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diff --git a/Documentation/filesystems/9p.rst b/Documentation/filesystems/9p.rst new file mode 100644 index 000000000..7b5964bc8 --- /dev/null +++ b/Documentation/filesystems/9p.rst @@ -0,0 +1,195 @@ +.. 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: + + https://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 https://9fans.github.io/plan9port/ |