text: /*
   * File operations used by nfsd. Some of these have been ripped from
   * other parts of the kernel because they weren't exported, others
   * are partial duplicates with added or changed functionality.
   *
   * Note that several functions dget() the dentry upon which they want
   * to act, most notably those that create directory entries. Response
   * dentry's are dput()'d if necessary in the release callback.
   * So if you notice code paths that apparently fail to dput() the
   * dentry, don't worry--they have been taken care of.
   *
   * Copyright (C) 1995-1999 Olaf Kirch <okir@monad.swb.de>
   * Zerocpy NFS support (C) 2002 Hirokazu Takahashi <taka@valinux.co.jp>
   */
  
  #include <linux/fs.h>
  #include <linux/file.h>
  #include <linux/splice.h>
  #include <linux/fcntl.h>
  #include <linux/namei.h>
  #include <linux/delay.h>
  #include <linux/fsnotify.h>
  #include <linux/posix_acl_xattr.h>
  #include <linux/xattr.h>
  #include <linux/jhash.h>
  #include <linux/ima.h>
  #include <linux/slab.h>
  #include <asm/uaccess.h>
  #include <linux/exportfs.h>
  #include <linux/writeback.h>
  #include <linux/security.h>
  
  #ifdef CONFIG_NFSD_V3
  #include "xdr3.h"
  #endif /* CONFIG_NFSD_V3 */
  
  #ifdef CONFIG_NFSD_V4
  #include "acl.h"
  #include "idmap.h"
  #endif /* CONFIG_NFSD_V4 */
  
  #include "nfsd.h"
  #include "vfs.h"
  
  #define NFSDDBG_FACILITY		NFSDDBG_FILEOP
  
  
  /*
   * This is a cache of readahead params that help us choose the proper
   * readahead strategy. Initially, we set all readahead parameters to 0
   * and let the VFS handle things.
   * If you increase the number of cached files very much, you'll need to
   * add a hash table here.
   */
  struct raparms {
  	struct raparms		*p_next;
  	unsigned int		p_count;
  	ino_t			p_ino;
  	dev_t			p_dev;
  	int			p_set;
  	struct file_ra_state	p_ra;
  	unsigned int		p_hindex;
  };
  
  struct raparm_hbucket {
  	struct raparms		*pb_head;
  	spinlock_t		pb_lock;
  } ____cacheline_aligned_in_smp;
  
  #define RAPARM_HASH_BITS	4
  #define RAPARM_HASH_SIZE	(1<<RAPARM_HASH_BITS)
  #define RAPARM_HASH_MASK	(RAPARM_HASH_SIZE-1)
  static struct raparm_hbucket	raparm_hash[RAPARM_HASH_SIZE];
  
  /* 
   * Called from nfsd_lookup and encode_dirent. Check if we have crossed 
   * a mount point.
   * Returns -EAGAIN or -ETIMEDOUT leaving *dpp and *expp unchanged,
   *  or nfs_ok having possibly changed *dpp and *expp
   */
  int
  nfsd_cross_mnt(struct svc_rqst *rqstp, struct dentry **dpp, 
  		        struct svc_export **expp)
  {
  	struct svc_export *exp = *expp, *exp2 = NULL;
  	struct dentry *dentry = *dpp;
  	struct path path = {.mnt = mntget(exp->ex_path.mnt),
  			    .dentry = dget(dentry)};
  	int err = 0;
  
  	err = follow_down(&path);
  	if (err < 0)
  		goto out;
  
  	exp2 = rqst_exp_get_by_name(rqstp, &path);
  	if (IS_ERR(exp2)) {
  		err = PTR_ERR(exp2);
  		/*
  		 * We normally allow NFS clients to continue
  		 * "underneath" a mountpoint that is not exported.
  		 * The exception is V4ROOT, where no traversal is ever
  		 * allowed without an explicit export of the new
  		 * directory.
  		 */
  		if (err == -ENOENT && !(exp->ex_flags & NFSEXP_V4ROOT))
  			err = 0;
  		path_put(&path);
  		goto out;
  	}
  	if (nfsd_v4client(rqstp) ||
  		(exp->ex_flags & NFSEXP_CROSSMOUNT) || EX_NOHIDE(exp2)) {
  		/* successfully crossed mount point */
  		/*
  		 * This is subtle: path.dentry is *not* on path.mnt
  		 * at this point.  The only reason we are safe is that
  		 * original mnt is pinned down by exp, so we should
  		 * put path *before* putting exp
  		 */
  		*dpp = path.dentry;
  		path.dentry = dentry;
  		*expp = exp2;
  		exp2 = exp;
  	}
  	path_put(&path);
  	exp_put(exp2);
  out:
  	return err;
  }
  
  static void follow_to_parent(struct path *path)
  {
  	struct dentry *dp;
  
  	while (path->dentry == path->mnt->mnt_root && follow_up(path))
  		;
  	dp = dget_parent(path->dentry);
  	dput(path->dentry);
  	path->dentry = dp;
  }
  
  static int nfsd_lookup_parent(struct svc_rqst *rqstp, struct dentry *dparent, struct svc_export **exp, struct dentry **dentryp)
  {
  	struct svc_export *exp2;
  	struct path path = {.mnt = mntget((*exp)->ex_path.mnt),
  			    .dentry = dget(dparent)};
  
  	follow_to_parent(&path);
  
  	exp2 = rqst_exp_parent(rqstp, &path);
  	if (PTR_ERR(exp2) == -ENOENT) {
  		*dentryp = dget(dparent);
  	} else if (IS_ERR(exp2)) {
  		path_put(&path);
  		return PTR_ERR(exp2);
  	} else {
  		*dentryp = dget(path.dentry);
  		exp_put(*exp);
  		*exp = exp2;
  	}
  	path_put(&path);
  	return 0;
  }
  
  /*
   * For nfsd purposes, we treat V4ROOT exports as though there was an
   * export at *every* directory.
   */
  int nfsd_mountpoint(struct dentry *dentry, struct svc_export *exp)
  {
  	if (d_mountpoint(dentry))
  		return 1;
  	if (nfsd4_is_junction(dentry))
  		return 1;
  	if (!(exp->ex_flags & NFSEXP_V4ROOT))
  		return 0;
  	return dentry->d_inode != NULL;
  }
  
  __be32
  nfsd_lookup_dentry(struct svc_rqst *rqstp, struct svc_fh *fhp,
  		   const char *name, unsigned int len,
  		   struct svc_export **exp_ret, struct dentry **dentry_ret)
  {
  	struct svc_export	*exp;
  	struct dentry		*dparent;
  	struct dentry		*dentry;
  	int			host_err;
  
  	dprintk("nfsd: nfsd_lookup(fh %s, %.*s)\n", SVCFH_fmt(fhp), len,name);
  
  	dparent = fhp->fh_dentry;
  	exp = exp_get(fhp->fh_export);
  
  	/* Lookup the name, but don't follow links */
  	if (isdotent(name, len)) {
  		if (len==1)
  			dentry = dget(dparent);
  		else if (dparent != exp->ex_path.dentry)
  			dentry = dget_parent(dparent);
  		else if (!EX_NOHIDE(exp) && !nfsd_v4client(rqstp))
  			dentry = dget(dparent); /* .. == . just like at / */
  		else {
  			/* checking mountpoint crossing is very different when stepping up */
  			host_err = nfsd_lookup_parent(rqstp, dparent, &exp, &dentry);
  			if (host_err)
  				goto out_nfserr;
  		}
  	} else {
  		/*
  		 * In the nfsd4_open() case, this may be held across
  		 * subsequent open and delegation acquisition which may
  		 * need to take the child's i_mutex:
  		 */
  		fh_lock_nested(fhp, I_MUTEX_PARENT);
  		dentry = lookup_one_len(name, dparent, len);
  		host_err = PTR_ERR(dentry);
  		if (IS_ERR(dentry))
  			goto out_nfserr;
  		/*
  		 * check if we have crossed a mount point ...
  		 */
  		if (nfsd_mountpoint(dentry, exp)) {
  			if ((host_err = nfsd_cross_mnt(rqstp, &dentry, &exp))) {
  				dput(dentry);
  				goto out_nfserr;
  			}
  		}
  	}
  	*dentry_ret = dentry;
  	*exp_ret = exp;
  	return 0;
  
  out_nfserr:
  	exp_put(exp);
  	return nfserrno(host_err);
  }
  
  /*
   * Look up one component of a pathname.
   * N.B. After this call _both_ fhp and resfh need an fh_put
   *
   * If the lookup would cross a mountpoint, and the mounted filesystem
   * is exported to the client with NFSEXP_NOHIDE, then the lookup is
   * accepted as it stands and the mounted directory is
   * returned. Otherwise the covered directory is returned.
   * NOTE: this mountpoint crossing is not supported properly by all
   *   clients and is explicitly disallowed for NFSv3
   *      NeilBrown <neilb@cse.unsw.edu.au>
   */
  __be32
  nfsd_lookup(struct svc_rqst *rqstp, struct svc_fh *fhp, const char *name,
  				unsigned int len, struct svc_fh *resfh)
  {
  	struct svc_export	*exp;
  	struct dentry		*dentry;
  	__be32 err;
  
  	err = fh_verify(rqstp, fhp, S_IFDIR, NFSD_MAY_EXEC);
  	if (err)
  		return err;
  	err = nfsd_lookup_dentry(rqstp, fhp, name, len, &exp, &dentry);
  	if (err)
  		return err;
  	err = check_nfsd_access(exp, rqstp);
  	if (err)
  		goto out;
  	/*
  	 * Note: we compose the file handle now, but as the
  	 * dentry may be negative, it may need to be updated.
  	 */
  	err = fh_compose(resfh, exp, dentry, fhp);
  	if (!err && !dentry->d_inode)
  		err = nfserr_noent;
  out:
  	dput(dentry);
  	exp_put(exp);
  	return err;
  }
  
