/* AFS volume location 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/slab.h>

  #include <linux/init.h>

  #include <linux/sched.h>

  #include "internal.h"

  static unsigned afs_vlocation_timeout = 10;	/* volume location timeout in seconds */
  static unsigned afs_vlocation_update_timeout = 10 * 60;

  static void afs_vlocation_reaper(struct work_struct *);
  static void afs_vlocation_updater(struct work_struct *);

  static LIST_HEAD(afs_vlocation_updates);
  static LIST_HEAD(afs_vlocation_graveyard);
  static DEFINE_SPINLOCK(afs_vlocation_updates_lock);
  static DEFINE_SPINLOCK(afs_vlocation_graveyard_lock);
  static DECLARE_DELAYED_WORK(afs_vlocation_reap, afs_vlocation_reaper);
  static DECLARE_DELAYED_WORK(afs_vlocation_update, afs_vlocation_updater);
  static struct workqueue_struct *afs_vlocation_update_worker;

  /*
   * iterate through the VL servers in a cell until one of them admits knowing
   * about the volume in question

   */

  static int afs_vlocation_access_vl_by_name(struct afs_vlocation *vl,

  					   struct key *key,

  					   struct afs_cache_vlocation *vldb)
  {

  	struct afs_cell *cell = vl->cell;
  	struct in_addr addr;

  	int count, ret;

  	_enter("%s,%s", cell->name, vl->vldb.name);

  	down_write(&vl->cell->vl_sem);

  	ret = -ENOMEDIUM;
  	for (count = cell->vl_naddrs; count > 0; count--) {

  		addr = cell->vl_addrs[cell->vl_curr_svix];
  
  		_debug("CellServ[%hu]: %08x", cell->vl_curr_svix, addr.s_addr);

  
  		/* attempt to access the VL server */

  		ret = afs_vl_get_entry_by_name(&addr, key, vl->vldb.name, vldb,

  					       &afs_sync_call);

  		switch (ret) {
  		case 0:

  			goto out;
  		case -ENOMEM:
  		case -ENONET:
  		case -ENETUNREACH:
  		case -EHOSTUNREACH:
  		case -ECONNREFUSED:

  			if (ret == -ENOMEM || ret == -ENONET)
  				goto out;
  			goto rotate;
  		case -ENOMEDIUM:

  		case -EKEYREJECTED:
  		case -EKEYEXPIRED:

  			goto out;
  		default:

  			ret = -EIO;

  			goto rotate;
  		}
  
  		/* rotate the server records upon lookup failure */
  	rotate:
  		cell->vl_curr_svix++;
  		cell->vl_curr_svix %= cell->vl_naddrs;
  	}

  out:

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

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

  }

  /*
   * iterate through the VL servers in a cell until one of them admits knowing
   * about the volume in question

   */

  static int afs_vlocation_access_vl_by_id(struct afs_vlocation *vl,

  					 struct key *key,

  					 afs_volid_t volid,
  					 afs_voltype_t voltype,
  					 struct afs_cache_vlocation *vldb)
  {

  	struct afs_cell *cell = vl->cell;
  	struct in_addr addr;

  	int count, ret;
  
  	_enter("%s,%x,%d,", cell->name, volid, voltype);

  	down_write(&vl->cell->vl_sem);

  	ret = -ENOMEDIUM;
  	for (count = cell->vl_naddrs; count > 0; count--) {

  		addr = cell->vl_addrs[cell->vl_curr_svix];
  
  		_debug("CellServ[%hu]: %08x", cell->vl_curr_svix, addr.s_addr);

