/*
   * linux/fs/nfs/delegation.c
   *
   * Copyright (C) 2004 Trond Myklebust
   *
   * NFS file delegation management
   *
   */

  #include <linux/completion.h>

  #include <linux/kthread.h>

  #include <linux/module.h>
  #include <linux/sched.h>

  #include <linux/slab.h>

  #include <linux/spinlock.h>
  
  #include <linux/nfs4.h>
  #include <linux/nfs_fs.h>
  #include <linux/nfs_xdr.h>

  #include "nfs4_fs.h"

  #include "delegation.h"

  #include "internal.h"

  #include "nfs4trace.h"

  static void nfs_free_delegation(struct nfs_delegation *delegation)
  {

  	if (delegation->cred) {
  		put_rpccred(delegation->cred);
  		delegation->cred = NULL;
  	}

  	kfree_rcu(delegation, rcu);

  }

  /**
   * nfs_mark_delegation_referenced - set delegation's REFERENCED flag
   * @delegation: delegation to process
   *
   */

  void nfs_mark_delegation_referenced(struct nfs_delegation *delegation)
  {
  	set_bit(NFS_DELEGATION_REFERENCED, &delegation->flags);
  }

  static bool
  nfs4_is_valid_delegation(const struct nfs_delegation *delegation,
  		fmode_t flags)
  {
  	if (delegation != NULL && (delegation->type & flags) == flags &&
  	    !test_bit(NFS_DELEGATION_REVOKED, &delegation->flags) &&
  	    !test_bit(NFS_DELEGATION_RETURNING, &delegation->flags))
  		return true;
  	return false;
  }

  static int
  nfs4_do_check_delegation(struct inode *inode, fmode_t flags, bool mark)

  {
  	struct nfs_delegation *delegation;
  	int ret = 0;
  
  	flags &= FMODE_READ|FMODE_WRITE;
  	rcu_read_lock();
  	delegation = rcu_dereference(NFS_I(inode)->delegation);

  	if (nfs4_is_valid_delegation(delegation, flags)) {

  		if (mark)
  			nfs_mark_delegation_referenced(delegation);

  		ret = 1;
  	}
  	rcu_read_unlock();
  	return ret;
  }

  /**
   * nfs_have_delegation - check if inode has a delegation, mark it
   * NFS_DELEGATION_REFERENCED if there is one.
   * @inode: inode to check
   * @flags: delegation types to check for
   *
   * Returns one if inode has the indicated delegation, otherwise zero.
   */
  int nfs4_have_delegation(struct inode *inode, fmode_t flags)
  {
  	return nfs4_do_check_delegation(inode, flags, true);
  }
  
  /*
   * nfs4_check_delegation - check if inode has a delegation, do not mark
   * NFS_DELEGATION_REFERENCED if it has one.
   */
  int nfs4_check_delegation(struct inode *inode, fmode_t flags)
  {
  	return nfs4_do_check_delegation(inode, flags, false);
  }

  static int nfs_delegation_claim_locks(struct nfs_open_context *ctx, struct nfs4_state *state, const nfs4_stateid *stateid)

  {
  	struct inode *inode = state->inode;
  	struct file_lock *fl;

  	struct file_lock_context *flctx = inode->i_flctx;
  	struct list_head *list;

  	int status = 0;

  	if (flctx == NULL)

  		goto out;

  	list = &flctx->flc_posix;

  	spin_lock(&flctx->flc_lock);

  restart:
  	list_for_each_entry(fl, list, fl_list) {

  		if (nfs_file_open_context(fl->fl_file) != ctx)

  			continue;

  		spin_unlock(&flctx->flc_lock);

  		status = nfs4_lock_delegation_recall(fl, state, stateid);

  		if (status < 0)

  			goto out;

  		spin_lock(&flctx->flc_lock);

  	}

  	if (list == &flctx->flc_posix) {
  		list = &flctx->flc_flock;
  		goto restart;

  	}

  	spin_unlock(&flctx->flc_lock);

  out:

  	return status;
  }

  static int nfs_delegation_claim_opens(struct inode *inode,
  		const nfs4_stateid *stateid, fmode_t type)

  {
  	struct nfs_inode *nfsi = NFS_I(inode);
  	struct nfs_open_context *ctx;

  	struct nfs4_state_owner *sp;

  	struct nfs4_state *state;

  	unsigned int seq;

  	int err;

  
  again:
  	spin_lock(&inode->i_lock);
  	list_for_each_entry(ctx, &nfsi->open_files, list) {
  		state = ctx->state;
  		if (state == NULL)
  			continue;
  		if (!test_bit(NFS_DELEGATED_STATE, &state->flags))
  			continue;

  		if (!nfs4_valid_open_stateid(state))
  			continue;

  		if (!nfs4_stateid_match(&state->stateid, stateid))

  			continue;

  		get_nfs_open_context(ctx);
  		spin_unlock(&inode->i_lock);

  		sp = state->owner;

