minix/servers/ext2/path.c

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/* This file contains the procedures that look up path names in the directory
* system and determine the inode number that goes with a given path name.
*
* The entry points into this file are
* eat_path: the 'main' routine of the path-to-inode conversion mechanism
* last_dir: find the final directory on a given path
* advance: parse one component of a path name
* search_dir: search a directory for a string and return its inode number
*
* Created (MFS based):
* February 2010 (Evgeniy Ivanov)
*/
#include "fs.h"
#include <assert.h>
#include <string.h>
#include <minix/endpoint.h>
#include <sys/stat.h>
#include <sys/types.h>
#include "buf.h"
#include "inode.h"
#include "super.h"
#include <minix/vfsif.h>
#include <minix/libminixfs.h>
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char dot1[2] = "."; /* used for search_dir to bypass the access */
char dot2[3] = ".."; /* permissions for . and .. */
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static char *get_name(char *name, char string[NAME_MAX+1]);
static int ltraverse(struct inode *rip, char *suffix);
static int parse_path(ino_t dir_ino, ino_t root_ino, int flags, struct
inode **res_inop, size_t *offsetp, int *symlinkp);
/*===========================================================================*
* fs_lookup *
*===========================================================================*/
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int fs_lookup()
{
cp_grant_id_t grant;
int r, r1, flags, symlinks;
unsigned int len;
size_t offset = 0, path_size;
ino_t dir_ino, root_ino;
struct inode *rip;
grant = (cp_grant_id_t) fs_m_in.REQ_GRANT;
path_size = (size_t) fs_m_in.REQ_PATH_SIZE; /* Size of the buffer */
len = (int) fs_m_in.REQ_PATH_LEN; /* including terminating nul */
dir_ino = (ino_t) fs_m_in.REQ_DIR_INO;
root_ino = (ino_t) fs_m_in.REQ_ROOT_INO;
flags = (int) fs_m_in.REQ_FLAGS;
/* Check length. */
if(len > sizeof(user_path)) return(E2BIG); /* too big for buffer */
if(len == 0) return(EINVAL); /* too small */
/* Copy the pathname and set up caller's user and group id */
r = sys_safecopyfrom(VFS_PROC_NR, grant, /*offset*/ 0,
(vir_bytes) user_path, (size_t) len);
if(r != OK) return(r);
/* Verify this is a null-terminated path. */
if(user_path[len - 1] != '\0') return(EINVAL);
memset(&credentials, 0, sizeof(credentials));
if(!(flags & PATH_GET_UCRED)) { /* Do we have to copy uid/gid credentials? */
caller_uid = (uid_t) fs_m_in.REQ_UID;
caller_gid = (gid_t) fs_m_in.REQ_GID;
} else {
if((r=fs_lookup_credentials(&credentials,
&caller_uid, &caller_gid,
(cp_grant_id_t) fs_m_in.REQ_GRANT2,
(size_t) fs_m_in.REQ_UCRED_SIZE)) != OK)
return r;
}
/* Lookup inode */
rip = NULL;
r = parse_path(dir_ino, root_ino, flags, &rip, &offset, &symlinks);
if(symlinks != 0 && (r == ELEAVEMOUNT || r == EENTERMOUNT || r == ESYMLINK)){
len = strlen(user_path)+1;
if(len > path_size) return(ENAMETOOLONG);
r1 = sys_safecopyto(VFS_PROC_NR, grant, (vir_bytes) 0,
(vir_bytes) user_path, (size_t) len);
if (r1 != OK) return(r1);
}
if(r == ELEAVEMOUNT || r == ESYMLINK) {
/* Report offset and the error */
fs_m_out.RES_OFFSET = offset;
fs_m_out.RES_SYMLOOP = symlinks;
return(r);
}
if (r != OK && r != EENTERMOUNT) return(r);
fs_m_out.RES_INODE_NR = rip->i_num;
fs_m_out.RES_MODE = rip->i_mode;
fs_m_out.RES_FILE_SIZE_LO = rip->i_size;
fs_m_out.RES_SYMLOOP = symlinks;
fs_m_out.RES_UID = rip->i_uid;
fs_m_out.RES_GID = rip->i_gid;
/* This is only valid for block and character specials. But it doesn't
* cause any harm to set RES_DEV always. */
fs_m_out.RES_DEV = (dev_t) rip->i_block[0];
if(r == EENTERMOUNT) {
fs_m_out.RES_OFFSET = offset;
put_inode(rip); /* Only return a reference to the final object */
}
return(r);
}
/*===========================================================================*
* parse_path *
*===========================================================================*/
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static int parse_path(dir_ino, root_ino, flags, res_inop, offsetp, symlinkp)
ino_t dir_ino;
ino_t root_ino;
int flags;
struct inode **res_inop;
size_t *offsetp;
int *symlinkp;
{
/* Parse the path in user_path, starting at dir_ino. If the path is the empty
* string, just return dir_ino. It is upto the caller to treat an empty
* path in a special way. Otherwise, if the path consists of just one or
* more slash ('/') characters, the path is replaced with ".". Otherwise,
* just look up the first (or only) component in path after skipping any
* leading slashes.
