50b06261b6
Implemented by changing write_map to accept a WMAP_FREE flag. In that case, it doesn't update the datablock (creating indirect zones as necessary) pointer, but it frees the datablock if present. Also it frees the single and double indirect blocks if unused. This makes the implementation of truncate_inode() simpler. truncate_inode() now accepts a truncation length which makes implementing truncate() and ftruncate() simple. This also allowed implementing the F_FREESP fcntl().
487 lines
17 KiB
C
487 lines
17 KiB
C
/* This file contains the procedures that look up path names in the directory
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* system and determine the inode number that goes with a given path name.
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*
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* The entry points into this file are
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* eat_path: the 'main' routine of the path-to-inode conversion mechanism
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* last_dir: find the final directory on a given path
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* advance: parse one component of a path name
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* search_dir: search a directory for a string and return its inode number
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*
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*/
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#include "fs.h"
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#include <string.h>
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#include <minix/callnr.h>
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#include <sys/stat.h>
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#include "buf.h"
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#include "file.h"
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#include "fproc.h"
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#include "inode.h"
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#include "super.h"
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PUBLIC char dot1[2] = "."; /* used for search_dir to bypass the access */
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PUBLIC char dot2[3] = ".."; /* permissions for . and .. */
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FORWARD _PROTOTYPE( char *get_name, (char *old_name, char string [NAME_MAX]) );
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FORWARD _PROTOTYPE( struct inode *ltraverse, (struct inode *rip,
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char *path, char *suffix, struct inode *ldip) );
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/*===========================================================================*
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* parse_path *
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*===========================================================================*/
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PUBLIC struct inode *parse_path(path, string, action)
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char *path; /* the path name to be parsed */
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char string[NAME_MAX]; /* the final component is returned here */
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int action; /* action on last part of path */
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{
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/* This is the actual code for last_dir and eat_path. Return the inode of
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* the last directory and the name of object within that directory, or the
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* inode of the last object (an empty name will be returned). Names are
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* returned in string. If string is null the name is discarded. The action
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* code determines how "last" is defined. If an error occurs, NIL_INODE
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* will be returned with an error code in err_code.
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*/
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struct inode *rip, *dir_ip;
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char *new_name;
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int symloop;
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char lstring[NAME_MAX];
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/* Is the path absolute or relative? Initialize 'rip' accordingly. */
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rip = (*path == '/' ? fp->fp_rootdir : fp->fp_workdir);
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/* If dir has been removed or path is empty, return ENOENT. */
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if (rip->i_nlinks == 0 || *path == '\0') {
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err_code = ENOENT;
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return(NIL_INODE);
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}
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dup_inode(rip); /* inode will be returned with put_inode */
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symloop = 0; /* symbolic link traversal count */
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if (string == (char *) 0) string = lstring;
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/* Scan the path component by component. */
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while (TRUE) {
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/* Extract one component. */
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if ( (new_name = get_name(path, string)) == (char*) 0) {
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put_inode(rip); /* bad path in user space */
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return(NIL_INODE);
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}
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if (*new_name == '\0' && (action & PATH_PENULTIMATE)) {
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if ( (rip->i_mode & I_TYPE) == I_DIRECTORY) {
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return(rip); /* normal exit */
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} else {
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/* last file of path prefix is not a directory */
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put_inode(rip);
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err_code = ENOTDIR;
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return(NIL_INODE);
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}
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}
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/* There is more path. Keep parsing. */
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dir_ip = rip;
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rip = advance(&dir_ip, string);
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if (rip == NIL_INODE) {
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if (*new_name == '\0' && (action & PATH_NONSYMBOLIC) != 0)
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return(dir_ip);
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else {
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put_inode(dir_ip);
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return(NIL_INODE);
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}
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}
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/* The call to advance() succeeded. Fetch next component. */
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if (S_ISLNK(rip->i_mode)) {
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if (*new_name != '\0' || (action & PATH_OPAQUE) == 0) {
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if (*new_name != '\0') new_name--;
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rip = ltraverse(rip, path, new_name, dir_ip);
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put_inode(dir_ip);
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if (++symloop > SYMLOOP) {
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err_code = ELOOP;
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put_inode(rip);
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rip = NIL_INODE;
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}
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if (rip == NIL_INODE) return(NIL_INODE);
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continue;
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}
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} else if (*new_name != '\0') {
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put_inode(dir_ip);
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path = new_name;
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continue;
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}
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/* Either last name reached or symbolic link is opaque */
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if ((action & PATH_NONSYMBOLIC) != 0) {
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put_inode(rip);
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return(dir_ip);
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} else {
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put_inode(dir_ip);
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return(rip);
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}
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}
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}
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/*===========================================================================*
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* eat_path *
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*===========================================================================*/
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PUBLIC struct inode *eat_path(path)
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char *path; /* the path name to be parsed */
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{
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/* Parse the path 'path' and put its inode in the inode table. If not possible,
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* return NIL_INODE as function value and an error code in 'err_code'.
