fs/afs/volume.c - linux - Git at Google

 /* volume.c: AFS volume management
  *
  * Copyright (C) 2002 Red Hat, Inc. All Rights Reserved.
  * Written by David Howells (dhowells@redhat.com)
  *
  * This program is free software; you can redistribute it and/or
  * modify it under the terms of the GNU General Public License
  * as published by the Free Software Foundation; either version
  * 2 of the License, or (at your option) any later version.
  */

 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/init.h>
 #include <linux/slab.h>
 #include <linux/fs.h>
 #include <linux/pagemap.h>
 #include "volume.h"
 #include "vnode.h"
 #include "cell.h"
 #include "cache.h"
 #include "cmservice.h"
 #include "fsclient.h"
 #include "vlclient.h"
 #include "internal.h"

 #ifdef __KDEBUG
 static const char *afs_voltypes[] = { "R/W", "R/O", "BAK" };
 #endif

 #ifdef AFS_CACHING_SUPPORT
 static cachefs_match_val_t afs_volume_cache_match(void *target,
 						  const void *entry);
 static void afs_volume_cache_update(void *source, void *entry);

 struct cachefs_index_def afs_volume_cache_index_def = {
 	.name		= "volume",
 	.data_size	= sizeof(struct afs_cache_vhash),
 	.keys[0]	= { CACHEFS_INDEX_KEYS_BIN, 1 },
 	.keys[1]	= { CACHEFS_INDEX_KEYS_BIN, 1 },
 	.match		= afs_volume_cache_match,
 	.update		= afs_volume_cache_update,
 };
 #endif

 /*****************************************************************************/
 /*
  * lookup a volume by name
  * - this can be one of the following:
  *	"%[cell:]volume[.]"		R/W volume
  *	"#[cell:]volume[.]"		R/O or R/W volume (rwparent=0),
  *					 or R/W (rwparent=1) volume
  *	"%[cell:]volume.readonly"	R/O volume
  *	"#[cell:]volume.readonly"	R/O volume
  *	"%[cell:]volume.backup"		Backup volume
  *	"#[cell:]volume.backup"		Backup volume
  *
  * The cell name is optional, and defaults to the current cell.
  *
  * See "The Rules of Mount Point Traversal" in Chapter 5 of the AFS SysAdmin
  * Guide
  * - Rule 1: Explicit type suffix forces access of that type or nothing
  *           (no suffix, then use Rule 2 & 3)
  * - Rule 2: If parent volume is R/O, then mount R/O volume by preference, R/W
  *           if not available
  * - Rule 3: If parent volume is R/W, then only mount R/W volume unless
  *           explicitly told otherwise
  */
 int afs_volume_lookup(const char *name, struct afs_cell *cell, int rwpath,
 		      struct afs_volume **_volume)
 {
 	struct afs_vlocation *vlocation = NULL;
 	struct afs_volume *volume = NULL;
 	afs_voltype_t type;
 	const char *cellname, *volname, *suffix;
 	char srvtmask;
 	int force, ret, loop, cellnamesz, volnamesz;

 	_enter("%s,,%d,", name, rwpath);

 	if (!name || (name[0] != '%' && name[0] != '#') || !name[1]) {
 		printk("kAFS: unparsable volume name\n");
 		return -EINVAL;
 	}

 	/* determine the type of volume we're looking for */
 	force = 0;
 	type = AFSVL_ROVOL;

 	if (rwpath || name[0] == '%') {
 		type = AFSVL_RWVOL;
 		force = 1;
 	}

 	suffix = strrchr(name, '.');
 	if (suffix) {
 		if (strcmp(suffix, ".readonly") == 0) {
 			type = AFSVL_ROVOL;
 			force = 1;
 		}
 		else if (strcmp(suffix, ".backup") == 0) {
 			type = AFSVL_BACKVOL;
 			force = 1;
 		}
 		else if (suffix[1] == 0) {
 		}
 		else {
 			suffix = NULL;
 		}
 	}

 	/* split the cell and volume names */
 	name++;
 	volname = strchr(name, ':');
 	if (volname) {
 		cellname = name;
 		cellnamesz = volname - name;
 		volname++;
 	}
 	else {
 		volname = name;
 		cellname = NULL;
 		cellnamesz = 0;
 	}

 	volnamesz = suffix ? suffix - volname : strlen(volname);