  		/* Block nfs4_proc_unlck */
  		mutex_lock(&sp->so_delegreturn_mutex);

  		seq = raw_seqcount_begin(&sp->so_reclaim_seqcount);

  		err = nfs4_open_delegation_recall(ctx, state, stateid, type);

  		if (!err)

  			err = nfs_delegation_claim_locks(ctx, state, stateid);

  		if (!err && read_seqcount_retry(&sp->so_reclaim_seqcount, seq))
  			err = -EAGAIN;

  		mutex_unlock(&sp->so_delegreturn_mutex);

  		put_nfs_open_context(ctx);

  		if (err != 0)

  			return err;

  		goto again;
  	}
  	spin_unlock(&inode->i_lock);

  	return 0;

  }

  /**
   * nfs_inode_reclaim_delegation - process a delegation reclaim request
   * @inode: inode to process
   * @cred: credential to use for request
   * @res: new delegation state from server
   *

   */

  void nfs_inode_reclaim_delegation(struct inode *inode, struct rpc_cred *cred,
  				  struct nfs_openres *res)

  {

  	struct nfs_delegation *delegation;
  	struct rpc_cred *oldcred = NULL;

  	rcu_read_lock();
  	delegation = rcu_dereference(NFS_I(inode)->delegation);
  	if (delegation != NULL) {
  		spin_lock(&delegation->lock);
  		if (delegation->inode != NULL) {

  			nfs4_stateid_copy(&delegation->stateid, &res->delegation);

  			delegation->type = res->delegation_type;

  			delegation->pagemod_limit = res->pagemod_limit;

  			oldcred = delegation->cred;
  			delegation->cred = get_rpccred(cred);
  			clear_bit(NFS_DELEGATION_NEED_RECLAIM,
  				  &delegation->flags);

  			spin_unlock(&delegation->lock);

  			rcu_read_unlock();

  			put_rpccred(oldcred);

  			trace_nfs4_reclaim_delegation(inode, res->delegation_type);

  			return;

  		}

  		/* We appear to have raced with a delegation return. */
  		spin_unlock(&delegation->lock);

  	}

  	rcu_read_unlock();
  	nfs_inode_set_delegation(inode, cred, res);

  }

  static int nfs_do_return_delegation(struct inode *inode, struct nfs_delegation *delegation, int issync)
  {
  	int res = 0;

  	if (!test_bit(NFS_DELEGATION_REVOKED, &delegation->flags))
  		res = nfs4_proc_delegreturn(inode,
  				delegation->cred,
  				&delegation->stateid,
  				issync);

  	nfs_free_delegation(delegation);
  	return res;
  }

  static struct inode *nfs_delegation_grab_inode(struct nfs_delegation *delegation)
  {
  	struct inode *inode = NULL;
  
  	spin_lock(&delegation->lock);
  	if (delegation->inode != NULL)
  		inode = igrab(delegation->inode);
  	spin_unlock(&delegation->lock);
  	return inode;
  }

  static struct nfs_delegation *

  nfs_start_delegation_return_locked(struct nfs_inode *nfsi)
  {
  	struct nfs_delegation *ret = NULL;
  	struct nfs_delegation *delegation = rcu_dereference(nfsi->delegation);
  
  	if (delegation == NULL)
  		goto out;
  	spin_lock(&delegation->lock);
  	if (!test_and_set_bit(NFS_DELEGATION_RETURNING, &delegation->flags))
  		ret = delegation;
  	spin_unlock(&delegation->lock);
  out:
  	return ret;
  }
  
  static struct nfs_delegation *
  nfs_start_delegation_return(struct nfs_inode *nfsi)
  {
  	struct nfs_delegation *delegation;
  
  	rcu_read_lock();
  	delegation = nfs_start_delegation_return_locked(nfsi);
  	rcu_read_unlock();
  	return delegation;
  }
  
  static void
  nfs_abort_delegation_return(struct nfs_delegation *delegation,
  		struct nfs_client *clp)
  {
  
  	spin_lock(&delegation->lock);
  	clear_bit(NFS_DELEGATION_RETURNING, &delegation->flags);
  	set_bit(NFS_DELEGATION_RETURN, &delegation->flags);
  	spin_unlock(&delegation->lock);
  	set_bit(NFS4CLNT_DELEGRETURN, &clp->cl_state);
  }
  
  static struct nfs_delegation *

  nfs_detach_delegation_locked(struct nfs_inode *nfsi,

  		struct nfs_delegation *delegation,
  		struct nfs_client *clp)