  /*
   * Commit metadata changes to stable storage.
   */
  static int
  commit_metadata(struct svc_fh *fhp)
  {
  	struct inode *inode = fhp->fh_dentry->d_inode;
  	const struct export_operations *export_ops = inode->i_sb->s_export_op;
  
  	if (!EX_ISSYNC(fhp->fh_export))
  		return 0;
  
  	if (export_ops->commit_metadata)
  		return export_ops->commit_metadata(inode);
  	return sync_inode_metadata(inode, 1);
  }
  
  /*
   * Go over the attributes and take care of the small differences between
   * NFS semantics and what Linux expects.
   */
  static void
  nfsd_sanitize_attrs(struct inode *inode, struct iattr *iap)
  {
  	/* sanitize the mode change */
  	if (iap->ia_valid & ATTR_MODE) {
  		iap->ia_mode &= S_IALLUGO;
  		iap->ia_mode |= (inode->i_mode & ~S_IALLUGO);
  	}
  
  	/* Revoke setuid/setgid on chown */
  	if (!S_ISDIR(inode->i_mode) &&
  	    ((iap->ia_valid & ATTR_UID) || (iap->ia_valid & ATTR_GID))) {
  		iap->ia_valid |= ATTR_KILL_PRIV;
  		if (iap->ia_valid & ATTR_MODE) {
  			/* we're setting mode too, just clear the s*id bits */
  			iap->ia_mode &= ~S_ISUID;
  			if (iap->ia_mode & S_IXGRP)
  				iap->ia_mode &= ~S_ISGID;
  		} else {
  			/* set ATTR_KILL_* bits and let VFS handle it */
  			iap->ia_valid |= (ATTR_KILL_SUID | ATTR_KILL_SGID);
  		}
  	}
  }
  
  static __be32
  nfsd_get_write_access(struct svc_rqst *rqstp, struct svc_fh *fhp,
  		struct iattr *iap)
  {
  	struct inode *inode = fhp->fh_dentry->d_inode;
  	int host_err;
  
  	if (iap->ia_size < inode->i_size) {
  		__be32 err;
  
  		err = nfsd_permission(rqstp, fhp->fh_export, fhp->fh_dentry,
  				NFSD_MAY_TRUNC | NFSD_MAY_OWNER_OVERRIDE);
  		if (err)
  			return err;
  	}
  
  	host_err = get_write_access(inode);
  	if (host_err)
  		goto out_nfserrno;
  
  	host_err = locks_verify_truncate(inode, NULL, iap->ia_size);
  	if (host_err)
  		goto out_put_write_access;
  	return 0;
  
  out_put_write_access:
  	put_write_access(inode);
  out_nfserrno:
  	return nfserrno(host_err);
  }
  
  /*
   * Set various file attributes.  After this call fhp needs an fh_put.
   */
  __be32
  nfsd_setattr(struct svc_rqst *rqstp, struct svc_fh *fhp, struct iattr *iap,
  	     int check_guard, time_t guardtime)
  {
  	struct dentry	*dentry;
  	struct inode	*inode;
  	int		accmode = NFSD_MAY_SATTR;
  	umode_t		ftype = 0;
  	__be32		err;
  	int		host_err;
  	bool		get_write_count;
  	int		size_change = 0;
  
  	if (iap->ia_valid & (ATTR_ATIME | ATTR_MTIME | ATTR_SIZE))
  		accmode |= NFSD_MAY_WRITE|NFSD_MAY_OWNER_OVERRIDE;
  	if (iap->ia_valid & ATTR_SIZE)
  		ftype = S_IFREG;
  
  	/* Callers that do fh_verify should do the fh_want_write: */
  	get_write_count = !fhp->fh_dentry;
  
  	/* Get inode */
  	err = fh_verify(rqstp, fhp, ftype, accmode);
  	if (err)
  		goto out;
  	if (get_write_count) {
  		host_err = fh_want_write(fhp);
  		if (host_err)
  			return nfserrno(host_err);
  	}
  
  	dentry = fhp->fh_dentry;
  	inode = dentry->d_inode;
  
  	/* Ignore any mode updates on symlinks */
  	if (S_ISLNK(inode->i_mode))
  		iap->ia_valid &= ~ATTR_MODE;
  
  	if (!iap->ia_valid)
  		goto out;
  
  	nfsd_sanitize_attrs(inode, iap);
  
  	/*
  	 * The size case is special, it changes the file in addition to the
  	 * attributes.
  	 */
  	if (iap->ia_valid & ATTR_SIZE) {
  		err = nfsd_get_write_access(rqstp, fhp, iap);
  		if (err)
  			goto out;
  		size_change = 1;
  
  		/*
  		 * RFC5661, Section 18.30.4:
  		 *   Changing the size of a file with SETATTR indirectly
  		 *   changes the time_modify and change attributes.
  		 *
  		 * (and similar for the older RFCs)
  		 */
  		if (iap->ia_size != i_size_read(inode))
  			iap->ia_valid |= ATTR_MTIME;
  	}
  
  	iap->ia_valid |= ATTR_CTIME;
  
  	if (check_guard && guardtime != inode->i_ctime.tv_sec) {
  		err = nfserr_notsync;
  		goto out_put_write_access;
  	}
  
  	fh_lock(fhp);
  	host_err = notify_change(dentry, iap, NULL);
  	fh_unlock(fhp);
  	err = nfserrno(host_err);
  
  out_put_write_access:
  	if (size_change)
  		put_write_access(inode);
  	if (!err)
  		err = nfserrno(commit_metadata(fhp));
  out:
  	return err;
  }
  
  #if defined(CONFIG_NFSD_V4)
  /*
   * NFS junction information is stored in an extended attribute.
   */
  #define NFSD_JUNCTION_XATTR_NAME	XATTR_TRUSTED_PREFIX "junction.nfs"
  
  /**
   * nfsd4_is_junction - Test if an object could be an NFS junction
   *
   * @dentry: object to test
   *
   * Returns 1 if "dentry" appears to contain NFS junction information.
   * Otherwise 0 is returned.
   */
  int nfsd4_is_junction(struct dentry *dentry)
  {
  	struct inode *inode = dentry->d_inode;
  
  	if (inode == NULL)
  		return 0;
  	if (inode->i_mode & S_IXUGO)
  		return 0;
  	if (!(inode->i_mode & S_ISVTX))
  		return 0;
  	if (vfs_getxattr(dentry, NFSD_JUNCTION_XATTR_NAME, NULL, 0) <= 0)
  		return 0;
  	return 1;
  }
  #ifdef CONFIG_NFSD_V4_SECURITY_LABEL
  __be32 nfsd4_set_nfs4_label(struct svc_rqst *rqstp, struct svc_fh *fhp,
  		struct xdr_netobj *label)
  {
  	__be32 error;
  	int host_error;
  	struct dentry *dentry;
  
  	error = fh_verify(rqstp, fhp, 0 /* S_IFREG */, NFSD_MAY_SATTR);
  	if (error)
  		return error;
  
  	dentry = fhp->fh_dentry;
  
  	mutex_lock(&dentry->d_inode->i_mutex);
  	host_error = security_inode_setsecctx(dentry, label->data, label->len);
  	mutex_unlock(&dentry->d_inode->i_mutex);
  	return nfserrno(host_error);
  }
  #else
  __be32 nfsd4_set_nfs4_label(struct svc_rqst *rqstp, struct svc_fh *fhp,
  		struct xdr_netobj *label)
  {
  	return nfserr_notsupp;
  }
  #endif
  
  #endif /* defined(CONFIG_NFSD_V4) */
  
  #ifdef CONFIG_NFSD_V3
  /*
   * Check server access rights to a file system object
   */
  struct accessmap {
  	u32		access;
  	int		how;
  };
  static struct accessmap	nfs3_regaccess[] = {
      {	NFS3_ACCESS_READ,	NFSD_MAY_READ			},
      {	NFS3_ACCESS_EXECUTE,	NFSD_MAY_EXEC			},
      {	NFS3_ACCESS_MODIFY,	NFSD_MAY_WRITE|NFSD_MAY_TRUNC	},
      {	NFS3_ACCESS_EXTEND,	NFSD_MAY_WRITE			},
  
