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/*
 * Copyright (c) 2000 Silicon Graphics, Inc.  All Rights Reserved.
 * 
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of version 2 of the GNU General Public License as
 * published by the Free Software Foundation.
 * 
 * This program is distributed in the hope that it would be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
 * 
 * Further, this software is distributed without any warranty that it is
 * free of the rightful claim of any third person regarding infringement
 * or the like.  Any license provided herein, whether implied or
 * otherwise, applies only to this software file.  Patent licenses, if
 * any, provided herein do not apply to combinations of this program with
 * other software, or any other product whatsoever.
 * 
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, write the Free Software Foundation, Inc., 59
 * Temple Place - Suite 330, Boston MA 02111-1307, USA.
 * 
 * Contact information: Silicon Graphics, Inc., 1600 Amphitheatre Pkwy,
 * Mountain View, CA  94043, or:
 * 
 * http://www.sgi.com 
 * 
 * For further information regarding this notice, see: 
 * 
 * http://oss.sgi.com/projects/GenInfo/SGIGPLNoticeExplan/
 */

#include <errno.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#ifdef linux
#include <linux/types.h>
#include <unistd.h>
#include <syscall.h>
#include <xfs/xfs_fs.h>
#include <xfs/handle.h>
#include <asm/posix_types.h>
#include <linux/dirent.h>
#endif

#include <dmapi.h>
#include <dmapi_kern.h>
#include "dmapi_lib.h"


/* Originally this routine called SGI_OPEN_BY_HANDLE on the target object, did
   a fstat on it, then searched for the matching inode number in the directory
   pointed to by dirhanp.  There were a couple of problems with this.
   1. dm_handle_to_path is supposed to work for symlink target objects, but
      didn't because SGI_OPEN_BY_HANDLE only works for files and directories.
   2. The wrong pathname was sometimes returned if dirhanp and targhanp pointed
      to the same directory (a common request) because ".", ".." and/or various
      subdirectories could all be mount points and therefore all have the same
      inode number of 128.
   3. dm_handle_to_path wouldn't work if targhanp was a mount point because
      routine getcomp() sees only the mounted-on directory, not the mount point.

   This rework of dm_handle_to_path fixes all these problems, but at a price,
   because routine getcomp() must make one system call per directory entry.
   Someday these two methods should be combined.  If an SGI_OPEN_BY_HANDLE of
   targhanp works and if both dirhanp and targhanp have the same dev_t, then
   use the old method, otherwise use the current method.  This will remove
   the system call overhead in nearly all cases.
*/

static int getcomp(int dirfd, void *targhanp, size_t targhlen,
			char *bufp, size_t buflen, size_t *rlenp);


extern int
dm_handle_to_path(
	void		*dirhanp,	/* parent directory handle and length */
	size_t		dirhlen,
	void		*targhanp,	/* target object handle and length */
	size_t		targhlen,
	size_t		buflen,		/* length of pathbufp */
	char		*pathbufp,	/* buffer in which name is returned */
	size_t		*rlenp)		/* length of resultant pathname */
{
	int		dirfd = -1;	/* fd for parent directory */
	int		origfd = -1;	/* fd for current working directory */
	int		err;		/* a place to save errno */

	if (buflen == 0) {
		errno = EINVAL;
		return -1;
	}
	if (pathbufp == NULL || rlenp == NULL) {
		errno = EFAULT;
		return -1;
	}
	if ((origfd = open(".", O_RDONLY)) < 0)
		return -1;	/* leave errno set from open */

#if 0
	dirfd = (int)syssgi(SGI_OPEN_BY_HANDLE, dirhanp, dirhlen, O_RDONLY);
#else
	dirfd = open_by_handle(dirhanp, dirhlen, O_RDONLY);
#endif
	if (dirfd < 0) {
		err = errno;
	} else if (fchdir(dirfd)) {
		err = errno;
	} else {
		/* From here on the fchdir must always be undone! */

		if (!getcwd(pathbufp, buflen)) {
			if ((err = errno) == ERANGE)	/* buffer too small */
				err = E2BIG;
		} else {
			err = getcomp(dirfd, targhanp, targhlen, pathbufp,
					buflen, rlenp);
		}
		(void) fchdir(origfd);	/* can't do anything about a failure */
	}

	if (origfd >= 0)
		(void)close(origfd);
	if (dirfd >= 0)
		(void)close(dirfd);
	if (!err)
		return(0);

	if (err == E2BIG)
		*rlenp = 2 * buflen;	/* guess since we don't know */
	errno = err;
	return(-1);
}


/* Append the basename of the open file referenced by targfd found in the
   directory dirfd to dirfd's pathname in bufp.  The length of the entire
   path (including the NULL) is returned in *rlenp.

