source: branches/samba-3.5.x/source3/smbd/dmapi.c@ 737

Last change on this file since 737 was 414, checked in by Herwig Bauernfeind, 15 years ago

Samba 3.5.0: Initial import
File size: 9.0 KB
Line 
1/*
2 Unix SMB/CIFS implementation.
3 DMAPI Support routines
4
5 Copyright (C) James Peach 2006
6
7 This program is free software; you can redistribute it and/or modify
8 it under the terms of the GNU General Public License as published by
9 the Free Software Foundation; either version 3 of the License, or
10 (at your option) any later version.
11
12 This program is distributed in the hope that it will be useful,
13 but WITHOUT ANY WARRANTY; without even the implied warranty of
14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 GNU General Public License for more details.
16
17 You should have received a copy of the GNU General Public License
18 along with this program. If not, see <http://www.gnu.org/licenses/>.
19*/
20
21#include "includes.h"
22#include "smbd/globals.h"
23
24#undef DBGC_CLASS
25#define DBGC_CLASS DBGC_DMAPI
26
27#ifndef USE_DMAPI
28
29uint32 dmapi_file_flags(const char * const path) { return 0; }
30bool dmapi_have_session(void) { return False; }
31const void * dmapi_get_current_session(void) { return NULL; }
32
33#else /* USE_DMAPI */
34
35#ifdef HAVE_XFS_DMAPI_H
36#include <xfs/dmapi.h>
37#elif defined(HAVE_SYS_DMI_H)
38#include <sys/dmi.h>
39#elif defined(HAVE_SYS_JFSDMAPI_H)
40#include <sys/jfsdmapi.h>
41#elif defined(HAVE_SYS_DMAPI_H)
42#include <sys/dmapi.h>
43#elif defined(HAVE_DMAPI_H)
44#include <dmapi.h>
45#endif
46
47#define DMAPI_SESSION_NAME "samba"
48#define DMAPI_TRACE 10
49
50struct smbd_dmapi_context {
51 dm_sessid_t session;
52 unsigned session_num;
53};
54
55/*
56 Initialise DMAPI session. The session is persistant kernel state,
57 so it might already exist, in which case we merely want to
58 reconnect to it. This function should be called as root.
59*/
60static int dmapi_init_session(struct smbd_dmapi_context *ctx)
61{
62 char buf[DM_SESSION_INFO_LEN];
63 size_t buflen;
64 uint nsessions = 5;
65 dm_sessid_t *sessions = NULL;
66 char *version;
67 char *session_name;
68 TALLOC_CTX *tmp_ctx = talloc_new(NULL);
69
70 int i, err;
71
72 if (ctx->session_num == 0) {
73 session_name = talloc_strdup(tmp_ctx, DMAPI_SESSION_NAME);
74 } else {
75 session_name = talloc_asprintf(tmp_ctx, "%s%u", DMAPI_SESSION_NAME,
76 ctx->session_num);
77 }
78
79 if (session_name == NULL) {
80 DEBUG(0,("Out of memory in dmapi_init_session\n"));
81 talloc_free(tmp_ctx);
82 return -1;
83 }
84
85
86 if (dm_init_service(&version) < 0) {
87 DEBUG(0, ("dm_init_service failed - disabling DMAPI\n"));
88 talloc_free(tmp_ctx);
89 return -1;
90 }
91
92 ZERO_STRUCT(buf);
93
94 /* Fetch kernel DMAPI sessions until we get any of them */
95 do {
96 dm_sessid_t *new_sessions;
97 nsessions *= 2;
98 new_sessions = TALLOC_REALLOC_ARRAY(tmp_ctx, sessions,
99 dm_sessid_t, nsessions);
100 if (new_sessions == NULL) {
101 talloc_free(tmp_ctx);
102 return -1;
103 }
104
105 sessions = new_sessions;
106 err = dm_getall_sessions(nsessions, sessions, &nsessions);
107 } while (err == -1 && errno == E2BIG);
108
109 if (err == -1) {
110 DEBUGADD(DMAPI_TRACE,
111 ("failed to retrieve DMAPI sessions: %s\n",
112 strerror(errno)));
113 talloc_free(tmp_ctx);
114 return -1;
115 }
116
117 /* Look through existing kernel DMAPI sessions to find out ours */
