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.el6with RHBA-2013-1690. - Previously tracked via Bugzilla #886623
Workaround
- Set the
MOUNT_WAITparameter in/etc/sysconfig/autofsto a value of 40:
MOUNT_WAIT=40
Root Cause
-
In Red Hat Enterprise Linux 6.2
autofsdoes not do any probing of single mount entries, however in 6.3autofsnow probes latency even in single host entry cases. This probing of latency causes problems with RDMA asautofsdoes not probe RDMA but only TCP/UDP, this causes the probe to fail thus causingautofsto fail to mount the host entry. -
Setting the
MOUNT_WAITparameter to 40 effectively disables the probing functionality described above, as the recent changes toautofscheck to see ifdefault_get_mount_waitis equal to -1. Since the modification ofMOUNT_WAITmakes this value non-equal to -1 the probing stops.
Diagnostic Steps
- Enable
autofsdebugging by editing the/etc/sysconfig/autofsfile and modifying theOPTIONS=directive with the following:
OPTIONS="--debug"
- Reproduce the problem and investigate
/var/log/messagesfor the following messages, note theget_nfs_infocalls 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
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