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authorJ. Bruce Fields <bfields@redhat.com>2012-08-15 17:43:30 -0400
committerJ. Bruce Fields <bfields@redhat.com>2012-08-21 17:42:03 -0400
commit8a4c6e19cfed5e650045312affed7e6056383278 (patch)
tree339a910e1a4f18911ad6173bd2c304e8a0e699f9
parent65b2e6656bda2ad983727fcc725ac66b6d5035a7 (diff)
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nfsd: document kernel interfaces for nfsd configuration
These are only needed by nfs-utils. But I needed to remind myself how they worked recently and thought this might be helpful. It's short and incomplete for now as I was only interested in startup, shutdown, and configuration of listening sockets. Signed-off-by: J. Bruce Fields <bfields@redhat.com>
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diff --git a/Documentation/filesystems/nfs/nfsd-admin-interfaces.txt b/Documentation/filesystems/nfs/nfsd-admin-interfaces.txt
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+Administrative interfaces for nfsd
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Note that normally these interfaces are used only by the utilities in
+nfs-utils.
+
+nfsd is controlled mainly by pseudofiles under the "nfsd" filesystem,
+which is normally mounted at /proc/fs/nfsd/.
+
+The server is always started by the first write of a nonzero value to
+nfsd/threads.
+
+Before doing that, NFSD can be told which sockets to listen on by
+writing to nfsd/portlist; that write may be:
+
+ - an ascii-encoded file descriptor, which should refer to a
+ bound (and listening, for tcp) socket, or
+ - "transportname port", where transportname is currently either
+ "udp", "tcp", or "rdma".
+
+If nfsd is started without doing any of these, then it will create one
+udp and one tcp listener at port 2049 (see nfsd_init_socks).
+
+On startup, nfsd and lockd grace periods start.
+
+nfsd is shut down by a write of 0 to nfsd/threads. All locks and state
+are thrown away at that point.
+
+Between startup and shutdown, the number of threads may be adjusted up
+or down by additional writes to nfsd/threads or by writes to
+nfsd/pool_threads.
+
+For more detail about files under nfsd/ and what they control, see
+fs/nfsd/nfsctl.c; most of them have detailed comments.
+
+Implementation notes
+^^^^^^^^^^^^^^^^^^^^
+
+Note that the rpc server requires the caller to serialize addition and
+removal of listening sockets, and startup and shutdown of the server.
+For nfsd this is done using nfsd_mutex.
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