  
  		/* attempt to access the VL server */

  		ret = afs_vl_get_entry_by_id(&addr, key, volid, voltype, vldb,

  					     &afs_sync_call);

  		switch (ret) {
  		case 0:

  			goto out;
  		case -ENOMEM:
  		case -ENONET:
  		case -ENETUNREACH:
  		case -EHOSTUNREACH:
  		case -ECONNREFUSED:

  			if (ret == -ENOMEM || ret == -ENONET)
  				goto out;
  			goto rotate;

  		case -EBUSY:
  			vl->upd_busy_cnt++;
  			if (vl->upd_busy_cnt <= 3) {
  				if (vl->upd_busy_cnt > 1) {
  					/* second+ BUSY - sleep a little bit */
  					set_current_state(TASK_UNINTERRUPTIBLE);
  					schedule_timeout(1);
  					__set_current_state(TASK_RUNNING);
  				}
  				continue;
  			}
  			break;

  		case -ENOMEDIUM:

  			vl->upd_rej_cnt++;
  			goto rotate;

  		default:

  			ret = -EIO;

  			goto rotate;
  		}
  
  		/* rotate the server records upon lookup failure */
  	rotate:
  		cell->vl_curr_svix++;
  		cell->vl_curr_svix %= cell->vl_naddrs;

  		vl->upd_busy_cnt = 0;

  	}

  out:

  	if (ret < 0 && vl->upd_rej_cnt > 0) {
  		printk(KERN_NOTICE "kAFS:"
  		       " Active volume no longer valid '%s'
  ",
  		       vl->vldb.name);
  		vl->valid = 0;
  		ret = -ENOMEDIUM;
  	}
  
  	up_write(&vl->cell->vl_sem);

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

  }

  /*

   * allocate a volume location record

   */

  static struct afs_vlocation *afs_vlocation_alloc(struct afs_cell *cell,
  						 const char *name,
  						 size_t namesz)

  {

  	struct afs_vlocation *vl;
  
  	vl = kzalloc(sizeof(struct afs_vlocation), GFP_KERNEL);
  	if (vl) {
  		vl->cell = cell;
  		vl->state = AFS_VL_NEW;
  		atomic_set(&vl->usage, 1);
  		INIT_LIST_HEAD(&vl->link);
  		INIT_LIST_HEAD(&vl->grave);
  		INIT_LIST_HEAD(&vl->update);
  		init_waitqueue_head(&vl->waitq);

  		spin_lock_init(&vl->lock);

  		memcpy(vl->vldb.name, name, namesz);

  	}

  	_leave(" = %p", vl);
  	return vl;
  }

  /*
   * update record if we found it in the cache
   */
  static int afs_vlocation_update_record(struct afs_vlocation *vl,

  				       struct key *key,

  				       struct afs_cache_vlocation *vldb)
  {
  	afs_voltype_t voltype;
  	afs_volid_t vid;
  	int ret;

  	/* try to look up a cached volume in the cell VL databases by ID */

  	_debug("Locally Cached: %s %02x { %08x(%x) %08x(%x) %08x(%x) }",

  	       vl->vldb.name,
  	       vl->vldb.vidmask,
  	       ntohl(vl->vldb.servers[0].s_addr),
  	       vl->vldb.srvtmask[0],
  	       ntohl(vl->vldb.servers[1].s_addr),
  	       vl->vldb.srvtmask[1],
  	       ntohl(vl->vldb.servers[2].s_addr),
  	       vl->vldb.srvtmask[2]);

  
  	_debug("Vids: %08x %08x %08x",

  	       vl->vldb.vid[0],
  	       vl->vldb.vid[1],
  	       vl->vldb.vid[2]);

  	if (vl->vldb.vidmask & AFS_VOL_VTM_RW) {
  		vid = vl->vldb.vid[0];

  		voltype = AFSVL_RWVOL;

  	} else if (vl->vldb.vidmask & AFS_VOL_VTM_RO) {
  		vid = vl->vldb.vid[1];

  		voltype = AFSVL_ROVOL;

  	} else if (vl->vldb.vidmask & AFS_VOL_VTM_BAK) {
  		vid = vl->vldb.vid[2];

  		voltype = AFSVL_BACKVOL;

  	} else {

  		BUG();
  		vid = 0;
  		voltype = 0;
  	}

  	/* contact the server to make sure the volume is still available
  	 * - TODO: need to handle disconnected operation here
  	 */

  	ret = afs_vlocation_access_vl_by_id(vl, key, vid, voltype, vldb);

  	switch (ret) {
  		/* net error */
  	default:

  		printk(KERN_WARNING "kAFS:"
  		       " failed to update volume '%s' (%x) up in '%s': %d
  ",
  		       vl->vldb.name, vid, vl->cell->name, ret);
  		_leave(" = %d", ret);
  		return ret;

