Re: [PATCH 24/32] vfs: syscall: Add fsopen() to prepare for superblock creation [ver #9]

Yeah, Andy is right that we should *not* make "write()" have side effects.

Use it to queue things by all means, but not "do" things. Not unless
there's a very sane security model.

On Tue, Jul 10, 2018 at 4:59 PM Andy Lutomirski [off-list ref] wrote:

I think the right solution is one of:

(a) Pass a netlink-formatted blob to fsopen() and do the whole thing in one syscall. I don’t mean using netlink sockets — just the nlattr format.  Or you could use a different format. The part that matters is using just one syscall to do the whole thing.

Please no. Not another nasty marshalling thing.

(b) Keep the current structure but use a new syscall instead of write().

(c) Keep using write() but literally just buffer the data. Then have a new syscall to commit it.  In other words, replace “x” with a syscall and call all the fs_context_operations helpers in that context instead of from write().

But yeah, b-or-c sounds fine.

               Linus