forked from Minki/linux
1674 lines
49 KiB
Plaintext
1674 lines
49 KiB
Plaintext
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NOTE:
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This is one of the technical documents describing a component of
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Coda -- this document describes the client kernel-Venus interface.
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For more information:
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http://www.coda.cs.cmu.edu
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For user level software needed to run Coda:
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ftp://ftp.coda.cs.cmu.edu
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To run Coda you need to get a user level cache manager for the client,
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named Venus, as well as tools to manipulate ACLs, to log in, etc. The
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client needs to have the Coda filesystem selected in the kernel
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configuration.
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The server needs a user level server and at present does not depend on
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kernel support.
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The Venus kernel interface
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Peter J. Braam
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v1.0, Nov 9, 1997
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This document describes the communication between Venus and kernel
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level filesystem code needed for the operation of the Coda file sys-
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tem. This document version is meant to describe the current interface
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(version 1.0) as well as improvements we envisage.
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______________________________________________________________________
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Table of Contents
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1. Introduction
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2. Servicing Coda filesystem calls
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3. The message layer
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3.1 Implementation details
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4. The interface at the call level
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4.1 Data structures shared by the kernel and Venus
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4.2 The pioctl interface
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4.3 root
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4.4 lookup
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4.5 getattr
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4.6 setattr
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4.7 access
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4.8 create
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4.9 mkdir
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4.10 link
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4.11 symlink
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4.12 remove
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4.13 rmdir
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4.14 readlink
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4.15 open
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4.16 close
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4.17 ioctl
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4.18 rename
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4.19 readdir
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4.20 vget
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4.21 fsync
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4.22 inactive
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4.23 rdwr
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4.24 odymount
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4.25 ody_lookup
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4.26 ody_expand
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4.27 prefetch
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4.28 signal
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5. The minicache and downcalls
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5.1 INVALIDATE
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5.2 FLUSH
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5.3 PURGEUSER
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5.4 ZAPFILE
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5.5 ZAPDIR
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5.6 ZAPVNODE
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5.7 PURGEFID
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5.8 REPLACE
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6. Initialization and cleanup
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6.1 Requirements
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______________________________________________________________________
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0wpage
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11.. IInnttrroodduuccttiioonn
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A key component in the Coda Distributed File System is the cache
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manager, _V_e_n_u_s.
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When processes on a Coda enabled system access files in the Coda
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filesystem, requests are directed at the filesystem layer in the
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operating system. The operating system will communicate with Venus to
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service the request for the process. Venus manages a persistent
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client cache and makes remote procedure calls to Coda file servers and
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related servers (such as authentication servers) to service these
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requests it receives from the operating system. When Venus has
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serviced a request it replies to the operating system with appropriate
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return codes, and other data related to the request. Optionally the
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kernel support for Coda may maintain a minicache of recently processed
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requests to limit the number of interactions with Venus. Venus
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possesses the facility to inform the kernel when elements from its
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minicache are no longer valid.
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This document describes precisely this communication between the
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kernel and Venus. The definitions of so called upcalls and downcalls
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will be given with the format of the data they handle. We shall also
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describe the semantic invariants resulting from the calls.
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Historically Coda was implemented in a BSD file system in Mach 2.6.
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The interface between the kernel and Venus is very similar to the BSD
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VFS interface. Similar functionality is provided, and the format of
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the parameters and returned data is very similar to the BSD VFS. This
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leads to an almost natural environment for implementing a kernel-level
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filesystem driver for Coda in a BSD system. However, other operating
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systems such as Linux and Windows 95 and NT have virtual filesystem
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with different interfaces.
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To implement Coda on these systems some reverse engineering of the
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Venus/Kernel protocol is necessary. Also it came to light that other
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systems could profit significantly from certain small optimizations
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and modifications to the protocol. To facilitate this work as well as
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to make future ports easier, communication between Venus and the
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kernel should be documented in great detail. This is the aim of this
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document.
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0wpage
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22.. SSeerrvviicciinngg CCooddaa ffiilleessyysstteemm ccaallllss
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The service of a request for a Coda file system service originates in
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a process PP which accessing a Coda file. It makes a system call which
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traps to the OS kernel. Examples of such calls trapping to the kernel
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are _r_e_a_d_, _w_r_i_t_e_, _o_p_e_n_, _c_l_o_s_e_, _c_r_e_a_t_e_, _m_k_d_i_r_, _r_m_d_i_r_, _c_h_m_o_d in a Unix
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context. Similar calls exist in the Win32 environment, and are named
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_C_r_e_a_t_e_F_i_l_e_, .
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Generally the operating system handles the request in a virtual
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filesystem (VFS) layer, which is named I/O Manager in NT and IFS
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manager in Windows 95. The VFS is responsible for partial processing
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of the request and for locating the specific filesystem(s) which will
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service parts of the request. Usually the information in the path
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assists in locating the correct FS drivers. Sometimes after extensive
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pre-processing, the VFS starts invoking exported routines in the FS
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driver. This is the point where the FS specific processing of the
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request starts, and here the Coda specific kernel code comes into
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play.
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The FS layer for Coda must expose and implement several interfaces.
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First and foremost the VFS must be able to make all necessary calls to
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the Coda FS layer, so the Coda FS driver must expose the VFS interface
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as applicable in the operating system. These differ very significantly
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among operating systems, but share features such as facilities to
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read/write and create and remove objects. The Coda FS layer services
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such VFS requests by invoking one or more well defined services
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offered by the cache manager Venus. When the replies from Venus have
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come back to the FS driver, servicing of the VFS call continues and
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finishes with a reply to the kernel's VFS. Finally the VFS layer
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returns to the process.
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As a result of this design a basic interface exposed by the FS driver
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must allow Venus to manage message traffic. In particular Venus must
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be able to retrieve and place messages and to be notified of the
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arrival of a new message. The notification must be through a mechanism
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which does not block Venus since Venus must attend to other tasks even
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when no messages are waiting or being processed.
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Interfaces of the Coda FS Driver
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Furthermore the FS layer provides for a special path of communication
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between a user process and Venus, called the pioctl interface. The
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pioctl interface is used for Coda specific services, such as
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requesting detailed information about the persistent cache managed by
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Venus. Here the involvement of the kernel is minimal. It identifies
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the calling process and passes the information on to Venus. When
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Venus replies the response is passed back to the caller in unmodified
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form.
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Finally Venus allows the kernel FS driver to cache the results from
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certain services. This is done to avoid excessive context switches
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and results in an efficient system. However, Venus may acquire
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information, for example from the network which implies that cached
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information must be flushed or replaced. Venus then makes a downcall
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to the Coda FS layer to request flushes or updates in the cache. The
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kernel FS driver handles such requests synchronously.
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Among these interfaces the VFS interface and the facility to place,
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receive and be notified of messages are platform specific. We will
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not go into the calls exported to the VFS layer but we will state the
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requirements of the message exchange mechanism.
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0wpage
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33.. TThhee mmeessssaaggee llaayyeerr
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At the lowest level the communication between Venus and the FS driver
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proceeds through messages. The synchronization between processes
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requesting Coda file service and Venus relies on blocking and waking
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up processes. The Coda FS driver processes VFS- and pioctl-requests
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on behalf of a process P, creates messages for Venus, awaits replies
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and finally returns to the caller. The implementation of the exchange
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of messages is platform specific, but the semantics have (so far)
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appeared to be generally applicable. Data buffers are created by the
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FS Driver in kernel memory on behalf of P and copied to user memory in
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Venus.