  
  		/* pulled from local cache into memory */
  	case 0:

  		_leave(" = 0");
  		return 0;

  
  		/* uh oh... looks like the volume got deleted */
  	case -ENOMEDIUM:

  		printk(KERN_ERR "kAFS:"
  		       " volume '%s' (%x) does not exist '%s'
  ",
  		       vl->vldb.name, vid, vl->cell->name);

  
  		/* TODO: make existing record unavailable */

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

  	}

  }

  /*
   * apply the update to a VL record
   */
  static void afs_vlocation_apply_update(struct afs_vlocation *vl,
  				       struct afs_cache_vlocation *vldb)
  {
  	_debug("Done VL Lookup: %s %02x { %08x(%x) %08x(%x) %08x(%x) }",
  	       vldb->name, vldb->vidmask,
  	       ntohl(vldb->servers[0].s_addr), vldb->srvtmask[0],
  	       ntohl(vldb->servers[1].s_addr), vldb->srvtmask[1],
  	       ntohl(vldb->servers[2].s_addr), vldb->srvtmask[2]);

  	_debug("Vids: %08x %08x %08x",
  	       vldb->vid[0], vldb->vid[1], vldb->vid[2]);

  	if (strcmp(vldb->name, vl->vldb.name) != 0)
  		printk(KERN_NOTICE "kAFS:"
  		       " name of volume '%s' changed to '%s' on server
  ",
  		       vl->vldb.name, vldb->name);

  	vl->vldb = *vldb;

  #ifdef CONFIG_AFS_FSCACHE
  	fscache_update_cookie(vl->cache);

  #endif

  }

  /*

   * fill in a volume location record, consulting the cache and the VL server
   * both

   */

  static int afs_vlocation_fill_in_record(struct afs_vlocation *vl,
  					struct key *key)

  {

  	struct afs_cache_vlocation vldb;
  	int ret;

  	_enter("");

  	ASSERTCMP(vl->valid, ==, 0);

  	memset(&vldb, 0, sizeof(vldb));

  	/* see if we have an in-cache copy (will set vl->valid if there is) */

  #ifdef CONFIG_AFS_FSCACHE
  	vl->cache = fscache_acquire_cookie(vl->cell->cache,
  					   &afs_vlocation_cache_index_def, vl);

  #endif

  	if (vl->valid) {
  		/* try to update a known volume in the cell VL databases by
  		 * ID as the name may have changed */
  		_debug("found in cache");

  		ret = afs_vlocation_update_record(vl, key, &vldb);

  	} else {
  		/* try to look up an unknown volume in the cell VL databases by
  		 * name */

  		ret = afs_vlocation_access_vl_by_name(vl, key, &vldb);

  		if (ret < 0) {
  			printk("kAFS: failed to locate '%s' in cell '%s'
  ",
  			       vl->vldb.name, vl->cell->name);
  			return ret;
  		}

  	}

  	afs_vlocation_apply_update(vl, &vldb);
  	_leave(" = 0");
  	return 0;

  }

  /*

   * queue a vlocation record for updates

   */

  static void afs_vlocation_queue_for_updates(struct afs_vlocation *vl)

  {

  	struct afs_vlocation *xvl;

  	/* wait at least 10 minutes before updating... */
  	vl->update_at = get_seconds() + afs_vlocation_update_timeout;
  
  	spin_lock(&afs_vlocation_updates_lock);
  
  	if (!list_empty(&afs_vlocation_updates)) {
  		/* ... but wait at least 1 second more than the newest record
  		 * already queued so that we don't spam the VL server suddenly
  		 * with lots of requests
  		 */
  		xvl = list_entry(afs_vlocation_updates.prev,
  				 struct afs_vlocation, update);
  		if (vl->update_at <= xvl->update_at)
  			vl->update_at = xvl->update_at + 1;
  	} else {
  		queue_delayed_work(afs_vlocation_update_worker,
  				   &afs_vlocation_update,
  				   afs_vlocation_update_timeout * HZ);

