1VFS_FILEID(8) System Administration tools VFS_FILEID(8)
2
6 vfs_fileid - Generates file_id structs with unique device id values for
7 cluster setups. It also adds ways to deliberately break lock coherency
8 for specific inodes
9
11 vfs objects = fileid
12
14 This VFS module is part of the samba(7) suite.
15 Samba uses file_id structs to uniquely identify files for locking
17 purpose. By default the file_id contains the device and inode number
18 returned by the stat() system call. As the file_id is a unique
19 identifier of a file, it must be the same on all nodes in a cluster
20 setup. This module overloads the SMB_VFS_FILE_ID_CREATE() operation and
21 generates the device number based on the configured algorithm (see the
22 "fileid:algorithm" option).
23 When using the fsname or fsid algorithm a stat() and statfs() call is
25 required for all mounted file systems to generate the file_id. If e.g.
26 an NFS file system is unresponsive such a call might block and the smbd
27 process will become unresponsive. Use the "fileid:fstype deny",
28 "fileid:fstype allow", "fileid:mntdir deny", or "fileid:mntdir allow"
29 options to ignore potentially unresponsive file systems.
30
32 fileid:algorithm = ALGORITHM
33 Available algorithms are fsname, fsid, next_module. The default
34 value is fsname. As well as the following legacy algorithms:
35 fsname_nodirs, fsname_norootdir, fsname_norootdir_ext and hostname.
36 The fsname algorithm generates device id by hashing the kernel
38 device name.
39 The fsid algorithm generates the device id from the f_fsid returned
41 from the statfs() syscall.
42 The next_module algorithm lets the next vfs module in the module
44 chain generate the id. This is mainly used in combination with the
45 various 'nolock' features the fileid module provides.
46 The legacy hostname algorithm generates unique devid by hashing the
48 hostname and low level device id. It also implies
49 fileid:nolock_all_inodes=yes. This can be used to deliberately
50 break lock coherency in a cluster and with fileid:nolock_max_slots
51 also between local processes within a node. NOTE: Do not use this
52 without knowing what you are doing! It breaks SMB semantics and it
53 can lead to data corruption! This implies
54 fileid:nolock_all_inodes=yes.
55 The legacy fsname_nodirs algorithm is an alias for using the fsname
57 algorithm together with fileid:nolock_all_dirs=yes. NOTE: Do not
58 use this without knowing what you are doing! It breaks SMB
59 semantics! See fileid:nolock_paths for a more fine grained
60 approach.
61 The legacy fsname_norootdir algorithm is an alias for using the
63 fsname algorithm together with fileid:nolock_paths= “.”. It means
64 this can be used to deliberately break lock coherency in a cluster
65 for the root directory of a share.
66 The legacy fsname_norootdir_ext algorithm is an alias for using the
68 fsname algorithm together with fileid:nolock_paths= “.” and
69 fileid:nolock_max_slots = 18446744073709551615. It means this can
70 be used to deliberately break lock coherency completely for the
71 root directory of a share. Even local processes are no longer lock
72 coherent.
73 fileid:mapping = ALGORITHM
75 This option is the legacy version of the fileid:algorithm option,
76 which was used in earlier versions of fileid mapping feature in
77 custom Samba 3.0 versions.
78 fileid:fstype deny = LIST
80 List of file system types to be ignored for file_id generation.
81 fileid:fstype allow = LIST
83 List of file system types to be allowed for file_id generation. If
84 this option is set, file system types not listed here are ignored.
85 fileid:mntdir deny = LIST
87 List of file system mount points to be ignored for file_id
88 generation.
89 fileid:mntdir allow = LIST
91 List of file system mount points to be allowed for file_id
92 generation. If this option is set, file system mount points not
93 listed here are ignored.
94 fileid:nolock_max_slots = NUMBER(1-18446744073709551615)
96 This option alters the behavior of the nolock algorithm in a ways
97 that it also breaks the lock coherency between individual processes
98 on the same host. The default is to have just 1 concurrent slot
99 available per host. By incressing the number of slots you can
100 specify how many concurrent processes can work on a given inode
101 without contention, the number should typically be larger than the
102 a number of logical cpus, maybe 2 times of num_cpus.
103 fileid:nolock_all_dirs = BOOL
105 This option triggers the use of the fileid nolock behavior for all
106 directory inodes, which can be used to deliberately break the lock
107 coherency for all directories. NOTE: Do not use this without
108 knowing what you are doing! It breaks SMB semantics! See
109 fileid:nolock_paths for a more fine grained approach.
110 fileid:nolock_all_inodes = BOOL
112 This option triggers the use of the fileid nolock algorithm for all
113 directoriy inode, which can be used to deliberately break the lock
114 coherency for all directories. NOTE: Do not use this without
115 knowing what you are doing! It breaks SMB semantics and it can lead
116 to data corruption! See fileid:nolock_paths for a more fine grained
117 approach.
118 fileid:nolock_paths = LIST
120 This option specifies a path list referring to files and/or
121 directories, which should use fileid nolock algorithm in order to
122 deliberately break the lock coherency for them. The specified paths
123 can be relative to the share root directory or absolute. The names
124 are case sensitive unix pathnames! Note all paths are only
125 evaluated at tree connect time, when the share is being connected,
126 from there on only the related device and inode numbers from the
127 stat() syscall are compared. Non existing paths will generate a log
128 level 0 message. NOTE: This option should be used with care as it
129 breaks SMB semantics! But it may help in situation where a specific
130 (commonly read-only) inode is highly contended.
131 fileid:nolockinode = NUMBER
133 This legacy option triggers use of the fileid nolock behavior for
134 the configured inode, while ignoring and device id. This can be
135 used to deliberately break lock coherency for the corresponding
136 file or directory in a cluster. Using the fileid:nolock_paths
137 option is much more flexible and simpler to use.
138
140 Usage of the fileid module with the fsid algorithm:
141 [global]
143 vfs objects = fileid
144 fileid:algorithm = fsid
145 Usage of the fileid module in order avoid load on heavily contended
147 (most likely read-only) inodes.
148 [global]
150 vfs objects = fileid
151 fileid:algorithm = next_module
152 fileid:nolock_paths = . ContendedFolder1 /path/to/contended.exe
153 fileid:nolock_max_slots = 256
154
156 This man page is part of version 4.19.3 of the Samba suite.
157
159 The original Samba software and related utilities were created by
160 Andrew Tridgell. Samba is now developed by the Samba Team as an Open
161 Source project similar to the way the Linux kernel is developed.
162Samba 4.19.3 11/27/2023 VFS_FILEID(8)