/* AFS volume management
   *
   * Copyright (C) 2002, 2007 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 <linux/sched.h>
  #include "internal.h"
  
  static const char *afs_voltypes[] = { "R/W", "R/O", "BAK" };
  
  /*
   * 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
   */
  struct afs_volume *afs_volume_lookup(struct afs_mount_params *params)
  {
  	struct afs_vlocation *vlocation = NULL;
  	struct afs_volume *volume = NULL;
  	struct afs_server *server = NULL;
  	char srvtmask;
  	int ret, loop;
  
  	_enter("{%*.*s,%d}",
  	       params->volnamesz, params->volnamesz, params->volname, params->rwpath);
  
  	/* lookup the volume location record */
  	vlocation = afs_vlocation_lookup(params->cell, params->key,
  					 params->volname, params->volnamesz);
  	if (IS_ERR(vlocation)) {
  		ret = PTR_ERR(vlocation);
  		vlocation = NULL;
  		goto error;
  	}
  
  	/* make the final decision on the type we want */
  	ret = -ENOMEDIUM;
  	if (params->force && !(vlocation->vldb.vidmask & (1 << params->type)))
  		goto error;
  
  	srvtmask = 0;
  	for (loop = 0; loop < vlocation->vldb.nservers; loop++)
  		srvtmask |= vlocation->vldb.srvtmask[loop];
  
  	if (params->force) {
  		if (!(srvtmask & (1 << params->type)))
  			goto error;
  	} else if (srvtmask & AFS_VOL_VTM_RO) {
  		params->type = AFSVL_ROVOL;
  	} else if (srvtmask & AFS_VOL_VTM_RW) {
  		params->type = AFSVL_RWVOL;
  	} else {
  		goto error;
  	}
  
  	down_write(&params->cell->vl_sem);
  
  	/* is the volume already active? */
  	if (vlocation->vols[params->type]) {
  		/* yes - re-use it */
  		volume = vlocation->vols[params->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		= params->type;
  	volume->type_force	= params->force;
  	volume->cell		= params->cell;
  	volume->vid		= vlocation->vldb.vid[params->type];
  
  	ret = bdi_setup_and_register(&volume->bdi, "afs", BDI_CAP_MAP_COPY);
  	if (ret)
  		goto error_bdi;
  
  	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)) {
  			server = afs_lookup_server(
  			       volume->cell, &vlocation->vldb.servers[loop]);
  			if (IS_ERR(server)) {
  				ret = PTR_ERR(server);
  				goto error_discard;
  			}
  
  			volume->servers[volume->nservers] = server;
  			volume->nservers++;
  		}
  	}
  
  	/* attach the cache and volume location */
  #ifdef CONFIG_AFS_FSCACHE
  	volume->cache = fscache_acquire_cookie(vlocation->cache,
  					       &afs_volume_cache_index_def,
  					       volume, true);
  #endif
  	afs_get_vlocation(vlocation);
  	volume->vlocation = vlocation;
  
  	vlocation->vols[volume->type] = volume;
  
  success:
  	_debug("kAFS selected %s volume %08x",
  	       afs_voltypes[volume->type], volume->vid);
  	up_write(&params->cell->vl_sem);
  	afs_put_vlocation(vlocation);
  	_leave(" = %p", volume);
  	return volume;
  
  	/* clean up */
  error_up:
  	up_write(&params->cell->vl_sem);
  error:
  	afs_put_vlocation(vlocation);
  	_leave(" = %d", ret);
  	return ERR_PTR(ret);
  
  error_discard:
  	bdi_destroy(&volume->bdi);
  error_bdi:
  	up_write(&params->cell->vl_sem);
  
  	for (loop = volume->nservers - 1; loop >= 0; loop--)
  		afs_put_server(volume->servers[loop]);
  
  	kfree(volume);
  	goto error;
  }
  
  /*
   * destroy a volume record
   */
  void afs_put_volume(struct afs_volume *volume)
  {
  	struct afs_vlocation *vlocation;
  	int loop;
  
  	if (!volume)
  		return;
  
  	_enter("%p", volume);
  
  	ASSERTCMP(atomic_read(&volume->usage), >, 0);
  
  	vlocation = volume->vlocation;
  
  	/* 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 CONFIG_AFS_FSCACHE
  	fscache_relinquish_cookie(volume->cache, 0);
  #endif
  	afs_put_vlocation(vlocation);
  
  	for (loop = volume->nservers - 1; loop >= 0; loop--)
  		afs_put_server(volume->servers[loop]);
  
  	bdi_destroy(&volume->bdi);
  	kfree(volume);
  
  	_leave(" [destroyed]");
  }
  
  /*
   * pick a server to use to try accessing this volume
   * - returns with an elevated usage count on the server chosen
   */
  struct afs_server *afs_volume_pick_fileserver(struct afs_vnode *vnode)
  {
  	struct afs_volume *volume = vnode->volume;
  	struct afs_server *server;
  	int ret, state, loop;
  
  	_enter("%s", volume->vlocation->vldb.name);
  
  	/* stick with the server we're already using if we can */
  	if (vnode->server && vnode->server->fs_state == 0) {
  		afs_get_server(vnode->server);
  		_leave(" = %p [current]", vnode->server);
  		return vnode->server;
  	}
  
  	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 ERR_PTR(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;
  
  		_debug("consider %d [%d]", loop, state);
  
  		switch (state) {
  			/* found an apparently healthy server */
  		case 0:
  			afs_get_server(server);
  			up_read(&volume->server_sem);
  			_leave(" = %p (picked %08x)",
  			       server, ntohl(server->addr.s_addr));
  			return server;
  
  		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 ERR_PTR(ret);
  }
  
  /*
   * 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
   * - the caller must release the server struct if result was 0
   */
  int afs_volume_release_fileserver(struct afs_vnode *vnode,
  				  struct afs_server *server,
  				  int result)
  {
  	struct afs_volume *volume = vnode->volume;
  	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;
  		server->fs_state = 0;
  		_leave("");
  		return 1;
  
  		/* the fileserver denied all knowledge of the volume */
  	case -ENOMEDIUM:
  		server->fs_act_jif = jiffies;
  		down_write(&volume->server_sem);
  
  		/* firstly, 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 -ETIME:
  	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
  ", result);
  		}
  		spin_unlock(&server->fs_lock);
  		goto try_next_server;
  
  		/* miscellaneous error */
  	default:
  		server->fs_act_jif = jiffies;
  	case -ENOMEM:
  	case -ENONET:
  		/* tell the caller to accept the result */
  		afs_put_server(server);
  		_leave(" [local failure]");
  		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;
  }