| Message ID | 20130111172015.GG17909@fieldses.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
Thanks! 11.01.2013 21:20, J. Bruce Fields ?????: > On Fri, Jan 11, 2013 at 12:03:12PM -0500, J. Bruce Fields wrote: >> On Fri, Jan 11, 2013 at 06:56:58PM +0400, Stanislav Kinsbursky wrote: >>> 11.12.2012 19:35, J. Bruce Fields ?????: >>>> 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? > > The following is untested, ugly, and almost certainly insufficient and > wrong, but maybe it's a starting point: > > --b. > > diff --git a/net/sunrpc/cache.c b/net/sunrpc/cache.c > index 9f84703..f15e4c1 100644 > --- a/net/sunrpc/cache.c > +++ b/net/sunrpc/cache.c > @@ -744,6 +744,7 @@ struct cache_request { > char * buf; > int len; > int readers; > + void (*cache_request)(struct cache_detail *, struct cache_head *, char **, int *); > }; > struct cache_reader { > struct cache_queue q; > @@ -785,10 +786,19 @@ static ssize_t cache_read(struct file *filp, char __user *buf, size_t count, > spin_unlock(&queue_lock); > > if (rp->offset == 0 && !test_bit(CACHE_PENDING, &rq->item->flags)) { > + char *bp; > + int len = PAGE_SIZE; > + > err = -EAGAIN; > spin_lock(&queue_lock); > list_move(&rp->q.list, &rq->q.list); > spin_unlock(&queue_lock); > + > + bp = rq->buf; > + rq->cache_request(cd, rq->item, &bp, &len); > + if (rq->len < 0) > + goto out; > + rq->len = PAGE_SIZE - len; > } else { > if (rp->offset + count > rq->len) > count = rq->len - rp->offset; > @@ -1149,8 +1159,6 @@ int sunrpc_cache_pipe_upcall(struct cache_detail *detail, struct cache_head *h, > > char *buf; > struct cache_request *crq; > - char *bp; > - int len; > > if (!cache_listeners_exist(detail)) { > warn_no_listener(detail); > @@ -1167,19 +1175,10 @@ int sunrpc_cache_pipe_upcall(struct cache_detail *detail, struct cache_head *h, > return -EAGAIN; > } > > - bp = buf; len = PAGE_SIZE; > - > - cache_request(detail, h, &bp, &len); > - > - if (len < 0) { > - kfree(buf); > - kfree(crq); > - return -EAGAIN; > - } > + crq->cache_request = cache_request; > crq->q.reader = 0; > crq->item = cache_get(h); > crq->buf = buf; > - crq->len = PAGE_SIZE - len; > crq->readers = 0; > spin_lock(&queue_lock); > list_add_tail(&crq->q.list, &detail->queue); >
diff --git a/net/sunrpc/cache.c b/net/sunrpc/cache.c index 9f84703..f15e4c1 100644 --- a/net/sunrpc/cache.c +++ b/net/sunrpc/cache.c @@ -744,6 +744,7 @@ struct cache_request { char * buf; int len; int readers; + void (*cache_request)(struct cache_detail *, struct cache_head *, char **, int *); }; struct cache_reader { struct cache_queue q; @@ -785,10 +786,19 @@ static ssize_t cache_read(struct file *filp, char __user *buf, size_t count, spin_unlock(&queue_lock); if (rp->offset == 0 && !test_bit(CACHE_PENDING, &rq->item->flags)) { + char *bp; + int len = PAGE_SIZE; + err = -EAGAIN; spin_lock(&queue_lock); list_move(&rp->q.list, &rq->q.list); spin_unlock(&queue_lock); + + bp = rq->buf; + rq->cache_request(cd, rq->item, &bp, &len); + if (rq->len < 0) + goto out; + rq->len = PAGE_SIZE - len; } else { if (rp->offset + count > rq->len) count = rq->len - rp->offset; @@ -1149,8 +1159,6 @@ int sunrpc_cache_pipe_upcall(struct cache_detail *detail, struct cache_head *h, char *buf; struct cache_request *crq; - char *bp; - int len; if (!cache_listeners_exist(detail)) { warn_no_listener(detail); @@ -1167,19 +1175,10 @@ int sunrpc_cache_pipe_upcall(struct cache_detail *detail, struct cache_head *h, return -EAGAIN; } - bp = buf; len = PAGE_SIZE; - - cache_request(detail, h, &bp, &len); - - if (len < 0) { - kfree(buf); - kfree(crq); - return -EAGAIN; - } + crq->cache_request = cache_request; crq->q.reader = 0; crq->item = cache_get(h); crq->buf = buf; - crq->len = PAGE_SIZE - len; crq->readers = 0; spin_lock(&queue_lock); list_add_tail(&crq->q.list, &detail->queue);