      {	0,			0				}
  };
  
  static struct accessmap	nfs3_diraccess[] = {
      {	NFS3_ACCESS_READ,	NFSD_MAY_READ			},
      {	NFS3_ACCESS_LOOKUP,	NFSD_MAY_EXEC			},
      {	NFS3_ACCESS_MODIFY,	NFSD_MAY_EXEC|NFSD_MAY_WRITE|NFSD_MAY_TRUNC},
      {	NFS3_ACCESS_EXTEND,	NFSD_MAY_EXEC|NFSD_MAY_WRITE	},
      {	NFS3_ACCESS_DELETE,	NFSD_MAY_REMOVE			},
  
      {	0,			0				}
  };
  
  static struct accessmap	nfs3_anyaccess[] = {
  	/* Some clients - Solaris 2.6 at least, make an access call
  	 * to the server to check for access for things like /dev/null
  	 * (which really, the server doesn't care about).  So
  	 * We provide simple access checking for them, looking
  	 * mainly at mode bits, and we make sure to ignore read-only
  	 * filesystem checks
  	 */
      {	NFS3_ACCESS_READ,	NFSD_MAY_READ			},
      {	NFS3_ACCESS_EXECUTE,	NFSD_MAY_EXEC			},
      {	NFS3_ACCESS_MODIFY,	NFSD_MAY_WRITE|NFSD_MAY_LOCAL_ACCESS	},
      {	NFS3_ACCESS_EXTEND,	NFSD_MAY_WRITE|NFSD_MAY_LOCAL_ACCESS	},
  
      {	0,			0				}
  };
  
  __be32
  nfsd_access(struct svc_rqst *rqstp, struct svc_fh *fhp, u32 *access, u32 *supported)
  {
  	struct accessmap	*map;
  	struct svc_export	*export;
  	struct dentry		*dentry;
  	u32			query, result = 0, sresult = 0;
  	__be32			error;
  
  	error = fh_verify(rqstp, fhp, 0, NFSD_MAY_NOP);
  	if (error)
  		goto out;
  
  	export = fhp->fh_export;
  	dentry = fhp->fh_dentry;
  
  	if (S_ISREG(dentry->d_inode->i_mode))
  		map = nfs3_regaccess;
  	else if (S_ISDIR(dentry->d_inode->i_mode))
  		map = nfs3_diraccess;
  	else
  		map = nfs3_anyaccess;
  
  
  	query = *access;
  	for  (; map->access; map++) {
  		if (map->access & query) {
  			__be32 err2;
  
  			sresult |= map->access;
  
  			err2 = nfsd_permission(rqstp, export, dentry, map->how);
  			switch (err2) {
  			case nfs_ok:
  				result |= map->access;
  				break;
  				
  			/* the following error codes just mean the access was not allowed,
  			 * rather than an error occurred */
  			case nfserr_rofs:
  			case nfserr_acces:
  			case nfserr_perm:
  				/* simply don't "or" in the access bit. */
  				break;
  			default:
  				error = err2;
  				goto out;
  			}
  		}
  	}
  	*access = result;
  	if (supported)
  		*supported = sresult;
  
   out:
  	return error;
  }
  #endif /* CONFIG_NFSD_V3 */
  
  static int nfsd_open_break_lease(struct inode *inode, int access)
  {
  	unsigned int mode;
  
  	if (access & NFSD_MAY_NOT_BREAK_LEASE)
  		return 0;
  	mode = (access & NFSD_MAY_WRITE) ? O_WRONLY : O_RDONLY;
  	return break_lease(inode, mode | O_NONBLOCK);
  }
  
  /*
   * Open an existing file or directory.
   * The may_flags argument indicates the type of open (read/write/lock)
   * and additional flags.
   * N.B. After this call fhp needs an fh_put
   */
  __be32
  nfsd_open(struct svc_rqst *rqstp, struct svc_fh *fhp, umode_t type,
  			int may_flags, struct file **filp)
  {
  	struct path	path;
  	struct inode	*inode;
  	struct file	*file;
  	int		flags = O_RDONLY|O_LARGEFILE;
  	__be32		err;
  	int		host_err = 0;
  
  	validate_process_creds();
  
  	/*
  	 * If we get here, then the client has already done an "open",
  	 * and (hopefully) checked permission - so allow OWNER_OVERRIDE
  	 * in case a chmod has now revoked permission.
  	 *
  	 * Arguably we should also allow the owner override for
  	 * directories, but we never have and it doesn't seem to have
  	 * caused anyone a problem.  If we were to change this, note
  	 * also that our filldir callbacks would need a variant of
  	 * lookup_one_len that doesn't check permissions.
  	 */
  	if (type == S_IFREG)
  		may_flags |= NFSD_MAY_OWNER_OVERRIDE;
  	err = fh_verify(rqstp, fhp, type, may_flags);
  	if (err)
  		goto out;
  
  	path.mnt = fhp->fh_export->ex_path.mnt;
  	path.dentry = fhp->fh_dentry;
  	inode = path.dentry->d_inode;
  
  	/* Disallow write access to files with the append-only bit set
  	 * or any access when mandatory locking enabled
  	 */
  	err = nfserr_perm;
  	if (IS_APPEND(inode) && (may_flags & NFSD_MAY_WRITE))
  		goto out;
  	/*
  	 * We must ignore files (but only files) which might have mandatory
  	 * locks on them because there is no way to know if the accesser has
  	 * the lock.
  	 */
  	if (S_ISREG((inode)->i_mode) && mandatory_lock(inode))
  		goto out;
  
  	if (!inode->i_fop)
  		goto out;
  
  	host_err = nfsd_open_break_lease(inode, may_flags);
  	if (host_err) /* NOMEM or WOULDBLOCK */
  		goto out_nfserr;
  
  	if (may_flags & NFSD_MAY_WRITE) {
  		if (may_flags & NFSD_MAY_READ)
  			flags = O_RDWR|O_LARGEFILE;
  		else
  			flags = O_WRONLY|O_LARGEFILE;
  	}
  
  	file = dentry_open(&path, flags, current_cred());
  	if (IS_ERR(file)) {
  		host_err = PTR_ERR(file);
  		goto out_nfserr;
  	}
  
  	host_err = ima_file_check(file, may_flags, 0);
  	if (host_err) {
  		nfsd_close(file);
  		goto out_nfserr;
  	}
  
  	if (may_flags & NFSD_MAY_64BIT_COOKIE)
  		file->f_mode |= FMODE_64BITHASH;
  	else
  		file->f_mode |= FMODE_32BITHASH;
  
  	*filp = file;
  out_nfserr:
  	err = nfserrno(host_err);
  out:
  	validate_process_creds();
  	return err;
  }
  
  /*
   * Close a file.
   */
  void
  nfsd_close(struct file *filp)
  {
  	fput(filp);
  }
  
  /*
   * Obtain the readahead parameters for the file
   * specified by (dev, ino).
   */
  
  static inline struct raparms *
  nfsd_get_raparms(dev_t dev, ino_t ino)
  {
  	struct raparms	*ra, **rap, **frap = NULL;
  	int depth = 0;
  	unsigned int hash;
  	struct raparm_hbucket *rab;
  
  	hash = jhash_2words(dev, ino, 0xfeedbeef) & RAPARM_HASH_MASK;
  	rab = &raparm_hash[hash];
  
  	spin_lock(&rab->pb_lock);
  	for (rap = &rab->pb_head; (ra = *rap); rap = &ra->p_next) {
  		if (ra->p_ino == ino && ra->p_dev == dev)
  			goto found;
  		depth++;
  		if (ra->p_count == 0)
  			frap = rap;
  	}
  	depth = nfsdstats.ra_size;
  	if (!frap) {	
  		spin_unlock(&rab->pb_lock);
  		return NULL;
  	}
  	rap = frap;
  	ra = *frap;
  	ra->p_dev = dev;
  	ra->p_ino = ino;
  	ra->p_set = 0;
  	ra->p_hindex = hash;
  found:
  	if (rap != &rab->pb_head) {
  		*rap = ra->p_next;
  		ra->p_next   = rab->pb_head;
  		rab->pb_head = ra;
  	}
  	ra->p_count++;
  	nfsdstats.ra_depth[depth*10/nfsdstats.ra_size]++;
  	spin_unlock(&rab->pb_lock);
  	return ra;
  }
  
