vfs_fileid — Generates file_id structs with unique device id values for cluster setups
vfs objects = fileid
This VFS module is part of the samba(7) suite.
Samba uses file_id structs to uniquely identify files
for locking purpose. By default the file_id contains the device
and inode number returned by the stat()
system call.
As the file_id is a unique identifier of a file, it must be the same
on all nodes in a cluster setup. This module overloads the
SMB_VFS_FILE_ID_CREATE()
operation and
generates the device number based on the configured algorithm
(see the "fileid:algorithm" option).
When using the fsname or fsid algorithm a
stat()
and statfs()
call is
required for all mounted file systems to generate the file_id. If e.g.
an NFS file system is unresponsive such a call might block and the smbd
process will become unresponsive. Use the "fileid:fstype deny",
"fileid:fstype allow", "fileid:mntdir deny", or "fileid:mntdir allow"
options to ignore potentially unresponsive file systems.
Available algorithms are fsname
,
fsname_nodirs
, fsid
and
hostname
. The default value is
fsname
.
The fsname
algorithm generates
device id by hashing the kernel device name.
The fsname_nodirs
algorithm generates
device id by hashing the kernel device name for files and by hashing
the hostname for directories. This can be used to deliberately
break lock coherency for directories in a cluster.
The fsid
algorithm generates
the device id from the f_fsid
returned
from the statfs()
syscall.
The hostname
algorithm generates device
id by hashing the hostname. This can be used to deliberately
break lock coherency in a cluster.
The fsname_norootdir
algorithm
generates device ids by hashing the kernel device name, except
for the root directory of shares where it will use the hostname
algorithm. This can be used to deliberately break lock coherency
in a cluster for the root directory of a share.
The fsname_norootdir_ext
algorithm
generates device ids by hashing the kernel device name, except
for the root directory of shares where it will use the hostname
algorithm. Additionally it generates an extid based on the
process pid. This can be used to deliberately break lock
coherency between all smbd processes in the whole cluster for
the root directory of a share.
This option is the legacy version of the
fileid:algorithm
option, which was used in earlier
versions of fileid mapping feature in custom Samba 3.0 versions.
List of file system types to be ignored for file_id generation.
List of file system types to be allowed for file_id generation. If this option is set, file system types not listed here are ignored.
List of file system mount points to be ignored for file_id generation.
List of file system mount points to be allowed for file_id generation. If this option is set, file system mount points not listed here are ignored.
This option triggers use of the fileid hostname algorithm for the configured inode which can be used to deliberately break lock coherency for the corresponding file or directory in a cluster.
Usage of the fileid
module with the
fsid
algorithm:
[global]
vfs objects = fileid
fileid:algorithm = fsid