 	_debug("CELL:%*.*s [%p] VOLUME:%*.*s SUFFIX:%s TYPE:%d%s",
 	       cellnamesz, cellnamesz, cellname ?: "", cell,
 	       volnamesz, volnamesz, volname, suffix ?: "-",
 	       type,
 	       force ? " FORCE" : "");

 	/* lookup the cell record */
 	if (cellname || !cell) {
 		ret = afs_cell_lookup(cellname, cellnamesz, &cell);
 		if (ret<0) {
 			printk("kAFS: unable to lookup cell '%s'\n",
 			       cellname ?: "");
 			goto error;
 		}
 	}
 	else {
 		afs_get_cell(cell);
 	}

 	/* lookup the volume location record */
 	ret = afs_vlocation_lookup(cell, volname, volnamesz, &vlocation);
 	if (ret < 0)
 		goto error;

 	/* make the final decision on the type we want */
 	ret = -ENOMEDIUM;
 	if (force && !(vlocation->vldb.vidmask & (1 << type)))
 		goto error;

 	srvtmask = 0;
 	for (loop = 0; loop < vlocation->vldb.nservers; loop++)
 		srvtmask |= vlocation->vldb.srvtmask[loop];

 	if (force) {
 		if (!(srvtmask & (1 << type)))
 			goto error;
 	}
 	else if (srvtmask & AFS_VOL_VTM_RO) {
 		type = AFSVL_ROVOL;
 	}
 	else if (srvtmask & AFS_VOL_VTM_RW) {
 		type = AFSVL_RWVOL;
 	}
 	else {
 		goto error;
 	}

 	down_write(&cell->vl_sem);

 	/* is the volume already active? */
 	if (vlocation->vols[type]) {
 		/* yes - re-use it */
 		volume = vlocation->vols[type];
 		afs_get_volume(volume);
 		goto success;
 	}

 	/* create a new volume record */
 	_debug("creating new volume record");

 	ret = -ENOMEM;
 	volume = kzalloc(sizeof(struct afs_volume), GFP_KERNEL);
 	if (!volume)
 		goto error_up;

 	atomic_set(&volume->usage, 1);
 	volume->type		= type;
 	volume->type_force	= force;
 	volume->cell		= cell;
 	volume->vid		= vlocation->vldb.vid[type];

 	init_rwsem(&volume->server_sem);

 	/* look up all the applicable server records */
 	for (loop = 0; loop < 8; loop++) {
 		if (vlocation->vldb.srvtmask[loop] & (1 << volume->type)) {
 			ret = afs_server_lookup(
 				volume->cell,
 				&vlocation->vldb.servers[loop],
 				&volume->servers[volume->nservers]);
 			if (ret < 0)
 				goto error_discard;

 			volume->nservers++;
 		}
 	}

 	/* attach the cache and volume location */
 #ifdef AFS_CACHING_SUPPORT
 	cachefs_acquire_cookie(vlocation->cache,
 			       &afs_vnode_cache_index_def,
 			       volume,
 			       &volume->cache);
 #endif

 	afs_get_vlocation(vlocation);
 	volume->vlocation = vlocation;

 	vlocation->vols[type] = volume;

  success:
 	_debug("kAFS selected %s volume %08x",
 	       afs_voltypes[volume->type], volume->vid);
 	*_volume = volume;
 	ret = 0;

 	/* clean up */
  error_up:
 	up_write(&cell->vl_sem);
  error:
 	afs_put_vlocation(vlocation);
 	afs_put_cell(cell);

 	_leave(" = %d (%p)", ret, volume);
 	return ret;

  error_discard:
 	up_write(&cell->vl_sem);

 	for (loop = volume->nservers - 1; loop >= 0; loop--)
 		afs_put_server(volume->servers[loop]);

 	kfree(volume);
 	goto error;
 } /* end afs_volume_lookup() */

 /*****************************************************************************/
 /*
  * destroy a volume record
  */
 void afs_put_volume(struct afs_volume *volume)
 {
 	struct afs_vlocation *vlocation;
 	int loop;

 	if (!volume)
 		return;

 	_enter("%p", volume);

 	vlocation = volume->vlocation;

 	/* sanity check */
 	BUG_ON(atomic_read(&volume->usage) <= 0);