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*/
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return parse_path(path, (char *) 0, EAT_PATH);
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}
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/*===========================================================================*
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* last_dir *
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*===========================================================================*/
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PUBLIC struct inode *last_dir(path, string)
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char *path; /* the path name to be parsed */
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char string[NAME_MAX]; /* the final component is returned here */
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{
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/* Given a path, 'path', located in the fs address space, parse it as
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* far as the last directory, fetch the inode for the last directory into
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* the inode table, and return a pointer to the inode. In
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* addition, return the final component of the path in 'string'.
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* If the last directory can't be opened, return NIL_INODE and
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* the reason for failure in 'err_code'.
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*/
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return parse_path(path, string, LAST_DIR);
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}
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/*===========================================================================*
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* ltraverse *
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*===========================================================================*/
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PRIVATE struct inode *ltraverse(rip, path, suffix, ldip)
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register struct inode *rip; /* symbolic link */
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char *path; /* path containing link */
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char *suffix; /* suffix following link within path */
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register struct inode *ldip; /* directory containing link */
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{
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/* Traverse a symbolic link. Copy the link text from the inode and insert
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* the text into the path. Return the inode of base directory and the
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* ammended path. The symbolic link inode is always freed. The inode
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* returned is already duplicated. NIL_INODE is returned on error.
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*/
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block_t b; /* block containing link text */
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struct inode *bip; /* inode of base directory */
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struct buf *bp; /* buffer containing link text */
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size_t sl; /* length of link */
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size_t tl; /* length of suffix */
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char *sp; /* start of link text */
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bip = NIL_INODE;
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bp = NIL_BUF;
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if ((b = read_map(rip, (off_t) 0)) != NO_BLOCK) {
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bp = get_block(rip->i_dev, b, NORMAL);
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sl = rip->i_size;
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sp = bp->b_data;
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/* Insert symbolic text into path name. */
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tl = strlen(suffix);
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if (sl > 0 && sl + tl <= PATH_MAX-1) {
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memmove(path+sl, suffix, tl);
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memmove(path, sp, sl);
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path[sl+tl] = 0;
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dup_inode(bip = path[0] == '/' ? fp->fp_rootdir : ldip);
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}
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}
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put_block(bp, DIRECTORY_BLOCK);
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put_inode(rip);
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if (bip == NIL_INODE)
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{
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err_code = ENOENT;
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}
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return (bip);
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}
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/*===========================================================================*
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* get_name *
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*===========================================================================*/
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PRIVATE char *get_name(old_name, string)
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char *old_name; /* path name to parse */
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char string[NAME_MAX]; /* component extracted from 'old_name' */
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{
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/* Given a pointer to a path name in fs space, 'old_name', copy the next
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* component to 'string' and pad with zeros. A pointer to that part of
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* the name as yet unparsed is returned. Roughly speaking,
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* 'get_name' = 'old_name' - 'string'.
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*
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* This routine follows the standard convention that /usr/ast, /usr//ast,
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* //usr///ast and /usr/ast/ are all equivalent.
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*/
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register int c;
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register char *np, *rnp;
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np = string; /* 'np' points to current position */
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rnp = old_name; /* 'rnp' points to unparsed string */
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while ( (c = *rnp) == '/') rnp++; /* skip leading slashes */
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/* Copy the unparsed path, 'old_name', to the array, 'string'. */
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while ( rnp < &old_name[PATH_MAX] && c != '/' && c != '\0') {
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if (np < &string[NAME_MAX]) *np++ = c;
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c = *++rnp; /* advance to next character */
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}
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/* To make /usr/ast/ equivalent to /usr/ast, skip trailing slashes. */
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while (c == '/' && rnp < &old_name[PATH_MAX]) c = *++rnp;
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if (np < &string[NAME_MAX]) *np = '\0'; /* Terminate string */
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if (rnp >= &old_name[PATH_MAX]) {
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err_code = ENAMETOOLONG;
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return((char *) 0);
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}
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return(rnp);
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}
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/*===========================================================================*
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* advance *
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*===========================================================================*/
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PUBLIC struct inode *advance(pdirp, string)
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struct inode **pdirp; /* inode for directory to be searched */
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char string[NAME_MAX]; /* component name to look for */
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{
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/* Given a directory and a component of a path, look up the component in
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* the directory, find the inode, open it, and return a pointer to its inode
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* slot. If it can't be done, return NIL_INODE.
