[PATCH V3] erofs: support flattened block device for multi-blob images

[Chao Yu]

On 2023/3/2 15:17, Jia Zhu wrote:
> In order to support mounting multi-blobs container image as a single
> block device, add flattened block device feature for EROFS.
> 
> In this mode, all meta/data contents will be mapped into one block
> address. User could compose a block device(by nbd/ublk/virtio-blk/
> vhost-user-blk) from multiple sources and mount the block device by
> EROFS directly. It can reduce the number of block devices used, and
> it's also benefits in both VM file passthrough and distributed storage
> scenarios.
> 
> You can test this using the method mentioned by:
> https://github.com/dragonflyoss/image-service/pull/1111
> 1. Compose a (nbd)block device from multi-blobs.
> 2. Mount EROFS on mntdir/.
> 3. Compare the md5sum between source dir and mntdir/.
> 
> Later, we could also use it to refer original tar blobs.
> 
> Signed-off-by: Jia Zhu <zhujia.zj at bytedance.com>
> Signed-off-by: Xin Yin <yinxin.x at bytedance.com>
> Reviewed-by: Jingbo Xu <jefflexu at linux.alibaba.com>

Acked-by: Chao Yu <chao at kernel.org>

Thanks,