118 for (i = 0; i < nsessions; ++i) {
119 err = dm_query_session(sessions[i], sizeof(buf), buf, &buflen);
120 buf[sizeof(buf) - 1] = '\0';
121 if (err == 0 && strcmp(session_name, buf) == 0) {
122 ctx->session = sessions[i];
123 DEBUGADD(DMAPI_TRACE,
124 ("attached to existing DMAPI session "
125 "named '%s'\n", buf));
126 break;
127 }
128 }
129
130 /* No session already defined. */
131 if (ctx->session == DM_NO_SESSION) {
132 err = dm_create_session(DM_NO_SESSION,
133 session_name,
134 &ctx->session);
135 if (err < 0) {
136 DEBUGADD(DMAPI_TRACE,
137 ("failed to create new DMAPI session: %s\n",
138 strerror(errno)));
139 ctx->session = DM_NO_SESSION;
140 talloc_free(tmp_ctx);
141 return -1;
142 }
143
144 DEBUG(0, ("created new DMAPI session named '%s' for %s\n",
145 session_name, version));
146 }
147
148 if (ctx->session != DM_NO_SESSION) {
149 set_effective_capability(DMAPI_ACCESS_CAPABILITY);
150 }
151
152 /*
153 Note that we never end the DMAPI session. It gets re-used if possiblie.
154 DMAPI session is a kernel resource that is usually lives until server reboot
155 and doesn't get destroed when an application finishes.
156
157 However, we free list of references to DMAPI sessions we've got from the kernel
158 as it is not needed anymore once we have found (or created) our session.
159 */
160
161 talloc_free(tmp_ctx);
162 return 0;
163}
164
165/*
166 Return a pointer to our DMAPI session, if available.
167 This assumes that you have called dmapi_have_session() first.
168*/
169const void *dmapi_get_current_session(void)
170{
171 if (!dmapi_ctx) {
172 return NULL;
173 }
174
175 if (dmapi_ctx->session == DM_NO_SESSION) {
176 return NULL;
177 }
178
179 return (void *)&dmapi_ctx->session;
180}
181
182/*
183 dmapi_have_session() must be the first DMAPI call you make in Samba. It will
184 initialize DMAPI, if available, and tell you if you can get a DMAPI session.
185 This should be called in the client-specific child process.
186*/
187
188bool dmapi_have_session(void)
189{
190 if (!dmapi_ctx) {
191 dmapi_ctx = talloc(talloc_autofree_context(),
192 struct smbd_dmapi_context);
193 if (!dmapi_ctx) {
194 exit_server("unable to allocate smbd_dmapi_context");
195 }
196 dmapi_ctx->session = DM_NO_SESSION;
197 dmapi_ctx->session_num = 0;
198
199 become_root();
200 dmapi_init_session(dmapi_ctx);
201 unbecome_root();
202
203 }
204
205 return dmapi_ctx->session != DM_NO_SESSION;
206}
207
208/*
209 only call this when you get back an EINVAL error indicating that the
210 session you are using is invalid. This destroys the existing session
211 and creates a new one.
212 */
213bool dmapi_new_session(void)
214{
215 if (dmapi_have_session()) {
216 /* try to destroy the old one - this may not succeed */
217 dm_destroy_session(dmapi_ctx->session);
218 }
219 dmapi_ctx->session = DM_NO_SESSION;
220 become_root();
221 dmapi_ctx->session_num++;
222 dmapi_init_session(dmapi_ctx);
223 unbecome_root();
224 return dmapi_ctx->session != DM_NO_SESSION;
225}
226
227/*
228 only call this when exiting from master smbd process. DMAPI sessions
229 are long-lived kernel resources we ought to share across smbd processes.
230 However, we must free them when all smbd processes are finished to
231 allow other subsystems clean up properly. Not freeing DMAPI session
232 blocks certain HSM implementations from proper shutdown.