  {

  	struct nfs_delegation *deleg_cur =

  		rcu_dereference_protected(nfsi->delegation,

  				lockdep_is_held(&clp->cl_lock));

  	if (deleg_cur == NULL || delegation != deleg_cur)
  		return NULL;

  	spin_lock(&delegation->lock);

  	set_bit(NFS_DELEGATION_RETURNING, &delegation->flags);

  	list_del_rcu(&delegation->super_list);

  	delegation->inode = NULL;

  	rcu_assign_pointer(nfsi->delegation, NULL);

  	spin_unlock(&delegation->lock);

  	return delegation;

  }

  static struct nfs_delegation *nfs_detach_delegation(struct nfs_inode *nfsi,

  		struct nfs_delegation *delegation,
  		struct nfs_server *server)

  {

  	struct nfs_client *clp = server->nfs_client;

  
  	spin_lock(&clp->cl_lock);

  	delegation = nfs_detach_delegation_locked(nfsi, delegation, clp);

  	spin_unlock(&clp->cl_lock);
  	return delegation;
  }

  static struct nfs_delegation *
  nfs_inode_detach_delegation(struct inode *inode)
  {
  	struct nfs_inode *nfsi = NFS_I(inode);
  	struct nfs_server *server = NFS_SERVER(inode);
  	struct nfs_delegation *delegation;
  
  	delegation = nfs_start_delegation_return(nfsi);
  	if (delegation == NULL)
  		return NULL;
  	return nfs_detach_delegation(nfsi, delegation, server);
  }

  static void
  nfs_update_inplace_delegation(struct nfs_delegation *delegation,
  		const struct nfs_delegation *update)
  {
  	if (nfs4_stateid_is_newer(&update->stateid, &delegation->stateid)) {
  		delegation->stateid.seqid = update->stateid.seqid;
  		smp_wmb();
  		delegation->type = update->type;
  	}
  }

  /**
   * nfs_inode_set_delegation - set up a delegation on an inode
   * @inode: inode to which delegation applies
   * @cred: cred to use for subsequent delegation processing
   * @res: new delegation state from server
   *
   * Returns zero on success, or a negative errno value.

   */
  int nfs_inode_set_delegation(struct inode *inode, struct rpc_cred *cred, struct nfs_openres *res)
  {

  	struct nfs_server *server = NFS_SERVER(inode);
  	struct nfs_client *clp = server->nfs_client;

  	struct nfs_inode *nfsi = NFS_I(inode);

  	struct nfs_delegation *delegation, *old_delegation;

  	struct nfs_delegation *freeme = NULL;

  	int status = 0;

  	delegation = kmalloc(sizeof(*delegation), GFP_NOFS);

  	if (delegation == NULL)
  		return -ENOMEM;

  	nfs4_stateid_copy(&delegation->stateid, &res->delegation);

  	delegation->type = res->delegation_type;

  	delegation->pagemod_limit = res->pagemod_limit;

  	delegation->change_attr = inode->i_version;

  	delegation->cred = get_rpccred(cred);
  	delegation->inode = inode;

  	delegation->flags = 1<<NFS_DELEGATION_REFERENCED;

  	spin_lock_init(&delegation->lock);

  
  	spin_lock(&clp->cl_lock);

  	old_delegation = rcu_dereference_protected(nfsi->delegation,

  					lockdep_is_held(&clp->cl_lock));

  	if (old_delegation != NULL) {

  		/* Is this an update of the existing delegation? */
  		if (nfs4_stateid_match_other(&old_delegation->stateid,
  					&delegation->stateid)) {
  			nfs_update_inplace_delegation(old_delegation,
  					delegation);

  			goto out;

  		}

  		/*
  		 * Deal with broken servers that hand out two
  		 * delegations for the same file.

  		 * Allow for upgrades to a WRITE delegation, but
  		 * nothing else.

  		 */
  		dfprintk(FILE, "%s: server %s handed out "
  				"a duplicate delegation!
  ",

  				__func__, clp->cl_hostname);

  		if (delegation->type == old_delegation->type ||
  		    !(delegation->type & FMODE_WRITE)) {

  			freeme = delegation;
  			delegation = NULL;
  			goto out;
  		}

  		if (test_and_set_bit(NFS_DELEGATION_RETURNING,
  					&old_delegation->flags))
  			goto out;
  		freeme = nfs_detach_delegation_locked(nfsi,

  				old_delegation, clp);
  		if (freeme == NULL)
  			goto out;

  	}

  	list_add_tail_rcu(&delegation->super_list, &server->delegations);

  	rcu_assign_pointer(nfsi->delegation, delegation);
  	delegation = NULL;

  	trace_nfs4_set_delegation(inode, res->delegation_type);

  out:

  	spin_unlock(&clp->cl_lock);

  	if (delegation != NULL)
  		nfs_free_delegation(delegation);

  	if (freeme != NULL)
  		nfs_do_return_delegation(inode, freeme, 0);

  	return status;
  }

  /*
   * Basic procedure for returning a delegation to the server
   */

  static int nfs_end_delegation_return(struct inode *inode, struct nfs_delegation *delegation, int issync)

