Commit 433d80d6 authored by Steve Wise's avatar Steve Wise Committed by Greg Kroah-Hartman

RDMA/iwcm: Use a default listen backlog if needed

commit 2f0304d21867476394cd51a54e97f7273d112261 upstream.

If the user creates a listening cm_id with backlog of 0 the IWCM ends
up not allowing any connection requests at all.  The correct behavior
is for the IWCM to pick a default value if the user backlog parameter
is zero.

Lustre from version 1.8.8 onward uses a backlog of 0, which breaks
iwarp support without this fix.
Signed-off-by: default avatarSteve Wise <>
Signed-off-by: default avatarRoland Dreier <>
Signed-off-by: default avatarGreg Kroah-Hartman <>
parent 26584e18
......@@ -46,6 +46,7 @@
#include <linux/completion.h>
#include <linux/slab.h>
#include <linux/module.h>
#include <linux/sysctl.h>
#include <rdma/iw_cm.h>
#include <rdma/ib_addr.h>
......@@ -65,6 +66,20 @@ struct iwcm_work {
struct list_head free_list;
static unsigned int default_backlog = 256;
static struct ctl_table_header *iwcm_ctl_table_hdr;
static struct ctl_table iwcm_ctl_table[] = {
.procname = "default_backlog",
.data = &default_backlog,
.maxlen = sizeof(default_backlog),
.mode = 0644,
.proc_handler = proc_dointvec,
{ }
* The following services provide a mechanism for pre-allocating iwcm_work
* elements. The design pre-allocates them based on the cm_id type:
......@@ -419,6 +434,9 @@ int iw_cm_listen(struct iw_cm_id *cm_id, int backlog)
cm_id_priv = container_of(cm_id, struct iwcm_id_private, id);
if (!backlog)
backlog = default_backlog;
ret = alloc_work_entries(cm_id_priv, backlog);
if (ret)
return ret;
......@@ -1024,11 +1042,20 @@ static int __init iw_cm_init(void)
if (!iwcm_wq)
return -ENOMEM;
iwcm_ctl_table_hdr = register_net_sysctl(&init_net, "net/iw_cm",
if (!iwcm_ctl_table_hdr) {
pr_err("iw_cm: couldn't register sysctl paths\n");
return -ENOMEM;
return 0;
static void __exit iw_cm_cleanup(void)
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