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1NOTE:
2This is one of the technical documents describing a component of
3Coda -- this document describes the client kernel-Venus interface.
4
5For more information:
6 http://www.coda.cs.cmu.edu
7For user level software needed to run Coda:
8 ftp://ftp.coda.cs.cmu.edu
9
10To run Coda you need to get a user level cache manager for the client,
11named Venus, as well as tools to manipulate ACLs, to log in, etc. The
12client needs to have the Coda filesystem selected in the kernel
13configuration.
14
15The server needs a user level server and at present does not depend on
16kernel support.
17
18
19
20
21
22
23
24 The Venus kernel interface
25 Peter J. Braam
26 v1.0, Nov 9, 1997
27
28 This document describes the communication between Venus and kernel
29 level filesystem code needed for the operation of the Coda file sys-
30 tem. This document version is meant to describe the current interface
31 (version 1.0) as well as improvements we envisage.
32 ______________________________________________________________________
33
34 Table of Contents
35
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89
90 1. Introduction
91
92 2. Servicing Coda filesystem calls
93
94 3. The message layer
95
96 3.1 Implementation details
97
98 4. The interface at the call level
99
100 4.1 Data structures shared by the kernel and Venus
101 4.2 The pioctl interface
102 4.3 root
103 4.4 lookup
104 4.5 getattr
105 4.6 setattr
106 4.7 access
107 4.8 create
108 4.9 mkdir
109 4.10 link
110 4.11 symlink
111 4.12 remove
112 4.13 rmdir
113 4.14 readlink
114 4.15 open
115 4.16 close
116 4.17 ioctl
117 4.18 rename
118 4.19 readdir
119 4.20 vget
120 4.21 fsync
121 4.22 inactive
122 4.23 rdwr
123 4.24 odymount
124 4.25 ody_lookup
125 4.26 ody_expand
126 4.27 prefetch
127 4.28 signal
128
129 5. The minicache and downcalls
130
131 5.1 INVALIDATE
132 5.2 FLUSH
133 5.3 PURGEUSER
134 5.4 ZAPFILE
135 5.5 ZAPDIR
136 5.6 ZAPVNODE
137 5.7 PURGEFID
138 5.8 REPLACE
139
140 6. Initialization and cleanup
141
142 6.1 Requirements
143
144
145 ______________________________________________________________________
146 0wpage
147
148 11.. IInnttrroodduuccttiioonn
149
150
151
152 A key component in the Coda Distributed File System is the cache
153 manager, _V_e_n_u_s.
154
155
156 When processes on a Coda enabled system access files in the Coda
157 filesystem, requests are directed at the filesystem layer in the
158 operating system. The operating system will communicate with Venus to
159 service the request for the process. Venus manages a persistent
160 client cache and makes remote procedure calls to Coda file servers and
161 related servers (such as authentication servers) to service these
162 requests it receives from the operating system. When Venus has
163 serviced a request it replies to the operating system with appropriate
164 return codes, and other data related to the request. Optionally the
165 kernel support for Coda may maintain a minicache of recently processed
166 requests to limit the number of interactions with Venus. Venus
167 possesses the facility to inform the kernel when elements from its
168 minicache are no longer valid.
169
170 This document describes precisely this communication between the
171 kernel and Venus. The definitions of so called upcalls and downcalls
172 will be given with the format of the data they handle. We shall also
173 describe the semantic invariants resulting from the calls.
174
175 Historically Coda was implemented in a BSD file system in Mach 2.6.
176 The interface between the kernel and Venus is very similar to the BSD
177 VFS interface. Similar functionality is provided, and the format of
178 the parameters and returned data is very similar to the BSD VFS. This
179 leads to an almost natural environment for implementing a kernel-level
180 filesystem driver for Coda in a BSD system. However, other operating
181 systems such as Linux and Windows 95 and NT have virtual filesystem
182 with different interfaces.
183
184 To implement Coda on these systems some reverse engineering of the
185 Venus/Kernel protocol is necessary. Also it came to light that other
186 systems could profit significantly from certain small optimizations
187 and modifications to the protocol. To facilitate this work as well as
188 to make future ports easier, communication between Venus and the
189 kernel should be documented in great detail. This is the aim of this
190 document.
191
192 0wpage
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194 22.. SSeerrvviicciinngg CCooddaa ffiilleessyysstteemm ccaallllss
195
196 The service of a request for a Coda file system service originates in
197 a process PP which accessing a Coda file. It makes a system call which
198 traps to the OS kernel. Examples of such calls trapping to the kernel
199 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
200 context. Similar calls exist in the Win32 environment, and are named
201 _C_r_e_a_t_e_F_i_l_e_, .
202
203 Generally the operating system handles the request in a virtual
204 filesystem (VFS) layer, which is named I/O Manager in NT and IFS
205 manager in Windows 95. The VFS is responsible for partial processing
206 of the request and for locating the specific filesystem(s) which will
207 service parts of the request. Usually the information in the path
208 assists in locating the correct FS drivers. Sometimes after extensive
209 pre-processing, the VFS starts invoking exported routines in the FS
210 driver. This is the point where the FS specific processing of the
211 request starts, and here the Coda specific kernel code comes into
212 play.
213
214 The FS layer for Coda must expose and implement several interfaces.
215 First and foremost the VFS must be able to make all necessary calls to
216 the Coda FS layer, so the Coda FS driver must expose the VFS interface
217 as applicable in the operating system. These differ very significantly
218 among operating systems, but share features such as facilities to
219 read/write and create and remove objects. The Coda FS layer services
220 such VFS requests by invoking one or more well defined services
221 offered by the cache manager Venus. When the replies from Venus have
222 come back to the FS driver, servicing of the VFS call continues and
223 finishes with a reply to the kernel's VFS. Finally the VFS layer
224 returns to the process.
225
226 As a result of this design a basic interface exposed by the FS driver
227 must allow Venus to manage message traffic. In particular Venus must
228 be able to retrieve and place messages and to be notified of the
229 arrival of a new message. The notification must be through a mechanism
230 which does not block Venus since Venus must attend to other tasks even
231 when no messages are waiting or being processed.
