/*
   *  Device operations for the pnfs client.
   *
   *  Copyright (c) 2002
   *  The Regents of the University of Michigan
   *  All Rights Reserved
   *
   *  Dean Hildebrand <dhildebz@umich.edu>
   *  Garth Goodson   <Garth.Goodson@netapp.com>
   *
   *  Permission is granted to use, copy, create derivative works, and
   *  redistribute this software and such derivative works for any purpose,
   *  so long as the name of the University of Michigan is not used in
   *  any advertising or publicity pertaining to the use or distribution
   *  of this software without specific, written prior authorization. If
   *  the above copyright notice or any other identification of the
   *  University of Michigan is included in any copy of any portion of
   *  this software, then the disclaimer below must also be included.
   *
   *  This software is provided as is, without representation or warranty
   *  of any kind either express or implied, including without limitation
   *  the implied warranties of merchantability, fitness for a particular
   *  purpose, or noninfringement.  The Regents of the University of
   *  Michigan shall not be liable for any damages, including special,
   *  indirect, incidental, or consequential damages, with respect to any
   *  claim arising out of or in connection with the use of the software,
   *  even if it has been or is hereafter advised of the possibility of
   *  such damages.
   */
  
  #include <linux/export.h>
  #include "pnfs.h"
  
  #define NFSDBG_FACILITY		NFSDBG_PNFS
  
  /*
   * Device ID RCU cache. A device ID is unique per server and layout type.
   */
  #define NFS4_DEVICE_ID_HASH_BITS	5
  #define NFS4_DEVICE_ID_HASH_SIZE	(1 << NFS4_DEVICE_ID_HASH_BITS)
  #define NFS4_DEVICE_ID_HASH_MASK	(NFS4_DEVICE_ID_HASH_SIZE - 1)
  
  #define PNFS_DEVICE_RETRY_TIMEOUT (120*HZ)
  
  static struct hlist_head nfs4_deviceid_cache[NFS4_DEVICE_ID_HASH_SIZE];
  static DEFINE_SPINLOCK(nfs4_deviceid_lock);
  
  #ifdef NFS_DEBUG
  void
  nfs4_print_deviceid(const struct nfs4_deviceid *id)
  {
  	u32 *p = (u32 *)id;
  
  	dprintk("%s: device id= [%x%x%x%x]
  ", __func__,
  		p[0], p[1], p[2], p[3]);
  }
  EXPORT_SYMBOL_GPL(nfs4_print_deviceid);
  #endif
  
  static inline u32
  nfs4_deviceid_hash(const struct nfs4_deviceid *id)
  {
  	unsigned char *cptr = (unsigned char *)id->data;
  	unsigned int nbytes = NFS4_DEVICEID4_SIZE;
  	u32 x = 0;
  
  	while (nbytes--) {
  		x *= 37;
  		x += *cptr++;
  	}
  	return x & NFS4_DEVICE_ID_HASH_MASK;
  }
  
  static struct nfs4_deviceid_node *
  _lookup_deviceid(const struct pnfs_layoutdriver_type *ld,
  		 const struct nfs_client *clp, const struct nfs4_deviceid *id,
  		 long hash)
  {
  	struct nfs4_deviceid_node *d;
  
  	hlist_for_each_entry_rcu(d, &nfs4_deviceid_cache[hash], node)
  		if (d->ld == ld && d->nfs_client == clp &&
  		    !memcmp(&d->deviceid, id, sizeof(*id))) {
  			if (atomic_read(&d->ref))
  				return d;
  			else
  				continue;
  		}
  	return NULL;
  }
  
  /*
   * Lookup a deviceid in cache and get a reference count on it if found
   *
   * @clp nfs_client associated with deviceid
   * @id deviceid to look up
   */
  static struct nfs4_deviceid_node *
  _find_get_deviceid(const struct pnfs_layoutdriver_type *ld,
  		   const struct nfs_client *clp, const struct nfs4_deviceid *id,
  		   long hash)
  {
  	struct nfs4_deviceid_node *d;
  
  	rcu_read_lock();
  	d = _lookup_deviceid(ld, clp, id, hash);
  	if (d != NULL)
  		atomic_inc(&d->ref);
  	rcu_read_unlock();
  	return d;
  }
  
  struct nfs4_deviceid_node *
  nfs4_find_get_deviceid(const struct pnfs_layoutdriver_type *ld,
  		       const struct nfs_client *clp, const struct nfs4_deviceid *id)
  {
  	return _find_get_deviceid(ld, clp, id, nfs4_deviceid_hash(id));
  }
  EXPORT_SYMBOL_GPL(nfs4_find_get_deviceid);
  
  /*
   * Remove a deviceid from cache
   *
   * @clp nfs_client associated with deviceid
   * @id the deviceid to unhash
   *
   * @ret the unhashed node, if found and dereferenced to zero, NULL otherwise.
   */
  void
  nfs4_delete_deviceid(const struct pnfs_layoutdriver_type *ld,
  			 const struct nfs_client *clp, const struct nfs4_deviceid *id)
  {
  	struct nfs4_deviceid_node *d;
  
  	spin_lock(&nfs4_deviceid_lock);
  	rcu_read_lock();
  	d = _lookup_deviceid(ld, clp, id, nfs4_deviceid_hash(id));
  	rcu_read_unlock();
  	if (!d) {
  		spin_unlock(&nfs4_deviceid_lock);
  		return;
  	}
  	hlist_del_init_rcu(&d->node);
  	spin_unlock(&nfs4_deviceid_lock);
  	synchronize_rcu();
  