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The FS Driver while servicing P makes upcalls to Venus. Such an
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upcall is dispatched to Venus by creating a message structure. The
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structure contains the identification of P, the message sequence
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number, the size of the request and a pointer to the data in kernel
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memory for the request. Since the data buffer is re-used to hold the
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reply from Venus, there is a field for the size of the reply. A flags
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field is used in the message to precisely record the status of the
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message. Additional platform dependent structures involve pointers to
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determine the position of the message on queues and pointers to
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synchronization objects. In the upcall routine the message structure
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is filled in, flags are set to 0, and it is placed on the _p_e_n_d_i_n_g
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queue. The routine calling upcall is responsible for allocating the
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data buffer; its structure will be described in the next section.
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A facility must exist to notify Venus that the message has been
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created, and implemented using available synchronization objects in
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the OS. This notification is done in the upcall context of the process
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P. When the message is on the pending queue, process P cannot proceed
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in upcall. The (kernel mode) processing of P in the filesystem
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request routine must be suspended until Venus has replied. Therefore
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the calling thread in P is blocked in upcall. A pointer in the
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message structure will locate the synchronization object on which P is
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sleeping.
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Venus detects the notification that a message has arrived, and the FS
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driver allow Venus to retrieve the message with a getmsg_from_kernel
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call. This action finishes in the kernel by putting the message on the
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queue of processing messages and setting flags to READ. Venus is
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passed the contents of the data buffer. The getmsg_from_kernel call
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now returns and Venus processes the request.
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At some later point the FS driver receives a message from Venus,
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namely when Venus calls sendmsg_to_kernel. At this moment the Coda FS
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driver looks at the contents of the message and decides if:
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+o the message is a reply for a suspended thread P. If so it removes
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the message from the processing queue and marks the message as
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WRITTEN. Finally, the FS driver unblocks P (still in the kernel
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mode context of Venus) and the sendmsg_to_kernel call returns to
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Venus. The process P will be scheduled at some point and continues
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processing its upcall with the data buffer replaced with the reply
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from Venus.
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+o The message is a _d_o_w_n_c_a_l_l. A downcall is a request from Venus to
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the FS Driver. The FS driver processes the request immediately
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(usually a cache eviction or replacement) and when it finishes
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sendmsg_to_kernel returns.
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Now P awakes and continues processing upcall. There are some
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subtleties to take account of. First P will determine if it was woken
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up in upcall by a signal from some other source (for example an
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attempt to terminate P) or as is normally the case by Venus in its
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sendmsg_to_kernel call. In the normal case, the upcall routine will
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deallocate the message structure and return. The FS routine can proceed
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with its processing.
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Sleeping and IPC arrangements
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In case P is woken up by a signal and not by Venus, it will first look
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at the flags field. If the message is not yet READ, the process P can
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handle its signal without notifying Venus. If Venus has READ, and
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the request should not be processed, P can send Venus a signal message
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to indicate that it should disregard the previous message. Such
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signals are put in the queue at the head, and read first by Venus. If
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the message is already marked as WRITTEN it is too late to stop the
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processing. The VFS routine will now continue. (-- If a VFS request
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involves more than one upcall, this can lead to complicated state, an
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extra field "handle_signals" could be added in the message structure
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to indicate points of no return have been passed.--)
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33..11.. IImmpplleemmeennttaattiioonn ddeettaaiillss
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The Unix implementation of this mechanism has been through the
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implementation of a character device associated with Coda. Venus
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retrieves messages by doing a read on the device, replies are sent
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with a write and notification is through the select system call on the
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file descriptor for the device. The process P is kept waiting on an
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interruptible wait queue object.
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In Windows NT and the DPMI Windows 95 implementation a DeviceIoControl
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call is used. The DeviceIoControl call is designed to copy buffers
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from user memory to kernel memory with OPCODES. The sendmsg_to_kernel
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is issued as a synchronous call, while the getmsg_from_kernel call is
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asynchronous. Windows EventObjects are used for notification of
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message arrival. The process P is kept waiting on a KernelEvent
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object in NT and a semaphore in Windows 95.
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0wpage
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44.. TThhee iinntteerrffaaccee aatt tthhee ccaallll lleevveell
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This section describes the upcalls a Coda FS driver can make to Venus.
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Each of these upcalls make use of two structures: inputArgs and
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outputArgs. In pseudo BNF form the structures take the following
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form:
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struct inputArgs {
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u_long opcode;
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u_long unique; /* Keep multiple outstanding msgs distinct */
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u_short pid; /* Common to all */
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u_short pgid; /* Common to all */
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struct CodaCred cred; /* Common to all */
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<union "in" of call dependent parts of inputArgs>
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};
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struct outputArgs {
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u_long opcode;
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u_long unique; /* Keep multiple outstanding msgs distinct */
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u_long result;
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<union "out" of call dependent parts of inputArgs>
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};
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Before going on let us elucidate the role of the various fields. The
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inputArgs start with the opcode which defines the type of service
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requested from Venus. There are approximately 30 upcalls at present
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which we will discuss. The unique field labels the inputArg with a
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unique number which will identify the message uniquely. A process and
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process group id are passed. Finally the credentials of the caller
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are included.
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Before delving into the specific calls we need to discuss a variety of
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data structures shared by the kernel and Venus.
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44..11.. DDaattaa ssttrruuccttuurreess sshhaarreedd bbyy tthhee kkeerrnneell aanndd VVeennuuss
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The CodaCred structure defines a variety of user and group ids as
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they are set for the calling process. The vuid_t and guid_t are 32 bit
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unsigned integers. It also defines group membership in an array. On
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Unix the CodaCred has proven sufficient to implement good security
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semantics for Coda but the structure may have to undergo modification
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for the Windows environment when these mature.
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struct CodaCred {
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|||
|
vuid_t cr_uid, cr_euid, cr_suid, cr_fsuid; /* Real, effective, set, fs uid*/
|
|||
|
vgid_t cr_gid, cr_egid, cr_sgid, cr_fsgid; /* same for groups */
|
|||
|
vgid_t cr_groups[NGROUPS]; /* Group membership for caller */
|
|||
|
};
|
|||
|
|
|||
|
|
|||
|
|
|||
|
NNOOTTEE It is questionable if we need CodaCreds in Venus. Finally Venus
|
|||
|
doesn't know about groups, although it does create files with the
|
|||
|
default uid/gid. Perhaps the list of group membership is superfluous.
|
|||
|
|
|||
|
|
|||
|
The next item is the fundamental identifier used to identify Coda
|
|||
|
files, the ViceFid. A fid of a file uniquely defines a file or
|
|||
|
directory in the Coda filesystem within a _c_e_l_l. (-- A _c_e_l_l is a
|
|||
|
group of Coda servers acting under the aegis of a single system
|
|||
|
control machine or SCM. See the Coda Administration manual for a
|
|||
|
detailed description of the role of the SCM.--)
|
|||
|
|
|||
|
|
|||
|
typedef struct ViceFid {
|
|||
|
VolumeId Volume;
|
|||
|
VnodeId Vnode;
|
|||
|
Unique_t Unique;
|
|||
|
} ViceFid;
|
|||
|
|
|||
|
|
|||
|
|
|||
|
Each of the constituent fields: VolumeId, VnodeId and Unique_t are
|
|||
|
unsigned 32 bit integers. We envisage that a further field will need
|
|||
|
to be prefixed to identify the Coda cell; this will probably take the
|
|||
|
form of a Ipv6 size IP address naming the Coda cell through DNS.
|
|||
|
|
|||
|
The next important structure shared between Venus and the kernel is
|
|||
|
the attributes of the file. The following structure is used to
|
|||
|
exchange information. It has room for future extensions such as
|
|||
|
support for device files (currently not present in Coda).
