1 /* AFS volume management
2  *
3  * Copyright (C) 2002, 2007 Red Hat, Inc. All Rights Reserved.
4  * Written by David Howells (dhowells@redhat.com)
5  *
6  * This program is free software; you can redistribute it and/or
7  * modify it under the terms of the GNU General Public License
8  * as published by the Free Software Foundation; either version
9  * 2 of the License, or (at your option) any later version.
10  */
11 
12 #include <linux/kernel.h>
13 #include <linux/module.h>
14 #include <linux/init.h>
15 #include <linux/slab.h>
16 #include <linux/fs.h>
17 #include <linux/pagemap.h>
18 #include <linux/sched.h>
19 #include "internal.h"
20 
21 static const char *afs_voltypes[] = { "R/W", "R/O", "BAK" };
22 
23 /*
24  * lookup a volume by name
25  * - this can be one of the following:
26  *	"%[cell:]volume[.]"		R/W volume
27  *	"#[cell:]volume[.]"		R/O or R/W volume (rwparent=0),
28  *					 or R/W (rwparent=1) volume
29  *	"%[cell:]volume.readonly"	R/O volume
30  *	"#[cell:]volume.readonly"	R/O volume
31  *	"%[cell:]volume.backup"		Backup volume
32  *	"#[cell:]volume.backup"		Backup volume
33  *
34  * The cell name is optional, and defaults to the current cell.
35  *
36  * See "The Rules of Mount Point Traversal" in Chapter 5 of the AFS SysAdmin
37  * Guide
38  * - Rule 1: Explicit type suffix forces access of that type or nothing
39  *           (no suffix, then use Rule 2 & 3)
40  * - Rule 2: If parent volume is R/O, then mount R/O volume by preference, R/W
41  *           if not available
42  * - Rule 3: If parent volume is R/W, then only mount R/W volume unless
43  *           explicitly told otherwise
44  */
afs_volume_lookup(struct afs_mount_params * params)45 struct afs_volume *afs_volume_lookup(struct afs_mount_params *params)
46 {
47 	struct afs_vlocation *vlocation = NULL;
48 	struct afs_volume *volume = NULL;
49 	struct afs_server *server = NULL;
50 	char srvtmask;
51 	int ret, loop;
52 
53 	_enter("{%*.*s,%d}",
54 	       params->volnamesz, params->volnamesz, params->volname, params->rwpath);
55 
56 	/* lookup the volume location record */
57 	vlocation = afs_vlocation_lookup(params->cell, params->key,
58 					 params->volname, params->volnamesz);
59 	if (IS_ERR(vlocation)) {
60 		ret = PTR_ERR(vlocation);
61 		vlocation = NULL;
62 		goto error;
63 	}
64 
65 	/* make the final decision on the type we want */
66 	ret = -ENOMEDIUM;
67 	if (params->force && !(vlocation->vldb.vidmask & (1 << params->type)))
68 		goto error;
69 
70 	srvtmask = 0;
71 	for (loop = 0; loop < vlocation->vldb.nservers; loop++)
72 		srvtmask |= vlocation->vldb.srvtmask[loop];
73 
74 	if (params->force) {
75 		if (!(srvtmask & (1 << params->type)))
76 			goto error;
77 	} else if (srvtmask & AFS_VOL_VTM_RO) {
78 		params->type = AFSVL_ROVOL;
79 	} else if (srvtmask & AFS_VOL_VTM_RW) {
80 		params->type = AFSVL_RWVOL;
81 	} else {
82 		goto error;
83 	}
84 
85 	down_write(&params->cell->vl_sem);
86 
87 	/* is the volume already active? */
88 	if (vlocation->vols[params->type]) {
89 		/* yes - re-use it */
90 		volume = vlocation->vols[params->type];
91 		afs_get_volume(volume);
92 		goto success;
93 	}
94 
95 	/* create a new volume record */
96 	_debug("creating new volume record");
97 
98 	ret = -ENOMEM;
99 	volume = kzalloc(sizeof(struct afs_volume), GFP_KERNEL);
100 	if (!volume)
101 		goto error_up;
102 
103 	atomic_set(&volume->usage, 1);
104 	volume->type		= params->type;
105 	volume->type_force	= params->force;
106 	volume->cell		= params->cell;
107 	volume->vid		= vlocation->vldb.vid[params->type];
108 
109 	ret = bdi_setup_and_register(&volume->bdi, "afs", BDI_CAP_MAP_COPY);
110 	if (ret)
111 		goto error_bdi;
112 
113 	init_rwsem(&volume->server_sem);
114 
115 	/* look up all the applicable server records */
116 	for (loop = 0; loop < 8; loop++) {
117 		if (vlocation->vldb.srvtmask[loop] & (1 << volume->type)) {
118 			server = afs_lookup_server(
119 			       volume->cell, &vlocation->vldb.servers[loop]);