  /*
   * Grab and keep cached pages associated with a file in the svc_rqst
   * so that they can be passed to the network sendmsg/sendpage routines
   * directly. They will be released after the sending has completed.
   */
  static int
  nfsd_splice_actor(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
  		  struct splice_desc *sd)
  {
  	struct svc_rqst *rqstp = sd->u.data;
  	struct page **pp = rqstp->rq_next_page;
  	struct page *page = buf->page;
  	size_t size;
  
  	size = sd->len;
  
  	if (rqstp->rq_res.page_len == 0) {
  		get_page(page);
  		put_page(*rqstp->rq_next_page);
  		*(rqstp->rq_next_page++) = page;
  		rqstp->rq_res.page_base = buf->offset;
  		rqstp->rq_res.page_len = size;
  	} else if (page != pp[-1]) {
  		get_page(page);
  		if (*rqstp->rq_next_page)
  			put_page(*rqstp->rq_next_page);
  		*(rqstp->rq_next_page++) = page;
  		rqstp->rq_res.page_len += size;
  	} else
  		rqstp->rq_res.page_len += size;
  
  	return size;
  }
  
  static int nfsd_direct_splice_actor(struct pipe_inode_info *pipe,
  				    struct splice_desc *sd)
  {
  	return __splice_from_pipe(pipe, sd, nfsd_splice_actor);
  }
  
  static __be32
  nfsd_finish_read(struct file *file, unsigned long *count, int host_err)
  {
  	if (host_err >= 0) {
  		nfsdstats.io_read += host_err;
  		*count = host_err;
  		fsnotify_access(file);
  		return 0;
  	} else 
  		return nfserrno(host_err);
  }
  
  __be32 nfsd_splice_read(struct svc_rqst *rqstp,
  		     struct file *file, loff_t offset, unsigned long *count)
  {
  	struct splice_desc sd = {
  		.len		= 0,
  		.total_len	= *count,
  		.pos		= offset,
  		.u.data		= rqstp,
  	};
  	int host_err;
  
  	rqstp->rq_next_page = rqstp->rq_respages + 1;
  	host_err = splice_direct_to_actor(file, &sd, nfsd_direct_splice_actor);
  	return nfsd_finish_read(file, count, host_err);
  }
  
  __be32 nfsd_readv(struct file *file, loff_t offset, struct kvec *vec, int vlen,
  		unsigned long *count)
  {
  	mm_segment_t oldfs;
  	int host_err;
  
  	oldfs = get_fs();
  	set_fs(KERNEL_DS);
  	host_err = vfs_readv(file, (struct iovec __user *)vec, vlen, &offset);
  	set_fs(oldfs);
  	return nfsd_finish_read(file, count, host_err);
  }
  
  static __be32
  nfsd_vfs_read(struct svc_rqst *rqstp, struct file *file,
  	      loff_t offset, struct kvec *vec, int vlen, unsigned long *count)
  {
  	if (file->f_op->splice_read && rqstp->rq_splice_ok)
  		return nfsd_splice_read(rqstp, file, offset, count);
  	else
  		return nfsd_readv(file, offset, vec, vlen, count);
  }
  
  /*
   * Gathered writes: If another process is currently writing to the file,
   * there's a high chance this is another nfsd (triggered by a bulk write
   * from a client's biod). Rather than syncing the file with each write
   * request, we sleep for 10 msec.
   *
   * I don't know if this roughly approximates C. Juszak's idea of
   * gathered writes, but it's a nice and simple solution (IMHO), and it
   * seems to work:-)
   *
   * Note: we do this only in the NFSv2 case, since v3 and higher have a
   * better tool (separate unstable writes and commits) for solving this
   * problem.
   */
  static int wait_for_concurrent_writes(struct file *file)
  {
  	struct inode *inode = file_inode(file);
  	static ino_t last_ino;
  	static dev_t last_dev;
  	int err = 0;
  
  	if (atomic_read(&inode->i_writecount) > 1
  	    || (last_ino == inode->i_ino && last_dev == inode->i_sb->s_dev)) {
  		dprintk("nfsd: write defer %d\n", task_pid_nr(current));
  		msleep(10);
  		dprintk("nfsd: write resume %d\n", task_pid_nr(current));
  	}
  
  	if (inode->i_state & I_DIRTY) {
  		dprintk("nfsd: write sync %d\n", task_pid_nr(current));
  		err = vfs_fsync(file, 0);
  	}
  	last_ino = inode->i_ino;
  	last_dev = inode->i_sb->s_dev;
  	return err;
  }
  
  static __be32
  nfsd_vfs_write(struct svc_rqst *rqstp, struct svc_fh *fhp, struct file *file,
  				loff_t offset, struct kvec *vec, int vlen,
  				unsigned long *cnt, int *stablep)
  {
  	struct svc_export	*exp;
  	struct dentry		*dentry;
  	struct inode		*inode;
  	mm_segment_t		oldfs;
  	__be32			err = 0;
  	int			host_err;
  	int			stable = *stablep;
  	int			use_wgather;
  	loff_t			pos = offset;
  	unsigned int		pflags = current->flags;
  
  	if (rqstp->rq_local)
  		/*
  		 * We want less throttling in balance_dirty_pages()
  		 * and shrink_inactive_list() so that nfs to
  		 * localhost doesn't cause nfsd to lock up due to all
  		 * the client's dirty pages or its congested queue.
  		 */
  		current->flags |= PF_LESS_THROTTLE;
  
  	dentry = file->f_path.dentry;
  	inode = dentry->d_inode;
  	exp   = fhp->fh_export;
  
  	use_wgather = (rqstp->rq_vers == 2) && EX_WGATHER(exp);
  
  	if (!EX_ISSYNC(exp))
  		stable = 0;
  
  	/* Write the data. */
  	oldfs = get_fs(); set_fs(KERNEL_DS);
  	host_err = vfs_writev(file, (struct iovec __user *)vec, vlen, &pos);
  	set_fs(oldfs);
  	if (host_err < 0)
  		goto out_nfserr;
  	*cnt = host_err;
  	nfsdstats.io_write += host_err;
  	fsnotify_modify(file);
  
  	if (stable) {
  		if (use_wgather)
  			host_err = wait_for_concurrent_writes(file);
  		else
  			host_err = vfs_fsync_range(file, offset, offset+*cnt, 0);
  	}
  
  out_nfserr:
  	dprintk("nfsd: write complete host_err=%d\n", host_err);
  	if (host_err >= 0)
  		err = 0;
  	else
  		err = nfserrno(host_err);
  	if (rqstp->rq_local)
  		tsk_restore_flags(current, pflags, PF_LESS_THROTTLE);
  	return err;
  }
  
  __be32 nfsd_get_tmp_read_open(struct svc_rqst *rqstp, struct svc_fh *fhp,
  		struct file **file, struct raparms **ra)
  {
  	struct inode *inode;
  	__be32 err;
  
  	err = nfsd_open(rqstp, fhp, S_IFREG, NFSD_MAY_READ, file);
  	if (err)
  		return err;
  
  	inode = file_inode(*file);
  
  	/* Get readahead parameters */
  	*ra = nfsd_get_raparms(inode->i_sb->s_dev, inode->i_ino);
  
  	if (*ra && (*ra)->p_set)
  		(*file)->f_ra = (*ra)->p_ra;
  	return nfs_ok;
  }
  
  void nfsd_put_tmp_read_open(struct file *file, struct raparms *ra)
  {
  	/* Write back readahead params */
  	if (ra) {
  		struct raparm_hbucket *rab = &raparm_hash[ra->p_hindex];
  		spin_lock(&rab->pb_lock);
  		ra->p_ra = file->f_ra;
  		ra->p_set = 1;
  		ra->p_count--;
  		spin_unlock(&rab->pb_lock);
  	}
  	nfsd_close(file);
  }
  
  /*
   * Read data from a file. count must contain the requested read count
   * on entry. On return, *count contains the number of bytes actually read.
   * N.B. After this call fhp needs an fh_put
   */
  __be32 nfsd_read(struct svc_rqst *rqstp, struct svc_fh *fhp,
  	loff_t offset, struct kvec *vec, int vlen, unsigned long *count)
  {
  	struct file *file;
  	struct raparms	*ra;
  	__be32 err;
  
  	err = nfsd_get_tmp_read_open(rqstp, fhp, &file, &ra);
  	if (err)
  		return err;
  
  	err = nfsd_vfs_read(rqstp, file, offset, vec, vlen, count);
  
  	nfsd_put_tmp_read_open(file, ra);
  
  	return err;
  }
  
  /*
   * Write data to a file.
   * The stable flag requests synchronous writes.
   * N.B. After this call fhp needs an fh_put
   */
  __be32
  nfsd_write(struct svc_rqst *rqstp, struct svc_fh *fhp, struct file *file,
  		loff_t offset, struct kvec *vec, int vlen, unsigned long *cnt,
  		int *stablep)
  {
  	__be32			err = 0;
  
  	if (file) {
  		err = nfsd_permission(rqstp, fhp->fh_export, fhp->fh_dentry,
  				NFSD_MAY_WRITE|NFSD_MAY_OWNER_OVERRIDE);
  		if (err)
  			goto out;
  		err = nfsd_vfs_write(rqstp, fhp, file, offset, vec, vlen, cnt,
  				stablep);
  	} else {
  		err = nfsd_open(rqstp, fhp, S_IFREG, NFSD_MAY_WRITE, &file);
  		if (err)
  			goto out;
  
  		if (cnt)
  			err = nfsd_vfs_write(rqstp, fhp, file, offset, vec, vlen,
  					     cnt, stablep);
  		nfsd_close(file);
  	}
  out:
  	return err;
  }
  