  	}

  
  	list_add_tail(&vl->update, &afs_vlocation_updates);
  	spin_unlock(&afs_vlocation_updates_lock);

  }

  /*

   * lookup volume location
   * - iterate through the VL servers in a cell until one of them admits knowing
   *   about the volume in question
   * - lookup in the local cache if not able to find on the VL server
   * - insert/update in the local cache if did get a VL response

   */

  struct afs_vlocation *afs_vlocation_lookup(struct afs_cell *cell,

  					   struct key *key,

  					   const char *name,
  					   size_t namesz)

  {

  	struct afs_vlocation *vl;
  	int ret;

  	_enter("{%s},{%x},%*.*s,%zu",
  	       cell->name, key_serial(key),
  	       (int) namesz, (int) namesz, name, namesz);

  	if (namesz >= sizeof(vl->vldb.name)) {

  		_leave(" = -ENAMETOOLONG");
  		return ERR_PTR(-ENAMETOOLONG);
  	}

  	/* see if we have an in-memory copy first */
  	down_write(&cell->vl_sem);
  	spin_lock(&cell->vl_lock);
  	list_for_each_entry(vl, &cell->vl_list, link) {
  		if (vl->vldb.name[namesz] != '\0')
  			continue;
  		if (memcmp(vl->vldb.name, name, namesz) == 0)
  			goto found_in_memory;

  	}

  	spin_unlock(&cell->vl_lock);

  	/* not in the cell's in-memory lists - create a new record */
  	vl = afs_vlocation_alloc(cell, name, namesz);
  	if (!vl) {
  		up_write(&cell->vl_sem);
  		return ERR_PTR(-ENOMEM);
  	}

  	afs_get_cell(cell);

  	list_add_tail(&vl->link, &cell->vl_list);
  	vl->state = AFS_VL_CREATING;
  	up_write(&cell->vl_sem);

  fill_in_record:

  	ret = afs_vlocation_fill_in_record(vl, key);

  	if (ret < 0)
  		goto error_abandon;

  	spin_lock(&vl->lock);

  	vl->state = AFS_VL_VALID;

  	spin_unlock(&vl->lock);

  	wake_up(&vl->waitq);

  	/* update volume entry in local cache */
  #ifdef CONFIG_AFS_FSCACHE
  	fscache_update_cookie(vl->cache);
  #endif

  	/* schedule for regular updates */
  	afs_vlocation_queue_for_updates(vl);
  	goto success;

  found_in_memory:
  	/* found in memory */
  	_debug("found in memory");
  	atomic_inc(&vl->usage);
  	spin_unlock(&cell->vl_lock);
  	if (!list_empty(&vl->grave)) {
  		spin_lock(&afs_vlocation_graveyard_lock);
  		list_del_init(&vl->grave);
  		spin_unlock(&afs_vlocation_graveyard_lock);

  	}

  	up_write(&cell->vl_sem);

  	/* see if it was an abandoned record that we might try filling in */

  	spin_lock(&vl->lock);

  	while (vl->state != AFS_VL_VALID) {
  		afs_vlocation_state_t state = vl->state;

  		_debug("invalid [state %d]", state);

  		if (state == AFS_VL_NEW || state == AFS_VL_NO_VOLUME) {

  			vl->state = AFS_VL_CREATING;
  			spin_unlock(&vl->lock);
  			goto fill_in_record;

  		}
  
  		/* must now wait for creation or update by someone else to
  		 * complete */
  		_debug("wait");

  		spin_unlock(&vl->lock);

  		ret = wait_event_interruptible(vl->waitq,
  					       vl->state == AFS_VL_NEW ||
  					       vl->state == AFS_VL_VALID ||
  					       vl->state == AFS_VL_NO_VOLUME);

  		if (ret < 0)
  			goto error;

  		spin_lock(&vl->lock);

  	}

  	spin_unlock(&vl->lock);

  success:

  	_leave(" = %p", vl);

  	return vl;
  
  error_abandon:

  	spin_lock(&vl->lock);

  	vl->state = AFS_VL_NEW;

  	spin_unlock(&vl->lock);

  	wake_up(&vl->waitq);

  error:
  	ASSERT(vl != NULL);
  	afs_put_vlocation(vl);

  	_leave(" = %d", ret);

  	return ERR_PTR(ret);

  }

  /*

   * finish using a volume location record

   */

  void afs_put_vlocation(struct afs_vlocation *vl)

  {

  	if (!vl)
  		return;

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

  	ASSERTCMP(atomic_read(&vl->usage), >, 0);

  	if (likely(!atomic_dec_and_test(&vl->usage))) {
  		_leave("");
  		return;
  	}

  	spin_lock(&afs_vlocation_graveyard_lock);
  	if (atomic_read(&vl->usage) == 0) {
  		_debug("buried");
  		list_move_tail(&vl->grave, &afs_vlocation_graveyard);
  		vl->time_of_death = get_seconds();

  		queue_delayed_work(afs_wq, &afs_vlocation_reap,
  				   afs_vlocation_timeout * HZ);

  
  		/* suspend updates on this record */
  		if (!list_empty(&vl->update)) {
  			spin_lock(&afs_vlocation_updates_lock);
  			list_del_init(&vl->update);
  			spin_unlock(&afs_vlocation_updates_lock);
  		}
  	}
  	spin_unlock(&afs_vlocation_graveyard_lock);
  	_leave(" [killed?]");

  }

  /*

   * destroy a dead volume location record

   */

  static void afs_vlocation_destroy(struct afs_vlocation *vl)

  {

  	_enter("%p", vl);

  #ifdef CONFIG_AFS_FSCACHE
  	fscache_relinquish_cookie(vl->cache, 0);

  #endif

  	afs_put_cell(vl->cell);
  	kfree(vl);
  }
  
  /*
   * reap dead volume location records
   */
  static void afs_vlocation_reaper(struct work_struct *work)
  {
  	LIST_HEAD(corpses);
  	struct afs_vlocation *vl;
  	unsigned long delay, expiry;
  	time_t now;

  	_enter("");

  	now = get_seconds();
  	spin_lock(&afs_vlocation_graveyard_lock);
  
  	while (!list_empty(&afs_vlocation_graveyard)) {
  		vl = list_entry(afs_vlocation_graveyard.next,
  				struct afs_vlocation, grave);
  
  		_debug("check %p", vl);
  
  		/* the queue is ordered most dead first */
  		expiry = vl->time_of_death + afs_vlocation_timeout;
  		if (expiry > now) {
  			delay = (expiry - now) * HZ;
  			_debug("delay %lu", delay);

  			if (!queue_delayed_work(afs_wq, &afs_vlocation_reap,
  						delay)) {

  				cancel_delayed_work(&afs_vlocation_reap);

  				queue_delayed_work(afs_wq, &afs_vlocation_reap,
  						   delay);

  			}
  			break;
  		}

  		spin_lock(&vl->cell->vl_lock);
  		if (atomic_read(&vl->usage) > 0) {
  			_debug("no reap");
  			list_del_init(&vl->grave);

  		} else {

  			_debug("reap");
  			list_move_tail(&vl->grave, &corpses);
  			list_del_init(&vl->link);

  		}

  		spin_unlock(&vl->cell->vl_lock);

  	}

  	spin_unlock(&afs_vlocation_graveyard_lock);

  	/* now reap the corpses we've extracted */
  	while (!list_empty(&corpses)) {
  		vl = list_entry(corpses.next, struct afs_vlocation, grave);
  		list_del(&vl->grave);
  		afs_vlocation_destroy(vl);

  	}
  
  	_leave("");

  }

  /*
   * initialise the VL update process
   */
  int __init afs_vlocation_update_init(void)
  {
  	afs_vlocation_update_worker =
  		create_singlethread_workqueue("kafs_vlupdated");
  	return afs_vlocation_update_worker ? 0 : -ENOMEM;
  }
  