120 			if (IS_ERR(server)) {
121 				ret = PTR_ERR(server);
122 				goto error_discard;
123 			}
124 
125 			volume->servers[volume->nservers] = server;
126 			volume->nservers++;
127 		}
128 	}
129 
130 	/* attach the cache and volume location */
131 #ifdef CONFIG_AFS_FSCACHE
132 	volume->cache = fscache_acquire_cookie(vlocation->cache,
133 					       &afs_volume_cache_index_def,
134 					       volume);
135 #endif
136 	afs_get_vlocation(vlocation);
137 	volume->vlocation = vlocation;
138 
139 	vlocation->vols[volume->type] = volume;
140 
141 success:
142 	_debug("kAFS selected %s volume %08x",
143 	       afs_voltypes[volume->type], volume->vid);
144 	up_write(&params->cell->vl_sem);
145 	afs_put_vlocation(vlocation);
146 	_leave(" = %p", volume);
147 	return volume;
148 
149 	/* clean up */
150 error_up:
151 	up_write(&params->cell->vl_sem);
152 error:
153 	afs_put_vlocation(vlocation);
154 	_leave(" = %d", ret);
155 	return ERR_PTR(ret);
156 
157 error_discard:
158 	bdi_destroy(&volume->bdi);
159 error_bdi:
160 	up_write(&params->cell->vl_sem);
161 
162 	for (loop = volume->nservers - 1; loop >= 0; loop--)
163 		afs_put_server(volume->servers[loop]);
164 
165 	kfree(volume);
166 	goto error;
167 }
168 
169 /*
170  * destroy a volume record
171  */
afs_put_volume(struct afs_volume * volume)172 void afs_put_volume(struct afs_volume *volume)
173 {
174 	struct afs_vlocation *vlocation;
175 	int loop;
176 
177 	if (!volume)
178 		return;
179 
180 	_enter("%p", volume);
181 
182 	ASSERTCMP(atomic_read(&volume->usage), >, 0);
183 
184 	vlocation = volume->vlocation;
185 
186 	/* to prevent a race, the decrement and the dequeue must be effectively
187 	 * atomic */
188 	down_write(&vlocation->cell->vl_sem);
189 
190 	if (likely(!atomic_dec_and_test(&volume->usage))) {
191 		up_write(&vlocation->cell->vl_sem);
192 		_leave("");
193 		return;
194 	}
195 
196 	vlocation->vols[volume->type] = NULL;
197 
198 	up_write(&vlocation->cell->vl_sem);
199 
200 	/* finish cleaning up the volume */
201 #ifdef CONFIG_AFS_FSCACHE
202 	fscache_relinquish_cookie(volume->cache, 0);
203 #endif
204 	afs_put_vlocation(vlocation);
205 
206 	for (loop = volume->nservers - 1; loop >= 0; loop--)
207 		afs_put_server(volume->servers[loop]);
208 
209 	bdi_destroy(&volume->bdi);
210 	kfree(volume);
211 
212 	_leave(" [destroyed]");
213 }
214 
215 /*
216  * pick a server to use to try accessing this volume
217  * - returns with an elevated usage count on the server chosen
218  */
afs_volume_pick_fileserver(struct afs_vnode * vnode)219 struct afs_server *afs_volume_pick_fileserver(struct afs_vnode *vnode)
220 {
221 	struct afs_volume *volume = vnode->volume;
222 	struct afs_server *server;
223 	int ret, state, loop;
224 
225 	_enter("%s", volume->vlocation->vldb.name);
226 
227 	/* stick with the server we're already using if we can */
228 	if (vnode->server && vnode->server->fs_state == 0) {
229 		afs_get_server(vnode->server);
230 		_leave(" = %p [current]", vnode->server);
231 		return vnode->server;
232 	}
233 
234 	down_read(&volume->server_sem);
235 
236 	/* handle the no-server case */
237 	if (volume->nservers == 0) {
238 		ret = volume->rjservers ? -ENOMEDIUM : -ESTALE;
239 		up_read(&volume->server_sem);
240 		_leave(" = %d [no servers]", ret);
241 		return ERR_PTR(ret);
242 	}
243 
244 	/* basically, just search the list for the first live server and use
245 	 * that */
246 	ret = 0;
247 	for (loop = 0; loop < volume->nservers; loop++) {
248 		server = volume->servers[loop];
249 		state = server->fs_state;
250 
251 		_debug("consider %d [%d]", loop, state);
252 
253 		switch (state) {
254 			/* found an apparently healthy server */
255 		case 0:
256 			afs_get_server(server);
257 			up_read(&volume->server_sem);
258 			_leave(" = %p (picked %08x)",
259 			       server, ntohl(server->addr.s_addr));
260 			return server;
261 
262 		case -ENETUNREACH:
263 			if (ret == 0)
264 				ret = state;