*/
int r, leaving_mount;
struct inode *rip, *dir_ip;
char *cp, *next_cp; /* component and next component */
char component[NAME_MAX+1];
/* Start parsing path at the first component in user_path */
cp = user_path;
/* No symlinks encountered yet */
*symlinkp = 0;
/* Find starting inode inode according to the request message */
if((rip = find_inode(fs_dev, dir_ino)) == NULL)
return(ENOENT);
/* If dir has been removed return ENOENT. */
if (rip->i_links_count == NO_LINK) return(ENOENT);
dup_inode(rip);
/* If the given start inode is a mountpoint, we must be here because the file
* system mounted on top returned an ELEAVEMOUNT error. In this case, we must
* only accept ".." as the first path component.
*/
leaving_mount = rip->i_mountpoint; /* True iff rip is a mountpoint */
/* Scan the path component by component. */
while (TRUE) {
if(cp[0] == '\0') {
/* We're done; either the path was empty or we've parsed all
components of the path */
*res_inop = rip;
*offsetp += cp - user_path;
/* Return EENTERMOUNT if we are at a mount point */
if (rip->i_mountpoint) return(EENTERMOUNT);
return(OK);
}
while(cp[0] == '/') cp++;
next_cp = get_name(cp, component);
if (next_cp == NULL) {
put_inode(rip);
return(err_code);
}
/* Special code for '..'. A process is not allowed to leave a chrooted
* environment. A lookup of '..' at the root of a mounted filesystem
* has to return ELEAVEMOUNT. In both cases, the caller needs search
* permission for the current inode, as it is used as directory.
*/
if(strcmp(component, "..") == 0) {
/* 'rip' is now accessed as directory */
if ((r = forbidden(rip, X_BIT)) != OK) {
put_inode(rip);
return(r);
}
if (rip->i_num == root_ino) {
cp = next_cp;
continue; /* Ignore the '..' at a process' root
and move on to the next component */
}
if (rip->i_num == ROOT_INODE && !rip->i_sp->s_is_root) {
/* Climbing up to parent FS */
put_inode(rip);
*offsetp += cp - user_path;
return(ELEAVEMOUNT);
}
}
/* Only check for a mount point if we are not coming from one. */
if (!leaving_mount && rip->i_mountpoint) {
/* Going to enter a child FS */
*res_inop = rip;
*offsetp += cp - user_path;
return(EENTERMOUNT);
}
/* There is more path. Keep parsing.
* If we're leaving a mountpoint, skip directory permission checks.
