1 '\" te
2 .\" Copyright (c) 2005 Sun Microsystems, Inc. All Rights Reserved.
3 .\" The contents of this file are subject to the terms of the Common Development and Distribution License (the "License"). You may not use this file except in compliance with the License.
4 .\" You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE or http://www.opensolaris.org/os/licensing. See the License for the specific language governing permissions and limitations under the License.
5 .\" When distributing Covered Code, include this CDDL HEADER in each file and include the License file at usr/src/OPENSOLARIS.LICENSE. If applicable, add the following below this CDDL HEADER, with the fields enclosed by brackets "[]" replaced with your own identifying information: Portions Copyright [yyyy] [name of copyright owner]
6 .TH MHD 7I "Mar 18, 2011"
7 .SH NAME
8 mhd \- multihost disk control operations
9 .SH SYNOPSIS
10 .LP
11 .nf
12 \fB#include\fR \fB<sys/mhd.h>\fR
13 .fi
14
15 .SH DESCRIPTION
16 .sp
17 .LP
18 The \fBmhd\fR \fBioctl\fR(2) control access rights of a multihost disk, using
19 disk reservations on the disk device.
20 .sp
21 .LP
22 The stability level of this interface (see \fBattributes\fR(5)) is evolving. As
23 a result, the interface is subject to change and you should limit your use of
24 it.
25 .sp
26 .LP
27 The mhd ioctls fall into two major categories: (1) ioctls for non-shared
28 multihost disks and (2) ioctls for shared multihost disks.
29 .sp
30 .LP
31 One ioctl, \fBMHIOCENFAILFAST\fR, is applicable to both non-shared and shared
32 multihost disks. It is described after the first two categories.
33 .sp
34 .LP
35 All the ioctls require root privilege.
36 .sp
37 .LP
38 For all of the ioctls, the caller should obtain the file descriptor for the
39 device by calling \fBopen\fR(2) with the \fBO_NDELAY\fR flag; without the
40 \fBO_NDELAY\fR flag, the open may fail due to another host already having a
41 conflicting reservation on the device. Some of the ioctls below permit the
42 caller to forcibly clear a conflicting reservation held by another host,
43 however, in order to call the ioctl, the caller must first obtain the open file
44 descriptor.
45 .SS "Non-shared multihost disks"
46 .sp
47 .LP
48 Non-shared multihost disks ioctls consist of \fBMHIOCTKOWN\fR,
49 \fBMHIOCRELEASE\fR, \fBHIOCSTATUS\fR, and \fBMHIOCQRESERVE\fR. These ioctl
50 requests control the access rights of non-shared multihost disks. A non-shared
51 multihost disk is one that supports serialized, mutually exclusive I/O mastery
52 by the connected hosts. This is in contrast to the shared-disk model, in which
53 concurrent access is allowed from more than one host (see below).
54 .sp
55 .LP
56 A non-shared multihost disk can be in one of two states:
57 .RS +4
58 .TP
59 .ie t \(bu
60 .el o
61 Exclusive access state, where only one connected host has I/O access
62 .RE
63 .RS +4
64 .TP
65 .ie t \(bu
66 .el o
67 Non-exclusive access state, where all connected hosts have I/O access. An
68 external hardware reset can cause the disk to enter the non-exclusive access
69 state.
70 .RE
71 .sp
72 .LP
73 Each multihost disk driver views the machine on which it's running as the
74 "local host"; each views all other machines as "remote hosts". For each I/O or
75 ioctl request, the requesting host is the local host.
76 .sp
77 .LP
78 Note that the non-shared ioctls are designed to work with SCSI-2 disks. The
79 SCSI-2 RESERVE/RELEASE command set is the underlying hardware facility in the
80 device that supports the non-shared ioctls.
