nfsd: Simplify code around svc_exit_thread() call in nfsd()

[ Upstream commit 18e4cf915543257eae2925671934937163f5639b ]

Previously a thread could exit asynchronously (due to a signal) so some
care was needed to hold nfsd_mutex over the last svc_put() call.  Now a
thread can only exit when svc_set_num_threads() is called, and this is
always called under nfsd_mutex.  So no care is needed.

Not only is the mutex held when a thread exits now, but the svc refcount
is elevated, so the svc_put() in svc_exit_thread() will never be a final
put, so the mutex isn't even needed at this point in the code.

Signed-off-by: NeilBrown <neilb@suse.de>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

diff --git a/fs/nfsd/nfssvc.c b/fs/nfsd/nfssvc.c
index a0ecec54d3d7d5d406ff8ae5d7dc66208ae8c02c..606347b104afde3df30fdb13ac08fc06981b7e72 100644 (file)
--- a/fs/nfsd/nfssvc.c
+++ b/fs/nfsd/nfssvc.c
@@ -991,31 +991,8 @@ nfsd(void *vrqstp)
        atomic_dec(&nfsdstats.th_cnt);
 
 out:
-       /* Take an extra ref so that the svc_put in svc_exit_thread()
-        * doesn't call svc_destroy()
-        */
-       svc_get(nn->nfsd_serv);
-
        /* Release the thread */
        svc_exit_thread(rqstp);
-
-       /* We need to drop a ref, but may not drop the last reference
-        * without holding nfsd_mutex, and we cannot wait for nfsd_mutex as that
-        * could deadlock with nfsd_shutdown_threads() waiting for us.
-        * So three options are:
-        * - drop a non-final reference,
-        * - get the mutex without waiting
-        * - sleep briefly andd try the above again
-        */
-       while (!svc_put_not_last(nn->nfsd_serv)) {
-               if (mutex_trylock(&nfsd_mutex)) {
-                       nfsd_put(net);
-                       mutex_unlock(&nfsd_mutex);
-                       break;
-               }
-               msleep(20);
-       }
-
        return 0;
 }
 

diff --git a/include/linux/sunrpc/svc.h b/include/linux/sunrpc/svc.h
index 53405c282209f0987aeae33a7c6c31cc63b2dc0d..6e48c1c88f1bb2a1ca9be061f62e9129e8558016 100644 (file)
--- a/include/linux/sunrpc/svc.h
+++ b/include/linux/sunrpc/svc.h
@@ -123,19 +123,6 @@ static inline void svc_put(struct svc_serv *serv)
        kref_put(&serv->sv_refcnt, svc_destroy);
 }
 
-/**
- * svc_put_not_last - decrement non-final reference count on SUNRPC serv
- * @serv:  the svc_serv to have count decremented
- *
- * Returns: %true is refcount was decremented.
- *
- * If the refcount is 1, it is not decremented and instead failure is reported.
- */
-static inline bool svc_put_not_last(struct svc_serv *serv)
-{
-       return refcount_dec_not_one(&serv->sv_refcnt.refcount);
-}
-
 /*
  * Maximum payload size supported by a kernel RPC server.
  * This is use to determine the max number of pages nfsd is