/*
   * fs/nfs/nfs4session.c
   *
   * Copyright (c) 2012 Trond Myklebust <Trond.Myklebust@netapp.com>
   *
   */
  #include <linux/kernel.h>
  #include <linux/errno.h>
  #include <linux/string.h>
  #include <linux/printk.h>
  #include <linux/slab.h>
  #include <linux/sunrpc/sched.h>
  #include <linux/sunrpc/bc_xprt.h>
  #include <linux/nfs.h>
  #include <linux/nfs4.h>
  #include <linux/nfs_fs.h>
  #include <linux/module.h>
  
  #include "nfs4_fs.h"
  #include "internal.h"
  #include "nfs4session.h"
  #include "callback.h"
  
  #define NFSDBG_FACILITY		NFSDBG_STATE
  
  static void nfs4_init_slot_table(struct nfs4_slot_table *tbl, const char *queue)
  {
  	tbl->highest_used_slotid = NFS4_NO_SLOT;
  	spin_lock_init(&tbl->slot_tbl_lock);
  	rpc_init_priority_wait_queue(&tbl->slot_tbl_waitq, queue);
  	init_completion(&tbl->complete);
  }
  
  /*
   * nfs4_shrink_slot_table - free retired slots from the slot table
   */
  static void nfs4_shrink_slot_table(struct nfs4_slot_table  *tbl, u32 newsize)
  {
  	struct nfs4_slot **p;
  	if (newsize >= tbl->max_slots)
  		return;
  
  	p = &tbl->slots;
  	while (newsize--)
  		p = &(*p)->next;
  	while (*p) {
  		struct nfs4_slot *slot = *p;
  
  		*p = slot->next;
  		kfree(slot);
  		tbl->max_slots--;
  	}
  }
  
  /**
   * nfs4_slot_tbl_drain_complete - wake waiters when drain is complete
   * @tbl - controlling slot table
   *
   */
  void nfs4_slot_tbl_drain_complete(struct nfs4_slot_table *tbl)
  {
  	if (nfs4_slot_tbl_draining(tbl))
  		complete(&tbl->complete);
  }
  
  /*
   * nfs4_free_slot - free a slot and efficiently update slot table.
   *
   * freeing a slot is trivially done by clearing its respective bit
   * in the bitmap.
   * If the freed slotid equals highest_used_slotid we want to update it
   * so that the server would be able to size down the slot table if needed,
   * otherwise we know that the highest_used_slotid is still in use.
   * When updating highest_used_slotid there may be "holes" in the bitmap
   * so we need to scan down from highest_used_slotid to 0 looking for the now
   * highest slotid in use.
   * If none found, highest_used_slotid is set to NFS4_NO_SLOT.
   *
   * Must be called while holding tbl->slot_tbl_lock
   */
  void nfs4_free_slot(struct nfs4_slot_table *tbl, struct nfs4_slot *slot)
  {
  	u32 slotid = slot->slot_nr;
  
  	/* clear used bit in bitmap */
  	__clear_bit(slotid, tbl->used_slots);
  
  	/* update highest_used_slotid when it is freed */
  	if (slotid == tbl->highest_used_slotid) {
  		u32 new_max = find_last_bit(tbl->used_slots, slotid);
  		if (new_max < slotid)
  			tbl->highest_used_slotid = new_max;
  		else {
  			tbl->highest_used_slotid = NFS4_NO_SLOT;
  			nfs4_slot_tbl_drain_complete(tbl);
  		}
  	}
  	dprintk("%s: slotid %u highest_used_slotid %u
  ", __func__,
  		slotid, tbl->highest_used_slotid);
  }
  
  static struct nfs4_slot *nfs4_new_slot(struct nfs4_slot_table  *tbl,
  		u32 slotid, u32 seq_init, gfp_t gfp_mask)
  {
  	struct nfs4_slot *slot;
  
  	slot = kzalloc(sizeof(*slot), gfp_mask);
  	if (slot) {
  		slot->table = tbl;
  		slot->slot_nr = slotid;
  		slot->seq_nr = seq_init;
  	}
  	return slot;
  }
  
  static struct nfs4_slot *nfs4_find_or_create_slot(struct nfs4_slot_table  *tbl,
  		u32 slotid, u32 seq_init, gfp_t gfp_mask)
  {
  	struct nfs4_slot **p, *slot;
  
  	p = &tbl->slots;
  	for (;;) {
  		if (*p == NULL) {
  			*p = nfs4_new_slot(tbl, tbl->max_slots,
  					seq_init, gfp_mask);
  			if (*p == NULL)
  				break;
  			tbl->max_slots++;
  		}
  		slot = *p;
  		if (slot->slot_nr == slotid)
  			return slot;
  		p = &slot->next;
  	}
  	return ERR_PTR(-ENOMEM);
  }
  
