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1.. SPDX-License-Identifier: GPL-2.0
2
3=======================================
4v9fs: Plan 9 Resource Sharing for Linux
5=======================================
6
7About
8=====
9
10v9fs is a Unix implementation of the Plan 9 9p remote filesystem protocol.
11
12This software was originally developed by Ron Minnich <rminnich@sandia.gov>
13and Maya Gokhale. Additional development by Greg Watson
14<gwatson@lanl.gov> and most recently Eric Van Hensbergen
15<ericvh@gmail.com>, Latchesar Ionkov <lucho@ionkov.net> and Russ Cox
16<rsc@swtch.com>.
17
18The best detailed explanation of the Linux implementation and applications of
19the 9p client is available in the form of a USENIX paper:
20
21 https://www.usenix.org/events/usenix05/tech/freenix/hensbergen.html
22
23Other applications are described in the following papers:
24
25 * XCPU & Clustering
26 http://xcpu.org/papers/xcpu-talk.pdf
27 * KVMFS: control file system for KVM
28 http://xcpu.org/papers/kvmfs.pdf
29 * CellFS: A New Programming Model for the Cell BE
30 http://xcpu.org/papers/cellfs-talk.pdf
31 * PROSE I/O: Using 9p to enable Application Partitions
32 http://plan9.escet.urjc.es/iwp9/cready/PROSE_iwp9_2006.pdf
33 * VirtFS: A Virtualization Aware File System pass-through
34 https://kernel.org/doc/ols/2010/ols2010-pages-109-120.pdf
35
36Usage
37=====
38
39For remote file server::
40
41 mount -t 9p 10.10.1.2 /mnt/9
42
43For Plan 9 From User Space applications (http://swtch.com/plan9)::
44
45 mount -t 9p `namespace`/acme /mnt/9 -o trans=unix,uname=$USER
46
47For server running on QEMU host with virtio transport::
48
49 mount -t 9p -o trans=virtio <mount_tag> /mnt/9
50
51where mount_tag is the tag generated by the server to each of the exported
52mount points. Each 9P export is seen by the client as a virtio device with an
53associated "mount_tag" property. Available mount tags can be
54seen by reading /sys/bus/virtio/drivers/9pnet_virtio/virtio<n>/mount_tag files.
55
56USBG Usage
57==========
58
59To mount a 9p FS on a USB Host accessible via the gadget at runtime::
60
61 mount -t 9p -o trans=usbg,aname=/path/to/fs <device> /mnt/9
62
63To mount a 9p FS on a USB Host accessible via the gadget as root filesystem::
64
65 root=<device> rootfstype=9p rootflags=trans=usbg,cache=loose,uname=root,access=0,dfltuid=0,dfltgid=0,aname=/path/to/rootfs
66
67where <device> is the tag associated by the usb gadget transport.
68It is defined by the configfs instance name.
69
70USBG Example
71============
72
73The USB host exports a filesystem, while the gadget on the USB device
74side makes it mountable.
75
76Diod (9pfs server) and the forwarder are on the development host, where
77the root filesystem is actually stored. The gadget is initialized during
78boot (or later) on the embedded board. Then the forwarder will find it
79on the USB bus and start forwarding requests.
80
81In this case the 9p requests come from the device and are handled by the
82host. The reason is that USB device ports are normally not available on
83PCs, so a connection in the other direction would not work.
84
85When using the usbg transport, for now there is no native usb host
86service capable to handle the requests from the gadget driver. For
87this we have to use the extra python tool p9_fwd.py from tools/usb.
88
89Just start the 9pfs capable network server like diod/nfs-ganesha e.g.::
90
91 $ diod -f -n -d 0 -S -l 0.0.0.0:9999 -e $PWD
92
93Optionaly scan your bus if there are more then one usbg gadgets to find their path::
94
95 $ python $kernel_dir/tools/usb/p9_fwd.py list
96
97 Bus | Addr | Manufacturer | Product | ID | Path
98 --- | ---- | ---------------- | ---------------- | --------- | ----
99 2 | 67 | unknown | unknown | 1d6b:0109 | 2-1.1.2
100 2 | 68 | unknown | unknown | 1d6b:0109 | 2-1.1.3
101
102Then start the python transport::
103
104 $ python $kernel_dir/tools/usb/p9_fwd.py --path 2-1.1.2 connect -p 9999
105
106After that the gadget driver can be used as described above.