|
|||
|
|
|||
|
|
|||
|
|
|||
|
|
|||
|
|
|||
|
|
|||
|
|
|||
|
|
|||
|
|
|||
|
|
|||
|
|
|||
|
|
|||
|
|
|||
|
|
|||
|
|
|||
|
|
|||
|
|
|||
|
|
|||
|
struct coda_vattr {
|
|||
|
enum coda_vtype va_type; /* vnode type (for create) */
|
|||
|
u_short va_mode; /* files access mode and type */
|
|||
|
short va_nlink; /* number of references to file */
|
|||
|
vuid_t va_uid; /* owner user id */
|
|||
|
vgid_t va_gid; /* owner group id */
|
|||
|
long va_fsid; /* file system id (dev for now) */
|
|||
|
long va_fileid; /* file id */
|
|||
|
u_quad_t va_size; /* file size in bytes */
|
|||
|
long va_blocksize; /* blocksize preferred for i/o */
|
|||
|
struct timespec va_atime; /* time of last access */
|
|||
|
struct timespec va_mtime; /* time of last modification */
|
|||
|
struct timespec va_ctime; /* time file changed */
|
|||
|
u_long va_gen; /* generation number of file */
|
|||
|
u_long va_flags; /* flags defined for file */
|
|||
|
dev_t va_rdev; /* device special file represents */
|
|||
|
u_quad_t va_bytes; /* bytes of disk space held by file */
|
|||
|
u_quad_t va_filerev; /* file modification number */
|
|||
|
u_int va_vaflags; /* operations flags, see below */
|
|||
|
long va_spare; /* remain quad aligned */
|
|||
|
};
|
|||
|
|
|||
|
|
|||
|
|
|||
|
|
|||
|
44..22.. TThhee ppiiooccttll iinntteerrffaaccee
|
|||
|
|
|||
|
|
|||
|
Coda specific requests can be made by application through the pioctl
|
|||
|
interface. The pioctl is implemented as an ordinary ioctl on a
|
|||
|
fictitious file /coda/.CONTROL. The pioctl call opens this file, gets
|
|||
|
a file handle and makes the ioctl call. Finally it closes the file.
|
|||
|
|
|||
|
The kernel involvement in this is limited to providing the facility to
|
|||
|
open and close and pass the ioctl message _a_n_d to verify that a path in
|
|||
|
the pioctl data buffers is a file in a Coda filesystem.
|
|||
|
|
|||
|
The kernel is handed a data packet of the form:
|
|||
|
|
|||
|
struct {
|
|||
|
const char *path;
|
|||
|
struct ViceIoctl vidata;
|
|||
|
int follow;
|
|||
|
} data;
|
|||
|
|
|||
|
|
|||
|
|
|||
|
where
|
|||
|
|
|||
|
|
|||
|
struct ViceIoctl {
|
|||
|
caddr_t in, out; /* Data to be transferred in, or out */
|
|||
|
short in_size; /* Size of input buffer <= 2K */
|
|||
|
short out_size; /* Maximum size of output buffer, <= 2K */
|
|||
|
};
|
|||
|
|
|||
|
|
|||
|
|
|||
|
The path must be a Coda file, otherwise the ioctl upcall will not be
|
|||
|
made.
|
|||
|
|
|||
|
NNOOTTEE The data structures and code are a mess. We need to clean this
|
|||
|
up.
|
|||
|
|
|||
|
We now proceed to document the individual calls:
|
|||
|
|
|||
|
0wpage
|
|||
|
|
|||
|
44..33.. rroooott
|
|||
|
|
|||
|
|
|||
|
AArrgguummeennttss
|
|||
|
|
|||
|
iinn empty
|
|||
|
|
|||
|
oouutt
|
|||
|
|
|||
|
struct cfs_root_out {
|
|||
|
ViceFid VFid;
|
|||
|
} cfs_root;
|
|||
|
|
|||
|
|
|||
|
|
|||
|
DDeessccrriippttiioonn This call is made to Venus during the initialization of
|
|||
|
the Coda filesystem. If the result is zero, the cfs_root structure
|
|||
|
contains the ViceFid of the root of the Coda filesystem. If a non-zero
|
|||
|
result is generated, its value is a platform dependent error code
|
|||
|
indicating the difficulty Venus encountered in locating the root of
|
|||
|
the Coda filesystem.
|
|||
|
|
|||
|
0wpage
|
|||
|
|
|||
|
44..44.. llooookkuupp
|
|||
|
|
|||
|
|
|||
|
SSuummmmaarryy Find the ViceFid and type of an object in a directory if it
|
|||
|
exists.
|
|||
|
|
|||
|
AArrgguummeennttss
|
|||
|
|
|||
|
iinn
|
|||
|
|
|||
|
struct cfs_lookup_in {
|
|||
|
ViceFid VFid;
|
|||
|
char *name; /* Place holder for data. */
|
|||
|
} cfs_lookup;
|
|||
|
|
|||
|
|
|||
|
|
|||
|
oouutt
|
|||
|
|
|||
|
struct cfs_lookup_out {
|
|||
|
ViceFid VFid;
|
|||
|
int vtype;
|
|||
|
} cfs_lookup;
|
|||
|
|
|||
|
|
|||
|
|
|||
|
DDeessccrriippttiioonn This call is made to determine the ViceFid and filetype of
|
|||
|
a directory entry. The directory entry requested carries name name
|
|||
|
and Venus will search the directory identified by cfs_lookup_in.VFid.
|
|||
|
The result may indicate that the name does not exist, or that
|
|||
|
difficulty was encountered in finding it (e.g. due to disconnection).
|
|||
|
If the result is zero, the field cfs_lookup_out.VFid contains the
|
|||
|
targets ViceFid and cfs_lookup_out.vtype the coda_vtype giving the
|
|||
|
type of object the name designates.
|
|||
|
|
|||
|
The name of the object is an 8 bit character string of maximum length
|
|||
|
CFS_MAXNAMLEN, currently set to 256 (including a 0 terminator.)
|
|||
|
|
|||
|
It is extremely important to realize that Venus bitwise ors the field
|
|||
|
cfs_lookup.vtype with CFS_NOCACHE to indicate that the object should
|
|||
|
not be put in the kernel name cache.
|
|||
|
|
|||
|
NNOOTTEE The type of the vtype is currently wrong. It should be
|
|||
|
coda_vtype. Linux does not take note of CFS_NOCACHE. It should.
|
|||
|
|
|||
|
0wpage
|
|||
|
|
|||
|
44..55.. ggeettaattttrr
|
|||
|
|
|||
|
|
|||
|
SSuummmmaarryy Get the attributes of a file.
|
|||
|
|
|||
|
AArrgguummeennttss
|
|||
|
|
|||
|
iinn
|
|||
|
|
|||
|
struct cfs_getattr_in {
|
|||
|
ViceFid VFid;
|
|||
|
struct coda_vattr attr; /* XXXXX */
|
|||
|
} cfs_getattr;
|
|||
|
|
|||
|
|
|||
|
|
|||
|
oouutt
|
|||
|
|
|||
|
struct cfs_getattr_out {
|
|||
|
struct coda_vattr attr;
|
|||
|
} cfs_getattr;
|
|||
|
|
|||
|
|
|||
|
|
|||
|
DDeessccrriippttiioonn This call returns the attributes of the file identified by
|
|||
|
fid.
|
|||
|
|
|||
|
EErrrroorrss Errors can occur if the object with fid does not exist, is
|
|||
|
unaccessible or if the caller does not have permission to fetch
|
|||
|
attributes.
|
|||
|
|
|||
|
NNoottee Many kernel FS drivers (Linux, NT and Windows 95) need to acquire
|
|||
|
the attributes as well as the Fid for the instantiation of an internal
|
|||
|
"inode" or "FileHandle". A significant improvement in performance on
|
|||
|
such systems could be made by combining the _l_o_o_k_u_p and _g_e_t_a_t_t_r calls
|
|||
|
both at the Venus/kernel interaction level and at the RPC level.
|
|||
|
|
|||
|
The vattr structure included in the input arguments is superfluous and
|
|||
|
should be removed.
