[LU-16443] "mount -t lustre ..." Does not work. (Backend fs=ZFS)

Wed, 4 Jan 2023 04:50:35 +0000

This is a single node(client+server) vm and backend FS is zfs. 'mkfs' works. However, mounting fails when called via 'mount -t lustre...". It works perfectly when called through "mount.lustre". I am not sure if this is general case. But this seem to be affecting me.

What works
mkfs (works ...) + followed by mount.lustre

$ mkfs -t lustre --reformat --index 0 --backfstype=zfs --fsname=lustre --mgsnode=192.168.50.117@tcp --mgs --mdt gpool/metadata /dev/loop0

$ mount.lustre -o localrecov gpool/metadata /mnt/zfsmdt
 
$ mount | grep mds1
gpool/metadata on /mnt/zfsmdt type lustre (rw,seclabel,svname=lustre-MDT0000,mgs,osd=osd-zfs)

However, with the same mkfs as above if mount is done via 'mount -t lustre' instead of 'mount.lustre' it fails.

What does not work; With same mkfs. (below does not work)

$ mount -t lustre -o localrecov gpool/metadata /mnt/zfsmdt
mount.lustre: gpool/metadata has not been formatted with mkfs.lustre or the backend filesystem type is not supported by this tool

Where exactly it is failing

It is failing under lustre/utils/mount_utils.c:load_backfs_module()

handle = dlopen(filename, RTLD_LAZY); /* where filename is /usr/lib/lustre/mount_osd_zfs.so */
libzfs.so.4: cannot open shared object file: No such file or directory (dlerror() output)

It cannot load the library. Therefore the callbacks for backfs_ops is all NULL. Making it fail.

For the mount.lustre case. The dlopen() call is a success. The callback for backend (zfs_init(), is_lustre(), etc) is properly registered.

filename = /usr/lib/lustre/mount_osd_zfs.so
libzfs.so.4: cannot open shared object file: No such file or directory

Other information:

$ uname -r
3.10.0-1160.15.2.el7.x86_64
$ cat /etc/redhat-release 
CentOS Linux release 7.9.2009 (Core)

ZFS libs are installed in non-standard path.

# pkg-config --cflags libzfs
-I/root/zfs/zfs_git_lustre_build/zfsbins/include/libzfs -I/root/zfs/zfs_git_lustre_build/zfsbins/include/libspl -I/usr/include/blkid -I/usr/include/uuid  
# pkg-config --libs libzfs
-L/root/zfs/zfs_git_lustre_build/zfsbins/lib -lzfs -lzfs_core -lnvpair

Whamcloud Community JIRA

[LU-16443] "mount -t lustre ..." Does not work. (Backend fs=ZFS)