  #ifdef CONFIG_NFSD_V3
  /*
   * Commit all pending writes to stable storage.
   *
   * Note: we only guarantee that data that lies within the range specified
   * by the 'offset' and 'count' parameters will be synced.
   *
   * Unfortunately we cannot lock the file to make sure we return full WCC
   * data to the client, as locking happens lower down in the filesystem.
   */
  __be32
  nfsd_commit(struct svc_rqst *rqstp, struct svc_fh *fhp,
                 loff_t offset, unsigned long count)
  {
  	struct file	*file;
  	loff_t		end = LLONG_MAX;
  	__be32		err = nfserr_inval;
  
  	if (offset < 0)
  		goto out;
  	if (count != 0) {
  		end = offset + (loff_t)count - 1;
  		if (end < offset)
  			goto out;
  	}
  
  	err = nfsd_open(rqstp, fhp, S_IFREG,
  			NFSD_MAY_WRITE|NFSD_MAY_NOT_BREAK_LEASE, &file);
  	if (err)
  		goto out;
  	if (EX_ISSYNC(fhp->fh_export)) {
  		int err2 = vfs_fsync_range(file, offset, end, 0);
  
  		if (err2 != -EINVAL)
  			err = nfserrno(err2);
  		else
  			err = nfserr_notsupp;
  	}
  
  	nfsd_close(file);
  out:
  	return err;
  }
  #endif /* CONFIG_NFSD_V3 */
  
  static __be32
  nfsd_create_setattr(struct svc_rqst *rqstp, struct svc_fh *resfhp,
  			struct iattr *iap)
  {
  	/*
  	 * Mode has already been set earlier in create:
  	 */
  	iap->ia_valid &= ~ATTR_MODE;
  	/*
  	 * Setting uid/gid works only for root.  Irix appears to
  	 * send along the gid on create when it tries to implement
  	 * setgid directories via NFS:
  	 */
  	if (!uid_eq(current_fsuid(), GLOBAL_ROOT_UID))
  		iap->ia_valid &= ~(ATTR_UID|ATTR_GID);
  	if (iap->ia_valid)
  		return nfsd_setattr(rqstp, resfhp, iap, 0, (time_t)0);
  	/* Callers expect file metadata to be committed here */
  	return nfserrno(commit_metadata(resfhp));
  }
  
  /* HPUX client sometimes creates a file in mode 000, and sets size to 0.
   * setting size to 0 may fail for some specific file systems by the permission
   * checking which requires WRITE permission but the mode is 000.
   * we ignore the resizing(to 0) on the just new created file, since the size is
   * 0 after file created.
   *
   * call this only after vfs_create() is called.
   * */
  static void
  nfsd_check_ignore_resizing(struct iattr *iap)
  {
  	if ((iap->ia_valid & ATTR_SIZE) && (iap->ia_size == 0))
  		iap->ia_valid &= ~ATTR_SIZE;
  }
  
  /*
   * Create a file (regular, directory, device, fifo); UNIX sockets 
   * not yet implemented.
   * If the response fh has been verified, the parent directory should
   * already be locked. Note that the parent directory is left locked.
   *
   * N.B. Every call to nfsd_create needs an fh_put for _both_ fhp and resfhp
   */
  __be32
  nfsd_create(struct svc_rqst *rqstp, struct svc_fh *fhp,
  		char *fname, int flen, struct iattr *iap,
  		int type, dev_t rdev, struct svc_fh *resfhp)
  {
  	struct dentry	*dentry, *dchild = NULL;
  	struct inode	*dirp;
  	__be32		err;
  	__be32		err2;
  	int		host_err;
  
  	err = nfserr_perm;
  	if (!flen)
  		goto out;
  	err = nfserr_exist;
  	if (isdotent(fname, flen))
  		goto out;
  
  	err = fh_verify(rqstp, fhp, S_IFDIR, NFSD_MAY_CREATE);
  	if (err)
  		goto out;
  
  	dentry = fhp->fh_dentry;
  	dirp = dentry->d_inode;
  
  	err = nfserr_notdir;
  	if (!dirp->i_op->lookup)
  		goto out;
  	/*
  	 * Check whether the response file handle has been verified yet.
  	 * If it has, the parent directory should already be locked.
  	 */
  	if (!resfhp->fh_dentry) {
  		host_err = fh_want_write(fhp);
  		if (host_err)
  			goto out_nfserr;
  
  		/* called from nfsd_proc_mkdir, or possibly nfsd3_proc_create */
  		fh_lock_nested(fhp, I_MUTEX_PARENT);
  		dchild = lookup_one_len(fname, dentry, flen);
  		host_err = PTR_ERR(dchild);
  		if (IS_ERR(dchild))
  			goto out_nfserr;
  		err = fh_compose(resfhp, fhp->fh_export, dchild, fhp);
  		if (err)
  			goto out;
  	} else {
  		/* called from nfsd_proc_create */
  		dchild = dget(resfhp->fh_dentry);
  		if (!fhp->fh_locked) {
  			/* not actually possible */
  			printk(KERN_ERR
  				"nfsd_create: parent %pd2 not locked!\n",
  				dentry);
  			err = nfserr_io;
  			goto out;
  		}
  	}
  	/*
  	 * Make sure the child dentry is still negative ...
  	 */
  	err = nfserr_exist;
  	if (dchild->d_inode) {
  		dprintk("nfsd_create: dentry %pd/%pd not negative!\n",
  			dentry, dchild);
  		goto out; 
  	}
  
  	if (!(iap->ia_valid & ATTR_MODE))
  		iap->ia_mode = 0;
  	iap->ia_mode = (iap->ia_mode & S_IALLUGO) | type;
  
  	err = nfserr_inval;
  	if (!S_ISREG(type) && !S_ISDIR(type) && !special_file(type)) {
  		printk(KERN_WARNING "nfsd: bad file type %o in nfsd_create\n",
  		       type);
  		goto out;
  	}
  
  	/*
  	 * Get the dir op function pointer.
  	 */
  	err = 0;
  	host_err = 0;
  	switch (type) {
  	case S_IFREG:
  		host_err = vfs_create(dirp, dchild, iap->ia_mode, true);
  		if (!host_err)
  			nfsd_check_ignore_resizing(iap);
  		break;
  	case S_IFDIR:
  		host_err = vfs_mkdir(dirp, dchild, iap->ia_mode);
  		break;
  	case S_IFCHR:
  	case S_IFBLK:
  	case S_IFIFO:
  	case S_IFSOCK:
  		host_err = vfs_mknod(dirp, dchild, iap->ia_mode, rdev);
  		break;
  	}
  	if (host_err < 0)
  		goto out_nfserr;
  
  	err = nfsd_create_setattr(rqstp, resfhp, iap);
  
  	/*
  	 * nfsd_create_setattr already committed the child.  Transactional
  	 * filesystems had a chance to commit changes for both parent and
  	 * child * simultaneously making the following commit_metadata a
  	 * noop.
  	 */
  	err2 = nfserrno(commit_metadata(fhp));
  	if (err2)
  		err = err2;
  	/*
  	 * Update the file handle to get the new inode info.
  	 */
  	if (!err)
  		err = fh_update(resfhp);
  out:
  	if (dchild && !IS_ERR(dchild))
  		dput(dchild);
  	return err;
  
  out_nfserr:
  	err = nfserrno(host_err);
  	goto out;
  }
  
  #ifdef CONFIG_NFSD_V3
  
  static inline int nfsd_create_is_exclusive(int createmode)
  {
  	return createmode == NFS3_CREATE_EXCLUSIVE
  	       || createmode == NFS4_CREATE_EXCLUSIVE4_1;
  }
  
  /*
   * NFSv3 and NFSv4 version of nfsd_create
   */
  __be32
  do_nfsd_create(struct svc_rqst *rqstp, struct svc_fh *fhp,
  		char *fname, int flen, struct iattr *iap,
  		struct svc_fh *resfhp, int createmode, u32 *verifier,
  	        bool *truncp, bool *created)
  {
  	struct dentry	*dentry, *dchild = NULL;
  	struct inode	*dirp;
  	__be32		err;
  	int		host_err;
  	__u32		v_mtime=0, v_atime=0;
  
  	err = nfserr_perm;
  	if (!flen)
  		goto out;
  	err = nfserr_exist;
  	if (isdotent(fname, flen))
  		goto out;
  	if (!(iap->ia_valid & ATTR_MODE))
  		iap->ia_mode = 0;
  	err = fh_verify(rqstp, fhp, S_IFDIR, NFSD_MAY_EXEC);
  	if (err)
  		goto out;
  
  	dentry = fhp->fh_dentry;
  	dirp = dentry->d_inode;
  