  /*
   * nfs4_alloc_slot - efficiently look for a free slot
   *
   * nfs4_alloc_slot looks for an unset bit in the used_slots bitmap.
   * If found, we mark the slot as used, update the highest_used_slotid,
   * and respectively set up the sequence operation args.
   *
   * Note: must be called with under the slot_tbl_lock.
   */
  struct nfs4_slot *nfs4_alloc_slot(struct nfs4_slot_table *tbl)
  {
  	struct nfs4_slot *ret = ERR_PTR(-EBUSY);
  	u32 slotid;
  
  	dprintk("--> %s used_slots=%04lx highest_used=%u max_slots=%u
  ",
  		__func__, tbl->used_slots[0], tbl->highest_used_slotid,
  		tbl->max_slotid + 1);
  	slotid = find_first_zero_bit(tbl->used_slots, tbl->max_slotid + 1);
  	if (slotid > tbl->max_slotid)
  		goto out;
  	ret = nfs4_find_or_create_slot(tbl, slotid, 1, GFP_NOWAIT);
  	if (IS_ERR(ret))
  		goto out;
  	__set_bit(slotid, tbl->used_slots);
  	if (slotid > tbl->highest_used_slotid ||
  			tbl->highest_used_slotid == NFS4_NO_SLOT)
  		tbl->highest_used_slotid = slotid;
  	ret->generation = tbl->generation;
  
  out:
  	dprintk("<-- %s used_slots=%04lx highest_used=%u slotid=%u
  ",
  		__func__, tbl->used_slots[0], tbl->highest_used_slotid,
  		!IS_ERR(ret) ? ret->slot_nr : NFS4_NO_SLOT);
  	return ret;
  }
  
  static int nfs4_grow_slot_table(struct nfs4_slot_table *tbl,
  		 u32 max_reqs, u32 ivalue)
  {
  	if (max_reqs <= tbl->max_slots)
  		return 0;
  	if (!IS_ERR(nfs4_find_or_create_slot(tbl, max_reqs - 1, ivalue, GFP_NOFS)))
  		return 0;
  	return -ENOMEM;
  }
  
  static void nfs4_reset_slot_table(struct nfs4_slot_table *tbl,
  		u32 server_highest_slotid,
  		u32 ivalue)
  {
  	struct nfs4_slot **p;
  
  	nfs4_shrink_slot_table(tbl, server_highest_slotid + 1);
  	p = &tbl->slots;
  	while (*p) {
  		(*p)->seq_nr = ivalue;
  		(*p)->interrupted = 0;
  		p = &(*p)->next;
  	}
  	tbl->highest_used_slotid = NFS4_NO_SLOT;
  	tbl->target_highest_slotid = server_highest_slotid;
  	tbl->server_highest_slotid = server_highest_slotid;
  	tbl->d_target_highest_slotid = 0;
  	tbl->d2_target_highest_slotid = 0;
  	tbl->max_slotid = server_highest_slotid;
  }
  
  /*
   * (re)Initialise a slot table
   */
  static int nfs4_realloc_slot_table(struct nfs4_slot_table *tbl,
  		u32 max_reqs, u32 ivalue)
  {
  	int ret;
  
  	dprintk("--> %s: max_reqs=%u, tbl->max_slots %u
  ", __func__,
  		max_reqs, tbl->max_slots);
  
  	if (max_reqs > NFS4_MAX_SLOT_TABLE)
  		max_reqs = NFS4_MAX_SLOT_TABLE;
  
  	ret = nfs4_grow_slot_table(tbl, max_reqs, ivalue);
  	if (ret)
  		goto out;
  
  	spin_lock(&tbl->slot_tbl_lock);
  	nfs4_reset_slot_table(tbl, max_reqs - 1, ivalue);
  	spin_unlock(&tbl->slot_tbl_lock);
  
  	dprintk("%s: tbl=%p slots=%p max_slots=%u
  ", __func__,
  		tbl, tbl->slots, tbl->max_slots);
  out:
  	dprintk("<-- %s: return %d
  ", __func__, ret);
  	return ret;
  }
  
