linux-kernel - overlayfs: EOPNOTSUPP when writing in overlayfs with nfs4 as lower dir

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Date:   Tue, 20 Sep 2016 15:45:10 +0200
From:   Frederik Himpe <fhimpe@....ac.be>
To:     linux-kernel@...r.kernel.org, linux-unionfs@...r.kernel.org,
        initramfs@...r.kernel.org
Subject: overlayfs: EOPNOTSUPP when writing in overlayfs with nfs4 as lower
 dir

I'm using FAI to automate Debian installs. Dracut 044+109+g3889234 is
used with the rootovl option, which mounts the nfsroot with NFS4 on
/sysroot on the client and then uses overlayfs to make this directory
writeable on the client.

When trying to write in a subdirectory of the /sysroot directory on the
client, I get the error EOPNOTSUPP. Writing in the /sysroot directory
itself works though.


dracut output showing the commands used to mount the overlayfs:

///lib/dracut/hooks/pre-pivot/10-overlay-mount.sh@13(source): modprobe overlay
///lib/dracut/hooks/pre-pivot/10-overlay-mount.sh@16(source): mount -o remount,nolock,noatime /sysroot
///lib/dracut/hooks/pre-pivot/10-overlay-mount.sh@21(source): mkdir -p /live/image
///lib/dracut/hooks/pre-pivot/10-overlay-mount.sh@22(source): mount --bind /sysroot /live/image
///lib/dracut/hooks/pre-pivot/10-overlay-mount.sh@23(source): umount /sysroot
///lib/dracut/hooks/pre-pivot/10-overlay-mount.sh@26(source): mkdir /cow
///lib/dracut/hooks/pre-pivot/10-overlay-mount.sh@27(source): mount -n -t tmpfs -o mode=0755 tmpfs /cow
///lib/dracut/hooks/pre-pivot/10-overlay-mount.sh@28(source): mkdir /cow/work /cow/rw
///lib/dracut/hooks/pre-pivot/10-overlay-mount.sh@31(source): mount -t overlay -o noatime,lowerdir=/live/image,upperdir=/cow/rw,workdir=/cow/work,default_permissions overlay /sysroot
///lib/dracut/hooks/pre-pivot/10-overlay-mount.sh@34(source): mkdir -p /sysroot/live/cow
///lib/dracut/hooks/pre-pivot/10-overlay-mount.sh@35(source): mkdir -p /sysroot/live/image
///lib/dracut/hooks/pre-pivot/10-overlay-mount.sh@36(source): mount --bind /cow/rw /sysroot/live/cow
///lib/dracut/hooks/pre-pivot/10-overlay-mount.sh@37(source): umount /cow
///lib/dracut/hooks/pre-pivot/10-overlay-mount.sh@38(source): mount --bind /live/image /sysroot/live/image
///lib/dracut/hooks/pre-pivot/10-overlay-mount.sh@39(source): umount /live/image


After that, this is what the mount command outputs:

rootfs on / type rootfs (rw)
proc on /proc type proc (rw,nosuid,nodev,noexec,relatime)
sysfs on /sys type sysfs (rw,nosuid,nodev,noexec,relatime)
devtmpfs on /dev type devtmpfs (rw,nosuid,noexec,size=16414576k,nr_inodes=4103644,mode=755)
devpts on /dev/pts type devpts (rw,nosuid,noexec,relatime,gid=5,mode=620,ptmxmode=000)
tmpfs on /run type tmpfs (rw,nosuid,nodev,noexec,mode=755)
rpc_pipefs on /var/lib/nfs/rpc_pipefs type rpc_pipefs (rw,relatime)
overlay on /sysroot type overlay (rw,noatime,lowerdir=/live/image,upperdir=/cow/rw,workdir=/cow/work,default_permissions)
tmpfs on /sysroot/live/cow type tmpfs (rw,relatime,mode=755)
master.testcluster.ai:/fai on /sysroot/live/image type nfs4 (ro,relatime,vers=4.0,rsize=524288,wsize=524288,namlen=255,hard,proto=tcp,port=0,timeo=600,retrans=2,sec=sys,clientaddr=192.168.0.1,local_lock=none,addr=192.168.0.254)


Then strace of a touch of an unexisting file in /sysroot/etc fails:

open("blah", O_WRONLY|O_CREAT|O_NOCTTY|O_NONBLOCK, 0666) = -1 EOPNOTSUPP (Operation not supported)

I have attached the file rdsosreport.txt with the complete dracut output.

What could be wrong here?

-- 
Frederik Himpe <fhimpe@....ac.be>
Vrije Universiteit Brussel
View attachment "rdsosreport.txt" of type "text/plain" (288108 bytes)