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*/
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register struct inode *rip, *dirp;
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register struct super_block *sp;
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int r, inumb;
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dev_t mnt_dev;
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ino_t numb;
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dirp = *pdirp;
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/* If 'string' is empty, yield same inode straight away. */
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if (string[0] == '\0') { return(get_inode(dirp->i_dev, (int) dirp->i_num)); }
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/* Check for NIL_INODE. */
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if (dirp == NIL_INODE) { return(NIL_INODE); }
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/* If 'string' is not present in the directory, signal error. */
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if ( (r = search_dir(dirp, string, &numb, LOOK_UP)) != OK) {
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err_code = r;
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return(NIL_INODE);
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}
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/* Don't go beyond the current root directory, unless the string is dot2. */
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if (dirp == fp->fp_rootdir && strcmp(string, "..") == 0 && string != dot2)
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return(get_inode(dirp->i_dev, (int) dirp->i_num));
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/* The component has been found in the directory. Get inode. */
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if ( (rip = get_inode(dirp->i_dev, (int) numb)) == NIL_INODE) {
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return(NIL_INODE);
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}
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/* The following test is for "mountpoint/.." where mountpoint is a
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* mountpoint. ".." will refer to the root of the mounted filesystem,
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* but has to become a reference to the parent of the 'mountpoint'
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* directory.
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*
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* This case is recognized by the looked up name pointing to a
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* root inode, and the directory in which it is held being a
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* root inode, _and_ the name[1] being '.'. (This is a test for '..'
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* and excludes '.'.)
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*/
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if (rip->i_num == ROOT_INODE)
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if (dirp->i_num == ROOT_INODE) {
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if (string[1] == '.') {
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for (sp = &super_block[1]; sp < &super_block[NR_SUPERS]; sp++){
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if (sp->s_dev == rip->i_dev) {
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/* Release the root inode. Replace by the
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* inode mounted on. Update parent.
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*/
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put_inode(rip);
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put_inode(dirp);
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mnt_dev = sp->s_imount->i_dev;
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inumb = (int) sp->s_imount->i_num;
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dirp = *pdirp = get_inode(mnt_dev, inumb);
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rip = advance(pdirp, string);
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break;
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}
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}
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}
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}
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if (rip == NIL_INODE) return(NIL_INODE);
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/* See if the inode is mounted on. If so, switch to root directory of the
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* mounted file system. The super_block provides the linkage between the
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* inode mounted on and the root directory of the mounted file system.
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*/
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while (rip != NIL_INODE && rip->i_mount == I_MOUNT) {
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/* The inode is indeed mounted on. */
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for (sp = &super_block[0]; sp < &super_block[NR_SUPERS]; sp++) {
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if (sp->s_imount == rip) {
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/* Release the inode mounted on. Replace by the
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* inode of the root inode of the mounted device.
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*/
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put_inode(rip);
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rip = get_inode(sp->s_dev, ROOT_INODE);
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break;
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}
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}
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}
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return(rip); /* return pointer to inode's component */
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}
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/*===========================================================================*
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* search_dir *
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*===========================================================================*/
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PUBLIC int search_dir(ldir_ptr, string, numb, flag)
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register struct inode *ldir_ptr; /* ptr to inode for dir to search */
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char string[NAME_MAX]; /* component to search for */
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ino_t *numb; /* pointer to inode number */
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int flag; /* LOOK_UP, ENTER, DELETE or IS_EMPTY */
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{
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/* This function searches the directory whose inode is pointed to by 'ldip':
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* if (flag == ENTER) enter 'string' in the directory with inode # '*numb';
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* if (flag == DELETE) delete 'string' from the directory;
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* if (flag == LOOK_UP) search for 'string' and return inode # in 'numb';
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* if (flag == IS_EMPTY) return OK if only . and .. in dir else ENOTEMPTY;
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*
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* if 'string' is dot1 or dot2, no access permissions are checked.