  {

  	struct nfs_client *clp = NFS_SERVER(inode)->nfs_client;

  	struct nfs_inode *nfsi = NFS_I(inode);

  	int err = 0;

  	if (delegation == NULL)
  		return 0;
  	do {

  		if (test_bit(NFS_DELEGATION_REVOKED, &delegation->flags))
  			break;

  		err = nfs_delegation_claim_opens(inode, &delegation->stateid,
  				delegation->type);

  		if (!issync || err != -EAGAIN)
  			break;
  		/*
  		 * Guard against state recovery
  		 */
  		err = nfs4_wait_clnt_recover(clp);
  	} while (err == 0);
  
  	if (err) {
  		nfs_abort_delegation_return(delegation, clp);
  		goto out;
  	}
  	if (!nfs_detach_delegation(nfsi, delegation, NFS_SERVER(inode)))

  		goto out;

  	err = nfs_do_return_delegation(inode, delegation, issync);
  out:
  	return err;

  }

  static bool nfs_delegation_need_return(struct nfs_delegation *delegation)
  {
  	bool ret = false;

  	if (test_bit(NFS_DELEGATION_RETURNING, &delegation->flags))
  		goto out;

  	if (test_and_clear_bit(NFS_DELEGATION_RETURN, &delegation->flags))
  		ret = true;
  	if (test_and_clear_bit(NFS_DELEGATION_RETURN_IF_CLOSED, &delegation->flags) && !ret) {
  		struct inode *inode;
  
  		spin_lock(&delegation->lock);
  		inode = delegation->inode;
  		if (inode && list_empty(&NFS_I(inode)->open_files))
  			ret = true;
  		spin_unlock(&delegation->lock);
  	}

  out:

  	return ret;
  }

  /**
   * nfs_client_return_marked_delegations - return previously marked delegations
   * @clp: nfs_client to process
   *

   * Note that this function is designed to be called by the state
   * manager thread. For this reason, it cannot flush the dirty data,
   * since that could deadlock in case of a state recovery error.
   *

   * Returns zero on success, or a negative errno value.

   */

  int nfs_client_return_marked_delegations(struct nfs_client *clp)

  {
  	struct nfs_delegation *delegation;

  	struct nfs_server *server;

  	struct inode *inode;

  	int err = 0;

  
  restart:
  	rcu_read_lock();

  	list_for_each_entry_rcu(server, &clp->cl_superblocks, client_link) {
  		list_for_each_entry_rcu(delegation, &server->delegations,
  								super_list) {

  			if (!nfs_delegation_need_return(delegation))

  				continue;

  			if (!nfs_sb_active(server->super))

  				continue;

  			inode = nfs_delegation_grab_inode(delegation);
  			if (inode == NULL) {
  				rcu_read_unlock();
  				nfs_sb_deactive(server->super);
  				goto restart;
  			}

  			delegation = nfs_start_delegation_return_locked(NFS_I(inode));

  			rcu_read_unlock();

  			err = nfs_end_delegation_return(inode, delegation, 0);

  			iput(inode);

  			nfs_sb_deactive(server->super);

  			if (!err)
  				goto restart;
  			set_bit(NFS4CLNT_DELEGRETURN, &clp->cl_state);
  			return err;

  		}

  	}
  	rcu_read_unlock();

  	return 0;

  }

  /**
   * nfs_inode_return_delegation_noreclaim - return delegation, don't reclaim opens
   * @inode: inode to process
   *
   * Does not protect against delegation reclaims, therefore really only safe
   * to be called from nfs4_clear_inode().

   */
  void nfs_inode_return_delegation_noreclaim(struct inode *inode)
  {

  	struct nfs_delegation *delegation;

  	delegation = nfs_inode_detach_delegation(inode);
  	if (delegation != NULL)

  		nfs_do_return_delegation(inode, delegation, 1);

  }

  /**
   * nfs_inode_return_delegation - synchronously return a delegation
   * @inode: inode to process
   *

   * This routine will always flush any dirty data to disk on the
   * assumption that if we need to return the delegation, then
   * we should stop caching.
   *

   * Returns zero on success, or a negative errno value.
   */

  int nfs4_inode_return_delegation(struct inode *inode)

  {

  	struct nfs_inode *nfsi = NFS_I(inode);
  	struct nfs_delegation *delegation;
  	int err = 0;

  	nfs_wb_all(inode);

  	delegation = nfs_start_delegation_return(nfsi);
  	if (delegation != NULL)
  		err = nfs_end_delegation_return(inode, delegation, 1);

  	return err;

