/*
   * linux/fs/nfs/namespace.c
   *
   * Copyright (C) 2005 Trond Myklebust <Trond.Myklebust@netapp.com>

   * - Modified by David Howells <dhowells@redhat.com>

   *
   * NFS namespace
   */

  #include <linux/dcache.h>

  #include <linux/gfp.h>

  #include <linux/mount.h>
  #include <linux/namei.h>
  #include <linux/nfs_fs.h>
  #include <linux/string.h>
  #include <linux/sunrpc/clnt.h>
  #include <linux/vfs.h>

  #include <linux/sunrpc/gss_api.h>

  #include "internal.h"

  
  #define NFSDBG_FACILITY		NFSDBG_VFS

  static void nfs_expire_automounts(struct work_struct *work);

  static LIST_HEAD(nfs_automount_list);

  static DECLARE_DELAYED_WORK(nfs_automount_task, nfs_expire_automounts);

  int nfs_mountpoint_expiry_timeout = 500 * HZ;

  static struct vfsmount *nfs_do_submount(struct dentry *dentry,

  					struct nfs_fh *fh,

  					struct nfs_fattr *fattr,
  					rpc_authflavor_t authflavor);

  /*

   * nfs_path - reconstruct the path given an arbitrary dentry

   * @base - used to return pointer to the end of devname part of path

   * @dentry - pointer to dentry
   * @buffer - result buffer
   * @buflen - length of buffer
   *

   * Helper function for constructing the server pathname
   * by arbitrary hashed dentry.

   *
   * This is mainly for use in figuring out the path on the

   * server side when automounting on top of an existing partition
   * and in generating /proc/mounts and friends.

   */

  char *nfs_path(char **p, struct dentry *dentry, char *buffer, ssize_t buflen)

  {

  	char *end;

  	int namelen;

  	unsigned seq;

  	const char *base;

  rename_retry:
  	end = buffer+buflen;

  	*--end = '\0';
  	buflen--;

  
  	seq = read_seqbegin(&rename_lock);
  	rcu_read_lock();

  	while (1) {
  		spin_lock(&dentry->d_lock);
  		if (IS_ROOT(dentry))
  			break;

  		namelen = dentry->d_name.len;
  		buflen -= namelen + 1;
  		if (buflen < 0)

  			goto Elong_unlock;

  		end -= namelen;
  		memcpy(end, dentry->d_name.name, namelen);
  		*--end = '/';

  		spin_unlock(&dentry->d_lock);

  		dentry = dentry->d_parent;
  	}

  	if (read_seqretry(&rename_lock, seq)) {
  		spin_unlock(&dentry->d_lock);
  		rcu_read_unlock();

  		goto rename_retry;

  	}

  	if (*end != '/') {

  		if (--buflen < 0) {
  			spin_unlock(&dentry->d_lock);
  			rcu_read_unlock();

  			goto Elong;

  		}

  		*--end = '/';
  	}

  	*p = end;
  	base = dentry->d_fsdata;
  	if (!base) {
  		spin_unlock(&dentry->d_lock);
  		rcu_read_unlock();
  		WARN_ON(1);
  		return end;
  	}

  	namelen = strlen(base);
  	/* Strip off excess slashes in base string */
  	while (namelen > 0 && base[namelen - 1] == '/')
  		namelen--;
  	buflen -= namelen;

  	if (buflen < 0) {

  		spin_unlock(&dentry->d_lock);

  		rcu_read_unlock();

  		goto Elong;

  	}

  	end -= namelen;
  	memcpy(end, base, namelen);

  	spin_unlock(&dentry->d_lock);
  	rcu_read_unlock();

  	return end;

  Elong_unlock:

  	spin_unlock(&dentry->d_lock);

  	rcu_read_unlock();
  	if (read_seqretry(&rename_lock, seq))
  		goto rename_retry;

  Elong:
  	return ERR_PTR(-ENAMETOOLONG);
  }

  #ifdef CONFIG_NFS_V4

  rpc_authflavor_t nfs_find_best_sec(struct nfs4_secinfo_flavors *flavors)

