[lustre-devel] [LSF/MM/BPF TOPIC] [DRAFT] Lustre client upstreaming

[NeilBrown]

On Sun, 19 Jan 2025, Day, Timothy wrote:
> 
> On the other hand, I wonder if we upstream the whole thing all at once. Beside
> the code being a bit nicer, the client isn't really that much closer to being upstream
> than the server is. And no one else can test the client without having a Lustre
> server on-hand. So no-one can easily run xfstests or similar. And doing everything
> all at once would preempt questions of client/server split or the server upstreaming
> timeline. But upstreaming so much all at once is probably more unrealistic.

The main difference I see between server and client in upstreaming terms
is the storage backend.  It would need to use un-patched ext4 - ideally
using VFS interfaces though we might be able to negotiate with the ext4
team to get some exports.  I don't know much about the delta between
ldiskfs and ext4 and understand it is much smaller than it once was, but
it would need to be zero.  I'm working towards getting the pdirop patch
upstreamable.  Andreas would know what else is needed better than I.

The other difference is that a lot of the "revise code to match upstream
style" work has focused on client and ignored server-only code.

It might be sensible to set the goal as "client and server" including
only the ext4 backend and possibly only the socklnd network interface.
It will be a big code drop either way.  People aren't going to go over
every line with a fine-tooth-comb.  They will mostly look at whichever
bit particularly interests them, and look at the process and community
behind the code.

Being able to build a pure upstream kernel, add a user-space tools
package, and test would certainly be a plus.  That would be something
worth canvassing at LSF - is there any value in landing the client
without the server?

NeilBrown