fs/nfs/nfs4session.c - kernel/msm-5.4 - Gitiles

 /*
  * 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_waitqueue_head(&tbl->slot_waitq);
 	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\n", __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);
 }

 static void nfs4_lock_slot(struct nfs4_slot_table *tbl,
 		struct nfs4_slot *slot)
 {
 	u32 slotid = slot->slot_nr;

 	__set_bit(slotid, tbl->used_slots);
 	if (slotid > tbl->highest_used_slotid ||
 	    tbl->highest_used_slotid == NFS4_NO_SLOT)
 		tbl->highest_used_slotid = slotid;
 	slot->generation = tbl->generation;
 }

 /*
  * nfs4_try_to_lock_slot - Given a slot try to allocate it
  *
  * Note: must be called with the slot_tbl_lock held.
  */
 bool nfs4_try_to_lock_slot(struct nfs4_slot_table *tbl, struct nfs4_slot *slot)
 {
 	if (nfs4_test_locked_slot(tbl, slot->slot_nr))
 		return false;
 	nfs4_lock_slot(tbl, slot);
 	return true;
 }

 /*
  * nfs4_lookup_slot - Find a slot but don't allocate it
  *
  * Note: must be called with the slot_tbl_lock held.
  */
 struct nfs4_slot *nfs4_lookup_slot(struct nfs4_slot_table *tbl, u32 slotid)
 {
 	if (slotid <= tbl->max_slotid)
 		return nfs4_find_or_create_slot(tbl, slotid, 0, GFP_NOWAIT);
 	return ERR_PTR(-E2BIG);
 }

 static int nfs4_slot_get_seqid(struct nfs4_slot_table  *tbl, u32 slotid,
 		u32 *seq_nr)
 	__must_hold(&tbl->slot_tbl_lock)
 {
 	struct nfs4_slot *slot;
 	int ret;

 	slot = nfs4_lookup_slot(tbl, slotid);
 	ret = PTR_ERR_OR_ZERO(slot);
 	if (!ret)
 		*seq_nr = slot->seq_nr;

 	return ret;
 }

 /*
  * nfs4_slot_seqid_in_use - test if a slot sequence id is still in use
  *
  * Given a slot table, slot id and sequence number, determine if the
  * RPC call in question is still in flight. This function is mainly
  * intended for use by the callback channel.
  */
 static bool nfs4_slot_seqid_in_use(struct nfs4_slot_table *tbl,
 		u32 slotid, u32 seq_nr)
 {
 	u32 cur_seq = 0;
 	bool ret = false;

 	spin_lock(&tbl->slot_tbl_lock);
 	if (nfs4_slot_get_seqid(tbl, slotid, &cur_seq) == 0 &&
 	    cur_seq == seq_nr && test_bit(slotid, tbl->used_slots))
 		ret = true;
 	spin_unlock(&tbl->slot_tbl_lock);
 	return ret;
 }

 /*
  * nfs4_slot_wait_on_seqid - wait until a slot sequence id is complete
  *
  * Given a slot table, slot id and sequence number, wait until the
  * corresponding RPC call completes. This function is mainly
  * intended for use by the callback channel.
  */
 int nfs4_slot_wait_on_seqid(struct nfs4_slot_table *tbl,
 		u32 slotid, u32 seq_nr,
 		unsigned long timeout)
 {
 	if (wait_event_timeout(tbl->slot_waitq,
 			!nfs4_slot_seqid_in_use(tbl, slotid, seq_nr),
 			timeout) == 0)
 		return -ETIMEDOUT;
 	return 0;
 }

 /*
  * 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\n",
 		__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) {
 		ret = nfs4_find_or_create_slot(tbl, slotid, 1, GFP_NOWAIT);
 		if (!IS_ERR(ret))
 			nfs4_lock_slot(tbl, ret);
 	}
 	dprintk("<-- %s used_slots=%04lx highest_used=%u slotid=%u\n",
 		__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\n", __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\n", __func__,
 		tbl, tbl->slots, tbl->max_slots);
 out:
 	dprintk("<-- %s: return %d\n", __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\n", __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;
 	const struct cred *cred;

 	cred = nfs4_get_clid_cred(session->clp);
 	nfs4_proc_destroy_session(session, cred);
 	put_cred(cred);

 	rcu_read_lock();
 	xprt = rcu_dereference(session->clp->cl_rpcclient->cl_xprt);
 	rcu_read_unlock();
 	dprintk("%s Destroy backchannel for xprt %p\n",
 		__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) */
	/*
	* 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_waitqueue_head(&tbl->slot_waitq);
	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\n", __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);
	}

	static void nfs4_lock_slot(struct nfs4_slot_table *tbl,
	struct nfs4_slot *slot)
	{
	u32 slotid = slot->slot_nr;