  {
  	struct gss_api_mech *mech;
  	struct xdr_netobj oid;
  	int i;
  	rpc_authflavor_t pseudoflavor = RPC_AUTH_UNIX;
  
  	for (i = 0; i < flavors->num_flavors; i++) {
  		struct nfs4_secinfo_flavor *flavor;
  		flavor = &flavors->flavors[i];
  
  		if (flavor->flavor == RPC_AUTH_NULL || flavor->flavor == RPC_AUTH_UNIX) {
  			pseudoflavor = flavor->flavor;
  			break;
  		} else if (flavor->flavor == RPC_AUTH_GSS) {
  			oid.len  = flavor->gss.sec_oid4.len;
  			oid.data = flavor->gss.sec_oid4.data;
  			mech = gss_mech_get_by_OID(&oid);
  			if (!mech)
  				continue;
  			pseudoflavor = gss_svc_to_pseudoflavor(mech, flavor->gss.service);
  			gss_mech_put(mech);
  			break;
  		}
  	}
  
  	return pseudoflavor;
  }

  static int nfs_negotiate_security(const struct dentry *parent,
  				  const struct dentry *dentry,
  				  rpc_authflavor_t *flavor)

  {

  	struct page *page;
  	struct nfs4_secinfo_flavors *flavors;
  	int (*secinfo)(struct inode *, const struct qstr *, struct nfs4_secinfo_flavors *);

  	int ret = -EPERM;

  
  	secinfo = NFS_PROTO(parent->d_inode)->secinfo;
  	if (secinfo != NULL) {
  		page = alloc_page(GFP_KERNEL);
  		if (!page) {

  			ret = -ENOMEM;

  			goto out;
  		}
  		flavors = page_address(page);

  		ret = secinfo(parent->d_inode, &dentry->d_name, flavors);

  		*flavor = nfs_find_best_sec(flavors);

  		put_page(page);
  	}

  out:

  	return ret;

  }

  static int nfs_lookup_with_sec(struct nfs_server *server, struct dentry *parent,
  			       struct dentry *dentry, struct path *path,
  			       struct nfs_fh *fh, struct nfs_fattr *fattr,
  			       rpc_authflavor_t *flavor)

  {

  	struct rpc_clnt *clone;
  	struct rpc_auth *auth;
  	int err;

  	err = nfs_negotiate_security(parent, path->dentry, flavor);
  	if (err < 0)

  		goto out;
  	clone  = rpc_clone_client(server->client);

  	auth   = rpcauth_create(*flavor, clone);

  	if (!auth) {

  		err = -EIO;

  		goto out_shutdown;

  	}
  	err = server->nfs_client->rpc_ops->lookup(clone, parent->d_inode,
  						  &path->dentry->d_name,
  						  fh, fattr);

  out_shutdown:
  	rpc_shutdown_client(clone);

  out:

  	return err;

  }
  #else /* CONFIG_NFS_V4 */

  static inline int nfs_lookup_with_sec(struct nfs_server *server,
  				      struct dentry *parent, struct dentry *dentry,
  				      struct path *path, struct nfs_fh *fh,
  				      struct nfs_fattr *fattr,
  				      rpc_authflavor_t *flavor)

  {
  	return -EPERM;
  }
  #endif /* CONFIG_NFS_V4 */

  /*

   * nfs_d_automount - Handle crossing a mountpoint on the server
   * @path - The mountpoint

   *
   * When we encounter a mountpoint on the server, we want to set up
   * a mountpoint on the client too, to prevent inode numbers from
   * colliding, and to allow "df" to work properly.
   * On NFSv4, we also want to allow for the fact that different
   * filesystems may be migrated to different servers in a failover
   * situation, and that different filesystems may want to use
   * different security flavours.
   */

  struct vfsmount *nfs_d_automount(struct path *path)

  {
  	struct vfsmount *mnt;

  	struct nfs_server *server = NFS_SERVER(path->dentry->d_inode);

  	struct dentry *parent;

  	struct nfs_fh *fh = NULL;
  	struct nfs_fattr *fattr = NULL;

  	int err;

  	rpc_authflavor_t flavor = RPC_AUTH_UNIX;

  	dprintk("--> nfs_d_automount()
  ");

  	mnt = ERR_PTR(-ESTALE);
  	if (IS_ROOT(path->dentry))
  		goto out_nofree;

  	mnt = ERR_PTR(-ENOMEM);

  	fh = nfs_alloc_fhandle();
  	fattr = nfs_alloc_fattr();
  	if (fh == NULL || fattr == NULL)

  		goto out;

  	dprintk("%s: enter
  ", __func__);

