/*
   * 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);
  }
  
  /**
   * nfs_have_delegation - check if inode has a delegation
   * @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)
  {
  	struct nfs_delegation *delegation;
  	int ret = 0;
  
  	flags &= FMODE_READ|FMODE_WRITE;
  	rcu_read_lock();
  	delegation = rcu_dereference(NFS_I(inode)->delegation);
  	if (delegation != NULL && (delegation->type & flags) == flags &&
  	    !test_bit(NFS_DELEGATION_RETURNING, &delegation->flags)) {
  		nfs_mark_delegation_referenced(delegation);
  		ret = 1;
  	}
  	rcu_read_unlock();
  	return ret;
  }
  
  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;
  	int status = 0;
  
  	if (inode->i_flock == NULL)
  		goto out;
  
  	/* Protect inode->i_flock using the i_lock */
  	spin_lock(&inode->i_lock);
  	for (fl = inode->i_flock; fl != NULL; fl = fl->fl_next) {
  		if (!(fl->fl_flags & (FL_POSIX|FL_FLOCK)))
  			continue;
  		if (nfs_file_open_context(fl->fl_file) != ctx)
  			continue;
  		spin_unlock(&inode->i_lock);
  		status = nfs4_lock_delegation_recall(fl, state, stateid);
  		if (status < 0)
  			goto out;
  		spin_lock(&inode->i_lock);
  	}
  	spin_unlock(&inode->i_lock);
  out:
  	return status;
  }
  
  static int nfs_delegation_claim_opens(struct inode *inode, const nfs4_stateid *stateid)
  {
  	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);
  		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->maxsize = res->maxsize;
  			oldcred = delegation->cred;
  			delegation->cred = get_rpccred(cred);
  			clear_bit(NFS_DELEGATION_NEED_RECLAIM,
  				  &delegation->flags);
  			NFS_I(inode)->delegation_state = delegation->type;
  			spin_unlock(&delegation->lock);
  			put_rpccred(oldcred);
  			rcu_read_unlock();
  			trace_nfs4_reclaim_delegation(inode, res->delegation_type);
  		} else {
  			/* We appear to have raced with a delegation return. */
  			spin_unlock(&delegation->lock);
  			rcu_read_unlock();
  			nfs_inode_set_delegation(inode, cred, res);
  		}
  	} else {
  		rcu_read_unlock();
  	}
  }
  
  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;
  	nfsi->delegation_state = 0;
  	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);
  }
  
  /**
   * 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->maxsize = res->maxsize;
  	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) {
  		if (nfs4_stateid_match(&delegation->stateid,
  					&old_delegation->stateid) &&
  				delegation->type == old_delegation->type) {
  			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;
  		}
  		freeme = nfs_detach_delegation_locked(nfsi, 
  				old_delegation, clp);
  		if (freeme == NULL)
  			goto out;
  	}
  	list_add_rcu(&delegation->super_list, &server->delegations);
  	nfsi->delegation_state = delegation->type;
  	rcu_assign_pointer(nfsi->delegation, delegation);
  	delegation = NULL;
  
  	/* Ensure we revalidate the attributes and page cache! */
  	spin_lock(&inode->i_lock);
  	nfsi->cache_validity |= NFS_INO_REVAL_FORCED;
  	spin_unlock(&inode->i_lock);
  	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);
  		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_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);
  	}
  	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;
  			inode = nfs_delegation_grab_inode(delegation);
  			if (inode == NULL)
  				continue;
  			delegation = nfs_start_delegation_return_locked(NFS_I(inode));
  			rcu_read_unlock();
  
  			err = nfs_end_delegation_return(inode, delegation, 0);
  			iput(inode);
  			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, 0);
  }
  
  /**
   * 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_revoke_delegation(struct inode *inode)
  {
  	struct nfs_delegation *delegation;
  	rcu_read_lock();
  	delegation = rcu_dereference(NFS_I(inode)->delegation);
  	if (delegation != NULL) {
  		set_bit(NFS_DELEGATION_REVOKED, &delegation->flags);
  		nfs_mark_return_delegation(NFS_SERVER(inode), delegation);
  	}
  	rcu_read_unlock();
  }
  
  void nfs_remove_bad_delegation(struct inode *inode)
  {
  	struct nfs_delegation *delegation;
  
  	nfs_revoke_delegation(inode);
  	delegation = nfs_inode_detach_delegation(inode);
  	if (delegation) {
  		nfs_inode_find_state_and_recover(inode, &delegation->stateid);
  		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;
  
  	filemap_flush(inode->i_mapping);
  
  	rcu_read_lock();
  	delegation = rcu_dereference(NFS_I(inode)->delegation);
  	if (delegation == NULL)
  		goto out_enoent;
  
  	if (!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)
  		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_NEED_RECLAIM,
  						&delegation->flags) == 0)
  				continue;
  			inode = nfs_delegation_grab_inode(delegation);
  			if (inode == NULL)
  				continue;
  			delegation = nfs_detach_delegation(NFS_I(inode),
  					delegation, server);
  			rcu_read_unlock();
  
  			if (delegation != NULL)
  				nfs_free_delegation(delegation);
  			iput(inode);
  			goto restart;
  		}
  	}
  	rcu_read_unlock();
  }
  
  /**
   * 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
   * @dst: stateid data structure to fill in
   * @inode: inode to check
   * @flags: delegation type requirement
   *
   * Returns "true" and fills in "dst->data" * if inode had a delegation,
   * otherwise "false" is returned.
   */
  bool nfs4_copy_delegation_stateid(nfs4_stateid *dst, struct inode *inode,
  		fmode_t flags)
  {
  	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 = (delegation != NULL && (delegation->type & flags) == flags);
  	if (ret) {
  		nfs4_stateid_copy(dst, &delegation->stateid);
  		nfs_mark_delegation_referenced(delegation);
  	}
  	rcu_read_unlock();
  	return ret;
  }