81 .sp
82 .LP
83 The function prototypes for the non-shared ioctls are:
84 .sp
85 .in +2
86 .nf
87 ioctl(fd, MHIOCTKOWN);
88 ioctl(fd, MHIOCRELEASE);
89 ioctl(fd, MHIOCSTATUS);
90 ioctl(fd, MHIOCQRESERVE);
91 .fi
92 .in -2
93
94 .sp
95 .ne 2
96 .na
97 \fB\fBMHIOCTKOWN\fR \fR
98 .ad
99 .RS 18n
100 Forcefully acquires exclusive access rights to the multihost disk for the local
101 host. Revokes all access rights to the multihost disk from remote hosts.
102 Causes the disk to enter the exclusive access state.
103 .sp
104 Implementation Note: Reservations (exclusive access rights) broken via random
105 resets should be reinstated by the driver upon their detection, for example, in
106 the automatic probe function described below.
107 .RE
108
109 .sp
110 .ne 2
111 .na
112 \fB\fBMHIOCRELEASE\fR \fR
113 .ad
114 .RS 18n
115 Relinquishes exclusive access rights to the multihost disk for the local host.
116 On success, causes the disk to enter the non- exclusive access state.
117 .RE
118
119 .sp
120 .ne 2
121 .na
122 \fB\fBMHIOCSTATUS\fR \fR
123 .ad
124 .RS 18n
125 Probes a multihost disk to determine whether the local host has access rights
126 to the disk. Returns \fB0\fR if the local host has access to the disk,
127 \fB1\fR if it doesn't, and \fB-1\fR with errno set to \fBEIO\fR if the probe
128 failed for some other reason.
129 .RE
130
131 .sp
132 .ne 2
133 .na
134 \fB\fBMHIOCQRESERVE\fR \fR
135 .ad
136 .RS 18n
137 Issues, simply and only, a SCSI-2 Reserve command. If the attempt to reserve
138 fails due to the SCSI error Reservation Conflict (which implies that some other
139 host has the device reserved), then the ioctl will return \fB-1\fR with errno
140 set to \fBEACCES\fR. The \fBMHIOCQRESERVE\fR ioctl does NOT issue a bus device
141 reset or bus reset prior to attempting the SCSI-2 reserve command. It also
142 does not take care of re-instating reservations that disappear due to bus
143 resets or bus device resets; if that behavior is desired, then the caller can
144 call \fBMHIOCTKOWN\fR after the \fBMHIOCQRESERVE\fR has returned success. If
145 the device does not support the SCSI-2 Reserve command, then the ioctl returns
146 \fB-1\fR with \fBerrno\fR set to \fBENOTSUP.\fR The \fBMHIOCQRESERVE\fR ioctl
147 is intended to be used by high-availability or clustering software for a
148 "quorum" disk, hence, the "Q" in the name of the ioctl.
149 .RE
150
151 .SS "Shared Multihost Disks"
152 .sp
153 .LP
154 Shared multihost disks ioctls control access to shared multihost disks. The
155 ioctls are merely a veneer on the SCSI-3 Persistent Reservation facility.
156 Therefore, the underlying semantic model is not described in detail here, see
157 instead the SCSI-3 standard. The SCSI-3 Persistent Reservations support the
158 concept of a group of hosts all sharing access to a disk.
159 .sp
160 .LP
161 The function prototypes and descriptions for the shared multihost ioctls are as
162 follows:
163 .sp
164 .ne 2
165 .na
166 \fB\fBioctl\fR(\fBfd\fR, \fBMHIOCGRP_INKEYS\fR, (\fBmhioc_inkeys_t\fR)
167 \fI*k\fR\fB);\fR\fR
168 .ad
169 .sp .6
170 .RS 4n
171 Issues the SCSI-3 command Persistent Reserve In Read Keys to the device. On
172 input, the field \fBk->li\fR should be initialized by the caller with
173 \fBk->li.listsize\fR reflecting how big of an array the caller has allocated
174 for the \fBk->li.list\fR field and with \fBk->li.listlen\fR \fB==\fR \fB0.\fR
175 On return, the field \fBk->li.listlen\fR is updated to indicate the number of
176 reservation keys the device currently has: if this value is larger than
177 \fBk->li.listsize\fR then that indicates that the caller should have passed a
178 bigger \fBk->li.list\fR array with a bigger \fBk->li.listsize.\fR The number of
179 array elements actually written by the callee into \fBk->li.list\fR is the
180 minimum of \fBk->li.listlen\fR and \fBk->li.listsize.\fR The field
181 k->generation is updated with the generation information returned by the SCSI-3
182 Read Keys query. If the device does not support SCSI-3 Persistent Reservations,
183 then this ioctl returns \fB-1\fR with \fBerrno\fR set to \fBENOTSUP\fR.
