--- /dev/null
+.. SPDX-License-Identifier: GPL-2.0
+
+=======================================
+v9fs: Plan 9 Resource Sharing for Linux
+=======================================
+
+About
+=====
+
+v9fs is a Unix implementation of the Plan 9 9p remote filesystem protocol.
+
+This software was originally developed by Ron Minnich <rminnich@sandia.gov>
+and Maya Gokhale. Additional development by Greg Watson
+<gwatson@lanl.gov> and most recently Eric Van Hensbergen
+<ericvh@gmail.com>, Latchesar Ionkov <lucho@ionkov.net> and Russ Cox
+<rsc@swtch.com>.
+
+The best detailed explanation of the Linux implementation and applications of
+the 9p client is available in the form of a USENIX paper:
+
+ http://www.usenix.org/events/usenix05/tech/freenix/hensbergen.html
+
+Other applications are described in the following papers:
+
+ * XCPU & Clustering
+ http://xcpu.org/papers/xcpu-talk.pdf
+ * KVMFS: control file system for KVM
+ http://xcpu.org/papers/kvmfs.pdf
+ * CellFS: A New Programming Model for the Cell BE
+ http://xcpu.org/papers/cellfs-talk.pdf
+ * PROSE I/O: Using 9p to enable Application Partitions
+ http://plan9.escet.urjc.es/iwp9/cready/PROSE_iwp9_2006.pdf
+ * VirtFS: A Virtualization Aware File System pass-through
+ http://goo.gl/3WPDg
+
+Usage
+=====
+
+For remote file server::
+
+ mount -t 9p 10.10.1.2 /mnt/9
+
+For Plan 9 From User Space applications (http://swtch.com/plan9)::
+
+ mount -t 9p `namespace`/acme /mnt/9 -o trans=unix,uname=$USER
+
+For server running on QEMU host with virtio transport::
+
+ mount -t 9p -o trans=virtio <mount_tag> /mnt/9
+
+where mount_tag is the tag associated by the server to each of the exported
+mount points. Each 9P export is seen by the client as a virtio device with an
+associated "mount_tag" property. Available mount tags can be
+seen by reading /sys/bus/virtio/drivers/9pnet_virtio/virtio<n>/mount_tag files.
+
+Options
+=======
+
+ ============= ===============================================================
+ trans=name select an alternative transport. Valid options are
+ currently:
+
+ ======== ============================================
+ unix specifying a named pipe mount point
+ tcp specifying a normal TCP/IP connection
+ fd used passed file descriptors for connection
+ (see rfdno and wfdno)
+ virtio connect to the next virtio channel available
+ (from QEMU with trans_virtio module)
+ rdma connect to a specified RDMA channel
+ ======== ============================================
+
+ uname=name user name to attempt mount as on the remote server. The
+ server may override or ignore this value. Certain user
+ names may require authentication.
+
+ aname=name aname specifies the file tree to access when the server is
+ offering several exported file systems.
+
+ cache=mode specifies a caching policy. By default, no caches are used.
+
+ none
+ default no cache policy, metadata and data
+ alike are synchronous.
+ loose
+ no attempts are made at consistency,
+ intended for exclusive, read-only mounts
+ fscache
+ use FS-Cache for a persistent, read-only
+ cache backend.
+ mmap
+ minimal cache that is only used for read-write
+ mmap. Northing else is cached, like cache=none
+
+ debug=n specifies debug level. The debug level is a bitmask.
+
+ ===== ================================
+ 0x01 display verbose error messages
+ 0x02 developer debug (DEBUG_CURRENT)
+ 0x04 display 9p trace
+ 0x08 display VFS trace
+ 0x10 display Marshalling debug
+ 0x20 display RPC debug
+ 0x40 display transport debug
+ 0x80 display allocation debug
+ 0x100 display protocol message debug
+ 0x200 display Fid debug
+ 0x400 display packet debug
+ 0x800 display fscache tracing debug
+ ===== ================================
+
+ rfdno=n the file descriptor for reading with trans=fd
+
+ wfdno=n the file descriptor for writing with trans=fd
+
+ msize=n the number of bytes to use for 9p packet payload
+
+ port=n port to connect to on the remote server
+
+ noextend force legacy mode (no 9p2000.u or 9p2000.L semantics)
+
+ version=name Select 9P protocol version. Valid options are:
+
+ ======== ==============================
+ 9p2000 Legacy mode (same as noextend)
+ 9p2000.u Use 9P2000.u protocol
+ 9p2000.L Use 9P2000.L protocol
+ ======== ==============================
+
+ dfltuid attempt to mount as a particular uid
+
+ dfltgid attempt to mount with a particular gid
+
+ afid security channel - used by Plan 9 authentication protocols
+
+ nodevmap do not map special files - represent them as normal files.
+ This can be used to share devices/named pipes/sockets between
+ hosts. This functionality will be expanded in later versions.
+
+ access there are four access modes.
+ user
+ if a user tries to access a file on v9fs
+ filesystem for the first time, v9fs sends an
+ attach command (Tattach) for that user.
+ This is the default mode.
+ <uid>
+ allows only user with uid=<uid> to access
+ the files on the mounted filesystem
+ any
+ v9fs does single attach and performs all
+ operations as one user
+ clien
+ ACL based access check on the 9p client
+ side for access validation
+
+ cachetag cache tag to use the specified persistent cache.
+ cache tags for existing cache sessions can be listed at
+ /sys/fs/9p/caches. (applies only to cache=fscache)
+ ============= ===============================================================
+
++Behavior
++========
++
++This section aims at describing 9p 'quirks' that can be different
++from a local filesystem behaviors.
++
++ - Setting O_NONBLOCK on a file will make client reads return as early
++ as the server returns some data instead of trying to fill the read
++ buffer with the requested amount of bytes or end of file is reached.
++
+Resources
+=========
+
+Protocol specifications are maintained on github:
+http://ericvh.github.com/9p-rfc/
+
+9p client and server implementations are listed on
+http://9p.cat-v.org/implementations
+
+A 9p2000.L server is being developed by LLNL and can be found
+at http://code.google.com/p/diod/
+
+There are user and developer mailing lists available through the v9fs project
+on sourceforge (http://sourceforge.net/projects/v9fs).
+
+News and other information is maintained on a Wiki.
+(http://sf.net/apps/mediawiki/v9fs/index.php).
+
+Bug reports are best issued via the mailing list.
+
+For more information on the Plan 9 Operating System check out
+http://plan9.bell-labs.com/plan9
+
+For information on Plan 9 from User Space (Plan 9 applications and libraries
+ported to Linux/BSD/OSX/etc) check out http://swtch.com/plan9
projects / linux-2.6-microblaze.git / commitdiff