107
108One use-case is to use it as an alternative to NFS root booting during
109the development of embedded Linux devices.
110
111Options
112=======
113
114 ============= ===============================================================
115 trans=name select an alternative transport. Valid options are
116 currently:
117
118 ======== ============================================
119 unix specifying a named pipe mount point
120 tcp specifying a normal TCP/IP connection
121 fd used passed file descriptors for connection
122 (see rfdno and wfdno)
123 virtio connect to the next virtio channel available
124 (from QEMU with trans_virtio module)
125 rdma connect to a specified RDMA channel
126 usbg connect to a specified usb gadget channel
127 ======== ============================================
128
129 uname=name user name to attempt mount as on the remote server. The
130 server may override or ignore this value. Certain user
131 names may require authentication.
132
133 aname=name aname specifies the file tree to access when the server is
134 offering several exported file systems.
135
136 cache=mode specifies a caching policy. By default, no caches are used.
137 The mode can be specified as a bitmask or by using one of the
138 preexisting common 'shortcuts'.
139 The bitmask is described below: (unspecified bits are reserved)
140
141 ========== ====================================================
142 0b00000000 all caches disabled, mmap disabled
143 0b00000001 file caches enabled
144 0b00000010 meta-data caches enabled
145 0b00000100 writeback behavior (as opposed to writethrough)
146 0b00001000 loose caches (no explicit consistency with server)
147 0b10000000 fscache enabled for persistent caching
148 ========== ====================================================
149
150 The current shortcuts and their associated bitmask are:
151
152 ========= ====================================================
153 none 0b00000000 (no caching)
154 readahead 0b00000001 (only read-ahead file caching)
155 mmap 0b00000101 (read-ahead + writeback file cache)
156 loose 0b00001111 (non-coherent file and meta-data caches)
157 fscache 0b10001111 (persistent loose cache)
158 ========= ====================================================
159
160 NOTE: only these shortcuts are tested modes of operation at the
161 moment, so using other combinations of bit-patterns is not
162 known to work. Work on better cache support is in progress.
163
164 IMPORTANT: loose caches (and by extension at the moment fscache)
165 do not necessarily validate cached values on the server. In other
166 words changes on the server are not guaranteed to be reflected
167 on the client system. Only use this mode of operation if you
168 have an exclusive mount and the server will modify the filesystem
169 underneath you.
170
171 debug=n specifies debug level. The debug level is a bitmask.
172
173 ===== ================================
174 0x01 display verbose error messages
175 0x02 developer debug (DEBUG_CURRENT)
176 0x04 display 9p trace
177 0x08 display VFS trace
178 0x10 display Marshalling debug
179 0x20 display RPC debug
180 0x40 display transport debug
181 0x80 display allocation debug
182 0x100 display protocol message debug
183 0x200 display Fid debug
184 0x400 display packet debug
185 0x800 display fscache tracing debug
186 ===== ================================
187
188 rfdno=n the file descriptor for reading with trans=fd
189
190 wfdno=n the file descriptor for writing with trans=fd
191
192 msize=n the number of bytes to use for 9p packet payload
193
194 port=n port to connect to on the remote server
195
196 noextend force legacy mode (no 9p2000.u or 9p2000.L semantics)
197
198 version=name Select 9P protocol version. Valid options are:
199
200 ======== ==============================
201 9p2000 Legacy mode (same as noextend)
202 9p2000.u Use 9P2000.u protocol
203 9p2000.L Use 9P2000.L protocol
204 ======== ==============================
205
206 dfltuid attempt to mount as a particular uid
207
208 dfltgid attempt to mount with a particular gid
209
210 afid security channel - used by Plan 9 authentication protocols
211
212 nodevmap do not map special files - represent them as normal files.
213 This can be used to share devices/named pipes/sockets between
214 hosts. This functionality will be expanded in later versions.
215
216 directio bypass page cache on all read/write operations
217
218 ignoreqv ignore qid.version==0 as a marker to ignore cache
219
220 noxattr do not offer xattr functions on this mount.
221
222 access there are four access modes.