184 .RE
185
186 .sp
187 .ne 2
188 .na
189 \fB\fBioctl\fR(\fBfd\fR, \fBMHIOCGRP_INRESV\fR, (\fBmhioc_inresvs_t\fR)
190 \fI*r\fR\fB);\fR\fR
191 .ad
192 .sp .6
193 .RS 4n
194 Issues the SCSI-3 command Persistent Reserve In Read Reservations to the
195 device. Remarks similar to \fBMHIOCGRP_INKEYS\fR apply to the array
196 manipulation. If the device does not support SCSI-3 Persistent Reservations,
197 then this ioctl returns \fB-1\fR with \fBerrno\fR set to \fBENOTSUP\fR.
198 .RE
199
200 .sp
201 .ne 2
202 .na
203 \fB\fBioctl\fR(\fBfd\fR, \fBMHIOCGRP_REGISTER\fR, (\fBmhioc_register_t\fR)
204 \fI*r\fR\fB);\fR\fR
205 .ad
206 .sp .6
207 .RS 4n
208 Issues the SCSI-3 command Persistent Reserve Out Register. The fields of
209 structure \fIr\fR are all inputs; none of the fields are modified by the ioctl.
210 The field \fBr->aptpl\fR should be set to true to specify that registrations
211 and reservations should persist across device power failures, or to false to
212 specify that registrations and reservations should be cleared upon device power
213 failure; true is the recommended setting. The field \fBr->oldkey\fR is the key
214 that the caller believes the device may already have for this host initiator;
215 if the caller believes that that this host initiator is not already registered
216 with this device, it should pass the special key of all zeros. To achieve the
217 effect of unregistering with the device, the caller should pass its current key
218 for the \fBr->oldkey\fR field and an \fBr->newkey\fR field containing the
219 special key of all zeros. If the device returns the SCSI error code
220 Reservation Conflict, this ioctl returns \fB-1\fR with \fBerrno\fR set to
221 \fBEACCES\fR.
222 .RE
223
224 .sp
225 .ne 2
226 .na
227 \fB\fBioctl\fR(\fBfd\fR, \fBMHIOCGRP_RESERVE\fR, (\fBmhioc_resv_desc_t\fR)
228 \fI*r\fR\fB);\fR\fR
229 .ad
230 .sp .6
231 .RS 4n
232 Issues the SCSI-3 command Persistent Reserve Out Reserve. The fields of
233 structure \fIr\fR are all inputs; none of the fields are modified by the ioctl.
234 If the device returns the SCSI error code Reservation Conflict, this ioctl
235 returns \fB-1\fR with \fBerrno\fR set to \fBEACCES.\fR
236 .RE
237
238 .sp
239 .ne 2
240 .na
241 \fB\fBioctl\fR(\fBfd\fR, \fBMHIOCGRP_PREEMPTANDABORT\fR,
242 (\fBmhioc_preemptandabort_t\fR) \fI*r\fR\fB);\fR\fR
243 .ad
244 .sp .6
245 .RS 4n
246 Issues the SCSI-3 command Persistent Reserve Out Preempt-And-Abort. The fields
247 of structure \fIr\fR are all inputs; none of the fields are modified by the
248 ioctl. The key of the victim host is specified by the field
249 \fBr->victim_key\fR. The field \fBr->resvdesc\fR supplies the preempter's key
250 and the reservation that it is requesting as part of the SCSI-3
251 Preempt-And-Abort command. If the device returns the SCSI error code
252 Reservation Conflict, this ioctl returns \fB-1\fR with \fBerrno\fR set to
253 \fBEACCES.\fR
254 .RE
255
256 .sp
257 .ne 2
258 .na
259 \fB\fBioctl\fR(\fBfd\fR, \fBMHIOCGRP_PREEMPT\fR,
260 (\fBmhioc_preemptandabort_t\fR) \fI*r\fR\fB);\fR\fR
261 .ad
262 .sp .6
263 .RS 4n
264 Similar to \fBMHIOCGRP_PREEMPTANDABORT\fR, but instead issues the SCSI-3
265 command Persistent Reserve Out Preempt. (Note: This command is not
266 implemented).