  }

  static void nfs_mark_return_if_closed_delegation(struct nfs_server *server,
  		struct nfs_delegation *delegation)
  {
  	set_bit(NFS_DELEGATION_RETURN_IF_CLOSED, &delegation->flags);
  	set_bit(NFS4CLNT_DELEGRETURN, &server->nfs_client->cl_state);
  }

  static void nfs_mark_return_delegation(struct nfs_server *server,
  		struct nfs_delegation *delegation)

  {
  	set_bit(NFS_DELEGATION_RETURN, &delegation->flags);

  	set_bit(NFS4CLNT_DELEGRETURN, &server->nfs_client->cl_state);

  }

  static bool nfs_server_mark_return_all_delegations(struct nfs_server *server)
  {
  	struct nfs_delegation *delegation;
  	bool ret = false;
  
  	list_for_each_entry_rcu(delegation, &server->delegations, super_list) {
  		nfs_mark_return_delegation(server, delegation);
  		ret = true;
  	}
  	return ret;
  }

  static void nfs_client_mark_return_all_delegations(struct nfs_client *clp)
  {
  	struct nfs_server *server;
  
  	rcu_read_lock();
  	list_for_each_entry_rcu(server, &clp->cl_superblocks, client_link)
  		nfs_server_mark_return_all_delegations(server);
  	rcu_read_unlock();
  }
  
  static void nfs_delegation_run_state_manager(struct nfs_client *clp)
  {
  	if (test_bit(NFS4CLNT_DELEGRETURN, &clp->cl_state))
  		nfs4_schedule_state_manager(clp);
  }
  
  /**
   * nfs_expire_all_delegations
   * @clp: client to process
   *
   */
  void nfs_expire_all_delegations(struct nfs_client *clp)
  {
  	nfs_client_mark_return_all_delegations(clp);
  	nfs_delegation_run_state_manager(clp);
  }

  /**
   * nfs_super_return_all_delegations - return delegations for one superblock
   * @sb: sb to process
   *

   */

  void nfs_server_return_all_delegations(struct nfs_server *server)

  {

  	struct nfs_client *clp = server->nfs_client;

  	bool need_wait;

  
  	if (clp == NULL)
  		return;

  	rcu_read_lock();

  	need_wait = nfs_server_mark_return_all_delegations(server);

  	rcu_read_unlock();

  	if (need_wait) {

  		nfs4_schedule_state_manager(clp);

  		nfs4_wait_clnt_recover(clp);
  	}

  }

  static void nfs_mark_return_unused_delegation_types(struct nfs_server *server,

  						 fmode_t flags)

  {
  	struct nfs_delegation *delegation;

  	list_for_each_entry_rcu(delegation, &server->delegations, super_list) {

  		if ((delegation->type == (FMODE_READ|FMODE_WRITE)) && !(flags & FMODE_WRITE))
  			continue;
  		if (delegation->type & flags)

  			nfs_mark_return_if_closed_delegation(server, delegation);

  	}

  }

  static void nfs_client_mark_return_unused_delegation_types(struct nfs_client *clp,

  							fmode_t flags)
  {
  	struct nfs_server *server;
  
  	rcu_read_lock();
  	list_for_each_entry_rcu(server, &clp->cl_superblocks, client_link)

  		nfs_mark_return_unused_delegation_types(server, flags);

  	rcu_read_unlock();

  }

  static void nfs_mark_delegation_revoked(struct nfs_server *server,
  		struct nfs_delegation *delegation)
  {
  	set_bit(NFS_DELEGATION_REVOKED, &delegation->flags);

  	delegation->stateid.type = NFS4_INVALID_STATEID_TYPE;

  	nfs_mark_return_delegation(server, delegation);
  }
  
  static bool nfs_revoke_delegation(struct inode *inode,
  		const nfs4_stateid *stateid)

  {
  	struct nfs_delegation *delegation;

  	nfs4_stateid tmp;

  	bool ret = false;

  	rcu_read_lock();
  	delegation = rcu_dereference(NFS_I(inode)->delegation);

  	if (delegation == NULL)
  		goto out;

  	if (stateid == NULL) {
  		nfs4_stateid_copy(&tmp, &delegation->stateid);
  		stateid = &tmp;
  	} else if (!nfs4_stateid_match(stateid, &delegation->stateid))

  		goto out;
  	nfs_mark_delegation_revoked(NFS_SERVER(inode), delegation);
  	ret = true;
  out:

  	rcu_read_unlock();

  	if (ret)
  		nfs_inode_find_state_and_recover(inode, stateid);

  	return ret;

  }

  void nfs_remove_bad_delegation(struct inode *inode,
  		const nfs4_stateid *stateid)