   Returns zero if successful, an appropriate errno if not.
*/

#define READDIRSZ	16384	/* 6.x kernels use 16k buffer */

static int
getcomp(
	int		dirfd,
	void		*targhanp,
	size_t		targhlen,
	char		*bufp,
	size_t		buflen,
	size_t		*rlenp)
{
	char		buf[READDIRSZ];	/* directory entry data buffer */
	int		loc = 0;	/* byte offset of entry in the buffer */
	int		size = 0;	/* number of bytes of data in buffer */
	int		eof = 0;	/* did last ngetdents exhaust dir.? */
#if 0
/* XXX */
	struct dirent64 *dp;		/* pointer to directory entry */
#else
	struct dirent	*dp;
#endif
	char		hbuf[DM_MAX_HANDLE_SIZE];
	size_t		hlen;
	size_t		dirlen;		/* length of dirfd's pathname */
	size_t		totlen;		/* length of targfd's pathname */
	dm_ino_t	ino;		/* target object's inode # */

	if (dm_handle_to_ino(targhanp, targhlen, &ino))
		return -1;      /* leave errno set from dm_handle_to_ino */

	/* Append a "/" to the directory name unless the directory is root. */

	dirlen = strlen(bufp);
	if (dirlen > 1) {
		if (buflen < dirlen + 1 + 1)
			return(E2BIG);
		bufp[dirlen++] = '/';
	}

	/* Examine each entry in the directory looking for one with a
	   matching target handle.
	*/

	for(;;) {
		if (size > 0) {
			dp = (struct dirent *)&buf[loc];
			loc += dp->d_reclen;
		}
		if (loc >= size) {
			if (eof) {
				return(ENOENT);
			}
			loc = size = 0;
		}
		if (size == 0) {	/* refill buffer */
#ifdef linux
			int cnt;

			do {
				cnt = syscall(SYS_getdents, dirfd,
					      (struct dirent *)buf,
					      sizeof(buf));
				if (cnt > 0 )
					size += cnt;
				if (cnt < 0)
					size = cnt;
			} while( cnt > 0 );

#else
			size = ngetdents64(dirfd, (struct dirent *)buf,
				    sizeof(buf), &eof);
#endif
			if (size == 0)	{	/* This also means EOF */
				return(ENOENT);
			}
			if (size < 0) {		/* error */
				return(errno);
			}
		}
		dp = (struct dirent *)&buf[loc];

		if (dp->d_ino != ino)
			continue;	/* wrong inode; try again */
		totlen = dirlen + strlen(dp->d_name) + 1;
		if (buflen < totlen)
			return(E2BIG);
		(void)strcpy(bufp + dirlen, dp->d_name);

		if (dmi(DM_PATH_TO_HANDLE, bufp, hbuf, &hlen))
			continue;	/* must have been removed/renamed */
		if (!dm_handle_cmp(targhanp, targhlen, hbuf, hlen))
			break;
	}

	/* We have a match based upon the target handle.  Clean up the end
	   cases before returning the path to the caller.
	*/

	if (!strcmp(dp->d_name, ".")) {		/* the directory itself */
		if (dirlen > 1)
			dirlen--;
		bufp[dirlen] = '\0';		/* trim the trailing "/." */
		*rlenp = dirlen + 1;
		return(0);
	}
	if (!strcmp(dp->d_name, "..")) {	/* the parent directory */
		char	*slash;

		if (dirlen > 1)
			dirlen--;
		bufp[dirlen] = '\0';
		if ((slash = strrchr(bufp, '/')) == NULL)
			return(ENXIO);		/* getcwd screwed up */
		if (slash == bufp)		/* don't whack "/" */
			slash++;
		*slash = '\0';			/* remove the last component */
		*rlenp = strlen(bufp) + 1;
		return(0);
	}

	*rlenp = totlen;		/* success! */
	return(0);
}