232
233
234
235
236
237
238 Interfaces of the Coda FS Driver
239
240 Furthermore the FS layer provides for a special path of communication
241 between a user process and Venus, called the pioctl interface. The
242 pioctl interface is used for Coda specific services, such as
243 requesting detailed information about the persistent cache managed by
244 Venus. Here the involvement of the kernel is minimal. It identifies
245 the calling process and passes the information on to Venus. When
246 Venus replies the response is passed back to the caller in unmodified
247 form.
248
249 Finally Venus allows the kernel FS driver to cache the results from
250 certain services. This is done to avoid excessive context switches
251 and results in an efficient system. However, Venus may acquire
252 information, for example from the network which implies that cached
253 information must be flushed or replaced. Venus then makes a downcall
254 to the Coda FS layer to request flushes or updates in the cache. The
255 kernel FS driver handles such requests synchronously.
256
257 Among these interfaces the VFS interface and the facility to place,
258 receive and be notified of messages are platform specific. We will
259 not go into the calls exported to the VFS layer but we will state the
260 requirements of the message exchange mechanism.
261
262 0wpage
263
264 33.. TThhee mmeessssaaggee llaayyeerr
265
266
267
268 At the lowest level the communication between Venus and the FS driver
269 proceeds through messages. The synchronization between processes
270 requesting Coda file service and Venus relies on blocking and waking
271 up processes. The Coda FS driver processes VFS- and pioctl-requests
272 on behalf of a process P, creates messages for Venus, awaits replies
273 and finally returns to the caller. The implementation of the exchange
274 of messages is platform specific, but the semantics have (so far)
275 appeared to be generally applicable. Data buffers are created by the
276 FS Driver in kernel memory on behalf of P and copied to user memory in
277 Venus.
278
279 The FS Driver while servicing P makes upcalls to Venus. Such an
280 upcall is dispatched to Venus by creating a message structure. The
281 structure contains the identification of P, the message sequence
282 number, the size of the request and a pointer to the data in kernel
283 memory for the request. Since the data buffer is re-used to hold the
284 reply from Venus, there is a field for the size of the reply. A flags
285 field is used in the message to precisely record the status of the
286 message. Additional platform dependent structures involve pointers to
287 determine the position of the message on queues and pointers to
288 synchronization objects. In the upcall routine the message structure
289 is filled in, flags are set to 0, and it is placed on the _p_e_n_d_i_n_g
290 queue. The routine calling upcall is responsible for allocating the
291 data buffer; its structure will be described in the next section.
292
293 A facility must exist to notify Venus that the message has been
294 created, and implemented using available synchronization objects in
295 the OS. This notification is done in the upcall context of the process
296 P. When the message is on the pending queue, process P cannot proceed
297 in upcall. The (kernel mode) processing of P in the filesystem
298 request routine must be suspended until Venus has replied. Therefore
299 the calling thread in P is blocked in upcall. A pointer in the
300 message structure will locate the synchronization object on which P is
301 sleeping.
302
303 Venus detects the notification that a message has arrived, and the FS
304 driver allow Venus to retrieve the message with a getmsg_from_kernel
305 call. This action finishes in the kernel by putting the message on the
306 queue of processing messages and setting flags to READ. Venus is
307 passed the contents of the data buffer. The getmsg_from_kernel call
308 now returns and Venus processes the request.
309
310 At some later point the FS driver receives a message from Venus,
311 namely when Venus calls sendmsg_to_kernel. At this moment the Coda FS
312 driver looks at the contents of the message and decides if:
313
314
315 +o the message is a reply for a suspended thread P. If so it removes
316 the message from the processing queue and marks the message as
317 WRITTEN. Finally, the FS driver unblocks P (still in the kernel
318 mode context of Venus) and the sendmsg_to_kernel call returns to
319 Venus. The process P will be scheduled at some point and continues
320 processing its upcall with the data buffer replaced with the reply
321 from Venus.
322
323 +o The message is a _d_o_w_n_c_a_l_l. A downcall is a request from Venus to
324 the FS Driver. The FS driver processes the request immediately
325 (usually a cache eviction or replacement) and when it finishes
326 sendmsg_to_kernel returns.
327
328 Now P awakes and continues processing upcall. There are some
329 subtleties to take account of. First P will determine if it was woken
330 up in upcall by a signal from some other source (for example an
331 attempt to terminate P) or as is normally the case by Venus in its
332 sendmsg_to_kernel call. In the normal case, the upcall routine will
333 deallocate the message structure and return. The FS routine can proceed
334 with its processing.
335
336
337
338
339
340
341
342 Sleeping and IPC arrangements
343
344 In case P is woken up by a signal and not by Venus, it will first look
345 at the flags field. If the message is not yet READ, the process P can
346 handle its signal without notifying Venus. If Venus has READ, and
347 the request should not be processed, P can send Venus a signal message
348 to indicate that it should disregard the previous message. Such
349 signals are put in the queue at the head, and read first by Venus. If
350 the message is already marked as WRITTEN it is too late to stop the
351 processing. The VFS routine will now continue. (-- If a VFS request
352 involves more than one upcall, this can lead to complicated state, an
353 extra field "handle_signals" could be added in the message structure
354 to indicate points of no return have been passed.--)
355
356
357
358 33..11.. IImmpplleemmeennttaattiioonn ddeettaaiillss
359
360 The Unix implementation of this mechanism has been through the
361 implementation of a character device associated with Coda. Venus
362 retrieves messages by doing a read on the device, replies are sent
363 with a write and notification is through the select system call on the
364 file descriptor for the device. The process P is kept waiting on an
365 interruptible wait queue object.
366
367 In Windows NT and the DPMI Windows 95 implementation a DeviceIoControl
368 call is used. The DeviceIoControl call is designed to copy buffers
369 from user memory to kernel memory with OPCODES. The sendmsg_to_kernel
370 is issued as a synchronous call, while the getmsg_from_kernel call is
371 asynchronous. Windows EventObjects are used for notification of
372 message arrival. The process P is kept waiting on a KernelEvent
373 object in NT and a semaphore in Windows 95.