  /*
   * nfs4_release_slot_table - release all slot table entries
   */
  static void nfs4_release_slot_table(struct nfs4_slot_table *tbl)
  {
  	nfs4_shrink_slot_table(tbl, 0);
  }
  
  /**
   * nfs4_shutdown_slot_table - release resources attached to a slot table
   * @tbl: slot table to shut down
   *
   */
  void nfs4_shutdown_slot_table(struct nfs4_slot_table *tbl)
  {
  	nfs4_release_slot_table(tbl);
  	rpc_destroy_wait_queue(&tbl->slot_tbl_waitq);
  }
  
  /**
   * nfs4_setup_slot_table - prepare a stand-alone slot table for use
   * @tbl: slot table to set up
   * @max_reqs: maximum number of requests allowed
   * @queue: name to give RPC wait queue
   *
   * Returns zero on success, or a negative errno.
   */
  int nfs4_setup_slot_table(struct nfs4_slot_table *tbl, unsigned int max_reqs,
  		const char *queue)
  {
  	nfs4_init_slot_table(tbl, queue);
  	return nfs4_realloc_slot_table(tbl, max_reqs, 0);
  }
  
  static bool nfs41_assign_slot(struct rpc_task *task, void *pslot)
  {
  	struct nfs4_sequence_args *args = task->tk_msg.rpc_argp;
  	struct nfs4_sequence_res *res = task->tk_msg.rpc_resp;
  	struct nfs4_slot *slot = pslot;
  	struct nfs4_slot_table *tbl = slot->table;
  
  	if (nfs4_slot_tbl_draining(tbl) && !args->sa_privileged)
  		return false;
  	slot->generation = tbl->generation;
  	args->sa_slot = slot;
  	res->sr_timestamp = jiffies;
  	res->sr_slot = slot;
  	res->sr_status_flags = 0;
  	res->sr_status = 1;
  	return true;
  }
  
  static bool __nfs41_wake_and_assign_slot(struct nfs4_slot_table *tbl,
  		struct nfs4_slot *slot)
  {
  	if (rpc_wake_up_first(&tbl->slot_tbl_waitq, nfs41_assign_slot, slot))
  		return true;
  	return false;
  }
  
  bool nfs41_wake_and_assign_slot(struct nfs4_slot_table *tbl,
  		struct nfs4_slot *slot)
  {
  	if (slot->slot_nr > tbl->max_slotid)
  		return false;
  	return __nfs41_wake_and_assign_slot(tbl, slot);
  }
  
  static bool nfs41_try_wake_next_slot_table_entry(struct nfs4_slot_table *tbl)
  {
  	struct nfs4_slot *slot = nfs4_alloc_slot(tbl);
  	if (!IS_ERR(slot)) {
  		bool ret = __nfs41_wake_and_assign_slot(tbl, slot);
  		if (ret)
  			return ret;
  		nfs4_free_slot(tbl, slot);
  	}
  	return false;
  }
  
  void nfs41_wake_slot_table(struct nfs4_slot_table *tbl)
  {
  	for (;;) {
  		if (!nfs41_try_wake_next_slot_table_entry(tbl))
  			break;
  	}
  }
  
  #if defined(CONFIG_NFS_V4_1)
  
  static void nfs41_set_max_slotid_locked(struct nfs4_slot_table *tbl,
  		u32 target_highest_slotid)
  {
  	u32 max_slotid;
  
  	max_slotid = min(NFS4_MAX_SLOT_TABLE - 1, target_highest_slotid);
  	if (max_slotid > tbl->server_highest_slotid)
  		max_slotid = tbl->server_highest_slotid;
  	if (max_slotid > tbl->target_highest_slotid)
  		max_slotid = tbl->target_highest_slotid;
  	tbl->max_slotid = max_slotid;
  	nfs41_wake_slot_table(tbl);
  }
  