265 			break;
266 
267 		case -EHOSTUNREACH:
268 			if (ret == 0 ||
269 			    ret == -ENETUNREACH)
270 				ret = state;
271 			break;
272 
273 		case -ECONNREFUSED:
274 			if (ret == 0 ||
275 			    ret == -ENETUNREACH ||
276 			    ret == -EHOSTUNREACH)
277 				ret = state;
278 			break;
279 
280 		default:
281 		case -EREMOTEIO:
282 			if (ret == 0 ||
283 			    ret == -ENETUNREACH ||
284 			    ret == -EHOSTUNREACH ||
285 			    ret == -ECONNREFUSED)
286 				ret = state;
287 			break;
288 		}
289 	}
290 
291 	/* no available servers
292 	 * - TODO: handle the no active servers case better
293 	 */
294 	up_read(&volume->server_sem);
295 	_leave(" = %d", ret);
296 	return ERR_PTR(ret);
297 }
298 
299 /*
300  * release a server after use
301  * - releases the ref on the server struct that was acquired by picking
302  * - records result of using a particular server to access a volume
303  * - return 0 to try again, 1 if okay or to issue error
304  * - the caller must release the server struct if result was 0
305  */
afs_volume_release_fileserver(struct afs_vnode * vnode,struct afs_server * server,int result)306 int afs_volume_release_fileserver(struct afs_vnode *vnode,
307 				  struct afs_server *server,
308 				  int result)
309 {
310 	struct afs_volume *volume = vnode->volume;
311 	unsigned loop;
312 
313 	_enter("%s,%08x,%d",
314 	       volume->vlocation->vldb.name, ntohl(server->addr.s_addr),
315 	       result);
316 
317 	switch (result) {
318 		/* success */
319 	case 0:
320 		server->fs_act_jif = jiffies;
321 		server->fs_state = 0;
322 		_leave("");
323 		return 1;
324 
325 		/* the fileserver denied all knowledge of the volume */
326 	case -ENOMEDIUM:
327 		server->fs_act_jif = jiffies;
328 		down_write(&volume->server_sem);
329 
330 		/* firstly, find where the server is in the active list (if it
331 		 * is) */
332 		for (loop = 0; loop < volume->nservers; loop++)
333 			if (volume->servers[loop] == server)
334 				goto present;
335 
336 		/* no longer there - may have been discarded by another op */
337 		goto try_next_server_upw;
338 
339 	present:
340 		volume->nservers--;
341 		memmove(&volume->servers[loop],
342 			&volume->servers[loop + 1],
343 			sizeof(volume->servers[loop]) *
344 			(volume->nservers - loop));
345 		volume->servers[volume->nservers] = NULL;
346 		afs_put_server(server);
347 		volume->rjservers++;
348 
349 		if (volume->nservers > 0)
350 			/* another server might acknowledge its existence */
351 			goto try_next_server_upw;
352 
353 		/* handle the case where all the fileservers have rejected the
354 		 * volume
355 		 * - TODO: try asking the fileservers for volume information
356 		 * - TODO: contact the VL server again to see if the volume is
357 		 *         no longer registered
358 		 */
359 		up_write(&volume->server_sem);
360 		afs_put_server(server);
361 		_leave(" [completely rejected]");
362 		return 1;
363 
364 		/* problem reaching the server */
365 	case -ENETUNREACH:
366 	case -EHOSTUNREACH:
367 	case -ECONNREFUSED:
368 	case -ETIME:
369 	case -ETIMEDOUT:
370 	case -EREMOTEIO:
371 		/* mark the server as dead
372 		 * TODO: vary dead timeout depending on error
373 		 */
374 		spin_lock(&server->fs_lock);
375 		if (!server->fs_state) {
376 			server->fs_dead_jif = jiffies + HZ * 10;
377 			server->fs_state = result;
378 			printk("kAFS: SERVER DEAD state=%d\n", result);
379 		}
380 		spin_unlock(&server->fs_lock);
381 		goto try_next_server;
382 
383 		/* miscellaneous error */
384 	default:
385 		server->fs_act_jif = jiffies;
386 	case -ENOMEM:
387 	case -ENONET:
388 		/* tell the caller to accept the result */
389 		afs_put_server(server);
390 		_leave(" [local failure]");
391 		return 1;
392 	}
393 
394 	/* tell the caller to loop around and try the next server */
395 try_next_server_upw:
396 	up_write(&volume->server_sem);
397 try_next_server:
398 	afs_put_server(server);
399 	_leave(" [try next server]");
400 	return 0;
401 }
402