  {
  	struct nfs_delegation *delegation;

  	if (!nfs_revoke_delegation(inode, stateid))
  		return;

  	delegation = nfs_inode_detach_delegation(inode);

  	if (delegation)

  		nfs_free_delegation(delegation);

  }

  EXPORT_SYMBOL_GPL(nfs_remove_bad_delegation);

  /**

   * nfs_expire_unused_delegation_types

   * @clp: client to process
   * @flags: delegation types to expire
   *
   */

  void nfs_expire_unused_delegation_types(struct nfs_client *clp, fmode_t flags)

  {

  	nfs_client_mark_return_unused_delegation_types(clp, flags);

  	nfs_delegation_run_state_manager(clp);

  }

  static void nfs_mark_return_unreferenced_delegations(struct nfs_server *server)

  {
  	struct nfs_delegation *delegation;

  	list_for_each_entry_rcu(delegation, &server->delegations, super_list) {

  		if (test_and_clear_bit(NFS_DELEGATION_REFERENCED, &delegation->flags))
  			continue;

  		nfs_mark_return_if_closed_delegation(server, delegation);

  	}

  }

  /**
   * nfs_expire_unreferenced_delegations - Eliminate unused delegations
   * @clp: nfs_client to process
   *
   */

  void nfs_expire_unreferenced_delegations(struct nfs_client *clp)
  {

  	struct nfs_server *server;
  
  	rcu_read_lock();
  	list_for_each_entry_rcu(server, &clp->cl_superblocks, client_link)
  		nfs_mark_return_unreferenced_delegations(server);
  	rcu_read_unlock();

  	nfs_delegation_run_state_manager(clp);
  }

  /**
   * nfs_async_inode_return_delegation - asynchronously return a delegation
   * @inode: inode to process

   * @stateid: state ID information

   *
   * Returns zero on success, or a negative errno value.

   */

  int nfs_async_inode_return_delegation(struct inode *inode,
  				      const nfs4_stateid *stateid)

  {

  	struct nfs_server *server = NFS_SERVER(inode);
  	struct nfs_client *clp = server->nfs_client;

  	struct nfs_delegation *delegation;

  	rcu_read_lock();
  	delegation = rcu_dereference(NFS_I(inode)->delegation);

  	if (delegation == NULL)
  		goto out_enoent;

  	if (stateid != NULL &&
  	    !clp->cl_mvops->match_stateid(&delegation->stateid, stateid))

  		goto out_enoent;

  	nfs_mark_return_delegation(server, delegation);

  	rcu_read_unlock();

  	nfs_delegation_run_state_manager(clp);
  	return 0;

  out_enoent:
  	rcu_read_unlock();
  	return -ENOENT;

  }

  static struct inode *
  nfs_delegation_find_inode_server(struct nfs_server *server,
  				 const struct nfs_fh *fhandle)

  {
  	struct nfs_delegation *delegation;
  	struct inode *res = NULL;

  
  	list_for_each_entry_rcu(delegation, &server->delegations, super_list) {

  		spin_lock(&delegation->lock);
  		if (delegation->inode != NULL &&
  		    nfs_compare_fh(fhandle, &NFS_I(delegation->inode)->fh) == 0) {

  			res = igrab(delegation->inode);

  		}

  		spin_unlock(&delegation->lock);
  		if (res != NULL)
  			break;

  	}

  	return res;
  }
  
  /**
   * nfs_delegation_find_inode - retrieve the inode associated with a delegation
   * @clp: client state handle
   * @fhandle: filehandle from a delegation recall
   *
   * Returns pointer to inode matching "fhandle," or NULL if a matching inode
   * cannot be found.
   */
  struct inode *nfs_delegation_find_inode(struct nfs_client *clp,
  					const struct nfs_fh *fhandle)
  {
  	struct nfs_server *server;
  	struct inode *res = NULL;
  
  	rcu_read_lock();
  	list_for_each_entry_rcu(server, &clp->cl_superblocks, client_link) {
  		res = nfs_delegation_find_inode_server(server, fhandle);
  		if (res != NULL)
  			break;
  	}

  	rcu_read_unlock();

  	return res;
  }

  static void nfs_delegation_mark_reclaim_server(struct nfs_server *server)
  {
  	struct nfs_delegation *delegation;

  	list_for_each_entry_rcu(delegation, &server->delegations, super_list) {
  		/*
  		 * If the delegation may have been admin revoked, then we
  		 * cannot reclaim it.
  		 */
  		if (test_bit(NFS_DELEGATION_TEST_EXPIRED, &delegation->flags))
  			continue;

  		set_bit(NFS_DELEGATION_NEED_RECLAIM, &delegation->flags);

  	}

  }
  
  /**
   * nfs_delegation_mark_reclaim - mark all delegations as needing to be reclaimed
   * @clp: nfs_client to process
   *

