Automounting NFS over RDMA fails
Environment
- Red Hat Enterprise Linux 6.3
- kernel 2.6.32-279.14.1.el6
- autofs-5.0.5-55.el6_3
Issue
- Automounting NFS over RDMA fails.
- Directly mounting an NFS share via RDMA functions as desired.
Resolution
- This issue was resolved in
autofs-5.0.5-77.el6
with RHBA-2013-1690. - Previously tracked via Bugzilla #886623
Workaround
- Set the
MOUNT_WAIT
parameter in/etc/sysconfig/autofs
to a value of 40:
MOUNT_WAIT=40
Root Cause
-
In Red Hat Enterprise Linux 6.2
autofs
does not do any probing of single mount entries, however in 6.3autofs
now probes latency even in single host entry cases. This probing of latency causes problems with RDMA asautofs
does not probe RDMA but only TCP/UDP, this causes the probe to fail thus causingautofs
to fail to mount the host entry. -
Setting the
MOUNT_WAIT
parameter to 40 effectively disables the probing functionality described above, as the recent changes toautofs
check to see ifdefault_get_mount_wait
is equal to -1. Since the modification ofMOUNT_WAIT
makes this value non-equal to -1 the probing stops.
Diagnostic Steps
- Enable
autofs
debugging by editing the/etc/sysconfig/autofs
file and modifying theOPTIONS=
directive with the following:
OPTIONS="--debug"
- Reproduce the problem and investigate
/var/log/messages
for the following messages, note theget_nfs_info
calls on both the TCP/UDP protocols but not RDMA:
sun_mount: parse(sun): mounting root /home, mountpoint hostname, what server.example.com:/share, fstype nfs, options nfsvers=4,rdma,port=2050,rw,nosuid,softq
mount_mount: mount(nfs): root=/home name=hostname what=server.example.com:/share, fstype=nfs, options=nfsvers=4,rdma,port=2050,rw,nosuid,softq
mount_mount: mount(nfs): nfs options="nfsvers=4,rdma,port=2050,rw,nosuid,softq", nosymlink=0, ro=0
get_nfs_info: called with host hostname(192.168.8.13) proto tcp version 0x70
get_nfs_info: called with host hostname(192.168.8.13) proto udp version 0x70
mount(nfs): no hosts available
This solution is part of Red Hat’s fast-track publication program, providing a huge library of solutions that Red Hat engineers have created while supporting our customers. To give you the knowledge you need the instant it becomes available, these articles may be presented in a raw and unedited form.
Comments