*/
dir_ip = rip;
rip = advance(dir_ip, leaving_mount ? dot2 : component, CHK_PERM);
if(err_code == ELEAVEMOUNT || err_code == EENTERMOUNT)
err_code = OK;
if (err_code != OK) {
put_inode(dir_ip);
return(err_code);
}
leaving_mount = 0;
/* The call to advance() succeeded. Fetch next component. */
if (S_ISLNK(rip->i_mode)) {
if (next_cp[0] == '\0' && (flags & PATH_RET_SYMLINK)) {
put_inode(dir_ip);
*res_inop = rip;
*offsetp += next_cp - user_path;
return(OK);
}
/* Extract path name from the symlink file */
r = ltraverse(rip, next_cp);
next_cp = user_path;
*offsetp = 0;
/* Symloop limit reached? */
if (++(*symlinkp) > SYMLOOP_MAX)
r = ELOOP;
if (r != OK) {
put_inode(dir_ip);
put_inode(rip);
return(r);
}
if (next_cp[0] == '/') {
put_inode(dir_ip);
put_inode(rip);
return(ESYMLINK);
}
put_inode(rip);
dup_inode(dir_ip);
rip = dir_ip;
}
put_inode(dir_ip);
cp = next_cp; /* Process subsequent component in next round */
}
}
/*===========================================================================*
* ltraverse *
*===========================================================================*/
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static int ltraverse(rip, suffix)
register struct inode *rip; /* symbolic link */
char *suffix; /* current remaining path. Has to point in the
* user_path buffer
*/
{
/* Traverse a symbolic link. Copy the link text from the inode and insert
* the text into the path. Return error code or report success. Base
* directory has to be determined according to the first character of the
* new pathname.
*/
block_t blink; /* block containing link text */
size_t llen; /* length of link */
size_t slen; /* length of suffix */
struct buf *bp; /* buffer containing link text */
const char *sp; /* start of link text */
llen = (size_t) rip->i_size;
if (llen >= MAX_FAST_SYMLINK_LENGTH) {
/* normal symlink */
if ((blink = read_map(rip, (off_t) 0)) == NO_BLOCK)
return(EIO);
bp = get_block(rip->i_dev, blink, NORMAL);
sp = b_data(bp);
} else {
/* fast symlink, stored in inode */
sp = (const char*) rip->i_block;
}
slen = strlen(suffix);
/* The path we're parsing looks like this:
* /already/processed/path/<link> or
* /already/processed/path/<link>/not/yet/processed/path
* After expanding the <link>, the path will look like
* <expandedlink> or
* <expandedlink>/not/yet/processed
* In both cases user_path must have enough room to hold <expandedlink>.
* However, in the latter case we have to move /not/yet/processed to the
* right place first, before we expand <link>. When strlen(<expandedlink>) is
* smaller than strlen(/already/processes/path), we move the suffix to the
* left. Is strlen(<expandedlink>) greater then we move it to the right. Else
* we do nothing.
*/
if (slen > 0) { /* Do we have path after the link? */
/* For simplicity we require that suffix starts with a slash */
if (suffix[0] != '/') {
panic("ltraverse: suffix does not start with a slash");
}
/* To be able to expand the <link>, we have to move the 'suffix'
* to the right place.
*/
if (slen + llen + 1 > sizeof(user_path))
return(ENAMETOOLONG);/* <expandedlink>+suffix+\0 does not fit*/
if ((unsigned)(suffix - user_path) != llen) {
/* Move suffix left or right if needed */
memmove(&user_path[llen], suffix, slen+1);
}
} else {
if (llen + 1 > sizeof(user_path))
return(ENAMETOOLONG); /* <expandedlink> + \0 does not fit */
/* Set terminating nul */
user_path[llen]= '\0';
}
/* Everything is set, now copy the expanded link to user_path */
memmove(user_path, sp, llen);
if (llen >= MAX_FAST_SYMLINK_LENGTH)
put_block(bp, DIRECTORY_BLOCK);
return(OK);
}
/*===========================================================================*
* advance *
*===========================================================================*/
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struct inode *advance(dirp, string, chk_perm)
struct inode *dirp; /* inode for directory to be searched */
char string[NAME_MAX + 1]; /* component name to look for */
int chk_perm; /* check permissions when string is looked up*/
{
/* Given a directory and a component of a path, look up the component in
* the directory, find the inode, open it, and return a pointer to its inode
* slot.
*/
ino_t numb;
struct inode *rip;
/* If 'string' is empty, return an error. */
if (string[0] == '\0') {
err_code = ENOENT;
return(NULL);
}
/* Check for NULL. */
if (dirp == NULL) return(NULL);
/* If 'string' is not present in the directory, signal error. */
if ( (err_code = search_dir(dirp, string, &numb, LOOK_UP,
chk_perm, 0)) != OK) {
return(NULL);
}
/* The component has been found in the directory. Get inode. */
if ( (rip = get_inode(dirp->i_dev, (int) numb)) == NULL) {
return(NULL);
}
/* The following test is for "mountpoint/.." where mountpoint is a
* mountpoint. ".." will refer to the root of the mounted filesystem,
* but has to become a reference to the parent of the 'mountpoint'
* directory.