   */

  void nfs_delegation_mark_reclaim(struct nfs_client *clp)

  {

  	struct nfs_server *server;

  	rcu_read_lock();

  	list_for_each_entry_rcu(server, &clp->cl_superblocks, client_link)
  		nfs_delegation_mark_reclaim_server(server);

  	rcu_read_unlock();

  }

  /**
   * nfs_delegation_reap_unclaimed - reap unclaimed delegations after reboot recovery is done
   * @clp: nfs_client to process
   *

   */

  void nfs_delegation_reap_unclaimed(struct nfs_client *clp)

  {

  	struct nfs_delegation *delegation;

  	struct nfs_server *server;

  	struct inode *inode;

  restart:
  	rcu_read_lock();

  	list_for_each_entry_rcu(server, &clp->cl_superblocks, client_link) {
  		list_for_each_entry_rcu(delegation, &server->delegations,
  								super_list) {

  			if (test_bit(NFS_DELEGATION_RETURNING,
  						&delegation->flags))
  				continue;

  			if (test_bit(NFS_DELEGATION_NEED_RECLAIM,
  						&delegation->flags) == 0)
  				continue;

  			if (!nfs_sb_active(server->super))

  				continue;

  			inode = nfs_delegation_grab_inode(delegation);
  			if (inode == NULL) {
  				rcu_read_unlock();
  				nfs_sb_deactive(server->super);
  				goto restart;
  			}

  			delegation = nfs_start_delegation_return_locked(NFS_I(inode));

  			rcu_read_unlock();

  			if (delegation != NULL) {
  				delegation = nfs_detach_delegation(NFS_I(inode),
  					delegation, server);
  				if (delegation != NULL)
  					nfs_free_delegation(delegation);
  			}

  			iput(inode);

  			nfs_sb_deactive(server->super);

  			goto restart;
  		}

  	}

  	rcu_read_unlock();

  }

  static inline bool nfs4_server_rebooted(const struct nfs_client *clp)
  {
  	return (clp->cl_state & (BIT(NFS4CLNT_CHECK_LEASE) |
  				BIT(NFS4CLNT_LEASE_EXPIRED) |
  				BIT(NFS4CLNT_SESSION_RESET))) != 0;
  }

  static void nfs_mark_test_expired_delegation(struct nfs_server *server,
  	    struct nfs_delegation *delegation)
  {

  	if (delegation->stateid.type == NFS4_INVALID_STATEID_TYPE)
  		return;

  	clear_bit(NFS_DELEGATION_NEED_RECLAIM, &delegation->flags);
  	set_bit(NFS_DELEGATION_TEST_EXPIRED, &delegation->flags);
  	set_bit(NFS4CLNT_DELEGATION_EXPIRED, &server->nfs_client->cl_state);
  }

  static void nfs_inode_mark_test_expired_delegation(struct nfs_server *server,
  		struct inode *inode)
  {
  	struct nfs_delegation *delegation;
  
  	rcu_read_lock();
  	delegation = rcu_dereference(NFS_I(inode)->delegation);
  	if (delegation)
  		nfs_mark_test_expired_delegation(server, delegation);
  	rcu_read_unlock();
  
  }

  static void nfs_delegation_mark_test_expired_server(struct nfs_server *server)
  {
  	struct nfs_delegation *delegation;
  
  	list_for_each_entry_rcu(delegation, &server->delegations, super_list)
  		nfs_mark_test_expired_delegation(server, delegation);
  }
  
  /**
   * nfs_mark_test_expired_all_delegations - mark all delegations for testing
   * @clp: nfs_client to process
   *
   * Iterates through all the delegations associated with this server and
   * marks them as needing to be checked for validity.
   */
  void nfs_mark_test_expired_all_delegations(struct nfs_client *clp)
  {
  	struct nfs_server *server;
  
  	rcu_read_lock();
  	list_for_each_entry_rcu(server, &clp->cl_superblocks, client_link)
  		nfs_delegation_mark_test_expired_server(server);
  	rcu_read_unlock();
  }
  
  /**
   * nfs_reap_expired_delegations - reap expired delegations
   * @clp: nfs_client to process
   *
   * Iterates through all the delegations associated with this server and
   * checks if they have may have been revoked. This function is usually
   * expected to be called in cases where the server may have lost its
   * lease.
   */
  void nfs_reap_expired_delegations(struct nfs_client *clp)
  {
  	const struct nfs4_minor_version_ops *ops = clp->cl_mvops;
  	struct nfs_delegation *delegation;
  	struct nfs_server *server;
  	struct inode *inode;
  	struct rpc_cred *cred;
  	nfs4_stateid stateid;
  