|
|||
|
|
|||
|
0wpage
|
|||
|
|
|||
|
44..66.. sseettaattttrr
|
|||
|
|
|||
|
|
|||
|
SSuummmmaarryy Set the attributes of a file.
|
|||
|
|
|||
|
AArrgguummeennttss
|
|||
|
|
|||
|
iinn
|
|||
|
|
|||
|
struct cfs_setattr_in {
|
|||
|
ViceFid VFid;
|
|||
|
struct coda_vattr attr;
|
|||
|
} cfs_setattr;
|
|||
|
|
|||
|
|
|||
|
|
|||
|
|
|||
|
oouutt
|
|||
|
empty
|
|||
|
|
|||
|
DDeessccrriippttiioonn The structure attr is filled with attributes to be changed
|
|||
|
in BSD style. Attributes not to be changed are set to -1, apart from
|
|||
|
vtype which is set to VNON. Other are set to the value to be assigned.
|
|||
|
The only attributes which the FS driver may request to change are the
|
|||
|
mode, owner, groupid, atime, mtime and ctime. The return value
|
|||
|
indicates success or failure.
|
|||
|
|
|||
|
EErrrroorrss A variety of errors can occur. The object may not exist, may
|
|||
|
be inaccessible, or permission may not be granted by Venus.
|
|||
|
|
|||
|
0wpage
|
|||
|
|
|||
|
44..77.. aacccceessss
|
|||
|
|
|||
|
|
|||
|
SSuummmmaarryy
|
|||
|
|
|||
|
AArrgguummeennttss
|
|||
|
|
|||
|
iinn
|
|||
|
|
|||
|
struct cfs_access_in {
|
|||
|
ViceFid VFid;
|
|||
|
int flags;
|
|||
|
} cfs_access;
|
|||
|
|
|||
|
|
|||
|
|
|||
|
oouutt
|
|||
|
empty
|
|||
|
|
|||
|
DDeessccrriippttiioonn Verify if access to the object identified by VFid for
|
|||
|
operations described by flags is permitted. The result indicates if
|
|||
|
access will be granted. It is important to remember that Coda uses
|
|||
|
ACLs to enforce protection and that ultimately the servers, not the
|
|||
|
clients enforce the security of the system. The result of this call
|
|||
|
will depend on whether a _t_o_k_e_n is held by the user.
|
|||
|
|
|||
|
EErrrroorrss The object may not exist, or the ACL describing the protection
|
|||
|
may not be accessible.
|
|||
|
|
|||
|
0wpage
|
|||
|
|
|||
|
44..88.. ccrreeaattee
|
|||
|
|
|||
|
|
|||
|
SSuummmmaarryy Invoked to create a file
|
|||
|
|
|||
|
AArrgguummeennttss
|
|||
|
|
|||
|
iinn
|
|||
|
|
|||
|
struct cfs_create_in {
|
|||
|
ViceFid VFid;
|
|||
|
struct coda_vattr attr;
|
|||
|
int excl;
|
|||
|
int mode;
|
|||
|
char *name; /* Place holder for data. */
|
|||
|
} cfs_create;
|
|||
|
|
|||
|
|
|||
|
|
|||
|
|
|||
|
oouutt
|
|||
|
|
|||
|
struct cfs_create_out {
|
|||
|
ViceFid VFid;
|
|||
|
struct coda_vattr attr;
|
|||
|
} cfs_create;
|
|||
|
|
|||
|
|
|||
|
|
|||
|
DDeessccrriippttiioonn This upcall is invoked to request creation of a file.
|
|||
|
The file will be created in the directory identified by VFid, its name
|
|||
|
will be name, and the mode will be mode. If excl is set an error will
|
|||
|
be returned if the file already exists. If the size field in attr is
|
|||
|
set to zero the file will be truncated. The uid and gid of the file
|
|||
|
are set by converting the CodaCred to a uid using a macro CRTOUID
|
|||
|
(this macro is platform dependent). Upon success the VFid and
|
|||
|
attributes of the file are returned. The Coda FS Driver will normally
|
|||
|
instantiate a vnode, inode or file handle at kernel level for the new
|
|||
|
object.
|
|||
|
|
|||
|
|
|||
|
EErrrroorrss A variety of errors can occur. Permissions may be insufficient.
|
|||
|
If the object exists and is not a file the error EISDIR is returned
|
|||
|
under Unix.
|
|||
|
|
|||
|
NNOOTTEE The packing of parameters is very inefficient and appears to
|
|||
|
indicate confusion between the system call creat and the VFS operation
|
|||
|
create. The VFS operation create is only called to create new objects.
|
|||
|
This create call differs from the Unix one in that it is not invoked
|
|||
|
to return a file descriptor. The truncate and exclusive options,
|
|||
|
together with the mode, could simply be part of the mode as it is
|
|||
|
under Unix. There should be no flags argument; this is used in open
|
|||
|
(2) to return a file descriptor for READ or WRITE mode.
|
|||
|
|
|||
|
The attributes of the directory should be returned too, since the size
|
|||
|
and mtime changed.
|
|||
|
|
|||
|
0wpage
|
|||
|
|
|||
|
44..99.. mmkkddiirr
|
|||
|
|
|||
|
|
|||
|
SSuummmmaarryy Create a new directory.
|
|||
|
|
|||
|
AArrgguummeennttss
|
|||
|
|
|||
|
iinn
|
|||
|
|
|||
|
struct cfs_mkdir_in {
|
|||
|
ViceFid VFid;
|
|||
|
struct coda_vattr attr;
|
|||
|
char *name; /* Place holder for data. */
|
|||
|
} cfs_mkdir;
|
|||
|
|
|||
|
|
|||
|
|
|||
|
oouutt
|
|||
|
|
|||
|
struct cfs_mkdir_out {
|
|||
|
ViceFid VFid;
|
|||
|
struct coda_vattr attr;
|
|||
|
} cfs_mkdir;
|
|||
|
|
|||
|
|
|||
|
|
|||
|
|
|||
|
DDeessccrriippttiioonn This call is similar to create but creates a directory.
|
|||
|
Only the mode field in the input parameters is used for creation.
|
|||
|
Upon successful creation, the attr returned contains the attributes of
|
|||
|
the new directory.
|
|||
|
|
|||
|
EErrrroorrss As for create.
|
|||
|
|
|||
|
NNOOTTEE The input parameter should be changed to mode instead of
|
|||
|
attributes.
|
|||
|
|
|||
|
The attributes of the parent should be returned since the size and
|
|||
|
mtime changes.
|
|||
|
|
|||
|
0wpage
|
|||
|
|
|||
|
44..1100.. lliinnkk
|
|||
|
|
|||
|
|
|||
|
SSuummmmaarryy Create a link to an existing file.
|
|||
|
|
|||
|
AArrgguummeennttss
|
|||
|
|
|||
|
iinn
|
|||
|
|
|||
|
struct cfs_link_in {
|
|||
|
ViceFid sourceFid; /* cnode to link *to* */
|
|||
|
ViceFid destFid; /* Directory in which to place link */
|
|||
|
char *tname; /* Place holder for data. */
|
|||
|
} cfs_link;
|
|||
|
|
|||
|
|
|||
|
|
|||
|
oouutt
|
|||
|
empty
|
|||
|
|
|||
|
DDeessccrriippttiioonn This call creates a link to the sourceFid in the directory
|
|||
|
identified by destFid with name tname. The source must reside in the
|
|||
|
target's parent, i.e. the source must be have parent destFid, i.e. Coda
|
|||
|
does not support cross directory hard links. Only the return value is
|
|||
|
relevant. It indicates success or the type of failure.