  	/* Look it up again to get its attributes */
  	parent = dget_parent(path->dentry);

  	err = server->nfs_client->rpc_ops->lookup(server->client, parent->d_inode,

  						  &path->dentry->d_name,

  						  fh, fattr);

  	if (err == -EPERM && NFS_PROTO(parent->d_inode)->secinfo != NULL)
  		err = nfs_lookup_with_sec(server, parent, path->dentry, path, fh, fattr, &flavor);

  	dput(parent);

  	if (err != 0) {
  		mnt = ERR_PTR(err);
  		goto out;
  	}

  	if (fattr->valid & NFS_ATTR_FATTR_V4_REFERRAL)

  		mnt = nfs_do_refmount(path->dentry);

  	else

  		mnt = nfs_do_submount(path->dentry, fh, fattr, flavor);

  	if (IS_ERR(mnt))

  		goto out;

  	dprintk("%s: done, success
  ", __func__);
  	mntget(mnt); /* prevent immediate expiration */
  	mnt_set_expiry(mnt, &nfs_automount_list);
  	schedule_delayed_work(&nfs_automount_task, nfs_mountpoint_expiry_timeout);

  out:

  	nfs_free_fattr(fattr);
  	nfs_free_fhandle(fh);

  out_nofree:
  	dprintk("<-- nfs_follow_mountpoint() = %p
  ", mnt);
  	return mnt;

  }

  const struct inode_operations nfs_mountpoint_inode_operations = {

  	.getattr	= nfs_getattr,
  };

  const struct inode_operations nfs_referral_inode_operations = {

  };

  static void nfs_expire_automounts(struct work_struct *work)

  {

  	struct list_head *list = &nfs_automount_list;

  
  	mark_mounts_for_expiry(list);
  	if (!list_empty(list))
  		schedule_delayed_work(&nfs_automount_task, nfs_mountpoint_expiry_timeout);
  }
  
  void nfs_release_automount_timer(void)
  {

  	if (list_empty(&nfs_automount_list))

  		cancel_delayed_work(&nfs_automount_task);

  }

  
  /*
   * Clone a mountpoint of the appropriate type
   */

  static struct vfsmount *nfs_do_clone_mount(struct nfs_server *server,
  					   const char *devname,

  					   struct nfs_clone_mount *mountdata)
  {
  #ifdef CONFIG_NFS_V4

  	struct vfsmount *mnt = ERR_PTR(-EINVAL);

  	switch (server->nfs_client->rpc_ops->version) {

  		case 2:
  		case 3:

  			mnt = vfs_kern_mount(&nfs_xdev_fs_type, 0, devname, mountdata);

  			break;
  		case 4:

  			mnt = vfs_kern_mount(&nfs4_xdev_fs_type, 0, devname, mountdata);

  	}
  	return mnt;
  #else

  	return vfs_kern_mount(&nfs_xdev_fs_type, 0, devname, mountdata);

  #endif
  }
  
  /**
   * nfs_do_submount - set up mountpoint when crossing a filesystem boundary

   * @dentry - parent directory
   * @fh - filehandle for new root dentry
   * @fattr - attributes for new root inode

   * @authflavor - security flavor to use when performing the mount

   *
   */

  static struct vfsmount *nfs_do_submount(struct dentry *dentry,

  					struct nfs_fh *fh,

  					struct nfs_fattr *fattr,
  					rpc_authflavor_t authflavor)

  {
  	struct nfs_clone_mount mountdata = {

  		.sb = dentry->d_sb,

  		.dentry = dentry,
  		.fh = fh,
  		.fattr = fattr,

  		.authflavor = authflavor,

  	};
  	struct vfsmount *mnt = ERR_PTR(-ENOMEM);
  	char *page = (char *) __get_free_page(GFP_USER);
  	char *devname;

  	dprintk("--> nfs_do_submount()
  ");

  	dprintk("%s: submounting on %s/%s
  ", __func__,

  			dentry->d_parent->d_name.name,
  			dentry->d_name.name);
  	if (page == NULL)
  		goto out;

  	devname = nfs_devname(dentry, page, PAGE_SIZE);

  	mnt = (struct vfsmount *)devname;
  	if (IS_ERR(devname))
  		goto free_page;

  	mnt = nfs_do_clone_mount(NFS_SB(dentry->d_sb), devname, &mountdata);

  free_page:
  	free_page((unsigned long)page);
  out:

  	dprintk("%s: done
  ", __func__);

  
  	dprintk("<-- nfs_do_submount() = %p
  ", mnt);

  	return mnt;
  }