  /*
   * discard all the volume location records for rmmod
   */

  void afs_vlocation_purge(void)

  {
  	afs_vlocation_timeout = 0;
  
  	spin_lock(&afs_vlocation_updates_lock);
  	list_del_init(&afs_vlocation_updates);
  	spin_unlock(&afs_vlocation_updates_lock);
  	cancel_delayed_work(&afs_vlocation_update);
  	queue_delayed_work(afs_vlocation_update_worker,
  			   &afs_vlocation_update, 0);
  	destroy_workqueue(afs_vlocation_update_worker);
  
  	cancel_delayed_work(&afs_vlocation_reap);

  	queue_delayed_work(afs_wq, &afs_vlocation_reap, 0);

  }

  /*

   * update a volume location

   */

  static void afs_vlocation_updater(struct work_struct *work)

  {
  	struct afs_cache_vlocation vldb;

  	struct afs_vlocation *vl, *xvl;
  	time_t now;
  	long timeout;

  	int ret;

  	_enter("");

  	now = get_seconds();

  	/* find a record to update */
  	spin_lock(&afs_vlocation_updates_lock);
  	for (;;) {
  		if (list_empty(&afs_vlocation_updates)) {
  			spin_unlock(&afs_vlocation_updates_lock);
  			_leave(" [nothing]");
  			return;
  		}

  		vl = list_entry(afs_vlocation_updates.next,
  				struct afs_vlocation, update);
  		if (atomic_read(&vl->usage) > 0)
  			break;
  		list_del_init(&vl->update);

  	}

  	timeout = vl->update_at - now;
  	if (timeout > 0) {
  		queue_delayed_work(afs_vlocation_update_worker,
  				   &afs_vlocation_update, timeout * HZ);
  		spin_unlock(&afs_vlocation_updates_lock);
  		_leave(" [nothing]");

  		return;
  	}

  	list_del_init(&vl->update);
  	atomic_inc(&vl->usage);
  	spin_unlock(&afs_vlocation_updates_lock);

  	/* we can now perform the update */
  	_debug("update %s", vl->vldb.name);
  	vl->state = AFS_VL_UPDATING;
  	vl->upd_rej_cnt = 0;
  	vl->upd_busy_cnt = 0;

  	ret = afs_vlocation_update_record(vl, NULL, &vldb);

  	spin_lock(&vl->lock);

  	switch (ret) {
  	case 0:
  		afs_vlocation_apply_update(vl, &vldb);
  		vl->state = AFS_VL_VALID;
  		break;
  	case -ENOMEDIUM:
  		vl->state = AFS_VL_VOLUME_DELETED;
  		break;
  	default:
  		vl->state = AFS_VL_UNCERTAIN;
  		break;
  	}

  	spin_unlock(&vl->lock);

  	wake_up(&vl->waitq);

  	/* and then reschedule */
  	_debug("reschedule");
  	vl->update_at = get_seconds() + afs_vlocation_update_timeout;

  	spin_lock(&afs_vlocation_updates_lock);

  	if (!list_empty(&afs_vlocation_updates)) {
  		/* next update in 10 minutes, but wait at least 1 second more
  		 * than the newest record already queued so that we don't spam
  		 * the VL server suddenly with lots of requests
  		 */
  		xvl = list_entry(afs_vlocation_updates.prev,
  				 struct afs_vlocation, update);
  		if (vl->update_at <= xvl->update_at)
  			vl->update_at = xvl->update_at + 1;
  		xvl = list_entry(afs_vlocation_updates.next,
  				 struct afs_vlocation, update);
  		timeout = xvl->update_at - now;
  		if (timeout < 0)
  			timeout = 0;
  	} else {
  		timeout = afs_vlocation_update_timeout;

  	}

  	ASSERT(list_empty(&vl->update));

  	list_add_tail(&vl->update, &afs_vlocation_updates);

  	_debug("timeout %ld", timeout);
  	queue_delayed_work(afs_vlocation_update_worker,
  			   &afs_vlocation_update, timeout * HZ);
  	spin_unlock(&afs_vlocation_updates_lock);
  	afs_put_vlocation(vl);

  }