374
375 0wpage
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377 44.. TThhee iinntteerrffaaccee aatt tthhee ccaallll lleevveell
378
379
380 This section describes the upcalls a Coda FS driver can make to Venus.
381 Each of these upcalls make use of two structures: inputArgs and
382 outputArgs. In pseudo BNF form the structures take the following
383 form:
384
385
386 struct inputArgs {
387 u_long opcode;
388 u_long unique; /* Keep multiple outstanding msgs distinct */
389 u_short pid; /* Common to all */
390 u_short pgid; /* Common to all */
391 struct CodaCred cred; /* Common to all */
392
393 <union "in" of call dependent parts of inputArgs>
394 };
395
396 struct outputArgs {
397 u_long opcode;
398 u_long unique; /* Keep multiple outstanding msgs distinct */
399 u_long result;
400
401 <union "out" of call dependent parts of inputArgs>
402 };
403
404
405
406 Before going on let us elucidate the role of the various fields. The
407 inputArgs start with the opcode which defines the type of service
408 requested from Venus. There are approximately 30 upcalls at present
409 which we will discuss. The unique field labels the inputArg with a
410 unique number which will identify the message uniquely. A process and
411 process group id are passed. Finally the credentials of the caller
412 are included.
413
414 Before delving into the specific calls we need to discuss a variety of
415 data structures shared by the kernel and Venus.
416
417
418
419
420 44..11.. DDaattaa ssttrruuccttuurreess sshhaarreedd bbyy tthhee kkeerrnneell aanndd VVeennuuss
421
422
423 The CodaCred structure defines a variety of user and group ids as
424 they are set for the calling process. The vuid_t and vgid_t are 32 bit
425 unsigned integers. It also defines group membership in an array. On
426 Unix the CodaCred has proven sufficient to implement good security
427 semantics for Coda but the structure may have to undergo modification
428 for the Windows environment when these mature.
429
430 struct CodaCred {
431 vuid_t cr_uid, cr_euid, cr_suid, cr_fsuid; /* Real, effective, set, fs uid */
432 vgid_t cr_gid, cr_egid, cr_sgid, cr_fsgid; /* same for groups */
433 vgid_t cr_groups[NGROUPS]; /* Group membership for caller */
434 };
435
436
437
438 NNOOTTEE It is questionable if we need CodaCreds in Venus. Finally Venus
439 doesn't know about groups, although it does create files with the
440 default uid/gid. Perhaps the list of group membership is superfluous.
441
442
443 The next item is the fundamental identifier used to identify Coda
444 files, the ViceFid. A fid of a file uniquely defines a file or
445 directory in the Coda filesystem within a _c_e_l_l. (-- A _c_e_l_l is a
446 group of Coda servers acting under the aegis of a single system
447 control machine or SCM. See the Coda Administration manual for a
448 detailed description of the role of the SCM.--)
449
450
451 typedef struct ViceFid {
452 VolumeId Volume;
453 VnodeId Vnode;
454 Unique_t Unique;
455 } ViceFid;
456
457
458
459 Each of the constituent fields: VolumeId, VnodeId and Unique_t are
460 unsigned 32 bit integers. We envisage that a further field will need
461 to be prefixed to identify the Coda cell; this will probably take the
462 form of a Ipv6 size IP address naming the Coda cell through DNS.
463
464 The next important structure shared between Venus and the kernel is
465 the attributes of the file. The following structure is used to
466 exchange information. It has room for future extensions such as
467 support for device files (currently not present in Coda).
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484 struct coda_timespec {
485 int64_t tv_sec; /* seconds */
486 long tv_nsec; /* nanoseconds */
487 };
488
489 struct coda_vattr {
490 enum coda_vtype va_type; /* vnode type (for create) */
491 u_short va_mode; /* files access mode and type */
492 short va_nlink; /* number of references to file */
493 vuid_t va_uid; /* owner user id */
494 vgid_t va_gid; /* owner group id */
495 long va_fsid; /* file system id (dev for now) */
496 long va_fileid; /* file id */
497 u_quad_t va_size; /* file size in bytes */
498 long va_blocksize; /* blocksize preferred for i/o */
499 struct coda_timespec va_atime; /* time of last access */
500 struct coda_timespec va_mtime; /* time of last modification */
501 struct coda_timespec va_ctime; /* time file changed */
502 u_long va_gen; /* generation number of file */
503 u_long va_flags; /* flags defined for file */
504 dev_t va_rdev; /* device special file represents */
505 u_quad_t va_bytes; /* bytes of disk space held by file */
506 u_quad_t va_filerev; /* file modification number */
507 u_int va_vaflags; /* operations flags, see below */
508 long va_spare; /* remain quad aligned */
509 };
510
511
512
513
514 44..22.. TThhee ppiiooccttll iinntteerrffaaccee
515
516
517 Coda specific requests can be made by application through the pioctl
518 interface. The pioctl is implemented as an ordinary ioctl on a
519 fictitious file /coda/.CONTROL. The pioctl call opens this file, gets
520 a file handle and makes the ioctl call. Finally it closes the file.
521
522 The kernel involvement in this is limited to providing the facility to
523 open and close and pass the ioctl message _a_n_d to verify that a path in
524 the pioctl data buffers is a file in a Coda filesystem.
525
526 The kernel is handed a data packet of the form:
527
528 struct {
529 const char *path;
530 struct ViceIoctl vidata;
531 int follow;
532 } data;
533
534
535
536 where
537
538
539 struct ViceIoctl {
540 caddr_t in, out; /* Data to be transferred in, or out */
541 short in_size; /* Size of input buffer <= 2K */
542 short out_size; /* Maximum size of output buffer, <= 2K */
543 };
544
545
546
547 The path must be a Coda file, otherwise the ioctl upcall will not be
548 made.
549
550 NNOOTTEE The data structures and code are a mess. We need to clean this
551 up.
552
553 We now proceed to document the individual calls:
554
555 0wpage
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557 44..33.. rroooott
558
559
560 AArrgguummeennttss
561
562 iinn empty
563
564 oouutt
565
566 struct cfs_root_out {
567 ViceFid VFid;
568 } cfs_root;
569
570
571
572 DDeessccrriippttiioonn This call is made to Venus during the initialization of
573 the Coda filesystem. If the result is zero, the cfs_root structure
574 contains the ViceFid of the root of the Coda filesystem. If a non-zero
575 result is generated, its value is a platform dependent error code
576 indicating the difficulty Venus encountered in locating the root of
577 the Coda filesystem.