267 .RE
268
269 .sp
270 .ne 2
271 .na
272 \fB\fBioctl\fR(\fBfd\fR, \fBMHIOCGRP_CLEAR\fR, (\fBmhioc_resv_key_t\fR)
273 \fI*r\fR\fB);\fR\fR
274 .ad
275 .sp .6
276 .RS 4n
277 Issues the SCSI-3 command Persistent Reserve Out Clear. The input parameter
278 \fIr\fR is the reservation key of the caller, which should have been already
279 registered with the device, by an earlier call to \fBMHIOCGRP_REGISTER\fR.
280 .RE
281
282 .sp
283 .LP
284 For each device, the non-shared ioctls should not be mixed with the Persistent
285 Reserve Out shared ioctls, and vice-versa, otherwise, the underlying device is
286 likely to return errors, because SCSI does not permit SCSI-2 reservations to be
287 mixed with SCSI-3 reservations on a single device. It is, however, legitimate
288 to call the Persistent Reserve In ioctls, because these are query only.
289 Issuing the \fBMHIOCGRP_INKEYS\fR ioctl is the recommended way for a caller to
290 determine if the device supports SCSI-3 Persistent Reservations (the ioctl
291 will return \fB-1\fR with \fBerrno\fR set to \fBENOTSUP\fR if the device does
292 not).
293 .SS "MHIOCENFAILFAST Ioctl"
294 .sp
295 .LP
296 The \fBMHIOCENFAILFAST\fR ioctl is applicable for both non-shared and shared
297 disks, and may be used with either the non-shared or shared ioctls.
298 .sp
299 .ne 2
300 .na
301 \fB\fBioctl\fR(\fBfd\fR, \fBMHIOENFAILFAST\fR, (unsigned int \fI*\fR)
302 \fImillisecs\fR\fB);\fR\fR
303 .ad
304 .sp .6
305 .RS 4n
306 Enables or disables the failfast option in the multihost disk driver and
307 enables or disables automatic probing of a multihost disk, described below.
308 The argument is an unsigned integer specifying the number of milliseconds to
309 wait between executions of the automatic probe function. An argument of zero
310 disables the failfast option and disables automatic probing. If the
311 \fBMHIOCENFAILFAST\fR ioctl is never called, the effect is defined to be that
312 both the failfast option and automatic probing are disabled.
313 .RE
314
315 .SS "Automatic Probing"
316 .sp
317 .LP
318 The \fBMHIOCENFAILFAST\fR ioctl sets up a timeout in the driver to periodically
319 schedule automatic probes of the disk. The automatic probe function works in
320 this manner: The driver is scheduled to probe the multihost disk every n
321 milliseconds, rounded up to the next integral multiple of the system clock's
322 resolution. If
323 .RS +4
324 .TP
325 1.
326 the local host no longer has access rights to the multihost disk, and
327 .RE
328 .RS +4
329 .TP
330 2.
331 access rights were expected to be held by the local host,
332 .RE
333 .sp
334 .LP
335 the driver immediately panics the machine to comply with the failfast model.
336 .sp
337 .LP
338 If the driver makes this discovery outside the timeout function, especially
339 during a read or write operation, it is imperative that it panic the system
340 then as well.
341 .SH RETURN VALUES
342 .sp
343 .LP
344 Each request returns \fB-1\fR on failure and sets \fBerrno\fR to indicate the
345 error.