|
|||
|
|
|||
|
EErrrroorrss The usual errors can occur.0wpage
|
|||
|
|
|||
|
44..1111.. ssyymmlliinnkk
|
|||
|
|
|||
|
|
|||
|
SSuummmmaarryy create a symbolic link
|
|||
|
|
|||
|
AArrgguummeennttss
|
|||
|
|
|||
|
iinn
|
|||
|
|
|||
|
struct cfs_symlink_in {
|
|||
|
ViceFid VFid; /* Directory to put symlink in */
|
|||
|
char *srcname;
|
|||
|
struct coda_vattr attr;
|
|||
|
char *tname;
|
|||
|
} cfs_symlink;
|
|||
|
|
|||
|
|
|||
|
|
|||
|
oouutt
|
|||
|
none
|
|||
|
|
|||
|
DDeessccrriippttiioonn Create a symbolic link. The link is to be placed in the
|
|||
|
directory identified by VFid and named tname. It should point to the
|
|||
|
pathname srcname. The attributes of the newly created object are to
|
|||
|
be set to attr.
|
|||
|
|
|||
|
EErrrroorrss
|
|||
|
|
|||
|
NNOOTTEE The attributes of the target directory should be returned since
|
|||
|
its size changed.
|
|||
|
|
|||
|
0wpage
|
|||
|
|
|||
|
44..1122.. rreemmoovvee
|
|||
|
|
|||
|
|
|||
|
SSuummmmaarryy Remove a file
|
|||
|
|
|||
|
AArrgguummeennttss
|
|||
|
|
|||
|
iinn
|
|||
|
|
|||
|
struct cfs_remove_in {
|
|||
|
ViceFid VFid;
|
|||
|
char *name; /* Place holder for data. */
|
|||
|
} cfs_remove;
|
|||
|
|
|||
|
|
|||
|
|
|||
|
oouutt
|
|||
|
none
|
|||
|
|
|||
|
DDeessccrriippttiioonn Remove file named cfs_remove_in.name in directory
|
|||
|
identified by VFid.
|
|||
|
|
|||
|
EErrrroorrss
|
|||
|
|
|||
|
NNOOTTEE The attributes of the directory should be returned since its
|
|||
|
mtime and size may change.
|
|||
|
|
|||
|
0wpage
|
|||
|
|
|||
|
44..1133.. rrmmddiirr
|
|||
|
|
|||
|
|
|||
|
SSuummmmaarryy Remove a directory
|
|||
|
|
|||
|
AArrgguummeennttss
|
|||
|
|
|||
|
iinn
|
|||
|
|
|||
|
struct cfs_rmdir_in {
|
|||
|
ViceFid VFid;
|
|||
|
char *name; /* Place holder for data. */
|
|||
|
} cfs_rmdir;
|
|||
|
|
|||
|
|
|||
|
|
|||
|
oouutt
|
|||
|
none
|
|||
|
|
|||
|
DDeessccrriippttiioonn Remove the directory with name name from the directory
|
|||
|
identified by VFid.
|
|||
|
|
|||
|
EErrrroorrss
|
|||
|
|
|||
|
NNOOTTEE The attributes of the parent directory should be returned since
|
|||
|
its mtime and size may change.
|
|||
|
|
|||
|
0wpage
|
|||
|
|
|||
|
44..1144.. rreeaaddlliinnkk
|
|||
|
|
|||
|
|
|||
|
SSuummmmaarryy Read the value of a symbolic link.
|
|||
|
|
|||
|
AArrgguummeennttss
|
|||
|
|
|||
|
iinn
|
|||
|
|
|||
|
struct cfs_readlink_in {
|
|||
|
ViceFid VFid;
|
|||
|
} cfs_readlink;
|
|||
|
|
|||
|
|
|||
|
|
|||
|
oouutt
|
|||
|
|
|||
|
struct cfs_readlink_out {
|
|||
|
int count;
|
|||
|
caddr_t data; /* Place holder for data. */
|
|||
|
} cfs_readlink;
|
|||
|
|
|||
|
|
|||
|
|
|||
|
DDeessccrriippttiioonn This routine reads the contents of symbolic link
|
|||
|
identified by VFid into the buffer data. The buffer data must be able
|
|||
|
to hold any name up to CFS_MAXNAMLEN (PATH or NAM??).
|
|||
|
|
|||
|
EErrrroorrss No unusual errors.
|
|||
|
|
|||
|
0wpage
|
|||
|
|
|||
|
44..1155.. ooppeenn
|
|||
|
|
|||
|
|
|||
|
SSuummmmaarryy Open a file.
|
|||
|
|
|||
|
AArrgguummeennttss
|
|||
|
|
|||
|
iinn
|
|||
|
|
|||
|
struct cfs_open_in {
|
|||
|
ViceFid VFid;
|
|||
|
int flags;
|
|||
|
} cfs_open;
|
|||
|
|
|||
|
|
|||
|
|
|||
|
oouutt
|
|||
|
|
|||
|
struct cfs_open_out {
|
|||
|
dev_t dev;
|
|||
|
ino_t inode;
|
|||
|
} cfs_open;
|
|||
|
|
|||
|
|
|||
|
|
|||
|
DDeessccrriippttiioonn This request asks Venus to place the file identified by
|
|||
|
VFid in its cache and to note that the calling process wishes to open
|
|||
|
it with flags as in open(2). The return value to the kernel differs
|
|||
|
for Unix and Windows systems. For Unix systems the Coda FS Driver is
|
|||
|
informed of the device and inode number of the container file in the
|
|||
|
fields dev and inode. For Windows the path of the container file is
|
|||
|
returned to the kernel.
|
|||
|
EErrrroorrss
|
|||
|
|
|||
|
NNOOTTEE Currently the cfs_open_out structure is not properly adapted to
|
|||
|
deal with the Windows case. It might be best to implement two
|
|||
|
upcalls, one to open aiming at a container file name, the other at a
|
|||
|
container file inode.
|
|||
|
|
|||
|
0wpage
|
|||
|
|
|||
|
44..1166.. cclloossee
|
|||
|
|
|||
|
|
|||
|
SSuummmmaarryy Close a file, update it on the servers.
|
|||
|
|
|||
|
AArrgguummeennttss
|
|||
|
|
|||
|
iinn
|
|||
|
|
|||
|
struct cfs_close_in {
|
|||
|
ViceFid VFid;
|
|||
|
int flags;
|
|||
|
} cfs_close;
|
|||
|
|
|||
|
|
|||
|
|
|||
|
oouutt
|
|||
|
none
|
|||
|
|
|||
|
DDeessccrriippttiioonn Close the file identified by VFid.
|
|||
|
|
|||
|
EErrrroorrss
|
|||
|
|
|||
|
NNOOTTEE The flags argument is bogus and not used. However, Venus' code
|
|||
|
has room to deal with an execp input field, probably this field should
|
|||
|
be used to inform Venus that the file was closed but is still memory
|
|||
|
mapped for execution. There are comments about fetching versus not
|
|||
|
fetching the data in Venus vproc_vfscalls. This seems silly. If a
|
|||
|
file is being closed, the data in the container file is to be the new
|
|||
|
data. Here again the execp flag might be in play to create confusion:
|
|||
|
currently Venus might think a file can be flushed from the cache when
|
|||
|
it is still memory mapped. This needs to be understood.
|
|||
|
|
|||
|
0wpage
|
|||
|
|
|||
|
44..1177.. iiooccttll
|
|||
|
|
|||
|
|
|||
|
SSuummmmaarryy Do an ioctl on a file. This includes the pioctl interface.