  /* Update the client's idea of target_highest_slotid */
  static void nfs41_set_target_slotid_locked(struct nfs4_slot_table *tbl,
  		u32 target_highest_slotid)
  {
  	if (tbl->target_highest_slotid == target_highest_slotid)
  		return;
  	tbl->target_highest_slotid = target_highest_slotid;
  	tbl->generation++;
  }
  
  void nfs41_set_target_slotid(struct nfs4_slot_table *tbl,
  		u32 target_highest_slotid)
  {
  	spin_lock(&tbl->slot_tbl_lock);
  	nfs41_set_target_slotid_locked(tbl, target_highest_slotid);
  	tbl->d_target_highest_slotid = 0;
  	tbl->d2_target_highest_slotid = 0;
  	nfs41_set_max_slotid_locked(tbl, target_highest_slotid);
  	spin_unlock(&tbl->slot_tbl_lock);
  }
  
  static void nfs41_set_server_slotid_locked(struct nfs4_slot_table *tbl,
  		u32 highest_slotid)
  {
  	if (tbl->server_highest_slotid == highest_slotid)
  		return;
  	if (tbl->highest_used_slotid > highest_slotid)
  		return;
  	/* Deallocate slots */
  	nfs4_shrink_slot_table(tbl, highest_slotid + 1);
  	tbl->server_highest_slotid = highest_slotid;
  }
  
  static s32 nfs41_derivative_target_slotid(s32 s1, s32 s2)
  {
  	s1 -= s2;
  	if (s1 == 0)
  		return 0;
  	if (s1 < 0)
  		return (s1 - 1) >> 1;
  	return (s1 + 1) >> 1;
  }
  
  static int nfs41_sign_s32(s32 s1)
  {
  	if (s1 > 0)
  		return 1;
  	if (s1 < 0)
  		return -1;
  	return 0;
  }
  
  static bool nfs41_same_sign_or_zero_s32(s32 s1, s32 s2)
  {
  	if (!s1 || !s2)
  		return true;
  	return nfs41_sign_s32(s1) == nfs41_sign_s32(s2);
  }
  
  /* Try to eliminate outliers by checking for sharp changes in the
   * derivatives and second derivatives
   */
  static bool nfs41_is_outlier_target_slotid(struct nfs4_slot_table *tbl,
  		u32 new_target)
  {
  	s32 d_target, d2_target;
  	bool ret = true;
  
  	d_target = nfs41_derivative_target_slotid(new_target,
  			tbl->target_highest_slotid);
  	d2_target = nfs41_derivative_target_slotid(d_target,
  			tbl->d_target_highest_slotid);
  	/* Is first derivative same sign? */
  	if (nfs41_same_sign_or_zero_s32(d_target, tbl->d_target_highest_slotid))
  		ret = false;
  	/* Is second derivative same sign? */
  	if (nfs41_same_sign_or_zero_s32(d2_target, tbl->d2_target_highest_slotid))
  		ret = false;
  	tbl->d_target_highest_slotid = d_target;
  	tbl->d2_target_highest_slotid = d2_target;
  	return ret;
  }
  
  void nfs41_update_target_slotid(struct nfs4_slot_table *tbl,
  		struct nfs4_slot *slot,
  		struct nfs4_sequence_res *res)
  {
  	spin_lock(&tbl->slot_tbl_lock);
  	if (!nfs41_is_outlier_target_slotid(tbl, res->sr_target_highest_slotid))
  		nfs41_set_target_slotid_locked(tbl, res->sr_target_highest_slotid);
  	if (tbl->generation == slot->generation)
  		nfs41_set_server_slotid_locked(tbl, res->sr_highest_slotid);
  	nfs41_set_max_slotid_locked(tbl, res->sr_target_highest_slotid);
  	spin_unlock(&tbl->slot_tbl_lock);
  }
  
  static void nfs4_release_session_slot_tables(struct nfs4_session *session)
  {
  	nfs4_release_slot_table(&session->fc_slot_table);
  	nfs4_release_slot_table(&session->bc_slot_table);
  }
  