346 .sp
347 .ne 2
348 .na
349 \fB\fBEPERM\fR \fR
350 .ad
351 .RS 14n
352 Caller is not root.
353 .RE
354
355 .sp
356 .ne 2
357 .na
358 \fB\fBEACCES\fR \fR
359 .ad
360 .RS 14n
361 Access rights were denied.
362 .RE
363
364 .sp
365 .ne 2
366 .na
367 \fB\fBEIO\fR\fR
368 .ad
369 .RS 14n
370 The multihost disk or controller was unable to successfully complete the
371 requested operation.
372 .RE
373
374 .sp
375 .ne 2
376 .na
377 \fB\fBEOPNOTSUP\fR \fR
378 .ad
379 .RS 14n
380 The multihost disk does not support the operation. For example, it does not
381 support the SCSI-2 Reserve/Release command set, or the SCSI-3 Persistent
382 Reservation command set.
383 .RE
384
385 .SH ATTRIBUTES
386 .sp
387 .LP
388 See \fBattributes\fR(5) for a description of the following attributes:
389 .sp
390
391 .sp
392 .TS
393 box;
394 c | c
395 l | l .
396 ATTRIBUTE TYPE ATTRIBUTE VALUE
397 _
398 Stability Evolving
399 .TE
400
401 .SH SEE ALSO
402 .sp
403 .LP
404 \fBioctl\fR(2), \fBopen\fR(2), \fBattributes\fR(5), open(2)
|
1 .\" Copyright (c) 2005 Sun Microsystems, Inc. All Rights Reserved.
2 .\" Copyright (c) 2017, Joyent, Inc.
3 .\" The contents of this file are subject to the terms of the
4 .\" Common Development and Distribution License (the "License").
5 .\" You may not use this file except in compliance with the License.
6 .\"
7 .\" You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
8 .\" or http://www.opensolaris.org/os/licensing.
9 .\" See the License for the specific language governing permissions
10 .\" and limitations under the License.
11 .\"
12 .\" When distributing Covered Code, include this CDDL HEADER in each
13 .\" file and include the License file at usr/src/OPENSOLARIS.LICENSE.
14 .\" If applicable, add the following below this CDDL HEADER, with the
15 .\" fields enclosed by brackets "[]" replaced with your own identifying
16 .\" information: Portions Copyright [yyyy] [name of copyright owner]
17 .Dd October 23, 2017
18 .Dt MHD 7I
19 .Os
20 .Sh NAME
21 .Nm mhd
22 .Nd multihost disk control operations
23 .Sh SYNOPSIS
24 .In sys/mhd.h
25 .Sh DESCRIPTION
26 The
27 .Nm
28 .Xr ioctl 2
29 control access rights of a multihost disk, using
30 disk reservations on the disk device.
31 .Pp
32 The stability level of this interface (see
33 .Xr attributes 5 )
34 is evolving.
35 As a result, the interface is subject to change and you should limit your use of
36 it.
37 .Pp
38 The mhd ioctls fall into two major categories: (1) ioctls for non-shared
39 multihost disks and (2) ioctls for shared multihost disks.
40 .Pp
41 One ioctl,
42 .Dv MHIOCENFAILFAST ,
43 is applicable to both non-shared and shared multihost disks.
44 It is described after the first two categories.
45 .Pp
46 All the ioctls require root privilege.
47 .Pp
48 For all of the ioctls, the caller should obtain the file descriptor for the
49 device by calling
50 .Xr open 2
51 with the
52 .Dv O_NDELAY
53 flag; without the
54 .Dv O_NDELAY
55 flag, the open may fail due to another host already having a
56 conflicting reservation on the device.
57 Some of the ioctls below permit the caller to forcibly clear a conflicting
58 reservation held by another host, however, in order to call the ioctl, the
59 caller must first obtain the open file descriptor.
60 .Ss "Non-shared multihost disks"
61 Non-shared multihost disks ioctls consist of
62 .Dv MHIOCTKOWN ,
63 .Dv MHIOCRELEASE ,
64 .Dv HIOCSTATUS ,
65 and
66 .Dv MHIOCQRESERVE .
67 These ioctl requests control the access rights of non-shared multihost disks.
68 A non-shared multihost disk is one that supports serialized, mutually exclusive
69 I/O mastery by the connected hosts.
70 This is in contrast to the shared-disk model, in which
71 concurrent access is allowed from more than one host (see below).