|
|||
|
|
|||
|
AArrgguummeennttss
|
|||
|
|
|||
|
iinn
|
|||
|
|
|||
|
struct cfs_ioctl_in {
|
|||
|
ViceFid VFid;
|
|||
|
int cmd;
|
|||
|
int len;
|
|||
|
int rwflag;
|
|||
|
char *data; /* Place holder for data. */
|
|||
|
} cfs_ioctl;
|
|||
|
|
|||
|
|
|||
|
|
|||
|
oouutt
|
|||
|
|
|||
|
|
|||
|
struct cfs_ioctl_out {
|
|||
|
int len;
|
|||
|
caddr_t data; /* Place holder for data. */
|
|||
|
} cfs_ioctl;
|
|||
|
|
|||
|
|
|||
|
|
|||
|
DDeessccrriippttiioonn Do an ioctl operation on a file. The command, len and
|
|||
|
data arguments are filled as usual. flags is not used by Venus.
|
|||
|
|
|||
|
EErrrroorrss
|
|||
|
|
|||
|
NNOOTTEE Another bogus parameter. flags is not used. What is the
|
|||
|
business about PREFETCHING in the Venus code?
|
|||
|
|
|||
|
|
|||
|
0wpage
|
|||
|
|
|||
|
44..1188.. rreennaammee
|
|||
|
|
|||
|
|
|||
|
SSuummmmaarryy Rename a fid.
|
|||
|
|
|||
|
AArrgguummeennttss
|
|||
|
|
|||
|
iinn
|
|||
|
|
|||
|
struct cfs_rename_in {
|
|||
|
ViceFid sourceFid;
|
|||
|
char *srcname;
|
|||
|
ViceFid destFid;
|
|||
|
char *destname;
|
|||
|
} cfs_rename;
|
|||
|
|
|||
|
|
|||
|
|
|||
|
oouutt
|
|||
|
none
|
|||
|
|
|||
|
DDeessccrriippttiioonn Rename the object with name srcname in directory
|
|||
|
sourceFid to destname in destFid. It is important that the names
|
|||
|
srcname and destname are 0 terminated strings. Strings in Unix
|
|||
|
kernels are not always null terminated.
|
|||
|
|
|||
|
EErrrroorrss
|
|||
|
|
|||
|
0wpage
|
|||
|
|
|||
|
44..1199.. rreeaaddddiirr
|
|||
|
|
|||
|
|
|||
|
SSuummmmaarryy Read directory entries.
|
|||
|
|
|||
|
AArrgguummeennttss
|
|||
|
|
|||
|
iinn
|
|||
|
|
|||
|
struct cfs_readdir_in {
|
|||
|
ViceFid VFid;
|
|||
|
int count;
|
|||
|
int offset;
|
|||
|
} cfs_readdir;
|
|||
|
|
|||
|
|
|||
|
|
|||
|
|
|||
|
oouutt
|
|||
|
|
|||
|
struct cfs_readdir_out {
|
|||
|
int size;
|
|||
|
caddr_t data; /* Place holder for data. */
|
|||
|
} cfs_readdir;
|
|||
|
|
|||
|
|
|||
|
|
|||
|
DDeessccrriippttiioonn Read directory entries from VFid starting at offset and
|
|||
|
read at most count bytes. Returns the data in data and returns
|
|||
|
the size in size.
|
|||
|
|
|||
|
EErrrroorrss
|
|||
|
|
|||
|
NNOOTTEE This call is not used. Readdir operations exploit container
|
|||
|
files. We will re-evaluate this during the directory revamp which is
|
|||
|
about to take place.
|
|||
|
|
|||
|
0wpage
|
|||
|
|
|||
|
44..2200.. vvggeett
|
|||
|
|
|||
|
|
|||
|
SSuummmmaarryy instructs Venus to do an FSDB->Get.
|
|||
|
|
|||
|
AArrgguummeennttss
|
|||
|
|
|||
|
iinn
|
|||
|
|
|||
|
struct cfs_vget_in {
|
|||
|
ViceFid VFid;
|
|||
|
} cfs_vget;
|
|||
|
|
|||
|
|
|||
|
|
|||
|
oouutt
|
|||
|
|
|||
|
struct cfs_vget_out {
|
|||
|
ViceFid VFid;
|
|||
|
int vtype;
|
|||
|
} cfs_vget;
|
|||
|
|
|||
|
|
|||
|
|
|||
|
DDeessccrriippttiioonn This upcall asks Venus to do a get operation on an fsobj
|
|||
|
labelled by VFid.
|
|||
|
|
|||
|
EErrrroorrss
|
|||
|
|
|||
|
NNOOTTEE This operation is not used. However, it is extremely useful
|
|||
|
since it can be used to deal with read/write memory mapped files.
|
|||
|
These can be "pinned" in the Venus cache using vget and released with
|
|||
|
inactive.
|
|||
|
|
|||
|
0wpage
|
|||
|
|
|||
|
44..2211.. ffssyynncc
|
|||
|
|
|||
|
|
|||
|
SSuummmmaarryy Tell Venus to update the RVM attributes of a file.
|
|||
|
|
|||
|
AArrgguummeennttss
|
|||
|
|
|||
|
iinn
|
|||
|
|
|||
|
struct cfs_fsync_in {
|
|||
|
ViceFid VFid;
|
|||
|
} cfs_fsync;
|
|||
|
|
|||
|
|
|||
|
|
|||
|
oouutt
|
|||
|
none
|
|||
|
|
|||
|
DDeessccrriippttiioonn Ask Venus to update RVM attributes of object VFid. This
|
|||
|
should be called as part of kernel level fsync type calls. The
|
|||
|
result indicates if the syncing was successful.
|
|||
|
|
|||
|
EErrrroorrss
|
|||
|
|
|||
|
NNOOTTEE Linux does not implement this call. It should.
|
|||
|
|
|||
|
0wpage
|
|||
|
|
|||
|
44..2222.. iinnaaccttiivvee
|
|||
|
|
|||
|
|
|||
|
SSuummmmaarryy Tell Venus a vnode is no longer in use.
|
|||
|
|
|||
|
AArrgguummeennttss
|
|||
|
|
|||
|
iinn
|
|||
|
|
|||
|
struct cfs_inactive_in {
|
|||
|
ViceFid VFid;
|
|||
|
} cfs_inactive;
|
|||
|
|
|||
|
|
|||
|
|
|||
|
oouutt
|
|||
|
none
|
|||
|
|
|||
|
DDeessccrriippttiioonn This operation returns EOPNOTSUPP.
|
|||
|
|
|||
|
EErrrroorrss
|
|||
|
|
|||
|
NNOOTTEE This should perhaps be removed.
|
|||
|
|
|||
|
0wpage
|
|||
|
|
|||
|
44..2233.. rrddwwrr
|
|||
|
|
|||
|
|
|||
|
SSuummmmaarryy Read or write from a file
|
|||
|
|
|||
|
AArrgguummeennttss
|
|||
|
|
|||
|
iinn
|
|||
|
|
|||
|
struct cfs_rdwr_in {
|
|||
|
ViceFid VFid;
|
|||
|
int rwflag;
|
|||
|
int count;
|
|||
|
int offset;
|
|||
|
int ioflag;
|
|||
|
caddr_t data; /* Place holder for data. */
|
|||
|
} cfs_rdwr;
|
|||
|
|
|||
|
|
|||
|
|
|||
|
|
|||
|
oouutt
|
|||
|
|
|||
|
struct cfs_rdwr_out {
|
|||
|
int rwflag;
|
|||
|
int count;
|
|||
|
caddr_t data; /* Place holder for data. */
|
|||
|
} cfs_rdwr;
|
|||
|
|
|||
|
|
|||
|
|
|||
|
DDeessccrriippttiioonn This upcall asks Venus to read or write from a file.
|
|||
|
|
|||
|
EErrrroorrss
|
|||
|
|
|||
|
NNOOTTEE It should be removed since it is against the Coda philosophy that
|
|||
|
read/write operations never reach Venus. I have been told the
|
|||
|
operation does not work. It is not currently used.