*
* This case is recognized by the looked up name pointing to a
* root inode, and the directory in which it is held being a
* root inode, _and_ the name[1] being '.'. (This is a test for '..'
* and excludes '.'.)
*/
if (rip->i_num == ROOT_INODE) {
if (dirp->i_num == ROOT_INODE) {
if (string[1] == '.') {
if (!rip->i_sp->s_is_root) {
/* Climbing up mountpoint */
err_code = ELEAVEMOUNT;
}
}
}
}
/* See if the inode is mounted on. If so, switch to root directory of the
* mounted file system. The super_block provides the linkage between the
* inode mounted on and the root directory of the mounted file system.
*/
if (rip->i_mountpoint) {
/* Mountpoint encountered, report it */
err_code = EENTERMOUNT;
}
return(rip);
}
/*===========================================================================*
* get_name *
*===========================================================================*/
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static char *get_name(path_name, string)
char *path_name; /* path name to parse */
char string[NAME_MAX+1]; /* component extracted from 'old_name' */
{
/* Given a pointer to a path name in fs space, 'path_name', copy the first
* component to 'string' (truncated if necessary, always nul terminated).
* A pointer to the string after the first component of the name as yet
* unparsed is returned. Roughly speaking,
* 'get_name' = 'path_name' - 'string'.
*
* This routine follows the standard convention that /usr/ast, /usr//ast,
* //usr///ast and /usr/ast/ are all equivalent.
*
* If len of component is greater, than allowed, then return 0.
*/
size_t len;
char *cp, *ep;
cp = path_name;
/* Skip leading slashes */
while (cp[0] == '/') cp++;
/* Find the end of the first component */
ep = cp;
while(ep[0] != '\0' && ep[0] != '/')
ep++;
len = (size_t) (ep - cp);
if (len > NAME_MAX || len > EXT2_NAME_MAX) {
err_code = ENAMETOOLONG;
return(NULL);
}
/* Special case of the string at cp is empty */
if (len == 0)
strlcpy(string, ".", NAME_MAX + 1); /* Return "." */
else {
memcpy(string, cp, len);
string[len]= '\0';
}
return(ep);
}
/*===========================================================================*
* search_dir *
*===========================================================================*/
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int search_dir(ldir_ptr, string, numb, flag, check_permissions, ftype)
register struct inode *ldir_ptr; /* ptr to inode for dir to search */
char string[NAME_MAX + 1]; /* component to search for */
ino_t *numb; /* pointer to inode number */
int flag; /* LOOK_UP, ENTER, DELETE or IS_EMPTY */
int check_permissions; /* check permissions when flag is !IS_EMPTY */
int ftype; /* used when ENTER and
* INCOMPAT_FILETYPE */
{
/* This function searches the directory whose inode is pointed to by 'ldip':
* if (flag == ENTER) enter 'string' in the directory with inode # '*numb';
* if (flag == DELETE) delete 'string' from the directory;
* if (flag == LOOK_UP) search for 'string' and return inode # in 'numb';
* if (flag == IS_EMPTY) return OK if only . and .. in dir else ENOTEMPTY;
*
* if 'string' is dot1 or dot2, no access permissions are checked.