 	/* to prevent a race, the decrement and the dequeue must be effectively
 	 * atomic */
 	down_write(&vlocation->cell->vl_sem);

 	if (likely(!atomic_dec_and_test(&volume->usage))) {
 		up_write(&vlocation->cell->vl_sem);
 		_leave("");
 		return;
 	}

 	vlocation->vols[volume->type] = NULL;

 	up_write(&vlocation->cell->vl_sem);

 	/* finish cleaning up the volume */
 #ifdef AFS_CACHING_SUPPORT
 	cachefs_relinquish_cookie(volume->cache, 0);
 #endif
 	afs_put_vlocation(vlocation);

 	for (loop = volume->nservers - 1; loop >= 0; loop--)
 		afs_put_server(volume->servers[loop]);

 	kfree(volume);

 	_leave(" [destroyed]");
 } /* end afs_put_volume() */

 /*****************************************************************************/
 /*
  * pick a server to use to try accessing this volume
  * - returns with an elevated usage count on the server chosen
  */
 int afs_volume_pick_fileserver(struct afs_volume *volume,
 			       struct afs_server **_server)
 {
 	struct afs_server *server;
 	int ret, state, loop;

 	_enter("%s", volume->vlocation->vldb.name);

 	down_read(&volume->server_sem);

 	/* handle the no-server case */
 	if (volume->nservers == 0) {
 		ret = volume->rjservers ? -ENOMEDIUM : -ESTALE;
 		up_read(&volume->server_sem);
 		_leave(" = %d [no servers]", ret);
 		return ret;
 	}

 	/* basically, just search the list for the first live server and use
 	 * that */
 	ret = 0;
 	for (loop = 0; loop < volume->nservers; loop++) {
 		server = volume->servers[loop];
 		state = server->fs_state;

 		switch (state) {
 			/* found an apparently healthy server */
 		case 0:
 			afs_get_server(server);
 			up_read(&volume->server_sem);
 			*_server = server;
 			_leave(" = 0 (picked %08x)",
 			       ntohl(server->addr.s_addr));
 			return 0;

 		case -ENETUNREACH:
 			if (ret == 0)
 				ret = state;
 			break;

 		case -EHOSTUNREACH:
 			if (ret == 0 ||
 			    ret == -ENETUNREACH)
 				ret = state;
 			break;

 		case -ECONNREFUSED:
 			if (ret == 0 ||
 			    ret == -ENETUNREACH ||
 			    ret == -EHOSTUNREACH)
 				ret = state;
 			break;

 		default:
 		case -EREMOTEIO:
 			if (ret == 0 ||
 			    ret == -ENETUNREACH ||
 			    ret == -EHOSTUNREACH ||
 			    ret == -ECONNREFUSED)
 				ret = state;
 			break;
 		}
 	}

 	/* no available servers
 	 * - TODO: handle the no active servers case better
 	 */
 	up_read(&volume->server_sem);
 	_leave(" = %d", ret);
 	return ret;
 } /* end afs_volume_pick_fileserver() */

 /*****************************************************************************/
 /*
  * release a server after use
  * - releases the ref on the server struct that was acquired by picking
  * - records result of using a particular server to access a volume
  * - return 0 to try again, 1 if okay or to issue error
  */
 int afs_volume_release_fileserver(struct afs_volume *volume,
 				  struct afs_server *server,
 				  int result)
 {
 	unsigned loop;

 	_enter("%s,%08x,%d",
 	       volume->vlocation->vldb.name, ntohl(server->addr.s_addr),
 	       result);

 	switch (result) {
 		/* success */
 	case 0:
 		server->fs_act_jif = jiffies;
 		break;

 		/* the fileserver denied all knowledge of the volume */
 	case -ENOMEDIUM:
 		server->fs_act_jif = jiffies;
 		down_write(&volume->server_sem);

 		/* first, find where the server is in the active list (if it
 		 * is) */
 		for (loop = 0; loop < volume->nservers; loop++)
 			if (volume->servers[loop] == server)
 				goto present;

 		/* no longer there - may have been discarded by another op */
 		goto try_next_server_upw;

 	present:
 		volume->nservers--;
 		memmove(&volume->servers[loop],
 			&volume->servers[loop + 1],
 			sizeof(volume->servers[loop]) *
 			(volume->nservers - loop));
 		volume->servers[volume->nservers] = NULL;
 		afs_put_server(server);
 		volume->rjservers++;

 		if (volume->nservers > 0)
 			/* another server might acknowledge its existence */
 			goto try_next_server_upw;