223 user
224 if a user tries to access a file on v9fs
225 filesystem for the first time, v9fs sends an
226 attach command (Tattach) for that user.
227 This is the default mode.
228 <uid>
229 allows only user with uid=<uid> to access
230 the files on the mounted filesystem
231 any
232 v9fs does single attach and performs all
233 operations as one user
234 clien
235 ACL based access check on the 9p client
236 side for access validation
237
238 cachetag cache tag to use the specified persistent cache.
239 cache tags for existing cache sessions can be listed at
240 /sys/fs/9p/caches. (applies only to cache=fscache)
241 ============= ===============================================================
242
243Behavior
244========
245
246This section aims at describing 9p 'quirks' that can be different
247from a local filesystem behaviors.
248
249 - Setting O_NONBLOCK on a file will make client reads return as early
250 as the server returns some data instead of trying to fill the read
251 buffer with the requested amount of bytes or end of file is reached.
252
253Resources
254=========
255
256Protocol specifications are maintained on github:
257http://ericvh.github.com/9p-rfc/
258
2599p client and server implementations are listed on
260http://9p.cat-v.org/implementations
261
262A 9p2000.L server is being developed by LLNL and can be found
263at http://code.google.com/p/diod/
264
265There are user and developer mailing lists available through the v9fs project
266on sourceforge (http://sourceforge.net/projects/v9fs).
267
268News and other information is maintained on a Wiki.
269(http://sf.net/apps/mediawiki/v9fs/index.php).
270
271Bug reports are best issued via the mailing list.
272
273For more information on the Plan 9 Operating System check out
274http://plan9.bell-labs.com/plan9
275
276For information on Plan 9 from User Space (Plan 9 applications and libraries
277ported to Linux/BSD/OSX/etc) check out https://9fans.github.io/plan9port/
1.. SPDX-License-Identifier: GPL-2.0
2
3=======================================
4v9fs: Plan 9 Resource Sharing for Linux
5=======================================
6
7About
8=====
9
10v9fs is a Unix implementation of the Plan 9 9p remote filesystem protocol.
11
12This software was originally developed by Ron Minnich <rminnich@sandia.gov>
13and Maya Gokhale. Additional development by Greg Watson
14<gwatson@lanl.gov> and most recently Eric Van Hensbergen
15<ericvh@gmail.com>, Latchesar Ionkov <lucho@ionkov.net> and Russ Cox
16<rsc@swtch.com>.
17
18The best detailed explanation of the Linux implementation and applications of
19the 9p client is available in the form of a USENIX paper:
20
21 https://www.usenix.org/events/usenix05/tech/freenix/hensbergen.html
22
23Other applications are described in the following papers:
24
25 * XCPU & Clustering
26 http://xcpu.org/papers/xcpu-talk.pdf
27 * KVMFS: control file system for KVM
28 http://xcpu.org/papers/kvmfs.pdf
29 * CellFS: A New Programming Model for the Cell BE
30 http://xcpu.org/papers/cellfs-talk.pdf
31 * PROSE I/O: Using 9p to enable Application Partitions
32 http://plan9.escet.urjc.es/iwp9/cready/PROSE_iwp9_2006.pdf
33 * VirtFS: A Virtualization Aware File System pass-through
34 http://goo.gl/3WPDg
35
36Usage
37=====
38
39For remote file server::
40
41 mount -t 9p 10.10.1.2 /mnt/9
42
43For Plan 9 From User Space applications (http://swtch.com/plan9)::
44
45 mount -t 9p `namespace`/acme /mnt/9 -o trans=unix,uname=$USER
46
47For server running on QEMU host with virtio transport::
48
49 mount -t 9p -o trans=virtio <mount_tag> /mnt/9
50
51where mount_tag is the tag associated by the server to each of the exported
52mount points. Each 9P export is seen by the client as a virtio device with an
53associated "mount_tag" property. Available mount tags can be
54seen by reading /sys/bus/virtio/drivers/9pnet_virtio/virtio<n>/mount_tag files.