*/
register struct ext2_disk_dir_desc *dp = NULL;
register struct ext2_disk_dir_desc *prev_dp = NULL;
register struct buf *bp = NULL;
int i, r, e_hit, t, match;
mode_t bits;
off_t pos;
unsigned new_slots;
block_t b;
int extended = 0;
int required_space = 0;
int string_len = 0;
/* If 'ldir_ptr' is not a pointer to a dir inode, error. */
if ( (ldir_ptr->i_mode & I_TYPE) != I_DIRECTORY) {
return(ENOTDIR);
}
r = OK;
if (flag != IS_EMPTY) {
bits = (flag == LOOK_UP ? X_BIT : W_BIT | X_BIT);
if (string == dot1 || string == dot2) {
if (flag != LOOK_UP) r = read_only(ldir_ptr);
/* only a writable device is required. */
} else if(check_permissions) {
r = forbidden(ldir_ptr, bits); /* check access permissions */
}
}
if (r != OK) return(r);
new_slots = 0;
e_hit = FALSE;
match = 0; /* set when a string match occurs */
pos = 0;
if (flag == ENTER) {
string_len = strlen(string);
required_space = MIN_DIR_ENTRY_SIZE + string_len;
required_space += (required_space & 0x03) == 0 ? 0 :
(DIR_ENTRY_ALIGN - (required_space & 0x03) );
if (ldir_ptr->i_last_dpos < ldir_ptr->i_size &&
ldir_ptr->i_last_dentry_size <= required_space)
pos = ldir_ptr->i_last_dpos;
}
for (; pos < ldir_ptr->i_size; pos += ldir_ptr->i_sp->s_block_size) {
b = read_map(ldir_ptr, pos); /* get block number */
/* Since directories don't have holes, 'b' cannot be NO_BLOCK. */
bp = get_block(ldir_ptr->i_dev, b, NORMAL); /* get a dir block */
prev_dp = NULL; /* New block - new first dentry, so no prev. */
if (bp == NO_BLOCK)
panic("get_block returned NO_BLOCK");
assert(bp != NULL);
/* Search a directory block.
* Note, we set prev_dp at the end of the loop.
*/
for (dp = (struct ext2_disk_dir_desc*) &b_data(bp);
CUR_DISC_DIR_POS(dp, &b_data(bp)) < ldir_ptr->i_sp->s_block_size;
dp = NEXT_DISC_DIR_DESC(dp) ) {
/* Match occurs if string found. */
if (flag != ENTER && dp->d_ino != NO_ENTRY) {
if (flag == IS_EMPTY) {
/* If this test succeeds, dir is not empty. */
if (ansi_strcmp(dp->d_name, ".", dp->d_name_len) != 0 &&
ansi_strcmp(dp->d_name, "..", dp->d_name_len) != 0) match = 1;
} else {
if (ansi_strcmp(dp->d_name, string, dp->d_name_len) == 0){
match = 1;
}
}
}
if (match) {
/* LOOK_UP or DELETE found what it wanted. */
r = OK;
if (flag == IS_EMPTY) r = ENOTEMPTY;
else if (flag == DELETE) {
if (dp->d_name_len >= sizeof(ino_t)) {
/* Save d_ino for recovery. */
t = dp->d_name_len - sizeof(ino_t);
*((ino_t *) &dp->d_name[t]) = dp->d_ino;
}
dp->d_ino = NO_ENTRY; /* erase entry */
lmfs_markdirty(bp);
/* If we don't support HTree (directory index),
* which is fully compatible ext2 feature,
* we should reset EXT2_INDEX_FL, when modify
* linked directory structure.
*
* @TODO: actually we could just reset it for
* each directory, but I added if() to not
* forget about it later, when add HTree
* support.
*/
if (!HAS_COMPAT_FEATURE(ldir_ptr->i_sp,
COMPAT_DIR_INDEX))
ldir_ptr->i_flags &= ~EXT2_INDEX_FL;
if (pos < ldir_ptr->i_last_dpos) {
ldir_ptr->i_last_dpos = pos;
ldir_ptr->i_last_dentry_size =
conv2(le_CPU, dp->d_rec_len);
}
ldir_ptr->i_update |= CTIME | MTIME;
ldir_ptr->i_dirt = IN_DIRTY;
/* Now we have cleared dentry, if it's not
* the first one, merge it with previous one.
* Since we assume, that existing dentry must be
* correct, there is no way to spann a data block.