578
579 0wpage
580
581 44..44.. llooookkuupp
582
583
584 SSuummmmaarryy Find the ViceFid and type of an object in a directory if it
585 exists.
586
587 AArrgguummeennttss
588
589 iinn
590
591 struct cfs_lookup_in {
592 ViceFid VFid;
593 char *name; /* Place holder for data. */
594 } cfs_lookup;
595
596
597
598 oouutt
599
600 struct cfs_lookup_out {
601 ViceFid VFid;
602 int vtype;
603 } cfs_lookup;
604
605
606
607 DDeessccrriippttiioonn This call is made to determine the ViceFid and filetype of
608 a directory entry. The directory entry requested carries name name
609 and Venus will search the directory identified by cfs_lookup_in.VFid.
610 The result may indicate that the name does not exist, or that
611 difficulty was encountered in finding it (e.g. due to disconnection).
612 If the result is zero, the field cfs_lookup_out.VFid contains the
613 targets ViceFid and cfs_lookup_out.vtype the coda_vtype giving the
614 type of object the name designates.
615
616 The name of the object is an 8 bit character string of maximum length
617 CFS_MAXNAMLEN, currently set to 256 (including a 0 terminator.)
618
619 It is extremely important to realize that Venus bitwise ors the field
620 cfs_lookup.vtype with CFS_NOCACHE to indicate that the object should
621 not be put in the kernel name cache.
622
623 NNOOTTEE The type of the vtype is currently wrong. It should be
624 coda_vtype. Linux does not take note of CFS_NOCACHE. It should.
625
626 0wpage
627
628 44..55.. ggeettaattttrr
629
630
631 SSuummmmaarryy Get the attributes of a file.
632
633 AArrgguummeennttss
634
635 iinn
636
637 struct cfs_getattr_in {
638 ViceFid VFid;
639 struct coda_vattr attr; /* XXXXX */
640 } cfs_getattr;
641
642
643
644 oouutt
645
646 struct cfs_getattr_out {
647 struct coda_vattr attr;
648 } cfs_getattr;
649
650
651
652 DDeessccrriippttiioonn This call returns the attributes of the file identified by
653 fid.
654
655 EErrrroorrss Errors can occur if the object with fid does not exist, is
656 unaccessible or if the caller does not have permission to fetch
657 attributes.
658
659 NNoottee Many kernel FS drivers (Linux, NT and Windows 95) need to acquire
660 the attributes as well as the Fid for the instantiation of an internal
661 "inode" or "FileHandle". A significant improvement in performance on
662 such systems could be made by combining the _l_o_o_k_u_p and _g_e_t_a_t_t_r calls
663 both at the Venus/kernel interaction level and at the RPC level.
664
665 The vattr structure included in the input arguments is superfluous and
666 should be removed.
667
668 0wpage
669
670 44..66.. sseettaattttrr
671
672
673 SSuummmmaarryy Set the attributes of a file.
674
675 AArrgguummeennttss
676
677 iinn
678
679 struct cfs_setattr_in {
680 ViceFid VFid;
681 struct coda_vattr attr;
682 } cfs_setattr;
683
684
685
686
687 oouutt
688 empty
689
690 DDeessccrriippttiioonn The structure attr is filled with attributes to be changed
691 in BSD style. Attributes not to be changed are set to -1, apart from
692 vtype which is set to VNON. Other are set to the value to be assigned.
693 The only attributes which the FS driver may request to change are the
694 mode, owner, groupid, atime, mtime and ctime. The return value
695 indicates success or failure.
696
697 EErrrroorrss A variety of errors can occur. The object may not exist, may
698 be inaccessible, or permission may not be granted by Venus.
699
700 0wpage
701
702 44..77.. aacccceessss
703
704
705 SSuummmmaarryy
706
707 AArrgguummeennttss
708
709 iinn
710
711 struct cfs_access_in {
712 ViceFid VFid;
713 int flags;
714 } cfs_access;
715
716
717
718 oouutt
719 empty
720
721 DDeessccrriippttiioonn Verify if access to the object identified by VFid for
722 operations described by flags is permitted. The result indicates if
723 access will be granted. It is important to remember that Coda uses
724 ACLs to enforce protection and that ultimately the servers, not the
725 clients enforce the security of the system. The result of this call
726 will depend on whether a _t_o_k_e_n is held by the user.
727
728 EErrrroorrss The object may not exist, or the ACL describing the protection
729 may not be accessible.
730
731 0wpage
732
733 44..88.. ccrreeaattee
734
735
736 SSuummmmaarryy Invoked to create a file
737
738 AArrgguummeennttss
739
740 iinn
741
742 struct cfs_create_in {
743 ViceFid VFid;
744 struct coda_vattr attr;
745 int excl;
746 int mode;
747 char *name; /* Place holder for data. */
748 } cfs_create;
749
750
751
752
753 oouutt
754
755 struct cfs_create_out {
756 ViceFid VFid;
757 struct coda_vattr attr;
758 } cfs_create;
759
760
761
762 DDeessccrriippttiioonn This upcall is invoked to request creation of a file.
763 The file will be created in the directory identified by VFid, its name
764 will be name, and the mode will be mode. If excl is set an error will
765 be returned if the file already exists. If the size field in attr is
766 set to zero the file will be truncated. The uid and gid of the file
767 are set by converting the CodaCred to a uid using a macro CRTOUID
768 (this macro is platform dependent). Upon success the VFid and
769 attributes of the file are returned. The Coda FS Driver will normally
770 instantiate a vnode, inode or file handle at kernel level for the new
771 object.
772
773
774 EErrrroorrss A variety of errors can occur. Permissions may be insufficient.
775 If the object exists and is not a file the error EISDIR is returned
776 under Unix.
777
778 NNOOTTEE The packing of parameters is very inefficient and appears to
779 indicate confusion between the system call creat and the VFS operation
780 create. The VFS operation create is only called to create new objects.
781 This create call differs from the Unix one in that it is not invoked
782 to return a file descriptor. The truncate and exclusive options,
783 together with the mode, could simply be part of the mode as it is
784 under Unix. There should be no flags argument; this is used in open
785 (2) to return a file descriptor for READ or WRITE mode.