 		/* handle the case where all the fileservers have rejected the
 		 * volume
 		 * - TODO: try asking the fileservers for volume information
 		 * - TODO: contact the VL server again to see if the volume is
 		 *         no longer registered
 		 */
 		up_write(&volume->server_sem);
 		afs_put_server(server);
 		_leave(" [completely rejected]");
 		return 1;

 		/* problem reaching the server */
 	case -ENETUNREACH:
 	case -EHOSTUNREACH:
 	case -ECONNREFUSED:
 	case -ETIMEDOUT:
 	case -EREMOTEIO:
 		/* mark the server as dead
 		 * TODO: vary dead timeout depending on error
 		 */
 		spin_lock(&server->fs_lock);
 		if (!server->fs_state) {
 			server->fs_dead_jif = jiffies + HZ * 10;
 			server->fs_state = result;
 			printk("kAFS: SERVER DEAD state=%d\n", result);
 		}
 		spin_unlock(&server->fs_lock);
 		goto try_next_server;

 		/* miscellaneous error */
 	default:
 		server->fs_act_jif = jiffies;
 	case -ENOMEM:
 	case -ENONET:
 		break;
 	}

 	/* tell the caller to accept the result */
 	afs_put_server(server);
 	_leave("");
 	return 1;

 	/* tell the caller to loop around and try the next server */
  try_next_server_upw:
 	up_write(&volume->server_sem);
  try_next_server:
 	afs_put_server(server);
 	_leave(" [try next server]");
 	return 0;

 } /* end afs_volume_release_fileserver() */

 /*****************************************************************************/
 /*
  * match a volume hash record stored in the cache
  */
 #ifdef AFS_CACHING_SUPPORT
 static cachefs_match_val_t afs_volume_cache_match(void *target,
 						  const void *entry)
 {
 	const struct afs_cache_vhash *vhash = entry;
 	struct afs_volume *volume = target;

 	_enter("{%u},{%u}", volume->type, vhash->vtype);

 	if (volume->type == vhash->vtype) {
 		_leave(" = SUCCESS");
 		return CACHEFS_MATCH_SUCCESS;
 	}

 	_leave(" = FAILED");
 	return CACHEFS_MATCH_FAILED;
 } /* end afs_volume_cache_match() */
 #endif

 /*****************************************************************************/
 /*
  * update a volume hash record stored in the cache
  */
 #ifdef AFS_CACHING_SUPPORT
 static void afs_volume_cache_update(void *source, void *entry)
 {
 	struct afs_cache_vhash *vhash = entry;
 	struct afs_volume *volume = source;

 	_enter("");

 	vhash->vtype = volume->type;

 } /* end afs_volume_cache_update() */
 #endif
	/* volume.c: AFS volume management
	*
	* Copyright (C) 2002 Red Hat, Inc. All Rights Reserved.
	* Written by David Howells (dhowells@redhat.com)
	*
	* This program is free software; you can redistribute it and/or
	* modify it under the terms of the GNU General Public License
	* as published by the Free Software Foundation; either version
	* 2 of the License, or (at your option) any later version.
	*/

	#include <linux/kernel.h>
	#include <linux/module.h>
	#include <linux/init.h>
	#include <linux/slab.h>
	#include <linux/fs.h>
	#include <linux/pagemap.h>
	#include "volume.h"
	#include "vnode.h"
	#include "cell.h"
	#include "cache.h"
	#include "cmservice.h"
	#include "fsclient.h"
	#include "vlclient.h"
	#include "internal.h"

	#ifdef __KDEBUG
	static const char *afs_voltypes[] = { "R/W", "R/O", "BAK" };
	#endif

	#ifdef AFS_CACHING_SUPPORT
	static cachefs_match_val_t afs_volume_cache_match(void *target,
	const void *entry);
	static void afs_volume_cache_update(void source, void entry);

	struct cachefs_index_def afs_volume_cache_index_def = {
	.name = "volume",
	.data_size = sizeof(struct afs_cache_vhash),
	.keys[0] = { CACHEFS_INDEX_KEYS_BIN, 1 },
	.keys[1] = { CACHEFS_INDEX_KEYS_BIN, 1 },
	.match = afs_volume_cache_match,
	.update = afs_volume_cache_update,
	};
	#endif

