Commit 18e4cf91 authored by NeilBrown's avatar NeilBrown Committed by Chuck Lever
Browse files

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



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: default avatarNeilBrown <neilb@suse.de>
Signed-off-by: default avatarChuck Lever <chuck.lever@oracle.com>
parent 39039024

fs/nfsd/nfssvc.c

+0 −23
Original line number Diff line number Diff line
@@ -992,31 +992,8 @@ 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;

}

include/linux/sunrpc/svc.h

+0 −13
Original line number Diff line number Diff line
@@ -120,19 +120,6 @@ 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