786
787 The attributes of the directory should be returned too, since the size
788 and mtime changed.
789
790 0wpage
791
792 44..99.. mmkkddiirr
793
794
795 SSuummmmaarryy Create a new directory.
796
797 AArrgguummeennttss
798
799 iinn
800
801 struct cfs_mkdir_in {
802 ViceFid VFid;
803 struct coda_vattr attr;
804 char *name; /* Place holder for data. */
805 } cfs_mkdir;
806
807
808
809 oouutt
810
811 struct cfs_mkdir_out {
812 ViceFid VFid;
813 struct coda_vattr attr;
814 } cfs_mkdir;
815
816
817
818
819 DDeessccrriippttiioonn This call is similar to create but creates a directory.
820 Only the mode field in the input parameters is used for creation.
821 Upon successful creation, the attr returned contains the attributes of
822 the new directory.
823
824 EErrrroorrss As for create.
825
826 NNOOTTEE The input parameter should be changed to mode instead of
827 attributes.
828
829 The attributes of the parent should be returned since the size and
830 mtime changes.
831
832 0wpage
833
834 44..1100.. lliinnkk
835
836
837 SSuummmmaarryy Create a link to an existing file.
838
839 AArrgguummeennttss
840
841 iinn
842
843 struct cfs_link_in {
844 ViceFid sourceFid; /* cnode to link *to* */
845 ViceFid destFid; /* Directory in which to place link */
846 char *tname; /* Place holder for data. */
847 } cfs_link;
848
849
850
851 oouutt
852 empty
853
854 DDeessccrriippttiioonn This call creates a link to the sourceFid in the directory
855 identified by destFid with name tname. The source must reside in the
856 target's parent, i.e. the source must be have parent destFid, i.e. Coda
857 does not support cross directory hard links. Only the return value is
858 relevant. It indicates success or the type of failure.
859
860 EErrrroorrss The usual errors can occur.0wpage
861
862 44..1111.. ssyymmlliinnkk
863
864
865 SSuummmmaarryy create a symbolic link
866
867 AArrgguummeennttss
868
869 iinn
870
871 struct cfs_symlink_in {
872 ViceFid VFid; /* Directory to put symlink in */
873 char *srcname;
874 struct coda_vattr attr;
875 char *tname;
876 } cfs_symlink;
877
878
879
880 oouutt
881 none
882
883 DDeessccrriippttiioonn Create a symbolic link. The link is to be placed in the
884 directory identified by VFid and named tname. It should point to the
885 pathname srcname. The attributes of the newly created object are to
886 be set to attr.
887
888 EErrrroorrss
889
890 NNOOTTEE The attributes of the target directory should be returned since
891 its size changed.
892
893 0wpage
894
895 44..1122.. rreemmoovvee
896
897
898 SSuummmmaarryy Remove a file
899
900 AArrgguummeennttss
901
902 iinn
903
904 struct cfs_remove_in {
905 ViceFid VFid;
906 char *name; /* Place holder for data. */
907 } cfs_remove;
908
909
910
911 oouutt
912 none
913
914 DDeessccrriippttiioonn Remove file named cfs_remove_in.name in directory
915 identified by VFid.
916
917 EErrrroorrss
918
919 NNOOTTEE The attributes of the directory should be returned since its
920 mtime and size may change.
921
922 0wpage
923
924 44..1133.. rrmmddiirr
925
926
927 SSuummmmaarryy Remove a directory
928
929 AArrgguummeennttss
930
931 iinn
932
933 struct cfs_rmdir_in {
934 ViceFid VFid;
935 char *name; /* Place holder for data. */
936 } cfs_rmdir;
937
938
939
940 oouutt
941 none
942
943 DDeessccrriippttiioonn Remove the directory with name name from the directory
944 identified by VFid.
945
946 EErrrroorrss
947
948 NNOOTTEE The attributes of the parent directory should be returned since
949 its mtime and size may change.
950
951 0wpage
952
953 44..1144.. rreeaaddlliinnkk
954
955
956 SSuummmmaarryy Read the value of a symbolic link.
957
958 AArrgguummeennttss
959
960 iinn
961
962 struct cfs_readlink_in {
963 ViceFid VFid;
964 } cfs_readlink;
965
966
967
968 oouutt
969
970 struct cfs_readlink_out {
971 int count;
972 caddr_t data; /* Place holder for data. */
973 } cfs_readlink;
974
975
976
977 DDeessccrriippttiioonn This routine reads the contents of symbolic link
978 identified by VFid into the buffer data. The buffer data must be able
979 to hold any name up to CFS_MAXNAMLEN (PATH or NAM??).
980
981 EErrrroorrss No unusual errors.
982
983 0wpage
984
985 44..1155.. ooppeenn
986
987
988 SSuummmmaarryy Open a file.
989
990 AArrgguummeennttss
991
992 iinn
993
994 struct cfs_open_in {
995 ViceFid VFid;
996 int flags;
997 } cfs_open;
998
999
1000
1001 oouutt
1002
1003 struct cfs_open_out {
1004 dev_t dev;
1005 ino_t inode;
1006 } cfs_open;
1007
1008
1009
1010 DDeessccrriippttiioonn This request asks Venus to place the file identified by
1011 VFid in its cache and to note that the calling process wishes to open
1012 it with flags as in open(2). The return value to the kernel differs
1013 for Unix and Windows systems. For Unix systems the Coda FS Driver is
1014 informed of the device and inode number of the container file in the
1015 fields dev and inode. For Windows the path of the container file is
1016 returned to the kernel.
1017 EErrrroorrss
1018
1019 NNOOTTEE Currently the cfs_open_out structure is not properly adapted to
1020 deal with the Windows case. It might be best to implement two
1021 upcalls, one to open aiming at a container file name, the other at a
1022 container file inode.
