Re: [Linux-cachefs] mount -o remount?

[David Howells <dhowells redhat com>]

Daire Byrne <Daire Byrne framestore com> wrote:

> Does FS-Cache support mounting an NFS filesystem without "fsc" and then
> later adding it with a remount?

No.  I hadn't thought about it.

> Is there any reason why it couldn't support this?

It could be done, but it would require iteration over all the in-RAM inodes in
the superblock to give them cache tokens, and possibly iteration over all
pages attached to those inodes to store any that aren't yet encached.

> The main reason I ask is that I would like to mount an NFS root filesystem
> using a simple basic initrd (busybox) but then use fs-cache once I have a
> more complete Linux distro available (i.e. diskless booting).

I don't know whether it helps, but you can tell NFS to start using the cache
before there is actually a cache.  Once the cache is started, NFS will
automatically start using it - at least for files opened since.

> On an unrelated note, have you tested cachefiles with ext4? It doesn't seem
> to work for me (CacheFiles: Lookup failed error -1).

I don't recall whether I tried ext4 or not.  I'll have a look.

David