  	/* Get all the sanity checks out of the way before
  	 * we lock the parent. */
  	err = nfserr_notdir;
  	if (!dirp->i_op->lookup)
  		goto out;
  
  	host_err = fh_want_write(fhp);
  	if (host_err)
  		goto out_nfserr;
  
  	fh_lock_nested(fhp, I_MUTEX_PARENT);
  
  	/*
  	 * Compose the response file handle.
  	 */
  	dchild = lookup_one_len(fname, dentry, flen);
  	host_err = PTR_ERR(dchild);
  	if (IS_ERR(dchild))
  		goto out_nfserr;
  
  	/* If file doesn't exist, check for permissions to create one */
  	if (!dchild->d_inode) {
  		err = fh_verify(rqstp, fhp, S_IFDIR, NFSD_MAY_CREATE);
  		if (err)
  			goto out;
  	}
  
  	err = fh_compose(resfhp, fhp->fh_export, dchild, fhp);
  	if (err)
  		goto out;
  
  	if (nfsd_create_is_exclusive(createmode)) {
  		/* solaris7 gets confused (bugid 4218508) if these have
  		 * the high bit set, so just clear the high bits. If this is
  		 * ever changed to use different attrs for storing the
  		 * verifier, then do_open_lookup() will also need to be fixed
  		 * accordingly.
  		 */
  		v_mtime = verifier[0]&0x7fffffff;
  		v_atime = verifier[1]&0x7fffffff;
  	}
  	
  	if (dchild->d_inode) {
  		err = 0;
  
  		switch (createmode) {
  		case NFS3_CREATE_UNCHECKED:
  			if (! S_ISREG(dchild->d_inode->i_mode))
  				goto out;
  			else if (truncp) {
  				/* in nfsv4, we need to treat this case a little
  				 * differently.  we don't want to truncate the
  				 * file now; this would be wrong if the OPEN
  				 * fails for some other reason.  furthermore,
  				 * if the size is nonzero, we should ignore it
  				 * according to spec!
  				 */
  				*truncp = (iap->ia_valid & ATTR_SIZE) && !iap->ia_size;
  			}
  			else {
  				iap->ia_valid &= ATTR_SIZE;
  				goto set_attr;
  			}
  			break;
  		case NFS3_CREATE_EXCLUSIVE:
  			if (   dchild->d_inode->i_mtime.tv_sec == v_mtime
  			    && dchild->d_inode->i_atime.tv_sec == v_atime
  			    && dchild->d_inode->i_size  == 0 ) {
  				if (created)
  					*created = 1;
  				break;
  			}
  		case NFS4_CREATE_EXCLUSIVE4_1:
  			if (   dchild->d_inode->i_mtime.tv_sec == v_mtime
  			    && dchild->d_inode->i_atime.tv_sec == v_atime
  			    && dchild->d_inode->i_size  == 0 ) {
  				if (created)
  					*created = 1;
  				goto set_attr;
  			}
  			 /* fallthru */
  		case NFS3_CREATE_GUARDED:
  			err = nfserr_exist;
  		}
  		fh_drop_write(fhp);
  		goto out;
  	}
  
  	host_err = vfs_create(dirp, dchild, iap->ia_mode, true);
  	if (host_err < 0) {
  		fh_drop_write(fhp);
  		goto out_nfserr;
  	}
  	if (created)
  		*created = 1;
  
  	nfsd_check_ignore_resizing(iap);
  
  	if (nfsd_create_is_exclusive(createmode)) {
  		/* Cram the verifier into atime/mtime */
  		iap->ia_valid = ATTR_MTIME|ATTR_ATIME
  			| ATTR_MTIME_SET|ATTR_ATIME_SET;
  		/* XXX someone who knows this better please fix it for nsec */ 
  		iap->ia_mtime.tv_sec = v_mtime;
  		iap->ia_atime.tv_sec = v_atime;
  		iap->ia_mtime.tv_nsec = 0;
  		iap->ia_atime.tv_nsec = 0;
  	}
  
   set_attr:
  	err = nfsd_create_setattr(rqstp, resfhp, iap);
  
  	/*
  	 * nfsd_create_setattr already committed the child
  	 * (and possibly also the parent).
  	 */
  	if (!err)
  		err = nfserrno(commit_metadata(fhp));
  
  	/*
  	 * Update the filehandle to get the new inode info.
  	 */
  	if (!err)
  		err = fh_update(resfhp);
  
   out:
  	fh_unlock(fhp);
  	if (dchild && !IS_ERR(dchild))
  		dput(dchild);
  	fh_drop_write(fhp);
   	return err;
   
   out_nfserr:
  	err = nfserrno(host_err);
  	goto out;
  }
  #endif /* CONFIG_NFSD_V3 */
  
  /*
   * Read a symlink. On entry, *lenp must contain the maximum path length that
   * fits into the buffer. On return, it contains the true length.
   * N.B. After this call fhp needs an fh_put
   */
  __be32
  nfsd_readlink(struct svc_rqst *rqstp, struct svc_fh *fhp, char *buf, int *lenp)
  {
  	struct inode	*inode;
  	mm_segment_t	oldfs;
  	__be32		err;
  	int		host_err;
  	struct path path;
  
  	err = fh_verify(rqstp, fhp, S_IFLNK, NFSD_MAY_NOP);
  	if (err)
  		goto out;
  
  	path.mnt = fhp->fh_export->ex_path.mnt;
  	path.dentry = fhp->fh_dentry;
  	inode = path.dentry->d_inode;
  
  	err = nfserr_inval;
  	if (!inode->i_op->readlink)
  		goto out;
  
  	touch_atime(&path);
  	/* N.B. Why does this call need a get_fs()??
  	 * Remove the set_fs and watch the fireworks:-) --okir
  	 */
  
  	oldfs = get_fs(); set_fs(KERNEL_DS);
  	host_err = inode->i_op->readlink(path.dentry, (char __user *)buf, *lenp);
  	set_fs(oldfs);
  
  	if (host_err < 0)
  		goto out_nfserr;
  	*lenp = host_err;
  	err = 0;
  out:
  	return err;
  
  out_nfserr:
  	err = nfserrno(host_err);
  	goto out;
  }
  
  /*
   * Create a symlink and look up its inode
   * N.B. After this call _both_ fhp and resfhp need an fh_put
   */
  __be32
  nfsd_symlink(struct svc_rqst *rqstp, struct svc_fh *fhp,
  				char *fname, int flen,
  				char *path,
  				struct svc_fh *resfhp)
  {
  	struct dentry	*dentry, *dnew;
  	__be32		err, cerr;
  	int		host_err;
  
  	err = nfserr_noent;
  	if (!flen || path[0] == '\0')
  		goto out;
  	err = nfserr_exist;
  	if (isdotent(fname, flen))
  		goto out;
  
  	err = fh_verify(rqstp, fhp, S_IFDIR, NFSD_MAY_CREATE);
  	if (err)
  		goto out;
  
  	host_err = fh_want_write(fhp);
  	if (host_err)
  		goto out_nfserr;
  
  	fh_lock(fhp);
  	dentry = fhp->fh_dentry;
  	dnew = lookup_one_len(fname, dentry, flen);
  	host_err = PTR_ERR(dnew);
  	if (IS_ERR(dnew))
  		goto out_nfserr;
  
  	host_err = vfs_symlink(dentry->d_inode, dnew, path);
  	err = nfserrno(host_err);
  	if (!err)
  		err = nfserrno(commit_metadata(fhp));
  	fh_unlock(fhp);
  
  	fh_drop_write(fhp);
  
  	cerr = fh_compose(resfhp, fhp->fh_export, dnew, fhp);
  	dput(dnew);
  	if (err==0) err = cerr;
  out:
  	return err;
  
  out_nfserr:
  	err = nfserrno(host_err);
  	goto out;
  }
  
  /*
   * Create a hardlink
   * N.B. After this call _both_ ffhp and tfhp need an fh_put
   */
  __be32
  nfsd_link(struct svc_rqst *rqstp, struct svc_fh *ffhp,
  				char *name, int len, struct svc_fh *tfhp)
  {
  	struct dentry	*ddir, *dnew, *dold;
  	struct inode	*dirp;
  	__be32		err;
  	int		host_err;
  
  	err = fh_verify(rqstp, ffhp, S_IFDIR, NFSD_MAY_CREATE);
  	if (err)
  		goto out;
  	err = fh_verify(rqstp, tfhp, 0, NFSD_MAY_NOP);
  	if (err)
  		goto out;
  	err = nfserr_isdir;
  	if (S_ISDIR(tfhp->fh_dentry->d_inode->i_mode))
  		goto out;
  	err = nfserr_perm;
  	if (!len)
  		goto out;
  	err = nfserr_exist;
  	if (isdotent(name, len))
  		goto out;
  
  	host_err = fh_want_write(tfhp);
  	if (host_err) {
  		err = nfserrno(host_err);
  		goto out;
  	}
  