1023
1024 0wpage
1025
1026 44..1166.. cclloossee
1027
1028
1029 SSuummmmaarryy Close a file, update it on the servers.
1030
1031 AArrgguummeennttss
1032
1033 iinn
1034
1035 struct cfs_close_in {
1036 ViceFid VFid;
1037 int flags;
1038 } cfs_close;
1039
1040
1041
1042 oouutt
1043 none
1044
1045 DDeessccrriippttiioonn Close the file identified by VFid.
1046
1047 EErrrroorrss
1048
1049 NNOOTTEE The flags argument is bogus and not used. However, Venus' code
1050 has room to deal with an execp input field, probably this field should
1051 be used to inform Venus that the file was closed but is still memory
1052 mapped for execution. There are comments about fetching versus not
1053 fetching the data in Venus vproc_vfscalls. This seems silly. If a
1054 file is being closed, the data in the container file is to be the new
1055 data. Here again the execp flag might be in play to create confusion:
1056 currently Venus might think a file can be flushed from the cache when
1057 it is still memory mapped. This needs to be understood.
1058
1059 0wpage
1060
1061 44..1177.. iiooccttll
1062
1063
1064 SSuummmmaarryy Do an ioctl on a file. This includes the pioctl interface.
1065
1066 AArrgguummeennttss
1067
1068 iinn
1069
1070 struct cfs_ioctl_in {
1071 ViceFid VFid;
1072 int cmd;
1073 int len;
1074 int rwflag;
1075 char *data; /* Place holder for data. */
1076 } cfs_ioctl;
1077
1078
1079
1080 oouutt
1081
1082
1083 struct cfs_ioctl_out {
1084 int len;
1085 caddr_t data; /* Place holder for data. */
1086 } cfs_ioctl;
1087
1088
1089
1090 DDeessccrriippttiioonn Do an ioctl operation on a file. The command, len and
1091 data arguments are filled as usual. flags is not used by Venus.
1092
1093 EErrrroorrss
1094
1095 NNOOTTEE Another bogus parameter. flags is not used. What is the
1096 business about PREFETCHING in the Venus code?
1097
1098
1099 0wpage
1100
1101 44..1188.. rreennaammee
1102
1103
1104 SSuummmmaarryy Rename a fid.
1105
1106 AArrgguummeennttss
1107
1108 iinn
1109
1110 struct cfs_rename_in {
1111 ViceFid sourceFid;
1112 char *srcname;
1113 ViceFid destFid;
1114 char *destname;
1115 } cfs_rename;
1116
1117
1118
1119 oouutt
1120 none
1121
1122 DDeessccrriippttiioonn Rename the object with name srcname in directory
1123 sourceFid to destname in destFid. It is important that the names
1124 srcname and destname are 0 terminated strings. Strings in Unix
1125 kernels are not always null terminated.
1126
1127 EErrrroorrss
1128
1129 0wpage
1130
1131 44..1199.. rreeaaddddiirr
1132
1133
1134 SSuummmmaarryy Read directory entries.
1135
1136 AArrgguummeennttss
1137
1138 iinn
1139
1140 struct cfs_readdir_in {
1141 ViceFid VFid;
1142 int count;
1143 int offset;
1144 } cfs_readdir;
1145
1146
1147
1148
1149 oouutt
1150
1151 struct cfs_readdir_out {
1152 int size;
1153 caddr_t data; /* Place holder for data. */
1154 } cfs_readdir;
1155
1156
1157
1158 DDeessccrriippttiioonn Read directory entries from VFid starting at offset and
1159 read at most count bytes. Returns the data in data and returns
1160 the size in size.
1161
1162 EErrrroorrss
1163
1164 NNOOTTEE This call is not used. Readdir operations exploit container
1165 files. We will re-evaluate this during the directory revamp which is
1166 about to take place.
1167
1168 0wpage
1169
1170 44..2200.. vvggeett
1171
1172
1173 SSuummmmaarryy instructs Venus to do an FSDB->Get.
1174
1175 AArrgguummeennttss
1176
1177 iinn
1178
1179 struct cfs_vget_in {
1180 ViceFid VFid;
1181 } cfs_vget;
1182
1183
1184
1185 oouutt
1186
1187 struct cfs_vget_out {
1188 ViceFid VFid;
1189 int vtype;
1190 } cfs_vget;
1191
1192
1193
1194 DDeessccrriippttiioonn This upcall asks Venus to do a get operation on an fsobj
1195 labelled by VFid.
1196
1197 EErrrroorrss
1198
1199 NNOOTTEE This operation is not used. However, it is extremely useful
1200 since it can be used to deal with read/write memory mapped files.
1201 These can be "pinned" in the Venus cache using vget and released with
1202 inactive.
1203
1204 0wpage
1205
1206 44..2211.. ffssyynncc
1207
1208
1209 SSuummmmaarryy Tell Venus to update the RVM attributes of a file.
1210
1211 AArrgguummeennttss
1212
1213 iinn
1214
1215 struct cfs_fsync_in {
1216 ViceFid VFid;
1217 } cfs_fsync;
1218
1219
1220
1221 oouutt
1222 none
1223
1224 DDeessccrriippttiioonn Ask Venus to update RVM attributes of object VFid. This
1225 should be called as part of kernel level fsync type calls. The
1226 result indicates if the syncing was successful.
1227
1228 EErrrroorrss
1229
1230 NNOOTTEE Linux does not implement this call. It should.
1231
1232 0wpage
1233
1234 44..2222.. iinnaaccttiivvee
1235
1236
1237 SSuummmmaarryy Tell Venus a vnode is no longer in use.
1238
1239 AArrgguummeennttss
1240
1241 iinn
1242
1243 struct cfs_inactive_in {
1244 ViceFid VFid;
1245 } cfs_inactive;
1246
1247
1248
1249 oouutt
1250 none
1251
1252 DDeessccrriippttiioonn This operation returns EOPNOTSUPP.
1253
1254 EErrrroorrss
1255
1256 NNOOTTEE This should perhaps be removed.
1257
1258 0wpage
1259
1260 44..2233.. rrddwwrr
1261
1262
1263 SSuummmmaarryy Read or write from a file
1264
1265 AArrgguummeennttss
1266
1267 iinn
1268
1269 struct cfs_rdwr_in {
1270 ViceFid VFid;
1271 int rwflag;
1272 int count;
1273 int offset;
1274 int ioflag;
1275 caddr_t data; /* Place holder for data. */
1276 } cfs_rdwr;
1277
1278
1279
1280
1281 oouutt
1282
1283 struct cfs_rdwr_out {
1284 int rwflag;
1285 int count;
1286 caddr_t data; /* Place holder for data. */
1287 } cfs_rdwr;
1288
1289
1290
1291 DDeessccrriippttiioonn This upcall asks Venus to read or write from a file.
1292
1293 EErrrroorrss
1294
1295 NNOOTTEE It should be removed since it is against the Coda philosophy that
1296 read/write operations never reach Venus. I have been told the
1297 operation does not work. It is not currently used.
