On Fri, Jan 11, 2013 at 06:56:58PM +0400, Stanislav Kinsbursky wrote: > 11.12.2012 19:35, J. Bruce Fields пишет: > >On Tue, Dec 11, 2012 at 10:20:36AM -0500, J. Bruce Fields wrote: > >>On Tue, Dec 11, 2012 at 07:07:00PM +0400, Stanislav Kinsbursky wrote: > >>>I don't really understand, how mountd's root can be wrong. I.e. > >>>its' always right as I see it. NFSd kthreads have to swap/use > >>>relative path/whatever to communicate with proper mountd. > >>>Or I'm missing something? > >> > >>Ugh, I see the problem: I thought svc_export_request was called at the > >>time mountd does the read, but instead its done at the time nfsd does > >>the upcall. > >> > >>I suspect that's wrong, and we really want this done in the context of > >>the mountd process when it does the read call. If d_path is called > >>there then we have no problem. > > > >Right, so I'd be happier if we could modify sunrpc_cache_pipe_upcall to > >skip calling cache_request and instead delay that until cache_read(). I > >think that should be possible. > > > > So, Bruce, what we going to do (or what you want me to do) with the rest of NFSd changes? > I.e. how I should solve this d_path() problem? > I.e. I don't understand what did you mean by "I'd be happier if we could modify sunrpc_cache_pipe_upcall to > skip calling cache_request and instead delay that until cache_read()". > Could you give me a hint? Definitely. So normally the way these upcalls happen are: 1. the kernel does a cache lookup, finds no matching item, and calls sunrpc_cache_pipe_upcall(). 2. sunrpc_cache_pipe_upcall() formats the upcall: it allocates a struct cache_request crq and fills crq->buf with the upcall data by calling the cache's ->cache_request() method. 3. Then rpc.mountd realizes there's data available in /proc/net/rpc/nfsd.fh/content, so it does a read on that file. 4. cache_read copies the formatted upcall from crq->buf to to userspace. So all I'm suggesting is that instead of calling ->cache_request() at step 2, we do it at step 4. Then cache_request will be called from rpc.mountd's read. So we'll know which container rpc.mountd is in. Does that make sense? --b. -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