72 .Pp
73 A non-shared multihost disk can be in one of two states:
74 .Bl -bullet -width indent
75 .It
76 Exclusive access state, where only one connected host has I/O access
77 .It
78 Non-exclusive access state, where all connected hosts have I/O access.
79 An external hardware reset can cause the disk to enter the non-exclusive access
80 state.
81 .El
82 .Pp
83 Each multihost disk driver views the machine on which it's running as the
84 .Dq local host ;
85 each views all other machines as
86 .Dq remote hosts .
87 For each I/O or ioctl request, the requesting host is the local host.
88 .Pp
89 Note that the non-shared ioctls are designed to work with SCSI-2 disks.
90 The
91 SCSI-2 RESERVE/RELEASE command set is the underlying hardware facility in the
92 device that supports the non-shared ioctls.
93 .Pp
94 The function prototypes for the non-shared ioctls are:
95 .Bd -literal -offset 2n
96 .Fn ioctl fd MHIOCTKOWN ;
97 .Fn ioctl fd MHIOCRELEASE ;
98 .Fn ioctl fd MHIOCSTATUS ;
99 .Fn ioctl fd MHIOCQRESERVE ;
100 .Ed
101 .Bl -tag -width MHIOCQRESERVE
102 .It Dv MHIOCTKOWN
103 Forcefully acquires exclusive access rights to the multihost disk for the local
104 host.
105 Revokes all access rights to the multihost disk from remote hosts.
106 Causes the disk to enter the exclusive access state.
107 .Pp
108 Implementation Note: Reservations (exclusive access rights) broken via random
109 resets should be reinstated by the driver upon their detection, for example, in
110 the automatic probe function described below.
111 .It Dv MHIOCRELEASE
112 Relinquishes exclusive access rights to the multihost disk for the local host.
113 On success, causes the disk to enter the non- exclusive access state.
114 .It Dv MHIOCSTATUS
115 Probes a multihost disk to determine whether the local host has access rights
116 to the disk.
117 Returns
118 .Sy 0
119 if the local host has access to the disk,
120 .Sy 1
121 if it doesn't, and
122 .Sy -1
123 with
124 .Va errno
125 set to
126 .Er EIO
127 if the probe failed for some other reason.
128 .It Dv MHIOCQRESERVE
129 Issues, simply and only, a SCSI-2 Reserve command.
130 If the attempt to reserve
131 fails due to the SCSI error Reservation Conflict (which implies that some other
132 host has the device reserved), then the ioctl will return
133 .Sy -1
134 with
135 .Va errno
136 set to
137 .Er EACCES .
138 The
139 .Dv MHIOCQRESERVE
140 ioctl does NOT issue a bus device
141 reset or bus reset prior to attempting the SCSI-2 reserve command.
142 It also
143 does not take care of re-instating reservations that disappear due to bus
144 resets or bus device resets; if that behavior is desired, then the caller can
145 call
146 .Dv MHIOCTKOWN
147 after the
148 .Dv MHIOCQRESERVE
149 has returned success.
150 If
151 the device does not support the SCSI-2 Reserve command, then the ioctl returns
152 .Er -1
153 with
154 .Va errno
155 set to
156 .Er ENOTSUP .
157 The
158 .Dv MHIOCQRESERVE
159 ioctl is intended to be used by high-availability or clustering software for a
160 .Dq quorum
161 disk, hence, the
162 .Dq Q
163 in the name of the ioctl.
164 .El
165 .Ss "Shared Multihost Disks"
166 Shared multihost disks ioctls control access to shared multihost disks.
167 The ioctls are merely a veneer on the SCSI-3 Persistent Reservation facility.
168 Therefore, the underlying semantic model is not described in detail here, see
169 instead the SCSI-3 standard.
170 The SCSI-3 Persistent Reservations support the
171 concept of a group of hosts all sharing access to a disk.