233*/
234bool dmapi_destroy_session(void)
235{
236 if (!dmapi_ctx) {
237 return true;
238 }
239 if (dmapi_ctx->session != DM_NO_SESSION) {
240 become_root();
241 if (0 == dm_destroy_session(dmapi_ctx->session)) {
242 dmapi_ctx->session_num--;
243 dmapi_ctx->session = DM_NO_SESSION;
244 } else {
245 DEBUG(0,("Couldn't destroy DMAPI session: %s\n",
246 strerror(errno)));
247 }
248 unbecome_root();
249 }
250 return dmapi_ctx->session == DM_NO_SESSION;
251}
252
253
254/*
255 This is default implementation of dmapi_file_flags() that is
256 called from VFS is_offline() call to know whether file is offline.
257 For GPFS-specific version see modules/vfs_tsmsm.c. It might be
258 that approach on quering existence of a specific attribute that
259 is used in vfs_tsmsm.c will work with other DMAPI-based HSM
260 implementations as well.
261*/
262uint32 dmapi_file_flags(const char * const path)
263{
264 int err;
265 dm_eventset_t events = {0};
266 uint nevents;
267
268 dm_sessid_t dmapi_session;
269 const void *dmapi_session_ptr;
270 void *dm_handle = NULL;
271 size_t dm_handle_len = 0;
272
273 uint32 flags = 0;
274
275 dmapi_session_ptr = dmapi_get_current_session();
276 if (dmapi_session_ptr == NULL) {
277 return 0;
278 }
279
280 dmapi_session = *(dm_sessid_t *)dmapi_session_ptr;
281 if (dmapi_session == DM_NO_SESSION) {
282 return 0;
283 }
284
285 /* AIX has DMAPI but no POSIX capablities support. In this case,
286 * we need to be root to do DMAPI manipulations.
287 */
288#ifndef HAVE_POSIX_CAPABILITIES
289 become_root();
290#endif
291
292 err = dm_path_to_handle(CONST_DISCARD(char *, path),
293 &dm_handle, &dm_handle_len);
294 if (err < 0) {
295 DEBUG(DMAPI_TRACE, ("dm_path_to_handle(%s): %s\n",
296 path, strerror(errno)));
297
298 if (errno != EPERM) {
299 goto done;
300 }
301
302 /* Linux capabilities are broken in that changing our
303 * user ID will clobber out effective capabilities irrespective
304 * of whether we have set PR_SET_KEEPCAPS. Fortunately, the
305 * capabilities are not removed from our permitted set, so we
306 * can re-acquire them if necessary.
307 */
308
309 set_effective_capability(DMAPI_ACCESS_CAPABILITY);
310
311 err = dm_path_to_handle(CONST_DISCARD(char *, path),
312 &dm_handle, &dm_handle_len);
313 if (err < 0) {
314 DEBUG(DMAPI_TRACE,
315 ("retrying dm_path_to_handle(%s): %s\n",
316 path, strerror(errno)));
317 goto done;
318 }
319 }
320
321 err = dm_get_eventlist(dmapi_session, dm_handle, dm_handle_len,
322 DM_NO_TOKEN, DM_EVENT_MAX, &events, &nevents);
323 if (err < 0) {
324 DEBUG(DMAPI_TRACE, ("dm_get_eventlist(%s): %s\n",
325 path, strerror(errno)));
326 dm_handle_free(dm_handle, dm_handle_len);
327 goto done;
328 }
329
330 /* We figure that the only reason a DMAPI application would be
331 * interested in trapping read events is that part of the file is
332 * offline.
333 */
334 DEBUG(DMAPI_TRACE, ("DMAPI event list for %s\n", path));
335 if (DMEV_ISSET(DM_EVENT_READ, events)) {
336 flags = FILE_ATTRIBUTE_OFFLINE;
337 }
338
339 dm_handle_free(dm_handle, dm_handle_len);
340
341 if (flags & FILE_ATTRIBUTE_OFFLINE) {
342 DEBUG(DMAPI_TRACE, ("%s is OFFLINE\n", path));
343 }
344
345done:
346
347#ifndef HAVE_POSIX_CAPABILITIES
348 unbecome_root();
349#endif
350
351 return flags;
352}
353
354
355#endif /* USE_DMAPI */
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