|
|||
|
|
|||
|
|
|||
|
0wpage
|
|||
|
|
|||
|
44..2244.. ooddyymmoouunntt
|
|||
|
|
|||
|
|
|||
|
SSuummmmaarryy Allows mounting multiple Coda "filesystems" on one Unix mount
|
|||
|
point.
|
|||
|
|
|||
|
AArrgguummeennttss
|
|||
|
|
|||
|
iinn
|
|||
|
|
|||
|
struct ody_mount_in {
|
|||
|
char *name; /* Place holder for data. */
|
|||
|
} ody_mount;
|
|||
|
|
|||
|
|
|||
|
|
|||
|
oouutt
|
|||
|
|
|||
|
struct ody_mount_out {
|
|||
|
ViceFid VFid;
|
|||
|
} ody_mount;
|
|||
|
|
|||
|
|
|||
|
|
|||
|
DDeessccrriippttiioonn Asks Venus to return the rootfid of a Coda system named
|
|||
|
name. The fid is returned in VFid.
|
|||
|
|
|||
|
EErrrroorrss
|
|||
|
|
|||
|
NNOOTTEE This call was used by David for dynamic sets. It should be
|
|||
|
removed since it causes a jungle of pointers in the VFS mounting area.
|
|||
|
It is not used by Coda proper. Call is not implemented by Venus.
|
|||
|
|
|||
|
0wpage
|
|||
|
|
|||
|
44..2255.. ooddyy__llooookkuupp
|
|||
|
|
|||
|
|
|||
|
SSuummmmaarryy Looks up something.
|
|||
|
|
|||
|
AArrgguummeennttss
|
|||
|
|
|||
|
iinn irrelevant
|
|||
|
|
|||
|
|
|||
|
oouutt
|
|||
|
irrelevant
|
|||
|
|
|||
|
DDeessccrriippttiioonn
|
|||
|
|
|||
|
EErrrroorrss
|
|||
|
|
|||
|
NNOOTTEE Gut it. Call is not implemented by Venus.
|
|||
|
|
|||
|
0wpage
|
|||
|
|
|||
|
44..2266.. ooddyy__eexxppaanndd
|
|||
|
|
|||
|
|
|||
|
SSuummmmaarryy expands something in a dynamic set.
|
|||
|
|
|||
|
AArrgguummeennttss
|
|||
|
|
|||
|
iinn irrelevant
|
|||
|
|
|||
|
oouutt
|
|||
|
irrelevant
|
|||
|
|
|||
|
DDeessccrriippttiioonn
|
|||
|
|
|||
|
EErrrroorrss
|
|||
|
|
|||
|
NNOOTTEE Gut it. Call is not implemented by Venus.
|
|||
|
|
|||
|
0wpage
|
|||
|
|
|||
|
44..2277.. pprreeffeettcchh
|
|||
|
|
|||
|
|
|||
|
SSuummmmaarryy Prefetch a dynamic set.
|
|||
|
|
|||
|
AArrgguummeennttss
|
|||
|
|
|||
|
iinn Not documented.
|
|||
|
|
|||
|
oouutt
|
|||
|
Not documented.
|
|||
|
|
|||
|
DDeessccrriippttiioonn Venus worker.cc has support for this call, although it is
|
|||
|
noted that it doesn't work. Not surprising, since the kernel does not
|
|||
|
have support for it. (ODY_PREFETCH is not a defined operation).
|
|||
|
|
|||
|
EErrrroorrss
|
|||
|
|
|||
|
NNOOTTEE Gut it. It isn't working and isn't used by Coda.
|
|||
|
|
|||
|
|
|||
|
0wpage
|
|||
|
|
|||
|
44..2288.. ssiiggnnaall
|
|||
|
|
|||
|
|
|||
|
SSuummmmaarryy Send Venus a signal about an upcall.
|
|||
|
|
|||
|
AArrgguummeennttss
|
|||
|
|
|||
|
iinn none
|
|||
|
|
|||
|
oouutt
|
|||
|
not applicable.
|
|||
|
|
|||
|
DDeessccrriippttiioonn This is an out-of-band upcall to Venus to inform Venus
|
|||
|
that the calling process received a signal after Venus read the
|
|||
|
message from the input queue. Venus is supposed to clean up the
|
|||
|
operation.
|
|||
|
|
|||
|
EErrrroorrss No reply is given.
|
|||
|
|
|||
|
NNOOTTEE We need to better understand what Venus needs to clean up and if
|
|||
|
it is doing this correctly. Also we need to handle multiple upcall
|
|||
|
per system call situations correctly. It would be important to know
|
|||
|
what state changes in Venus take place after an upcall for which the
|
|||
|
kernel is responsible for notifying Venus to clean up (e.g. open
|
|||
|
definitely is such a state change, but many others are maybe not).
|
|||
|
|
|||
|
0wpage
|
|||
|
|
|||
|
55.. TThhee mmiinniiccaacchhee aanndd ddoowwnnccaallllss
|
|||
|
|
|||
|
|
|||
|
The Coda FS Driver can cache results of lookup and access upcalls, to
|
|||
|
limit the frequency of upcalls. Upcalls carry a price since a process
|
|||
|
context switch needs to take place. The counterpart of caching the
|
|||
|
information is that Venus will notify the FS Driver that cached
|
|||
|
entries must be flushed or renamed.
|
|||
|
|
|||
|
The kernel code generally has to maintain a structure which links the
|
|||
|
internal file handles (called vnodes in BSD, inodes in Linux and
|
|||
|
FileHandles in Windows) with the ViceFid's which Venus maintains. The
|
|||
|
reason is that frequent translations back and forth are needed in
|
|||
|
order to make upcalls and use the results of upcalls. Such linking
|
|||
|
objects are called ccnnooddeess.
|
|||
|
|
|||
|
The current minicache implementations have cache entries which record
|
|||
|
the following:
|
|||
|
|
|||
|
1. the name of the file
|
|||
|
|
|||
|
2. the cnode of the directory containing the object
|
|||
|
|
|||
|
3. a list of CodaCred's for which the lookup is permitted.
|
|||
|
|
|||
|
4. the cnode of the object
|
|||
|
|
|||
|
The lookup call in the Coda FS Driver may request the cnode of the
|
|||
|
desired object from the cache, by passing its name, directory and the
|
|||
|
CodaCred's of the caller. The cache will return the cnode or indicate
|
|||
|
that it cannot be found. The Coda FS Driver must be careful to
|
|||
|
invalidate cache entries when it modifies or removes objects.
|
|||
|
|
|||
|
When Venus obtains information that indicates that cache entries are
|
|||
|
no longer valid, it will make a downcall to the kernel. Downcalls are
|
|||
|
intercepted by the Coda FS Driver and lead to cache invalidations of
|
|||
|
the kind described below. The Coda FS Driver does not return an error
|
|||
|
unless the downcall data could not be read into kernel memory.
|
|||
|
|
|||
|
|
|||
|
55..11.. IINNVVAALLIIDDAATTEE
|
|||
|
|
|||
|
|
|||
|
No information is available on this call.
|
|||
|
|
|||
|
|
|||
|
55..22.. FFLLUUSSHH
|
|||
|
|
|||
|
|
|||
|
|
|||
|
AArrgguummeennttss None
|
|||
|
|
|||
|
SSuummmmaarryy Flush the name cache entirely.
|
|||
|
|
|||
|
DDeessccrriippttiioonn Venus issues this call upon startup and when it dies. This
|
|||
|
is to prevent stale cache information being held. Some operating
|
|||
|
systems allow the kernel name cache to be switched off dynamically.
|
|||
|
When this is done, this downcall is made.