172 .Pp
173 The function prototypes and descriptions for the shared multihost ioctls are as
174 follows:
175 .Bl -tag -width 1n
176 .It Fn ioctl fd MHIOCGRP_INKEYS "(mhioc_inkeys_t *)k"
177 .Pp
178 Issues the SCSI-3 command Persistent Reserve In Read Keys to the device.
179 On input, the field
180 .Fa k->li
181 should be initialized by the caller with
182 .Fa k->li.listsize
183 reflecting how big of an array the caller has allocated for the
184 .Fa k->lilist
185 field and with
186 .Ql k->li.listlen\& ==\& 0 .
187 On return, the field
188 .Fa k->li.listlen
189 is updated to indicate the number of
190 reservation keys the device currently has: if this value is larger than
191 .Fa k->li.listsize
192 then that indicates that the caller should have passed a bigger
193 .Fa k->li.list
194 array with a bigger
195 .Fa k->li.listsize .
196 The number of array elements actually written by the callee into
197 .Fa k->li.list
198 is the minimum of
199 .Fa k->li.listlen
200 and
201 .Fa k->li.listsize .
202 The field
203 .Fa k->generation
204 is updated with the generation information returned by the SCSI-3
205 Read Keys query.
206 If the device does not support SCSI-3 Persistent Reservations,
207 then this ioctl returns
208 .Sy -1
209 with
210 .Va errno
211 set to
212 .Er ENOTSUP .
213 .It Fn ioctl fd MHIOCGRP_INRESV "(mhioc_inresvs_t *)r"
214 .Pp
215 Issues the SCSI-3 command Persistent Reserve In Read Reservations to the
216 device.
217 Remarks similar to
218 .Dv MHIOCGRP_INKEYS
219 apply to the array manipulation.
220 If the device does not support SCSI-3 Persistent Reservations,
221 then this ioctl returns
222 .Sy -1
223 with
224 .Va errno
225 set to
226 .Er ENOTSUP .
227 .It Fn ioctl fd MHIOCGRP_REGISTER "(mhioc_register_t *)r"
228 .Pp
229 Issues the SCSI-3 command Persistent Reserve Out Register.
230 The fields of structure
231 .Va r
232 are all inputs; none of the fields are modified by the ioctl.
233 The field
234 .Fa r->aptpl
235 should be set to true to specify that registrations
236 and reservations should persist across device power failures, or to false to
237 specify that registrations and reservations should be cleared upon device power
238 failure; true is the recommended setting.
239 The field
240 .Fa r->oldkey
241 is the key that the caller believes the device may already have for this host
242 initiator; if the caller believes that that this host initiator is not already
243 registered with this device, it should pass the special key of all zeros.
244 To achieve the effect of unregistering with the device, the caller should pass
245 its current key for the
246 .Fa r->oldkey
247 field and an
248 .Fa r->newkey
249 field containing the special key of all zeros.
250 If the device returns the SCSI error code
251 Reservation Conflict, this ioctl returns
252 .Sy -1
253 with
254 .Va errno
255 set to
256 .Er EACCES .
257 .It Fn ioctl fd MHIOCGRP_RESERVE "(mhioc_resv_desc_t *)r"
258 .Pp
259 Issues the SCSI-3 command Persistent Reserve Out Reserve.
260 The fields of
261 structure
262 .Va r
263 are all inputs; none of the fields are modified by the ioctl.
264 If the device returns the SCSI error code Reservation Conflict, this ioctl
265 returns
266 .Sy -1
267 with
268 .Va errno
269 set to
270 .Er EACCES .
271 .It Fn ioctl fd MHIOCGRP_PREEMPTANDABORT "(mhioc_preemptandabort_t *)r"
272 .Pp
273 Issues the SCSI-3 command Persistent Reserve Out Preempt-And-Abort.
274 The fields
275 of structure
276 .Va r
277 are all inputs; none of the fields are modified by the ioctl.
278 The key of the victim host is specified by the field
279 .Fa r->victim_key .
280 The field
281 .Fa r->resvdesc
282 supplies the preempter's key and the reservation that it is requesting as part
283 of the SCSI-3 Preempt-And-Abort command.