1298
1299
1300 0wpage
1301
1302 44..2244.. ooddyymmoouunntt
1303
1304
1305 SSuummmmaarryy Allows mounting multiple Coda "filesystems" on one Unix mount
1306 point.
1307
1308 AArrgguummeennttss
1309
1310 iinn
1311
1312 struct ody_mount_in {
1313 char *name; /* Place holder for data. */
1314 } ody_mount;
1315
1316
1317
1318 oouutt
1319
1320 struct ody_mount_out {
1321 ViceFid VFid;
1322 } ody_mount;
1323
1324
1325
1326 DDeessccrriippttiioonn Asks Venus to return the rootfid of a Coda system named
1327 name. The fid is returned in VFid.
1328
1329 EErrrroorrss
1330
1331 NNOOTTEE This call was used by David for dynamic sets. It should be
1332 removed since it causes a jungle of pointers in the VFS mounting area.
1333 It is not used by Coda proper. Call is not implemented by Venus.
1334
1335 0wpage
1336
1337 44..2255.. ooddyy__llooookkuupp
1338
1339
1340 SSuummmmaarryy Looks up something.
1341
1342 AArrgguummeennttss
1343
1344 iinn irrelevant
1345
1346
1347 oouutt
1348 irrelevant
1349
1350 DDeessccrriippttiioonn
1351
1352 EErrrroorrss
1353
1354 NNOOTTEE Gut it. Call is not implemented by Venus.
1355
1356 0wpage
1357
1358 44..2266.. ooddyy__eexxppaanndd
1359
1360
1361 SSuummmmaarryy expands something in a dynamic set.
1362
1363 AArrgguummeennttss
1364
1365 iinn irrelevant
1366
1367 oouutt
1368 irrelevant
1369
1370 DDeessccrriippttiioonn
1371
1372 EErrrroorrss
1373
1374 NNOOTTEE Gut it. Call is not implemented by Venus.
1375
1376 0wpage
1377
1378 44..2277.. pprreeffeettcchh
1379
1380
1381 SSuummmmaarryy Prefetch a dynamic set.
1382
1383 AArrgguummeennttss
1384
1385 iinn Not documented.
1386
1387 oouutt
1388 Not documented.
1389
1390 DDeessccrriippttiioonn Venus worker.cc has support for this call, although it is
1391 noted that it doesn't work. Not surprising, since the kernel does not
1392 have support for it. (ODY_PREFETCH is not a defined operation).
1393
1394 EErrrroorrss
1395
1396 NNOOTTEE Gut it. It isn't working and isn't used by Coda.
1397
1398
1399 0wpage
1400
1401 44..2288.. ssiiggnnaall
1402
1403
1404 SSuummmmaarryy Send Venus a signal about an upcall.
1405
1406 AArrgguummeennttss
1407
1408 iinn none
1409
1410 oouutt
1411 not applicable.
1412
1413 DDeessccrriippttiioonn This is an out-of-band upcall to Venus to inform Venus
1414 that the calling process received a signal after Venus read the
1415 message from the input queue. Venus is supposed to clean up the
1416 operation.
1417
1418 EErrrroorrss No reply is given.
1419
1420 NNOOTTEE We need to better understand what Venus needs to clean up and if
1421 it is doing this correctly. Also we need to handle multiple upcall
1422 per system call situations correctly. It would be important to know
1423 what state changes in Venus take place after an upcall for which the
1424 kernel is responsible for notifying Venus to clean up (e.g. open
1425 definitely is such a state change, but many others are maybe not).
1426
1427 0wpage
1428
1429 55.. TThhee mmiinniiccaacchhee aanndd ddoowwnnccaallllss
1430
1431
1432 The Coda FS Driver can cache results of lookup and access upcalls, to
1433 limit the frequency of upcalls. Upcalls carry a price since a process
1434 context switch needs to take place. The counterpart of caching the
1435 information is that Venus will notify the FS Driver that cached
1436 entries must be flushed or renamed.
1437
1438 The kernel code generally has to maintain a structure which links the
1439 internal file handles (called vnodes in BSD, inodes in Linux and
1440 FileHandles in Windows) with the ViceFid's which Venus maintains. The
1441 reason is that frequent translations back and forth are needed in
1442 order to make upcalls and use the results of upcalls. Such linking
1443 objects are called ccnnooddeess.
1444
1445 The current minicache implementations have cache entries which record
1446 the following:
1447
1448 1. the name of the file
1449
1450 2. the cnode of the directory containing the object
1451
1452 3. a list of CodaCred's for which the lookup is permitted.
1453
1454 4. the cnode of the object
1455
1456 The lookup call in the Coda FS Driver may request the cnode of the
1457 desired object from the cache, by passing its name, directory and the
1458 CodaCred's of the caller. The cache will return the cnode or indicate
1459 that it cannot be found. The Coda FS Driver must be careful to
1460 invalidate cache entries when it modifies or removes objects.
1461
1462 When Venus obtains information that indicates that cache entries are
1463 no longer valid, it will make a downcall to the kernel. Downcalls are
1464 intercepted by the Coda FS Driver and lead to cache invalidations of
1465 the kind described below. The Coda FS Driver does not return an error
1466 unless the downcall data could not be read into kernel memory.
1467
1468
1469 55..11.. IINNVVAALLIIDDAATTEE
1470
1471
1472 No information is available on this call.
1473
1474
1475 55..22.. FFLLUUSSHH
1476
1477
1478
1479 AArrgguummeennttss None
1480
1481 SSuummmmaarryy Flush the name cache entirely.
1482
1483 DDeessccrriippttiioonn Venus issues this call upon startup and when it dies. This
1484 is to prevent stale cache information being held. Some operating
1485 systems allow the kernel name cache to be switched off dynamically.