|
|||
|
|
|||
|
|
|||
|
55..33.. PPUURRGGEEUUSSEERR
|
|||
|
|
|||
|
|
|||
|
AArrgguummeennttss
|
|||
|
|
|||
|
struct cfs_purgeuser_out {/* CFS_PURGEUSER is a venus->kernel call */
|
|||
|
struct CodaCred cred;
|
|||
|
} cfs_purgeuser;
|
|||
|
|
|||
|
|
|||
|
|
|||
|
DDeessccrriippttiioonn Remove all entries in the cache carrying the Cred. This
|
|||
|
call is issued when tokens for a user expire or are flushed.
|
|||
|
|
|||
|
|
|||
|
55..44.. ZZAAPPFFIILLEE
|
|||
|
|
|||
|
|
|||
|
AArrgguummeennttss
|
|||
|
|
|||
|
struct cfs_zapfile_out { /* CFS_ZAPFILE is a venus->kernel call */
|
|||
|
ViceFid CodaFid;
|
|||
|
} cfs_zapfile;
|
|||
|
|
|||
|
|
|||
|
|
|||
|
DDeessccrriippttiioonn Remove all entries which have the (dir vnode, name) pair.
|
|||
|
This is issued as a result of an invalidation of cached attributes of
|
|||
|
a vnode.
|
|||
|
|
|||
|
NNOOTTEE Call is not named correctly in NetBSD and Mach. The minicache
|
|||
|
zapfile routine takes different arguments. Linux does not implement
|
|||
|
the invalidation of attributes correctly.
|
|||
|
|
|||
|
|
|||
|
|
|||
|
55..55.. ZZAAPPDDIIRR
|
|||
|
|
|||
|
|
|||
|
AArrgguummeennttss
|
|||
|
|
|||
|
struct cfs_zapdir_out { /* CFS_ZAPDIR is a venus->kernel call */
|
|||
|
ViceFid CodaFid;
|
|||
|
} cfs_zapdir;
|
|||
|
|
|||
|
|
|||
|
|
|||
|
DDeessccrriippttiioonn Remove all entries in the cache lying in a directory
|
|||
|
CodaFid, and all children of this directory. This call is issued when
|
|||
|
Venus receives a callback on the directory.
|
|||
|
|
|||
|
|
|||
|
55..66.. ZZAAPPVVNNOODDEE
|
|||
|
|
|||
|
|
|||
|
|
|||
|
AArrgguummeennttss
|
|||
|
|
|||
|
struct cfs_zapvnode_out { /* CFS_ZAPVNODE is a venus->kernel call */
|
|||
|
struct CodaCred cred;
|
|||
|
ViceFid VFid;
|
|||
|
} cfs_zapvnode;
|
|||
|
|
|||
|
|
|||
|
|
|||
|
DDeessccrriippttiioonn Remove all entries in the cache carrying the cred and VFid
|
|||
|
as in the arguments. This downcall is probably never issued.
|
|||
|
|
|||
|
|
|||
|
55..77.. PPUURRGGEEFFIIDD
|
|||
|
|
|||
|
|
|||
|
SSuummmmaarryy
|
|||
|
|
|||
|
AArrgguummeennttss
|
|||
|
|
|||
|
struct cfs_purgefid_out { /* CFS_PURGEFID is a venus->kernel call */
|
|||
|
ViceFid CodaFid;
|
|||
|
} cfs_purgefid;
|
|||
|
|
|||
|
|
|||
|
|
|||
|
DDeessccrriippttiioonn Flush the attribute for the file. If it is a dir (odd
|
|||
|
vnode), purge its children from the namecache and remove the file from the
|
|||
|
namecache.
|
|||
|
|
|||
|
|
|||
|
|
|||
|
55..88.. RREEPPLLAACCEE
|
|||
|
|
|||
|
|
|||
|
SSuummmmaarryy Replace the Fid's for a collection of names.
|
|||
|
|
|||
|
AArrgguummeennttss
|
|||
|
|
|||
|
struct cfs_replace_out { /* cfs_replace is a venus->kernel call */
|
|||
|
ViceFid NewFid;
|
|||
|
ViceFid OldFid;
|
|||
|
} cfs_replace;
|
|||
|
|
|||
|
|
|||
|
|
|||
|
DDeessccrriippttiioonn This routine replaces a ViceFid in the name cache with
|
|||
|
another. It is added to allow Venus during reintegration to replace
|
|||
|
locally allocated temp fids while disconnected with global fids even
|
|||
|
when the reference counts on those fids are not zero.
|
|||
|
|
|||
|
0wpage
|
|||
|
|
|||
|
66.. IInniittiiaalliizzaattiioonn aanndd cclleeaannuupp
|
|||
|
|
|||
|
|
|||
|
This section gives brief hints as to desirable features for the Coda
|
|||
|
FS Driver at startup and upon shutdown or Venus failures. Before
|
|||
|
entering the discussion it is useful to repeat that the Coda FS Driver
|
|||
|
maintains the following data:
|
|||
|
|
|||
|
|
|||
|
1. message queues
|
|||
|
|
|||
|
2. cnodes
|
|||
|
|
|||
|
3. name cache entries
|
|||
|
|
|||
|
The name cache entries are entirely private to the driver, so they
|
|||
|
can easily be manipulated. The message queues will generally have
|
|||
|
clear points of initialization and destruction. The cnodes are
|
|||
|
much more delicate. User processes hold reference counts in Coda
|
|||
|
filesystems and it can be difficult to clean up the cnodes.
|
|||
|
|
|||
|
It can expect requests through:
|
|||
|
|
|||
|
1. the message subsystem
|
|||
|
|
|||
|
2. the VFS layer
|
|||
|
|
|||
|
3. pioctl interface
|
|||
|
|
|||
|
Currently the _p_i_o_c_t_l passes through the VFS for Coda so we can
|
|||
|
treat these similarly.
|
|||
|
|
|||
|
|
|||
|
66..11.. RReeqquuiirreemmeennttss
|
|||
|
|
|||
|
|
|||
|
The following requirements should be accommodated:
|
|||
|
|
|||
|
1. The message queues should have open and close routines. On Unix
|
|||
|
the opening of the character devices are such routines.
|
|||
|
|
|||
|
+o Before opening, no messages can be placed.
|
|||
|
|
|||
|
+o Opening will remove any old messages still pending.
|
|||
|
|
|||
|
+o Close will notify any sleeping processes that their upcall cannot
|
|||
|
be completed.
|
|||
|
|
|||
|
+o Close will free all memory allocated by the message queues.
|
|||
|
|
|||
|
|
|||
|
2. At open the namecache shall be initialized to empty state.
|
|||
|
|
|||
|
3. Before the message queues are open, all VFS operations will fail.
|
|||
|
Fortunately this can be achieved by making sure than mounting the
|
|||
|
Coda filesystem cannot succeed before opening.
|
|||
|
|
|||
|
4. After closing of the queues, no VFS operations can succeed. Here
|
|||
|
one needs to be careful, since a few operations (lookup,
|
|||
|
read/write, readdir) can proceed without upcalls. These must be
|
|||
|
explicitly blocked.
|
|||
|
|
|||
|
5. Upon closing the namecache shall be flushed and disabled.
|
|||
|
|
|||
|
6. All memory held by cnodes can be freed without relying on upcalls.
|
|||
|
|
|||
|
7. Unmounting the file system can be done without relying on upcalls.
|
|||
|
|
|||
|
8. Mounting the Coda filesystem should fail gracefully if Venus cannot
|
|||
|
get the rootfid or the attributes of the rootfid. The latter is
|
|||
|
best implemented by Venus fetching these objects before attempting
|
|||
|
to mount.
|
|||
|
|
|||
|
NNOOTTEE NetBSD in particular but also Linux have not implemented the
|
|||
|
above requirements fully. For smooth operation this needs to be
|
|||
|
corrected.
|
|||
|
|
|||
|
|
|||
|
|