284 If the device returns the SCSI error code
285 Reservation Conflict, this ioctl returns
286 .Sy -1
287 with
288 .Va errno
289 set to
290 .Er EACCES .
291 .It Fn ioctl fd MHIOCGRP_PREEMPT "(mhioc_preemptandabort_t *)r"
292 .Pp
293 Similar to
294 .Dv MHIOCGRP_PREEMPTANDABORT ,
295 but instead issues the SCSI-3 command Persistent Reserve Out Preempt.
296 (Note: This command is not implemented).
297 .It Fn ioctl fd MHIOCGRP_CLEAR "(mhioc_resv_key_t *)r"
298 Issues the SCSI-3 command Persistent Reserve Out Clear.
299 The input parameter
300 .Va r
301 is the reservation key of the caller, which should have been already
302 registered with the device, by an earlier call to
303 .Dv MHIOCGRP_REGISTER .
304 .El
305 .Pp
306 For each device, the non-shared ioctls should not be mixed with the Persistent
307 Reserve Out shared ioctls, and vice-versa, otherwise, the underlying device is
308 likely to return errors, because SCSI does not permit SCSI-2 reservations to be
309 mixed with SCSI-3 reservations on a single device.
310 It is, however, legitimate
311 to call the Persistent Reserve In ioctls, because these are query only.
312 Issuing the
313 .Dv MHIOCGRP_INKEYS
314 ioctl is the recommended way for a caller to
315 determine if the device supports SCSI-3 Persistent Reservations (the ioctl
316 will return
317 .Sy -1
318 with
319 .Va errno
320 set to
321 .Er ENOTSUP
322 if the device does not).
323 .Ss "MHIOCENFAILFAST Ioctl"
324 The
325 .Dv MHIOCENFAILFAST
326 ioctl is applicable for both non-shared and shared
327 disks, and may be used with either the non-shared or shared ioctls.
328 .Bl -tag -width 1n
329 .It Fn ioctl fd MHIOENFAILFAST "(unsigned int *)millisecs"
330 .Pp
331 Enables or disables the failfast option in the multihost disk driver and
332 enables or disables automatic probing of a multihost disk, described below.
333 The argument is an unsigned integer specifying the number of milliseconds to
334 wait between executions of the automatic probe function.
335 An argument of zero disables the failfast option and disables automatic probing.
336 If the
337 .Dv MHIOCENFAILFAST
338 ioctl is never called, the effect is defined to be that
339 both the failfast option and automatic probing are disabled.
340 .El
341 .Ss "Automatic Probing"
342 The
343 .Dv MHIOCENFAILFAST
344 ioctl sets up a timeout in the driver to periodically
345 schedule automatic probes of the disk.
346 The automatic probe function works in this manner: The driver is scheduled to
347 probe the multihost disk every n milliseconds, rounded up to the next integral
348 multiple of the system clock's resolution.
349 If
350 .Bl -enum -offset indent
351 .It
352 the local host no longer has access rights to the multihost disk, and
353 .It
354 access rights were expected to be held by the local host,
355 .El
356 .Pp
357 the driver immediately panics the machine to comply with the failfast model.
358 .Pp
359 If the driver makes this discovery outside the timeout function, especially
360 during a read or write operation, it is imperative that it panic the system
361 then as well.
362 .Sh RETURN VALUES
363 Each request returns
364 .Sy -1
365 on failure and sets
366 .Va errno
367 to indicate the error.
368 .Bl -tag -width Er
369 .It Er EPERM
370 Caller is not root.
371 .It Er EACCES
372 Access rights were denied.
373 .It Er EIO
374 The multihost disk or controller was unable to successfully complete the
375 requested operation.
376 .It Er EOPNOTSUP
377 The multihost disk does not support the operation.
378 For example, it does not support the SCSI-2 Reserve/Release command set, or the
379 SCSI-3 Persistent Reservation command set.
380 .El
381 .Sh STABILITY
382 Uncommitted
383 .Sh SEE ALSO
384 .Xr ioctl 2 ,
385 .Xr open 2 ,
386 .Xr attributes 5
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