	/*****************************************************************************/
	/*
	* lookup a volume by name
	* - this can be one of the following:
	* "%[cell:]volume[.]" R/W volume
	* "#[cell:]volume[.]" R/O or R/W volume (rwparent=0),
	* or R/W (rwparent=1) volume
	* "%[cell:]volume.readonly" R/O volume
	* "#[cell:]volume.readonly" R/O volume
	* "%[cell:]volume.backup" Backup volume
	* "#[cell:]volume.backup" Backup volume
	*
	* The cell name is optional, and defaults to the current cell.
	*
	* See "The Rules of Mount Point Traversal" in Chapter 5 of the AFS SysAdmin
	* Guide
	* - Rule 1: Explicit type suffix forces access of that type or nothing
	* (no suffix, then use Rule 2 & 3)
	* - Rule 2: If parent volume is R/O, then mount R/O volume by preference, R/W
	* if not available
	* - Rule 3: If parent volume is R/W, then only mount R/W volume unless
	* explicitly told otherwise
	*/
	int afs_volume_lookup(const char name, struct afs_cell cell, int rwpath,
	struct afs_volume **_volume)
	{
	struct afs_vlocation *vlocation = NULL;
	struct afs_volume *volume = NULL;
	afs_voltype_t type;
	const char cellname, volname, *suffix;
	char srvtmask;
	int force, ret, loop, cellnamesz, volnamesz;

	_enter("%s,,%d,", name, rwpath);

	if (!name \|\| (name[0] != '%' && name[0] != '#') \|\| !name[1]) {
	printk("kAFS: unparsable volume name\n");
	return -EINVAL;
	}

	/* determine the type of volume we're looking for */
	force = 0;
	type = AFSVL_ROVOL;

	if (rwpath \|\| name[0] == '%') {
	type = AFSVL_RWVOL;
	force = 1;
	}

	suffix = strrchr(name, '.');
	if (suffix) {
	if (strcmp(suffix, ".readonly") == 0) {
	type = AFSVL_ROVOL;
	force = 1;
	}
	else if (strcmp(suffix, ".backup") == 0) {
	type = AFSVL_BACKVOL;
	force = 1;
	}
	else if (suffix[1] == 0) {
	}
	else {
	suffix = NULL;
	}
	}

	/* split the cell and volume names */
	name++;
	volname = strchr(name, ':');
	if (volname) {
	cellname = name;
	cellnamesz = volname - name;
	volname++;
	}
	else {
	volname = name;
	cellname = NULL;
	cellnamesz = 0;
	}

	volnamesz = suffix ? suffix - volname : strlen(volname);

	_debug("CELL:%.s [%p] VOLUME:%.s SUFFIX:%s TYPE:%d%s",
	cellnamesz, cellnamesz, cellname ?: "", cell,
	volnamesz, volnamesz, volname, suffix ?: "-",
	type,
	force ? " FORCE" : "");

	/* lookup the cell record */
	if (cellname \|\| !cell) {
	ret = afs_cell_lookup(cellname, cellnamesz, &cell);
	if (ret<0) {
	printk("kAFS: unable to lookup cell '%s'\n",
	cellname ?: "");
	goto error;
	}
	}
	else {
	afs_get_cell(cell);
	}

	/* lookup the volume location record */
	ret = afs_vlocation_lookup(cell, volname, volnamesz, &vlocation);
	if (ret < 0)
	goto error;

	/* make the final decision on the type we want */
	ret = -ENOMEDIUM;
	if (force && !(vlocation->vldb.vidmask & (1 << type)))
	goto error;

	srvtmask = 0;
	for (loop = 0; loop < vlocation->vldb.nservers; loop++)
	srvtmask \|= vlocation->vldb.srvtmask[loop];

	if (force) {
	if (!(srvtmask & (1 << type)))
	goto error;
	}
	else if (srvtmask & AFS_VOL_VTM_RO) {
	type = AFSVL_ROVOL;
	}
	else if (srvtmask & AFS_VOL_VTM_RW) {
	type = AFSVL_RWVOL;
	}
	else {
	goto error;
	}

	down_write(&cell->vl_sem);

	/* is the volume already active? */
	if (vlocation->vols[type]) {
	/* yes - re-use it */
	volume = vlocation->vols[type];
	afs_get_volume(volume);
	goto success;
	}

	/* create a new volume record */
	_debug("creating new volume record");

	ret = -ENOMEM;
	volume = kzalloc(sizeof(struct afs_volume), GFP_KERNEL);
	if (!volume)
	goto error_up;

	atomic_set(&volume->usage, 1);
	volume->type = type;
	volume->type_force = force;
	volume->cell = cell;
	volume->vid = vlocation->vldb.vid[type];

	init_rwsem(&volume->server_sem);

