/*
   * 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"

  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 nfs_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) {
  		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)
  {
  	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 file locks lock */
  	lock_flocks();

  	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;

  		unlock_flocks();

  		status = nfs4_lock_delegation_recall(state, fl);

  		if (status < 0)

  			goto out;

  		lock_flocks();

  	}

  	unlock_flocks();

  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 *state;

  	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 (memcmp(state->stateid.data, stateid->data, sizeof(state->stateid.data)) != 0)
  			continue;

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

  		err = nfs4_open_delegation_recall(ctx, state, stateid);

  		if (err >= 0)
  			err = nfs_delegation_claim_locks(ctx, state);

  		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) {
  			memcpy(delegation->stateid.data, res->delegation.data,
  			       sizeof(delegation->stateid.data));
  			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();
  		} 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;
  
  	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_detach_delegation_locked(struct nfs_inode *nfsi,

  			     struct nfs_server *server)

  {

  	struct nfs_delegation *delegation =
  		rcu_dereference_protected(nfsi->delegation,

  				lockdep_is_held(&server->nfs_client->cl_lock));

  
  	if (delegation == NULL)
  		goto nomatch;

  	spin_lock(&delegation->lock);

  	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;
  nomatch:
  	return NULL;
  }

  static struct nfs_delegation *nfs_detach_delegation(struct nfs_inode *nfsi,

  						    struct nfs_server *server)

  {

  	struct nfs_client *clp = server->nfs_client;

  	struct nfs_delegation *delegation;
  
  	spin_lock(&clp->cl_lock);

  	delegation = nfs_detach_delegation_locked(nfsi, server);

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

  /**
   * 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;
  	memcpy(delegation->stateid.data, res->delegation.data,
  			sizeof(delegation->stateid.data));
  	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 (memcmp(&delegation->stateid, &old_delegation->stateid,
  					sizeof(old_delegation->stateid)) == 0 &&
  				delegation->type == old_delegation->type) {

  			goto out;

  		}

  		/*
  		 * Deal with broken servers that hand out two
  		 * delegations for the same file.
  		 */
  		dfprintk(FILE, "%s: server %s handed out "
  				"a duplicate delegation!
  ",

  				__func__, clp->cl_hostname);

  		if (delegation->type <= old_delegation->type) {

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

  		freeme = nfs_detach_delegation_locked(nfsi, server);

  	}

  	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);

  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_inode_return_delegation(struct inode *inode, struct nfs_delegation *delegation, int issync)

  {

  	struct nfs_inode *nfsi = NFS_I(inode);

  	int err;

  	/*
  	 * Guard against new delegated open/lock/unlock calls and against
  	 * state recovery
  	 */

  	down_write(&nfsi->rwsem);

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

  	up_write(&nfsi->rwsem);

  	if (err)
  		goto out;

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

  }

  /**
   * nfs_client_return_marked_delegations - return previously marked delegations
   * @clp: nfs_client to process
   *
   * 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 (!test_and_clear_bit(NFS_DELEGATION_RETURN,
  							&delegation->flags))
  				continue;
  			inode = nfs_delegation_grab_inode(delegation);
  			if (inode == NULL)
  				continue;
  			delegation = nfs_detach_delegation(NFS_I(inode),
  								server);
  			rcu_read_unlock();
  
  			if (delegation != NULL) {
  				filemap_flush(inode->i_mapping);
  				err = __nfs_inode_return_delegation(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_server *server = NFS_SERVER(inode);

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

  	if (rcu_access_pointer(nfsi->delegation) != NULL) {

  		delegation = nfs_detach_delegation(nfsi, server);

  		if (delegation != NULL)
  			nfs_do_return_delegation(inode, delegation, 0);
  	}
  }

  /**
   * nfs_inode_return_delegation - synchronously return a delegation
   * @inode: inode to process
   *
   * Returns zero on success, or a negative errno value.
   */

  int nfs_inode_return_delegation(struct inode *inode)
  {

  	struct nfs_server *server = NFS_SERVER(inode);

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

  	if (rcu_access_pointer(nfsi->delegation) != NULL) {

  		delegation = nfs_detach_delegation(nfsi, server);

  		if (delegation != NULL) {

  			nfs_wb_all(inode);

  			err = __nfs_inode_return_delegation(inode, delegation, 1);
  		}

  	}
  	return err;

  }

  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);

  }

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

   */

  void nfs_super_return_all_delegations(struct super_block *sb)

  {

  	struct nfs_server *server = NFS_SB(sb);
  	struct nfs_client *clp = server->nfs_client;

  	struct nfs_delegation *delegation;

  
  	if (clp == NULL)
  		return;

  	rcu_read_lock();

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

  		spin_lock(&delegation->lock);

  		set_bit(NFS_DELEGATION_RETURN, &delegation->flags);

  		spin_unlock(&delegation->lock);

  	}

  	rcu_read_unlock();

  	if (nfs_client_return_marked_delegations(clp) != 0)
  		nfs4_schedule_state_manager(clp);

  }

  static void nfs_mark_return_all_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_delegation(server, delegation);

  	}

  }
  
  static void nfs_client_mark_return_all_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_all_delegation_types(server, flags);

  	rcu_read_unlock();

  }

  static void nfs_client_mark_return_all_delegations(struct nfs_client *clp)
  {
  	nfs_client_mark_return_all_delegation_types(clp, FMODE_READ|FMODE_WRITE);
  }

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

  void nfs_expire_all_delegation_types(struct nfs_client *clp, fmode_t flags)

  {

  	nfs_client_mark_return_all_delegation_types(clp, flags);

  	nfs_delegation_run_state_manager(clp);

  }

  /**
   * nfs_expire_all_delegations
   * @clp: client to process
   *
   */

  void nfs_expire_all_delegations(struct nfs_client *clp)
  {
  	nfs_expire_all_delegation_types(clp, FMODE_READ|FMODE_WRITE);
  }

  /**
   * nfs_handle_cb_pathdown - return all delegations after NFS4ERR_CB_PATH_DOWN
   * @clp: client to process
   *

   */

  void nfs_handle_cb_pathdown(struct nfs_client *clp)

  {

  	if (clp == NULL)
  		return;

  	nfs_client_mark_return_all_delegations(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_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 from CB_RECALL arguments
   *
   * 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 (!clp->cl_mvops->validate_stateid(delegation, stateid)) {

  		rcu_read_unlock();
  		return -ENOENT;
  	}

  	nfs_mark_return_delegation(server, delegation);

  	rcu_read_unlock();

  	nfs_delegation_run_state_manager(clp);
  	return 0;

  }

  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),
  								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
   *
   * Returns one and fills in "dst->data" * if inode had a delegation,
   * otherwise zero is returned.
   */

  int nfs4_copy_delegation_stateid(nfs4_stateid *dst, struct inode *inode)
  {

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

  	int ret = 0;

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

  	if (delegation != NULL) {
  		memcpy(dst->data, delegation->stateid.data, sizeof(dst->data));

  		ret = 1;

  	}

  	rcu_read_unlock();
  	return ret;

  }