  	fh_lock_nested(ffhp, I_MUTEX_PARENT);
  	ddir = ffhp->fh_dentry;
  	dirp = ddir->d_inode;
  
  	dnew = lookup_one_len(name, ddir, len);
  	host_err = PTR_ERR(dnew);
  	if (IS_ERR(dnew))
  		goto out_nfserr;
  
  	dold = tfhp->fh_dentry;
  
  	err = nfserr_noent;
  	if (!dold->d_inode)
  		goto out_dput;
  	host_err = vfs_link(dold, dirp, dnew, NULL);
  	if (!host_err) {
  		err = nfserrno(commit_metadata(ffhp));
  		if (!err)
  			err = nfserrno(commit_metadata(tfhp));
  	} else {
  		if (host_err == -EXDEV && rqstp->rq_vers == 2)
  			err = nfserr_acces;
  		else
  			err = nfserrno(host_err);
  	}
  out_dput:
  	dput(dnew);
  out_unlock:
  	fh_unlock(ffhp);
  	fh_drop_write(tfhp);
  out:
  	return err;
  
  out_nfserr:
  	err = nfserrno(host_err);
  	goto out_unlock;
  }
  
  /*
   * Rename a file
   * N.B. After this call _both_ ffhp and tfhp need an fh_put
   */
  __be32
  nfsd_rename(struct svc_rqst *rqstp, struct svc_fh *ffhp, char *fname, int flen,
  			    struct svc_fh *tfhp, char *tname, int tlen)
  {
  	struct dentry	*fdentry, *tdentry, *odentry, *ndentry, *trap;
  	struct inode	*fdir, *tdir;
  	__be32		err;
  	int		host_err;
  
  	err = fh_verify(rqstp, ffhp, S_IFDIR, NFSD_MAY_REMOVE);
  	if (err)
  		goto out;
  	err = fh_verify(rqstp, tfhp, S_IFDIR, NFSD_MAY_CREATE);
  	if (err)
  		goto out;
  
  	fdentry = ffhp->fh_dentry;
  	fdir = fdentry->d_inode;
  
  	tdentry = tfhp->fh_dentry;
  	tdir = tdentry->d_inode;
  
  	err = nfserr_perm;
  	if (!flen || isdotent(fname, flen) || !tlen || isdotent(tname, tlen))
  		goto out;
  
  	host_err = fh_want_write(ffhp);
  	if (host_err) {
  		err = nfserrno(host_err);
  		goto out;
  	}
  
  	/* cannot use fh_lock as we need deadlock protective ordering
  	 * so do it by hand */
  	trap = lock_rename(tdentry, fdentry);
  	ffhp->fh_locked = tfhp->fh_locked = 1;
  	fill_pre_wcc(ffhp);
  	fill_pre_wcc(tfhp);
  
  	odentry = lookup_one_len(fname, fdentry, flen);
  	host_err = PTR_ERR(odentry);
  	if (IS_ERR(odentry))
  		goto out_nfserr;
  
  	host_err = -ENOENT;
  	if (!odentry->d_inode)
  		goto out_dput_old;
  	host_err = -EINVAL;
  	if (odentry == trap)
  		goto out_dput_old;
  
  	ndentry = lookup_one_len(tname, tdentry, tlen);
  	host_err = PTR_ERR(ndentry);
  	if (IS_ERR(ndentry))
  		goto out_dput_old;
  	host_err = -ENOTEMPTY;
  	if (ndentry == trap)
  		goto out_dput_new;
  
  	host_err = -EXDEV;
  	if (ffhp->fh_export->ex_path.mnt != tfhp->fh_export->ex_path.mnt)
  		goto out_dput_new;
  	if (ffhp->fh_export->ex_path.dentry != tfhp->fh_export->ex_path.dentry)
  		goto out_dput_new;
  
  	host_err = vfs_rename(fdir, odentry, tdir, ndentry, NULL, 0);
  	if (!host_err) {
  		host_err = commit_metadata(tfhp);
  		if (!host_err)
  			host_err = commit_metadata(ffhp);
  	}
   out_dput_new:
  	dput(ndentry);
   out_dput_old:
  	dput(odentry);
   out_nfserr:
  	err = nfserrno(host_err);
  	/*
  	 * We cannot rely on fh_unlock on the two filehandles,
  	 * as that would do the wrong thing if the two directories
  	 * were the same, so again we do it by hand.
  	 */
  	fill_post_wcc(ffhp);
  	fill_post_wcc(tfhp);
  	unlock_rename(tdentry, fdentry);
  	ffhp->fh_locked = tfhp->fh_locked = 0;
  	fh_drop_write(ffhp);
  
  out:
  	return err;
  }
  
  /*
   * Unlink a file or directory
   * N.B. After this call fhp needs an fh_put
   */
  __be32
  nfsd_unlink(struct svc_rqst *rqstp, struct svc_fh *fhp, int type,
  				char *fname, int flen)
  {
  	struct dentry	*dentry, *rdentry;
  	struct inode	*dirp;
  	__be32		err;
  	int		host_err;
  
  	err = nfserr_acces;
  	if (!flen || isdotent(fname, flen))
  		goto out;
  	err = fh_verify(rqstp, fhp, S_IFDIR, NFSD_MAY_REMOVE);
  	if (err)
  		goto out;
  
  	host_err = fh_want_write(fhp);
  	if (host_err)
  		goto out_nfserr;
  
  	fh_lock_nested(fhp, I_MUTEX_PARENT);
  	dentry = fhp->fh_dentry;
  	dirp = dentry->d_inode;
  
  	rdentry = lookup_one_len(fname, dentry, flen);
  	host_err = PTR_ERR(rdentry);
  	if (IS_ERR(rdentry))
  		goto out_nfserr;
  
  	if (!rdentry->d_inode) {
  		dput(rdentry);
  		err = nfserr_noent;
  		goto out;
  	}
  
  	if (!type)
  		type = rdentry->d_inode->i_mode & S_IFMT;
  
  	if (type != S_IFDIR)
  		host_err = vfs_unlink(dirp, rdentry, NULL);
  	else
  		host_err = vfs_rmdir(dirp, rdentry);
  	if (!host_err)
  		host_err = commit_metadata(fhp);
  	dput(rdentry);
  
  out_nfserr:
  	err = nfserrno(host_err);
  out:
  	return err;
  }
  
  /*
   * We do this buffering because we must not call back into the file
   * system's ->lookup() method from the filldir callback. That may well
   * deadlock a number of file systems.
   *
   * This is based heavily on the implementation of same in XFS.
   */
  struct buffered_dirent {
  	u64		ino;
  	loff_t		offset;
  	int		namlen;
  	unsigned int	d_type;
  	char		name[];
  };
  
  struct readdir_data {
  	struct dir_context ctx;
  	char		*dirent;
  	size_t		used;
  	int		full;
  };
  
  static int nfsd_buffered_filldir(void *__buf, const char *name, int namlen,
  				 loff_t offset, u64 ino, unsigned int d_type)
  {
  	struct readdir_data *buf = __buf;
  	struct buffered_dirent *de = (void *)(buf->dirent + buf->used);
  	unsigned int reclen;
  
  	reclen = ALIGN(sizeof(struct buffered_dirent) + namlen, sizeof(u64));
  	if (buf->used + reclen > PAGE_SIZE) {
  		buf->full = 1;
  		return -EINVAL;
  	}
  
  	de->namlen = namlen;
  	de->offset = offset;
  	de->ino = ino;
  	de->d_type = d_type;
  	memcpy(de->name, name, namlen);
  	buf->used += reclen;
  
  	return 0;
  }
  
  static __be32 nfsd_buffered_readdir(struct file *file, filldir_t func,
  				    struct readdir_cd *cdp, loff_t *offsetp)
  {
  	struct buffered_dirent *de;
  	int host_err;
  	int size;
  	loff_t offset;
  	struct readdir_data buf = {
  		.ctx.actor = nfsd_buffered_filldir,
  		.dirent = (void *)__get_free_page(GFP_KERNEL)
  	};
  
  	if (!buf.dirent)
  		return nfserrno(-ENOMEM);
  
  	offset = *offsetp;
  
  	while (1) {
  		struct inode *dir_inode = file_inode(file);
  		unsigned int reclen;
  
  		cdp->err = nfserr_eof; /* will be cleared on successful read */
  		buf.used = 0;
  		buf.full = 0;
  
  		host_err = iterate_dir(file, &buf.ctx);
  		if (buf.full)
  			host_err = 0;
  
  		if (host_err < 0)
  			break;
  
  		size = buf.used;
  
  		if (!size)
  			break;
  
