs_inode_item buf;
> @@ -1769,6 +1885,10 @@ static int create_image_v2(struct btrfs_root *root,
>  			goto out;
>  		cur += len;
>  	}
> +	/* Handle the reserved ranges */
> +	ret = migrate_reserved_ranges(trans, root, &cctx->used, &buf, fd, ino,
> +				      cfg->num_bytes, datacsum);
> +
>  
>  	key.objectid = ino;
>  	key.type = BTRFS_INODE_ITEM_KEY;
> -- 
> 2.7.0
> 
> 
> 
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