1486 When this is done, this downcall is made.
1487
1488
1489 55..33.. PPUURRGGEEUUSSEERR
1490
1491
1492 AArrgguummeennttss
1493
1494 struct cfs_purgeuser_out {/* CFS_PURGEUSER is a venus->kernel call */
1495 struct CodaCred cred;
1496 } cfs_purgeuser;
1497
1498
1499
1500 DDeessccrriippttiioonn Remove all entries in the cache carrying the Cred. This
1501 call is issued when tokens for a user expire or are flushed.
1502
1503
1504 55..44.. ZZAAPPFFIILLEE
1505
1506
1507 AArrgguummeennttss
1508
1509 struct cfs_zapfile_out { /* CFS_ZAPFILE is a venus->kernel call */
1510 ViceFid CodaFid;
1511 } cfs_zapfile;
1512
1513
1514
1515 DDeessccrriippttiioonn Remove all entries which have the (dir vnode, name) pair.
1516 This is issued as a result of an invalidation of cached attributes of
1517 a vnode.
1518
1519 NNOOTTEE Call is not named correctly in NetBSD and Mach. The minicache
1520 zapfile routine takes different arguments. Linux does not implement
1521 the invalidation of attributes correctly.
1522
1523
1524
1525 55..55.. ZZAAPPDDIIRR
1526
1527
1528 AArrgguummeennttss
1529
1530 struct cfs_zapdir_out { /* CFS_ZAPDIR is a venus->kernel call */
1531 ViceFid CodaFid;
1532 } cfs_zapdir;
1533
1534
1535
1536 DDeessccrriippttiioonn Remove all entries in the cache lying in a directory
1537 CodaFid, and all children of this directory. This call is issued when
1538 Venus receives a callback on the directory.
1539
1540
1541 55..66.. ZZAAPPVVNNOODDEE
1542
1543
1544
1545 AArrgguummeennttss
1546
1547 struct cfs_zapvnode_out { /* CFS_ZAPVNODE is a venus->kernel call */
1548 struct CodaCred cred;
1549 ViceFid VFid;
1550 } cfs_zapvnode;
1551
1552
1553
1554 DDeessccrriippttiioonn Remove all entries in the cache carrying the cred and VFid
1555 as in the arguments. This downcall is probably never issued.
1556
1557
1558 55..77.. PPUURRGGEEFFIIDD
1559
1560
1561 SSuummmmaarryy
1562
1563 AArrgguummeennttss
1564
1565 struct cfs_purgefid_out { /* CFS_PURGEFID is a venus->kernel call */
1566 ViceFid CodaFid;
1567 } cfs_purgefid;
1568
1569
1570
1571 DDeessccrriippttiioonn Flush the attribute for the file. If it is a dir (odd
1572 vnode), purge its children from the namecache and remove the file from the
1573 namecache.
1574
1575
1576
1577 55..88.. RREEPPLLAACCEE
1578
1579
1580 SSuummmmaarryy Replace the Fid's for a collection of names.
1581
1582 AArrgguummeennttss
1583
1584 struct cfs_replace_out { /* cfs_replace is a venus->kernel call */
1585 ViceFid NewFid;
1586 ViceFid OldFid;
1587 } cfs_replace;
1588
1589
1590
1591 DDeessccrriippttiioonn This routine replaces a ViceFid in the name cache with
1592 another. It is added to allow Venus during reintegration to replace
1593 locally allocated temp fids while disconnected with global fids even
1594 when the reference counts on those fids are not zero.
1595
1596 0wpage
1597
1598 66.. IInniittiiaalliizzaattiioonn aanndd cclleeaannuupp
1599
1600
1601 This section gives brief hints as to desirable features for the Coda
1602 FS Driver at startup and upon shutdown or Venus failures. Before
1603 entering the discussion it is useful to repeat that the Coda FS Driver
1604 maintains the following data:
1605
1606
1607 1. message queues
1608
1609 2. cnodes
1610
1611 3. name cache entries
1612
1613 The name cache entries are entirely private to the driver, so they
1614 can easily be manipulated. The message queues will generally have
1615 clear points of initialization and destruction. The cnodes are
1616 much more delicate. User processes hold reference counts in Coda
1617 filesystems and it can be difficult to clean up the cnodes.
1618
1619 It can expect requests through:
1620
1621 1. the message subsystem
1622
1623 2. the VFS layer
1624
1625 3. pioctl interface
1626
1627 Currently the _p_i_o_c_t_l passes through the VFS for Coda so we can
1628 treat these similarly.
1629
1630
1631 66..11.. RReeqquuiirreemmeennttss
1632
1633
1634 The following requirements should be accommodated:
1635
1636 1. The message queues should have open and close routines. On Unix
1637 the opening of the character devices are such routines.
1638
1639 +o Before opening, no messages can be placed.
1640
1641 +o Opening will remove any old messages still pending.
1642
1643 +o Close will notify any sleeping processes that their upcall cannot
1644 be completed.
1645
1646 +o Close will free all memory allocated by the message queues.
1647
1648
1649 2. At open the namecache shall be initialized to empty state.
1650
1651 3. Before the message queues are open, all VFS operations will fail.
1652 Fortunately this can be achieved by making sure than mounting the
1653 Coda filesystem cannot succeed before opening.
1654
1655 4. After closing of the queues, no VFS operations can succeed. Here
1656 one needs to be careful, since a few operations (lookup,
1657 read/write, readdir) can proceed without upcalls. These must be
1658 explicitly blocked.
1659
1660 5. Upon closing the namecache shall be flushed and disabled.
1661
1662 6. All memory held by cnodes can be freed without relying on upcalls.
1663
1664 7. Unmounting the file system can be done without relying on upcalls.
1665
1666 8. Mounting the Coda filesystem should fail gracefully if Venus cannot
1667 get the rootfid or the attributes of the rootfid. The latter is
1668 best implemented by Venus fetching these objects before attempting
1669 to mount.
1670
1671 NNOOTTEE NetBSD in particular but also Linux have not implemented the
1672 above requirements fully. For smooth operation this needs to be
1673 corrected.
1674
1675
1676