*/
if (prev_dp) {
u16_t temp = conv2(le_CPU,
prev_dp->d_rec_len);
temp += conv2(le_CPU,
dp->d_rec_len);
prev_dp->d_rec_len = conv2(le_CPU,
temp);
}
} else {
/* 'flag' is LOOK_UP */
*numb = (ino_t) conv4(le_CPU, dp->d_ino);
}
put_block(bp, DIRECTORY_BLOCK);
return(r);
}
/* Check for free slot for the benefit of ENTER. */
if (flag == ENTER && dp->d_ino == NO_ENTRY) {
/* we found a free slot, check if it has enough space */
if (required_space <= conv2(le_CPU, dp->d_rec_len)) {
e_hit = TRUE; /* we found a free slot */
break;
}
}
/* Can we shrink dentry? */
if (flag == ENTER && required_space <= DIR_ENTRY_SHRINK(dp)) {
/* Shrink directory and create empty slot, now
* dp->d_rec_len = DIR_ENTRY_ACTUAL_SIZE + DIR_ENTRY_SHRINK.
*/
int new_slot_size = conv2(le_CPU, dp->d_rec_len);
int actual_size = DIR_ENTRY_ACTUAL_SIZE(dp);
new_slot_size -= actual_size;
dp->d_rec_len = conv2(le_CPU, actual_size);
dp = NEXT_DISC_DIR_DESC(dp);
dp->d_rec_len = conv2(le_CPU, new_slot_size);
/* if we fail before writing real ino */
dp->d_ino = NO_ENTRY;
lmfs_markdirty(bp);
e_hit = TRUE; /* we found a free slot */
break;
}
prev_dp = dp;
}
/* The whole block has been searched or ENTER has a free slot. */
if (e_hit) break; /* e_hit set if ENTER can be performed now */
put_block(bp, DIRECTORY_BLOCK); /* otherwise, continue searching dir */
}
/* The whole directory has now been searched. */
if (flag != ENTER) {
return(flag == IS_EMPTY ? OK : ENOENT);
}
/* When ENTER next time, start searching for free slot from
* i_last_dpos. It gives solid performance improvement.
*/
ldir_ptr->i_last_dpos = pos;
ldir_ptr->i_last_dentry_size = required_space;
/* This call is for ENTER. If no free slot has been found so far, try to
* extend directory.
*/
if (e_hit == FALSE) { /* directory is full and no room left in last block */
new_slots++; /* increase directory size by 1 entry */
if ( (bp = new_block(ldir_ptr, ldir_ptr->i_size)) == NULL)
return(err_code);
dp = (struct ext2_disk_dir_desc*) &b_data(bp);
dp->d_rec_len = conv2(le_CPU, ldir_ptr->i_sp->s_block_size);
dp->d_name_len = DIR_ENTRY_MAX_NAME_LEN(dp); /* for failure */
extended = 1;
}
/* 'bp' now points to a directory block with space. 'dp' points to slot. */
dp->d_name_len = string_len;
for (i = 0; i < NAME_MAX && i < dp->d_name_len && string[i]; i++)
dp->d_name[i] = string[i];
dp->d_ino = (int) conv4(le_CPU, *numb);
if (HAS_INCOMPAT_FEATURE(ldir_ptr->i_sp, INCOMPAT_FILETYPE)) {
/* Convert ftype (from inode.i_mode) to dp->d_file_type */
if (ftype == I_REGULAR)
dp->d_file_type = EXT2_FT_REG_FILE;
else if (ftype == I_DIRECTORY)
dp->d_file_type = EXT2_FT_DIR;
else if (ftype == I_SYMBOLIC_LINK)
dp->d_file_type = EXT2_FT_SYMLINK;
else if (ftype == I_BLOCK_SPECIAL)
dp->d_file_type = EXT2_FT_BLKDEV;
else if (ftype == I_CHAR_SPECIAL)
dp->d_file_type = EXT2_FT_CHRDEV;
else if (ftype == I_NAMED_PIPE)
dp->d_file_type = EXT2_FT_FIFO;
else
dp->d_file_type = EXT2_FT_UNKNOWN;
}
lmfs_markdirty(bp);
put_block(bp, DIRECTORY_BLOCK);
ldir_ptr->i_update |= CTIME | MTIME; /* mark mtime for update later */
ldir_ptr->i_dirt = IN_DIRTY;
if (new_slots == 1) {
ldir_ptr->i_size += (off_t) conv2(le_CPU, dp->d_rec_len);
/* Send the change to disk if the directory is extended. */
if (extended) rw_inode(ldir_ptr, WRITING);
}
return(OK);
}