	__set_bit(slotid, tbl->used_slots);
	if (slotid > tbl->highest_used_slotid \|\|
	tbl->highest_used_slotid == NFS4_NO_SLOT)
	tbl->highest_used_slotid = slotid;
	slot->generation = tbl->generation;
	}

	/*
	* nfs4_try_to_lock_slot - Given a slot try to allocate it
	*
	* Note: must be called with the slot_tbl_lock held.
	*/
	bool nfs4_try_to_lock_slot(struct nfs4_slot_table tbl, struct nfs4_slot slot)
	{
	if (nfs4_test_locked_slot(tbl, slot->slot_nr))
	return false;
	nfs4_lock_slot(tbl, slot);
	return true;
	}

	/*
	* nfs4_lookup_slot - Find a slot but don't allocate it
	*
	* Note: must be called with the slot_tbl_lock held.
	*/
	struct nfs4_slot nfs4_lookup_slot(struct nfs4_slot_table tbl, u32 slotid)
	{
	if (slotid <= tbl->max_slotid)
	return nfs4_find_or_create_slot(tbl, slotid, 0, GFP_NOWAIT);
	return ERR_PTR(-E2BIG);
	}

	static int nfs4_slot_get_seqid(struct nfs4_slot_table *tbl, u32 slotid,
	u32 *seq_nr)
	__must_hold(&tbl->slot_tbl_lock)
	{
	struct nfs4_slot *slot;
	int ret;

	slot = nfs4_lookup_slot(tbl, slotid);
	ret = PTR_ERR_OR_ZERO(slot);
	if (!ret)
	*seq_nr = slot->seq_nr;

	return ret;
	}

	/*
	* nfs4_slot_seqid_in_use - test if a slot sequence id is still in use
	*
	* Given a slot table, slot id and sequence number, determine if the
	* RPC call in question is still in flight. This function is mainly
	* intended for use by the callback channel.
	*/
	static bool nfs4_slot_seqid_in_use(struct nfs4_slot_table *tbl,
	u32 slotid, u32 seq_nr)
	{
	u32 cur_seq = 0;
	bool ret = false;

	spin_lock(&tbl->slot_tbl_lock);
	if (nfs4_slot_get_seqid(tbl, slotid, &cur_seq) == 0 &&
	cur_seq == seq_nr && test_bit(slotid, tbl->used_slots))
	ret = true;
	spin_unlock(&tbl->slot_tbl_lock);
	return ret;
	}

	/*
	* nfs4_slot_wait_on_seqid - wait until a slot sequence id is complete
	*
	* Given a slot table, slot id and sequence number, wait until the
	* corresponding RPC call completes. This function is mainly
	* intended for use by the callback channel.
	*/
	int nfs4_slot_wait_on_seqid(struct nfs4_slot_table *tbl,
	u32 slotid, u32 seq_nr,
	unsigned long timeout)
	{
	if (wait_event_timeout(tbl->slot_waitq,
	!nfs4_slot_seqid_in_use(tbl, slotid, seq_nr),
	timeout) == 0)
	return -ETIMEDOUT;
	return 0;
	}

	/*
	* 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\n",
	__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) {
	ret = nfs4_find_or_create_slot(tbl, slotid, 1, GFP_NOWAIT);
	if (!IS_ERR(ret))
	nfs4_lock_slot(tbl, ret);
	}
	dprintk("<-- %s used_slots=%04lx highest_used=%u slotid=%u\n",
	__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\n", __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\n", __func__,
	tbl, tbl->slots, tbl->max_slots);
	out:
	dprintk("<-- %s: return %d\n", __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\n", __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;
	const struct cred *cred;

	cred = nfs4_get_clid_cred(session->clp);
	nfs4_proc_destroy_session(session, cred);
	put_cred(cred);

	rcu_read_lock();
	xprt = rcu_dereference(session->clp->cl_rpcclient->cl_xprt);
	rcu_read_unlock();
	dprintk("%s Destroy backchannel for xprt %p\n",
	__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) */