  	/* balance the initial ref set in pnfs_insert_deviceid */
  	if (atomic_dec_and_test(&d->ref))
  		d->ld->free_deviceid_node(d);
  }
  EXPORT_SYMBOL_GPL(nfs4_delete_deviceid);
  
  void
  nfs4_init_deviceid_node(struct nfs4_deviceid_node *d,
  			const struct pnfs_layoutdriver_type *ld,
  			const struct nfs_client *nfs_client,
  			const struct nfs4_deviceid *id)
  {
  	INIT_HLIST_NODE(&d->node);
  	INIT_HLIST_NODE(&d->tmpnode);
  	d->ld = ld;
  	d->nfs_client = nfs_client;
  	d->flags = 0;
  	d->deviceid = *id;
  	atomic_set(&d->ref, 1);
  }
  EXPORT_SYMBOL_GPL(nfs4_init_deviceid_node);
  
  /*
   * Uniquely initialize and insert a deviceid node into cache
   *
   * @new new deviceid node
   *      Note that the caller must set up the following members:
   *        new->ld
   *        new->nfs_client
   *        new->deviceid
   *
   * @ret the inserted node, if none found, otherwise, the found entry.
   */
  struct nfs4_deviceid_node *
  nfs4_insert_deviceid_node(struct nfs4_deviceid_node *new)
  {
  	struct nfs4_deviceid_node *d;
  	long hash;
  
  	spin_lock(&nfs4_deviceid_lock);
  	hash = nfs4_deviceid_hash(&new->deviceid);
  	d = _find_get_deviceid(new->ld, new->nfs_client, &new->deviceid, hash);
  	if (d) {
  		spin_unlock(&nfs4_deviceid_lock);
  		return d;
  	}
  
  	hlist_add_head_rcu(&new->node, &nfs4_deviceid_cache[hash]);
  	spin_unlock(&nfs4_deviceid_lock);
  	atomic_inc(&new->ref);
  
  	return new;
  }
  EXPORT_SYMBOL_GPL(nfs4_insert_deviceid_node);
  
  /*
   * Dereference a deviceid node and delete it when its reference count drops
   * to zero.
   *
   * @d deviceid node to put
   *
   * return true iff the node was deleted
   * Note that since the test for d->ref == 0 is sufficient to establish
   * that the node is no longer hashed in the global device id cache.
   */
  bool
  nfs4_put_deviceid_node(struct nfs4_deviceid_node *d)
  {
  	if (!atomic_dec_and_test(&d->ref))
  		return false;
  	d->ld->free_deviceid_node(d);
  	return true;
  }
  EXPORT_SYMBOL_GPL(nfs4_put_deviceid_node);
  
  void
  nfs4_mark_deviceid_unavailable(struct nfs4_deviceid_node *node)
  {
  	node->timestamp_unavailable = jiffies;
  	set_bit(NFS_DEVICEID_UNAVAILABLE, &node->flags);
  }
  EXPORT_SYMBOL_GPL(nfs4_mark_deviceid_unavailable);
  
  bool
  nfs4_test_deviceid_unavailable(struct nfs4_deviceid_node *node)
  {
  	if (test_bit(NFS_DEVICEID_UNAVAILABLE, &node->flags)) {
  		unsigned long start, end;
  
  		end = jiffies;
  		start = end - PNFS_DEVICE_RETRY_TIMEOUT;
  		if (time_in_range(node->timestamp_unavailable, start, end))
  			return true;
  		clear_bit(NFS_DEVICEID_UNAVAILABLE, &node->flags);
  	}
  	return false;
  }
  EXPORT_SYMBOL_GPL(nfs4_test_deviceid_unavailable);
  
  static void
  _deviceid_purge_client(const struct nfs_client *clp, long hash)
  {
  	struct nfs4_deviceid_node *d;
  	HLIST_HEAD(tmp);
  
  	spin_lock(&nfs4_deviceid_lock);
  	rcu_read_lock();
  	hlist_for_each_entry_rcu(d, &nfs4_deviceid_cache[hash], node)
  		if (d->nfs_client == clp && atomic_read(&d->ref)) {
  			hlist_del_init_rcu(&d->node);
  			hlist_add_head(&d->tmpnode, &tmp);
  		}
  	rcu_read_unlock();
  	spin_unlock(&nfs4_deviceid_lock);
  
  	if (hlist_empty(&tmp))
  		return;
  
  	synchronize_rcu();
  	while (!hlist_empty(&tmp)) {
  		d = hlist_entry(tmp.first, struct nfs4_deviceid_node, tmpnode);
  		hlist_del(&d->tmpnode);
  		if (atomic_dec_and_test(&d->ref))
  			d->ld->free_deviceid_node(d);
  	}
  }
  
  void
  nfs4_deviceid_purge_client(const struct nfs_client *clp)
  {
  	long h;
  
  	if (!(clp->cl_exchange_flags & EXCHGID4_FLAG_USE_PNFS_MDS))
  		return;
  	for (h = 0; h < NFS4_DEVICE_ID_HASH_SIZE; h++)
  		_deviceid_purge_client(clp, h);
  }
  
  /*
   * Stop use of all deviceids associated with an nfs_client
   */
  void
  nfs4_deviceid_mark_client_invalid(struct nfs_client *clp)
  {
  	struct nfs4_deviceid_node *d;
  	int i;
  
  	rcu_read_lock();
  	for (i = 0; i < NFS4_DEVICE_ID_HASH_SIZE; i ++){
  		hlist_for_each_entry_rcu(d, &nfs4_deviceid_cache[i], node)
  			if (d->nfs_client == clp)
  				set_bit(NFS_DEVICEID_INVALID, &d->flags);
  	}
  	rcu_read_unlock();
  }