  		/*
  		 * Various filldir functions may end up calling back into
  		 * lookup_one_len() and the file system's ->lookup() method.
  		 * These expect i_mutex to be held, as it would within readdir.
  		 */
  		host_err = mutex_lock_killable(&dir_inode->i_mutex);
  		if (host_err)
  			break;
  
  		de = (struct buffered_dirent *)buf.dirent;
  		while (size > 0) {
  			offset = de->offset;
  
  			if (func(cdp, de->name, de->namlen, de->offset,
  				 de->ino, de->d_type))
  				break;
  
  			if (cdp->err != nfs_ok)
  				break;
  
  			reclen = ALIGN(sizeof(*de) + de->namlen,
  				       sizeof(u64));
  			size -= reclen;
  			de = (struct buffered_dirent *)((char *)de + reclen);
  		}
  		mutex_unlock(&dir_inode->i_mutex);
  		if (size > 0) /* We bailed out early */
  			break;
  
  		offset = vfs_llseek(file, 0, SEEK_CUR);
  	}
  
  	free_page((unsigned long)(buf.dirent));
  
  	if (host_err)
  		return nfserrno(host_err);
  
  	*offsetp = offset;
  	return cdp->err;
  }
  
  /*
   * Read entries from a directory.
   * The  NFSv3/4 verifier we ignore for now.
   */
  __be32
  nfsd_readdir(struct svc_rqst *rqstp, struct svc_fh *fhp, loff_t *offsetp, 
  	     struct readdir_cd *cdp, filldir_t func)
  {
  	__be32		err;
  	struct file	*file;
  	loff_t		offset = *offsetp;
  	int             may_flags = NFSD_MAY_READ;
  
  	/* NFSv2 only supports 32 bit cookies */
  	if (rqstp->rq_vers > 2)
  		may_flags |= NFSD_MAY_64BIT_COOKIE;
  
  	err = nfsd_open(rqstp, fhp, S_IFDIR, may_flags, &file);
  	if (err)
  		goto out;
  
  	offset = vfs_llseek(file, offset, SEEK_SET);
  	if (offset < 0) {
  		err = nfserrno((int)offset);
  		goto out_close;
  	}
  
  	err = nfsd_buffered_readdir(file, func, cdp, offsetp);
  
  	if (err == nfserr_eof || err == nfserr_toosmall)
  		err = nfs_ok; /* can still be found in ->err */
  out_close:
  	nfsd_close(file);
  out:
  	return err;
  }
  
  /*
   * Get file system stats
   * N.B. After this call fhp needs an fh_put
   */
  __be32
  nfsd_statfs(struct svc_rqst *rqstp, struct svc_fh *fhp, struct kstatfs *stat, int access)
  {
  	__be32 err;
  
  	err = fh_verify(rqstp, fhp, 0, NFSD_MAY_NOP | access);
  	if (!err) {
  		struct path path = {
  			.mnt	= fhp->fh_export->ex_path.mnt,
  			.dentry	= fhp->fh_dentry,
  		};
  		if (vfs_statfs(&path, stat))
  			err = nfserr_io;
  	}
  	return err;
  }
  
  static int exp_rdonly(struct svc_rqst *rqstp, struct svc_export *exp)
  {
  	return nfsexp_flags(rqstp, exp) & NFSEXP_READONLY;
  }
  
  /*
   * Check for a user's access permissions to this inode.
   */
  __be32
  nfsd_permission(struct svc_rqst *rqstp, struct svc_export *exp,
  					struct dentry *dentry, int acc)
  {
  	struct inode	*inode = dentry->d_inode;
  	int		err;
  
  	if ((acc & NFSD_MAY_MASK) == NFSD_MAY_NOP)
  		return 0;
  #if 0
  	dprintk("nfsd: permission 0x%x%s%s%s%s%s%s%s mode 0%o%s%s%s\n",
  		acc,
  		(acc & NFSD_MAY_READ)?	" read"  : "",
  		(acc & NFSD_MAY_WRITE)?	" write" : "",
  		(acc & NFSD_MAY_EXEC)?	" exec"  : "",
  		(acc & NFSD_MAY_SATTR)?	" sattr" : "",
  		(acc & NFSD_MAY_TRUNC)?	" trunc" : "",
  		(acc & NFSD_MAY_LOCK)?	" lock"  : "",
  		(acc & NFSD_MAY_OWNER_OVERRIDE)? " owneroverride" : "",
  		inode->i_mode,
  		IS_IMMUTABLE(inode)?	" immut" : "",
  		IS_APPEND(inode)?	" append" : "",
  		__mnt_is_readonly(exp->ex_path.mnt)?	" ro" : "");
  	dprintk("      owner %d/%d user %d/%d\n",
  		inode->i_uid, inode->i_gid, current_fsuid(), current_fsgid());
  #endif
  
  	/* Normally we reject any write/sattr etc access on a read-only file
  	 * system.  But if it is IRIX doing check on write-access for a 
  	 * device special file, we ignore rofs.
  	 */
  	if (!(acc & NFSD_MAY_LOCAL_ACCESS))
  		if (acc & (NFSD_MAY_WRITE | NFSD_MAY_SATTR | NFSD_MAY_TRUNC)) {
  			if (exp_rdonly(rqstp, exp) ||
  			    __mnt_is_readonly(exp->ex_path.mnt))
  				return nfserr_rofs;
  			if (/* (acc & NFSD_MAY_WRITE) && */ IS_IMMUTABLE(inode))
  				return nfserr_perm;
  		}
  	if ((acc & NFSD_MAY_TRUNC) && IS_APPEND(inode))
  		return nfserr_perm;
  
  	if (acc & NFSD_MAY_LOCK) {
  		/* If we cannot rely on authentication in NLM requests,
  		 * just allow locks, otherwise require read permission, or
  		 * ownership
  		 */
  		if (exp->ex_flags & NFSEXP_NOAUTHNLM)
  			return 0;
  		else
  			acc = NFSD_MAY_READ | NFSD_MAY_OWNER_OVERRIDE;
  	}
  	/*
  	 * The file owner always gets access permission for accesses that
  	 * would normally be checked at open time. This is to make
  	 * file access work even when the client has done a fchmod(fd, 0).
  	 *
  	 * However, `cp foo bar' should fail nevertheless when bar is
  	 * readonly. A sensible way to do this might be to reject all
  	 * attempts to truncate a read-only file, because a creat() call
  	 * always implies file truncation.
  	 * ... but this isn't really fair.  A process may reasonably call
  	 * ftruncate on an open file descriptor on a file with perm 000.
  	 * We must trust the client to do permission checking - using "ACCESS"
  	 * with NFSv3.
  	 */
  	if ((acc & NFSD_MAY_OWNER_OVERRIDE) &&
  	    uid_eq(inode->i_uid, current_fsuid()))
  		return 0;
  
  	/* This assumes  NFSD_MAY_{READ,WRITE,EXEC} == MAY_{READ,WRITE,EXEC} */
  	err = inode_permission(inode, acc & (MAY_READ|MAY_WRITE|MAY_EXEC));
  
  	/* Allow read access to binaries even when mode 111 */
  	if (err == -EACCES && S_ISREG(inode->i_mode) &&
  	     (acc == (NFSD_MAY_READ | NFSD_MAY_OWNER_OVERRIDE) ||
  	      acc == (NFSD_MAY_READ | NFSD_MAY_READ_IF_EXEC)))
  		err = inode_permission(inode, MAY_EXEC);
  
  	return err? nfserrno(err) : 0;
  }
  
  void
  nfsd_racache_shutdown(void)
  {
  	struct raparms *raparm, *last_raparm;
  	unsigned int i;
  
  	dprintk("nfsd: freeing readahead buffers.\n");
  
  	for (i = 0; i < RAPARM_HASH_SIZE; i++) {
  		raparm = raparm_hash[i].pb_head;
  		while(raparm) {
  			last_raparm = raparm;
  			raparm = raparm->p_next;
  			kfree(last_raparm);
  		}
  		raparm_hash[i].pb_head = NULL;
  	}
  }
  /*
   * Initialize readahead param cache
   */
  int
  nfsd_racache_init(int cache_size)
  {
  	int	i;
  	int	j = 0;
  	int	nperbucket;
  	struct raparms **raparm = NULL;
  
  
  	if (raparm_hash[0].pb_head)
  		return 0;
  	nperbucket = DIV_ROUND_UP(cache_size, RAPARM_HASH_SIZE);
  	nperbucket = max(2, nperbucket);
  	cache_size = nperbucket * RAPARM_HASH_SIZE;
  
  	dprintk("nfsd: allocating %d readahead buffers.\n", cache_size);
  
  	for (i = 0; i < RAPARM_HASH_SIZE; i++) {
  		spin_lock_init(&raparm_hash[i].pb_lock);
  
  		raparm = &raparm_hash[i].pb_head;
  		for (j = 0; j < nperbucket; j++) {
  			*raparm = kzalloc(sizeof(struct raparms), GFP_KERNEL);
  			if (!*raparm)
  				goto out_nomem;
  			raparm = &(*raparm)->p_next;
  		}
  		*raparm = NULL;
  	}
  
  	nfsdstats.ra_size = cache_size;
  	return 0;
  
  out_nomem:
  	dprintk("nfsd: kmalloc failed, freeing readahead buffers\n");
  	nfsd_racache_shutdown();
  	return -ENOMEM;
  }
  