	/* look up all the applicable server records */
	for (loop = 0; loop < 8; loop++) {
	if (vlocation->vldb.srvtmask[loop] & (1 << volume->type)) {
	ret = afs_server_lookup(
	volume->cell,
	&vlocation->vldb.servers[loop],
	&volume->servers[volume->nservers]);
	if (ret < 0)
	goto error_discard;

	volume->nservers++;
	}
	}

	/* attach the cache and volume location */
	#ifdef AFS_CACHING_SUPPORT
	cachefs_acquire_cookie(vlocation->cache,
	&afs_vnode_cache_index_def,
	volume,
	&volume->cache);
	#endif

	afs_get_vlocation(vlocation);
	volume->vlocation = vlocation;

	vlocation->vols[type] = volume;

	success:
	_debug("kAFS selected %s volume %08x",
	afs_voltypes[volume->type], volume->vid);
	*_volume = volume;
	ret = 0;

	/* clean up */
	error_up:
	up_write(&cell->vl_sem);
	error:
	afs_put_vlocation(vlocation);
	afs_put_cell(cell);

	_leave(" = %d (%p)", ret, volume);
	return ret;

	error_discard:
	up_write(&cell->vl_sem);

	for (loop = volume->nservers - 1; loop >= 0; loop--)
	afs_put_server(volume->servers[loop]);

	kfree(volume);
	goto error;
	} /* end afs_volume_lookup() */

	/*****************************************************************************/
	/*
	* destroy a volume record
	*/
	void afs_put_volume(struct afs_volume *volume)
	{
	struct afs_vlocation *vlocation;
	int loop;

	if (!volume)
	return;

	_enter("%p", volume);

	vlocation = volume->vlocation;

	/* sanity check */
	BUG_ON(atomic_read(&volume->usage) <= 0);

	/* to prevent a race, the decrement and the dequeue must be effectively
	* atomic */
	down_write(&vlocation->cell->vl_sem);

	if (likely(!atomic_dec_and_test(&volume->usage))) {
	up_write(&vlocation->cell->vl_sem);
	_leave("");
	return;
	}

	vlocation->vols[volume->type] = NULL;

	up_write(&vlocation->cell->vl_sem);

	/* finish cleaning up the volume */
	#ifdef AFS_CACHING_SUPPORT
	cachefs_relinquish_cookie(volume->cache, 0);
	#endif
	afs_put_vlocation(vlocation);

	for (loop = volume->nservers - 1; loop >= 0; loop--)
	afs_put_server(volume->servers[loop]);

	kfree(volume);

	_leave(" [destroyed]");
	} /* end afs_put_volume() */

	/*****************************************************************************/
	/*
	* pick a server to use to try accessing this volume
	* - returns with an elevated usage count on the server chosen
	*/
	int afs_volume_pick_fileserver(struct afs_volume *volume,
	struct afs_server **_server)
	{
	struct afs_server *server;
	int ret, state, loop;

	_enter("%s", volume->vlocation->vldb.name);

	down_read(&volume->server_sem);

	/* handle the no-server case */
	if (volume->nservers == 0) {
	ret = volume->rjservers ? -ENOMEDIUM : -ESTALE;
	up_read(&volume->server_sem);
	_leave(" = %d [no servers]", ret);
	return ret;
	}

	/* basically, just search the list for the first live server and use
	* that */
	ret = 0;
	for (loop = 0; loop < volume->nservers; loop++) {
	server = volume->servers[loop];
	state = server->fs_state;

	switch (state) {
	/* found an apparently healthy server */
	case 0:
	afs_get_server(server);
	up_read(&volume->server_sem);
	*_server = server;
	_leave(" = 0 (picked %08x)",
	ntohl(server->addr.s_addr));
	return 0;

	case -ENETUNREACH:
	if (ret == 0)
	ret = state;
	break;

	case -EHOSTUNREACH:
	if (ret == 0 \|\|
	ret == -ENETUNREACH)
	ret = state;
	break;

	case -ECONNREFUSED:
	if (ret == 0 \|\|
	ret == -ENETUNREACH \|\|
	ret == -EHOSTUNREACH)
	ret = state;
	break;

	default:
	case -EREMOTEIO:
	if (ret == 0 \|\|
	ret == -ENETUNREACH \|\|
	ret == -EHOSTUNREACH \|\|
	ret == -ECONNREFUSED)
	ret = state;
	break;
	}
	}

