Bug 2127397

Looks like the "nfs4" and "default" settings are messing up.

[root@ibm-z-509 ~]# cat /etc/nfs.conf
[nfsrahead]
 nfs=15000
 default=256                    <<<<<<<<<<<<<< IMO the v4 mount use this default value
[root@ibm-z-509 ~]# systemctl restart nfs-server
[root@ibm-z-509 ~]# mount localhost:/export_test/ /mnt_test/ -o vers=4
[root@ibm-z-509 ~]# cat /proc/self/mountinfo | grep test
336 95 0:46 / /mnt_test rw,relatime shared:178 - nfs4 localhost:/export_test rw,vers=4.2,rsize=1048576,wsize=1048576,namlen=2$5,hard,proto=tcp6,timeo=600,retrans=2,sec=sys,clientaddr=::1,local_lock=none,addr=::1
[root@ibm-z-509 ~]# cat /sys/class/bdi/0\:46/read_ahead_kb
128                             <<<<<<<<<<<<<<
[root@ibm-z-509 ~]# umount /mnt_test/
[root@ibm-z-509 ~]#



[root@ibm-z-509 ~]# vi /etc/nfs.conf
[root@ibm-z-509 ~]# cat /etc/nfs.conf
[nfsrahead]
 nfs=256
 nfs4=16000                    <<<<<<<<<<<<<<
[root@ibm-z-509 ~]# systemctl restart nfs-server
[root@ibm-z-509 ~]# mount localhost:/export_test/ /mnt_test/ -o vers=4
[root@ibm-z-509 ~]# cat /proc/self/mountinfo | grep test
336 95 0:46 / /mnt_test rw,relatime shared:178 - nfs4 localhost:/export_test rw,vers=4.2,rsize=1048576,wsize=1048576,namlen=2$5,hard,proto=tcp6,timeo=600,retrans=2,sec=sys,clientaddr=::1,local_lock=none,addr=::1
[root@ibm-z-509 ~]# cat /sys/class/bdi/0\:46/read_ahead_kb
128                             <<<<<<<<<<<<<<
[root@ibm-z-509 ~]# umount /mnt_test/
[root@ibm-z-509 ~]# mount localhost:/export_test/ /mnt_test/ -o vers=3
[root@ibm-z-509 ~]# cat /proc/self/mountinfo | grep test
334 95 0:45 / /mnt_test rw,relatime shared:178 - nfs localhost:/export_test/ rw,vers=3,rsize=1048576,wsize=1048576,namlen=255,
hard,proto=tcp6,timeo=600,retrans=2,sec=sys,mountaddr=::1,mountvers=3,mountport=20048,mountproto=udp6,local_lock=none,addr=::1
[root@ibm-z-509 ~]# cat /sys/class/bdi/0\:45/read_ahead_kb
256
[root@ibm-z-509 ~]# umount /mnt_test/


[root@ibm-z-509 ~]# vi /etc/nfs.conf
[root@ibm-z-509 ~]# cat /etc/nfs.conf
[nfsrahead]
 default=256                    <<<<<<<<<<<<<< IMO both v3 and v4 mount use this default value
[root@ibm-z-509 ~]# systemctl restart nfs-server
[root@ibm-z-509 ~]# mount localhost:/export_test/ /mnt_test/ -o vers=3
[root@ibm-z-509 ~]# cat /proc/self/mountinfo | grep test
334 95 0:45 / /mnt_test rw,relatime shared:178 - nfs localhost:/export_test/ rw,vers=3,rsize=1048576,wsize=1048576,namlen=255,hard,proto=tcp6,timeo=600,retrans=2,sec=sys,mountaddr=::1,mountvers=3,mountport=20048,mountproto=udp6,local_lock=none,addr=::1
[root@ibm-z-509 ~]# cat /sys/class/bdi/0\:45/read_ahead_kb
256
[root@ibm-z-509 ~]# umount /mnt_test/
[root@ibm-z-509 ~]# mount localhost:/export_test/ /mnt_test/ -o vers=4
[root@ibm-z-509 ~]# cat /proc/self/mountinfo | grep test
336 95 0:46 / /mnt_test rw,relatime shared:178 - nfs4 localhost:/export_test rw,vers=4.2,rsize=1048576,wsize=1048576,namlen=255,hard,proto=tcp6,timeo=600,retrans=2,sec=sys,clientaddr=::1,local_lock=none,addr=::1
[root@ibm-z-509 ~]# cat /sys/class/bdi/0\:46/read_ahead_kb
128                             <<<<<<<<<<<<<<
[root@ibm-z-509 ~]# umount /mnt_test/
[root@ibm-z-509 ~]#

Looks like there're more than one issue for now:

1. Within KVM hypervisor it fails to config the nfsrahead value randomly, e.g.
 - fail in KVM https://beaker.engineering.redhat.com/jobs/7137086
 - pass in non-KVM https://beaker.engineering.redhat.com/jobs/7137194


2. In arch s390x, the v4 config doesn't work and seemingly it always use the default value "128":
 - https://beaker.engineering.redhat.com/recipes/12794496
 ...
[09:52:08 root@ ~~]# mount -t nfs localhost:/exportdir /mnt/nfsmp -o vers=4.2
[09:52:08 root@ ~~]# cat /proc/self/mountinfo | grep /mnt/nfsmp
334 95 0:47 / /mnt/nfsmp rw,relatime shared:176 - nfs4 localhost:/exportdir rw,vers=4.2,rsize=1048576,wsize=1048576,namlen=255,hard,proto=tcp6,timeo=600,retrans=2,sec=sys,clientaddr=::1,local_lock=none,addr=::1
[09:52:08 root@ ~~]# /usr/libexec/nfsrahead -F -d 0:47
nfsrahead: setting /mnt/nfsmp readahead to 16000

16000
[09:52:08 root@ ~~]# cat /sys/class/bdi/0:47/read_ahead_kb
128


3. In arch ppc64le, sometimes the effect value is a bit lower than what we set:
 - https://beaker.engineering.redhat.com/recipes/12794501
 ...
[11:47:36 root@ ~~]# mount -t nfs localhost:/exportdir /mnt/nfsmp -o vers=3
[11:47:36 root@ ~~]# cat /proc/self/mountinfo | grep /mnt/nfsmp
413 96 0:46 / /mnt/nfsmp rw,relatime shared:217 - nfs localhost:/exportdir rw,vers=3,rsize=1048576,wsize=1048576,namlen=255,hard,proto=tcp6,timeo=600,retrans=2,sec=sys,mountaddr=::1,mountvers=3,mountport=20048,mountproto=udp6,local_lock=none,addr=::1
[11:47:36 root@ ~~]# /usr/libexec/nfsrahead -F -d 0:46
nfsrahead: setting /mnt/nfsmp readahead to 15000

15000
[11:47:37 root@ ~~]# cat /sys/class/bdi/0:46/read_ahead_kb
14976

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