  /*
   * Initialize or reset the forechannel and backchannel tables
   */
  int nfs4_setup_session_slot_tables(struct nfs4_session *ses)
  {
  	struct nfs4_slot_table *tbl;
  	int status;
  
  	dprintk("--> %s
  ", __func__);
  	/* Fore channel */
  	tbl = &ses->fc_slot_table;
  	tbl->session = ses;
  	status = nfs4_realloc_slot_table(tbl, ses->fc_attrs.max_reqs, 1);
  	if (status || !(ses->flags & SESSION4_BACK_CHAN)) /* -ENOMEM */
  		return status;
  	/* Back channel */
  	tbl = &ses->bc_slot_table;
  	tbl->session = ses;
  	status = nfs4_realloc_slot_table(tbl, ses->bc_attrs.max_reqs, 0);
  	if (status && tbl->slots == NULL)
  		/* Fore and back channel share a connection so get
  		 * both slot tables or neither */
  		nfs4_release_session_slot_tables(ses);
  	return status;
  }
  
  struct nfs4_session *nfs4_alloc_session(struct nfs_client *clp)
  {
  	struct nfs4_session *session;
  
  	session = kzalloc(sizeof(struct nfs4_session), GFP_NOFS);
  	if (!session)
  		return NULL;
  
  	nfs4_init_slot_table(&session->fc_slot_table, "ForeChannel Slot table");
  	nfs4_init_slot_table(&session->bc_slot_table, "BackChannel Slot table");
  	session->session_state = 1<<NFS4_SESSION_INITING;
  
  	session->clp = clp;
  	return session;
  }
  
  static void nfs4_destroy_session_slot_tables(struct nfs4_session *session)
  {
  	nfs4_shutdown_slot_table(&session->fc_slot_table);
  	nfs4_shutdown_slot_table(&session->bc_slot_table);
  }
  
  void nfs4_destroy_session(struct nfs4_session *session)
  {
  	struct rpc_xprt *xprt;
  	struct rpc_cred *cred;
  
  	cred = nfs4_get_clid_cred(session->clp);
  	nfs4_proc_destroy_session(session, cred);
  	if (cred)
  		put_rpccred(cred);
  
  	rcu_read_lock();
  	xprt = rcu_dereference(session->clp->cl_rpcclient->cl_xprt);
  	rcu_read_unlock();
  	dprintk("%s Destroy backchannel for xprt %p
  ",
  		__func__, xprt);
  	xprt_destroy_backchannel(xprt, NFS41_BC_MIN_CALLBACKS);
  	nfs4_destroy_session_slot_tables(session);
  	kfree(session);
  }
  
  /*
   * With sessions, the client is not marked ready until after a
   * successful EXCHANGE_ID and CREATE_SESSION.
   *
   * Map errors cl_cons_state errors to EPROTONOSUPPORT to indicate
   * other versions of NFS can be tried.
   */
  static int nfs41_check_session_ready(struct nfs_client *clp)
  {
  	int ret;
  	
  	if (clp->cl_cons_state == NFS_CS_SESSION_INITING) {
  		ret = nfs4_client_recover_expired_lease(clp);
  		if (ret)
  			return ret;
  	}
  	if (clp->cl_cons_state < NFS_CS_READY)
  		return -EPROTONOSUPPORT;
  	smp_rmb();
  	return 0;
  }
  
  int nfs4_init_session(struct nfs_client *clp)
  {
  	if (!nfs4_has_session(clp))
  		return 0;
  
  	clear_bit(NFS4_SESSION_INITING, &clp->cl_session->session_state);
  	return nfs41_check_session_ready(clp);
  }
  
  int nfs4_init_ds_session(struct nfs_client *clp, unsigned long lease_time)
  {
  	struct nfs4_session *session = clp->cl_session;
  	int ret;
  
  	spin_lock(&clp->cl_lock);
  	if (test_and_clear_bit(NFS4_SESSION_INITING, &session->session_state)) {
  		/*
  		 * Do not set NFS_CS_CHECK_LEASE_TIME instead set the
  		 * DS lease to be equal to the MDS lease.
  		 */
  		clp->cl_lease_time = lease_time;
  		clp->cl_last_renewal = jiffies;
  	}
  	spin_unlock(&clp->cl_lock);
  
  	ret = nfs41_check_session_ready(clp);
  	if (ret)
  		return ret;
  	/* Test for the DS role */
  	if (!is_ds_client(clp))
  		return -ENODEV;
  	return 0;
  }
  EXPORT_SYMBOL_GPL(nfs4_init_ds_session);
  
  #endif	/* defined(CONFIG_NFS_V4_1) */