[lustre-devel] [PATCH 25/34] lnet: swap 'then' and 'else' branches in lnet_startup_lndnet

[Doug Oucharek]

Hmm...if we made lnd_refcount atomic, could we get rid of unnecessary calls to lnet_net_lock(LNET_LOCK_EX) ?

Reviewed-by: Doug Oucharek <dougso at me.com>

Doug

On 9/6/18, 5:54 PM, "NeilBrown" <neilb at suse.com> wrote:

    This swap makes the diff for the next patch more readable.
    We also stop storing the return value from lnet_net_unique()
    as it is never used.
    
    This is part of
        8cbb8cd3e771e7f7e0f99cafc19fad32770dc015
           LU-7734 lnet: Multi-Rail local NI split
    
    Signed-off-by: NeilBrown <neilb at suse.com>
    ---
     drivers/staging/lustre/lnet/lnet/api-ni.c |   55 +++++++++++++++--------------
     1 file changed, 28 insertions(+), 27 deletions(-)
    
    diff --git a/drivers/staging/lustre/lnet/lnet/api-ni.c b/drivers/staging/lustre/lnet/lnet/api-ni.c
    index 2b5c25a1dc7c..ab4d093c04da 100644
    --- a/drivers/staging/lustre/lnet/lnet/api-ni.c
    +++ b/drivers/staging/lustre/lnet/lnet/api-ni.c
    @@ -1372,8 +1372,34 @@ lnet_startup_lndnet(struct lnet_net *net, struct lnet_lnd_tunables *tun)
     	LASSERT(libcfs_isknown_lnd(lnd_type));
     
     	/* Make sure this new NI is unique. */
    -	rc = lnet_net_unique(net->net_id, &the_lnet.ln_nets);
    -	if (!rc) {
    +	if (lnet_net_unique(net->net_id, &the_lnet.ln_nets)) {
    +		mutex_lock(&the_lnet.ln_lnd_mutex);
    +		lnd = lnet_find_lnd_by_type(lnd_type);
    +
    +		if (lnd == NULL) {
    +			mutex_unlock(&the_lnet.ln_lnd_mutex);
    +			rc = request_module("%s", libcfs_lnd2modname(lnd_type));
    +			mutex_lock(&the_lnet.ln_lnd_mutex);
    +
    +			lnd = lnet_find_lnd_by_type(lnd_type);
    +			if (lnd == NULL) {
    +				mutex_unlock(&the_lnet.ln_lnd_mutex);
    +				CERROR("Can't load LND %s, module %s, rc=%d\n",
    +				libcfs_lnd2str(lnd_type),
    +				libcfs_lnd2modname(lnd_type), rc);
    +				rc = -EINVAL;
    +				goto failed0;
    +			}
    +		}
    +
    +		lnet_net_lock(LNET_LOCK_EX);
    +		lnd->lnd_refcount++;
    +		lnet_net_unlock(LNET_LOCK_EX);
    +
    +		net->net_lnd = lnd;
    +
    +		mutex_unlock(&the_lnet.ln_lnd_mutex);
    +	} else {
     		if (lnd_type == LOLND) {
     			lnet_net_free(net);
     			return 0;
    @@ -1385,31 +1411,6 @@ lnet_startup_lndnet(struct lnet_net *net, struct lnet_lnd_tunables *tun)
     		goto failed0;
     	}
     
    -	mutex_lock(&the_lnet.ln_lnd_mutex);
    -	lnd = lnet_find_lnd_by_type(lnd_type);
    -
    -	if (!lnd) {
    -		mutex_unlock(&the_lnet.ln_lnd_mutex);
    -		rc = request_module("%s", libcfs_lnd2modname(lnd_type));
    -		mutex_lock(&the_lnet.ln_lnd_mutex);
    -
    -		lnd = lnet_find_lnd_by_type(lnd_type);
    -		if (!lnd) {
    -			mutex_unlock(&the_lnet.ln_lnd_mutex);
    -			CERROR("Can't load LND %s, module %s, rc=%d\n",
    -			       libcfs_lnd2str(lnd_type),
    -			       libcfs_lnd2modname(lnd_type), rc);
    -			rc = -EINVAL;
    -			goto failed0;
    -		}
    -	}
    -
    -	lnet_net_lock(LNET_LOCK_EX);
    -	lnd->lnd_refcount++;
    -	lnet_net_unlock(LNET_LOCK_EX);
    -	net->net_lnd = lnd;
    -	mutex_unlock(&the_lnet.ln_lnd_mutex);
    -
     	while (!list_empty(&net->net_ni_added)) {
     		ni = list_entry(net->net_ni_added.next, struct lnet_ni,
     				ni_netlist);