55
56Options
57=======
58
59 ============= ===============================================================
60 trans=name select an alternative transport. Valid options are
61 currently:
62
63 ======== ============================================
64 unix specifying a named pipe mount point
65 tcp specifying a normal TCP/IP connection
66 fd used passed file descriptors for connection
67 (see rfdno and wfdno)
68 virtio connect to the next virtio channel available
69 (from QEMU with trans_virtio module)
70 rdma connect to a specified RDMA channel
71 ======== ============================================
72
73 uname=name user name to attempt mount as on the remote server. The
74 server may override or ignore this value. Certain user
75 names may require authentication.
76
77 aname=name aname specifies the file tree to access when the server is
78 offering several exported file systems.
79
80 cache=mode specifies a caching policy. By default, no caches are used.
81
82 none
83 default no cache policy, metadata and data
84 alike are synchronous.
85 loose
86 no attempts are made at consistency,
87 intended for exclusive, read-only mounts
88 fscache
89 use FS-Cache for a persistent, read-only
90 cache backend.
91 mmap
92 minimal cache that is only used for read-write
93 mmap. Northing else is cached, like cache=none
94
95 debug=n specifies debug level. The debug level is a bitmask.
96
97 ===== ================================
98 0x01 display verbose error messages
99 0x02 developer debug (DEBUG_CURRENT)
100 0x04 display 9p trace
101 0x08 display VFS trace
102 0x10 display Marshalling debug
103 0x20 display RPC debug
104 0x40 display transport debug
105 0x80 display allocation debug
106 0x100 display protocol message debug
107 0x200 display Fid debug
108 0x400 display packet debug
109 0x800 display fscache tracing debug
110 ===== ================================
111
112 rfdno=n the file descriptor for reading with trans=fd
113
114 wfdno=n the file descriptor for writing with trans=fd
115
116 msize=n the number of bytes to use for 9p packet payload
117
118 port=n port to connect to on the remote server
119
120 noextend force legacy mode (no 9p2000.u or 9p2000.L semantics)
121
122 version=name Select 9P protocol version. Valid options are:
123
124 ======== ==============================
125 9p2000 Legacy mode (same as noextend)
126 9p2000.u Use 9P2000.u protocol
127 9p2000.L Use 9P2000.L protocol
128 ======== ==============================
129
130 dfltuid attempt to mount as a particular uid
131
132 dfltgid attempt to mount with a particular gid
133
134 afid security channel - used by Plan 9 authentication protocols
135
136 nodevmap do not map special files - represent them as normal files.
137 This can be used to share devices/named pipes/sockets between
138 hosts. This functionality will be expanded in later versions.
139
140 access there are four access modes.
141 user
142 if a user tries to access a file on v9fs
143 filesystem for the first time, v9fs sends an
144 attach command (Tattach) for that user.
145 This is the default mode.
146 <uid>
147 allows only user with uid=<uid> to access
148 the files on the mounted filesystem
149 any
150 v9fs does single attach and performs all
151 operations as one user
152 clien
153 ACL based access check on the 9p client
154 side for access validation
155
156 cachetag cache tag to use the specified persistent cache.
157 cache tags for existing cache sessions can be listed at
158 /sys/fs/9p/caches. (applies only to cache=fscache)
159 ============= ===============================================================
160
161Behavior
162========
163
164This section aims at describing 9p 'quirks' that can be different
165from a local filesystem behaviors.
166
167 - Setting O_NONBLOCK on a file will make client reads return as early
168 as the server returns some data instead of trying to fill the read
169 buffer with the requested amount of bytes or end of file is reached.
170
171Resources
172=========
173
174Protocol specifications are maintained on github:
175http://ericvh.github.com/9p-rfc/
176
1779p client and server implementations are listed on
178http://9p.cat-v.org/implementations
179
180A 9p2000.L server is being developed by LLNL and can be found
181at http://code.google.com/p/diod/
182
183There are user and developer mailing lists available through the v9fs project
184on sourceforge (http://sourceforge.net/projects/v9fs).
185
186News and other information is maintained on a Wiki.
187(http://sf.net/apps/mediawiki/v9fs/index.php).
188
189Bug reports are best issued via the mailing list.
190
191For more information on the Plan 9 Operating System check out
192http://plan9.bell-labs.com/plan9
193
194For information on Plan 9 from User Space (Plan 9 applications and libraries
195ported to Linux/BSD/OSX/etc) check out https://9fans.github.io/plan9port/