  restart:
  	rcu_read_lock();
  	list_for_each_entry_rcu(server, &clp->cl_superblocks, client_link) {
  		list_for_each_entry_rcu(delegation, &server->delegations,
  								super_list) {
  			if (test_bit(NFS_DELEGATION_RETURNING,
  						&delegation->flags))
  				continue;
  			if (test_bit(NFS_DELEGATION_TEST_EXPIRED,
  						&delegation->flags) == 0)
  				continue;
  			if (!nfs_sb_active(server->super))
  				continue;
  			inode = nfs_delegation_grab_inode(delegation);
  			if (inode == NULL) {
  				rcu_read_unlock();
  				nfs_sb_deactive(server->super);
  				goto restart;
  			}
  			cred = get_rpccred_rcu(delegation->cred);
  			nfs4_stateid_copy(&stateid, &delegation->stateid);
  			clear_bit(NFS_DELEGATION_TEST_EXPIRED, &delegation->flags);
  			rcu_read_unlock();
  			if (cred != NULL &&
  			    ops->test_and_free_expired(server, &stateid, cred) < 0) {
  				nfs_revoke_delegation(inode, &stateid);
  				nfs_inode_find_state_and_recover(inode, &stateid);
  			}
  			put_rpccred(cred);

  			if (nfs4_server_rebooted(clp)) {
  				nfs_inode_mark_test_expired_delegation(server,inode);
  				iput(inode);
  				nfs_sb_deactive(server->super);
  				return;
  			}

  			iput(inode);
  			nfs_sb_deactive(server->super);
  			goto restart;
  		}
  	}
  	rcu_read_unlock();
  }

  void nfs_inode_find_delegation_state_and_recover(struct inode *inode,
  		const nfs4_stateid *stateid)
  {
  	struct nfs_client *clp = NFS_SERVER(inode)->nfs_client;
  	struct nfs_delegation *delegation;
  	bool found = false;
  
  	rcu_read_lock();
  	delegation = rcu_dereference(NFS_I(inode)->delegation);
  	if (delegation &&
  	    nfs4_stateid_match_other(&delegation->stateid, stateid)) {
  		nfs_mark_test_expired_delegation(NFS_SERVER(inode), delegation);
  		found = true;
  	}
  	rcu_read_unlock();
  	if (found)
  		nfs4_schedule_state_manager(clp);
  }

  /**
   * nfs_delegations_present - check for existence of delegations
   * @clp: client state handle
   *
   * Returns one if there are any nfs_delegation structures attached
   * to this nfs_client.
   */
  int nfs_delegations_present(struct nfs_client *clp)
  {
  	struct nfs_server *server;
  	int ret = 0;
  
  	rcu_read_lock();
  	list_for_each_entry_rcu(server, &clp->cl_superblocks, client_link)
  		if (!list_empty(&server->delegations)) {
  			ret = 1;
  			break;
  		}
  	rcu_read_unlock();
  	return ret;
  }
  
  /**
   * nfs4_copy_delegation_stateid - Copy inode's state ID information

   * @inode: inode to check

   * @flags: delegation type requirement

   * @dst: stateid data structure to fill in
   * @cred: optional argument to retrieve credential

   *

   * Returns "true" and fills in "dst->data" * if inode had a delegation,
   * otherwise "false" is returned.

   */

  bool nfs4_copy_delegation_stateid(struct inode *inode, fmode_t flags,
  		nfs4_stateid *dst, struct rpc_cred **cred)

  {

  	struct nfs_inode *nfsi = NFS_I(inode);
  	struct nfs_delegation *delegation;

  	bool ret;

  	flags &= FMODE_READ|FMODE_WRITE;

  	rcu_read_lock();
  	delegation = rcu_dereference(nfsi->delegation);

  	ret = nfs4_is_valid_delegation(delegation, flags);

  	if (ret) {

  		nfs4_stateid_copy(dst, &delegation->stateid);

  		nfs_mark_delegation_referenced(delegation);

  		if (cred)
  			*cred = get_rpccred(delegation->cred);

  	}

  	rcu_read_unlock();
  	return ret;

  }

  
  /**
   * nfs4_delegation_flush_on_close - Check if we must flush file on close
   * @inode: inode to check
   *
   * This function checks the number of outstanding writes to the file
   * against the delegation 'space_limit' field to see if
   * the spec requires us to flush the file on close.
   */
  bool nfs4_delegation_flush_on_close(const struct inode *inode)
  {
  	struct nfs_inode *nfsi = NFS_I(inode);
  	struct nfs_delegation *delegation;
  	bool ret = true;
  
  	rcu_read_lock();
  	delegation = rcu_dereference(nfsi->delegation);
  	if (delegation == NULL || !(delegation->type & FMODE_WRITE))
  		goto out;

  	if (atomic_long_read(&nfsi->nrequests) < delegation->pagemod_limit)

  		ret = false;
  out:
  	rcu_read_unlock();
  	return ret;
  }