Re: [PATCH RFC 2/8] fs: add a global device to super block hash table

[Gao Xiang <hsiangkao@linux.alibaba.com>]

On 2026/6/16 20:34, Christoph Hellwig wrote:

> IMHO sharing devices between superblocks is a bad idea, but that ship
> has sailed, but please keep it contained inside of erofs.

I'm not sure why it's a bad idea, for example,
the immutable layer model is already applied to layered virtual
block formats (such as qcow2) and layered fs like overlayfs.

and I think device mappers may have some similar immutable
approaches as shared layers but works in a slight different
way.

The principle is that each instance uses shared blobs in a
read-only way, and that is almost a simple and safest way
to share data among filesystem instances.

Yet I don't want to argue with that since it's pretty common
for years and I've seen no practical risk using this model.

Thanks,
Gao Xiang