	/* no available servers
	* - TODO: handle the no active servers case better
	*/
	up_read(&volume->server_sem);
	_leave(" = %d", ret);
	return ret;
	} /* end afs_volume_pick_fileserver() */

	/*****************************************************************************/
	/*
	* release a server after use
	* - releases the ref on the server struct that was acquired by picking
	* - records result of using a particular server to access a volume
	* - return 0 to try again, 1 if okay or to issue error
	*/
	int afs_volume_release_fileserver(struct afs_volume *volume,
	struct afs_server *server,
	int result)
	{
	unsigned loop;

	_enter("%s,%08x,%d",
	volume->vlocation->vldb.name, ntohl(server->addr.s_addr),
	result);

	switch (result) {
	/* success */
	case 0:
	server->fs_act_jif = jiffies;
	break;

	/* the fileserver denied all knowledge of the volume */
	case -ENOMEDIUM:
	server->fs_act_jif = jiffies;
	down_write(&volume->server_sem);

	/* first, find where the server is in the active list (if it
	* is) */
	for (loop = 0; loop < volume->nservers; loop++)
	if (volume->servers[loop] == server)
	goto present;

	/* no longer there - may have been discarded by another op */
	goto try_next_server_upw;

	present:
	volume->nservers--;
	memmove(&volume->servers[loop],
	&volume->servers[loop + 1],
	sizeof(volume->servers[loop]) *
	(volume->nservers - loop));
	volume->servers[volume->nservers] = NULL;
	afs_put_server(server);
	volume->rjservers++;

	if (volume->nservers > 0)
	/* another server might acknowledge its existence */
	goto try_next_server_upw;

	/* handle the case where all the fileservers have rejected the
	* volume
	* - TODO: try asking the fileservers for volume information
	* - TODO: contact the VL server again to see if the volume is
	* no longer registered
	*/
	up_write(&volume->server_sem);
	afs_put_server(server);
	_leave(" [completely rejected]");
	return 1;

	/* problem reaching the server */
	case -ENETUNREACH:
	case -EHOSTUNREACH:
	case -ECONNREFUSED:
	case -ETIMEDOUT:
	case -EREMOTEIO:
	/* mark the server as dead
	* TODO: vary dead timeout depending on error
	*/
	spin_lock(&server->fs_lock);
	if (!server->fs_state) {
	server->fs_dead_jif = jiffies + HZ * 10;
	server->fs_state = result;
	printk("kAFS: SERVER DEAD state=%d\n", result);
	}
	spin_unlock(&server->fs_lock);
	goto try_next_server;

	/* miscellaneous error */
	default:
	server->fs_act_jif = jiffies;
	case -ENOMEM:
	case -ENONET:
	break;
	}

	/* tell the caller to accept the result */
	afs_put_server(server);
	_leave("");
	return 1;

	/* tell the caller to loop around and try the next server */
	try_next_server_upw:
	up_write(&volume->server_sem);
	try_next_server:
	afs_put_server(server);
	_leave(" [try next server]");
	return 0;

	} /* end afs_volume_release_fileserver() */

	/*****************************************************************************/
	/*
	* match a volume hash record stored in the cache
	*/
	#ifdef AFS_CACHING_SUPPORT
	static cachefs_match_val_t afs_volume_cache_match(void *target,
	const void *entry)
	{
	const struct afs_cache_vhash *vhash = entry;
	struct afs_volume *volume = target;

	_enter("{%u},{%u}", volume->type, vhash->vtype);

	if (volume->type == vhash->vtype) {
	_leave(" = SUCCESS");
	return CACHEFS_MATCH_SUCCESS;
	}

	_leave(" = FAILED");
	return CACHEFS_MATCH_FAILED;
	} /* end afs_volume_cache_match() */
	#endif

	/*****************************************************************************/
	/*
	* update a volume hash record stored in the cache
	*/
	#ifdef AFS_CACHING_SUPPORT
	static void afs_volume_cache_update(void source, void entry)
	{
	struct afs_cache_vhash *vhash = entry;
	struct afs_volume *volume = source;

	_enter("");

	vhash->vtype = volume->type;

	} /* end afs_volume_cache_update() */
	#endif