Re: [RFC[RAP]] fuse: use fs-iomap for better performance so we can containerize ext4

Miklos Szeredi
2025-06-12T05:54:23Z

On Wed, 11 Jun 2025 at 10:54, Amir Goldstein <amir73il@gmail.com> wrote:

> There is already a mount option 'rootmode' for st_mode of root inode
> so I suppose we could add the rootino mount option.
>
> Note that currently fuse_fill_super_common() instantiates the root inode
> before negotiating FUSE_INIT with the server.

I'd prefer not to add more mount options like this.

It would be nice to move away from async FUSE_INIT. It's one of those
things I wish I'd done differently.

Unfortunately I don't think adding FUSE_INIT_SYNC would be sufficient,
as servers might expect the first request to be always FUSE_INIT and
break if it isn't. Libfuse seems to be okay, but...

One idea is to add an ioctl that the server would call before
mounting, that explicitly allows FUSE_INIT_SYNC. It's somewhat ugly,
but I can't think of a better solution.

Thanks,
Miklos