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*/
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register struct direct *dp = NULL;
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register struct buf *bp = NULL;
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int i, r, e_hit, t, match;
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mode_t bits;
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off_t pos;
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unsigned new_slots, old_slots;
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block_t b;
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struct super_block *sp;
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int extended = 0;
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/* If 'ldir_ptr' is not a pointer to a dir inode, error. */
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if ( (ldir_ptr->i_mode & I_TYPE) != I_DIRECTORY) {
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return(ENOTDIR);
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}
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r = OK;
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if (flag != IS_EMPTY) {
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bits = (flag == LOOK_UP ? X_BIT : W_BIT | X_BIT);
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if (string == dot1 || string == dot2) {
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if (flag != LOOK_UP) r = read_only(ldir_ptr);
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/* only a writable device is required. */
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}
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else r = forbidden(ldir_ptr, bits); /* check access permissions */
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}
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if (r != OK) return(r);
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/* Step through the directory one block at a time. */
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old_slots = (unsigned) (ldir_ptr->i_size/DIR_ENTRY_SIZE);
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new_slots = 0;
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e_hit = FALSE;
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match = 0; /* set when a string match occurs */
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for (pos = 0; pos < ldir_ptr->i_size; pos += ldir_ptr->i_sp->s_block_size) {
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b = read_map(ldir_ptr, pos); /* get block number */
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/* Since directories don't have holes, 'b' cannot be NO_BLOCK. */
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bp = get_block(ldir_ptr->i_dev, b, NORMAL); /* get a dir block */
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if (bp == NO_BLOCK)
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panic(__FILE__,"get_block returned NO_BLOCK", NO_NUM);
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/* Search a directory block. */
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for (dp = &bp->b_dir[0];
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dp < &bp->b_dir[NR_DIR_ENTRIES(ldir_ptr->i_sp->s_block_size)];
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dp++) {
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if (++new_slots > old_slots) { /* not found, but room left */
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if (flag == ENTER) e_hit = TRUE;
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break;
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}
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/* Match occurs if string found. */
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if (flag != ENTER && dp->d_ino != 0) {
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if (flag == IS_EMPTY) {
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/* If this test succeeds, dir is not empty. */
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if (strcmp(dp->d_name, "." ) != 0 &&
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strcmp(dp->d_name, "..") != 0) match = 1;
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} else {
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if (strncmp(dp->d_name, string, NAME_MAX) == 0) {
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match = 1;
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}
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}
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}
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if (match) {
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/* LOOK_UP or DELETE found what it wanted. */
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r = OK;
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if (flag == IS_EMPTY) r = ENOTEMPTY;
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else if (flag == DELETE) {
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/* Save d_ino for recovery. */
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t = NAME_MAX - sizeof(ino_t);
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*((ino_t *) &dp->d_name[t]) = dp->d_ino;
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dp->d_ino = 0; /* erase entry */
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bp->b_dirt = DIRTY;
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ldir_ptr->i_update |= CTIME | MTIME;
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ldir_ptr->i_dirt = DIRTY;
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} else {
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sp = ldir_ptr->i_sp; /* 'flag' is LOOK_UP */
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*numb = conv4(sp->s_native, (int) dp->d_ino);
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}
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put_block(bp, DIRECTORY_BLOCK);
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return(r);
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}
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/* Check for free slot for the benefit of ENTER. */
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if (flag == ENTER && dp->d_ino == 0) {
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e_hit = TRUE; /* we found a free slot */
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break;
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}
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}
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/* The whole block has been searched or ENTER has a free slot. */
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if (e_hit) break; /* e_hit set if ENTER can be performed now */
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put_block(bp, DIRECTORY_BLOCK); /* otherwise, continue searching dir */
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}
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/* The whole directory has now been searched. */
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if (flag != ENTER) {
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return(flag == IS_EMPTY ? OK : ENOENT);
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}
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/* This call is for ENTER. If no free slot has been found so far, try to
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* extend directory.
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*/
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if (e_hit == FALSE) { /* directory is full and no room left in last block */
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new_slots++; /* increase directory size by 1 entry */
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if (new_slots == 0) return(EFBIG); /* dir size limited by slot count */
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if ( (bp = new_block(ldir_ptr, ldir_ptr->i_size)) == NIL_BUF)
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return(err_code);
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dp = &bp->b_dir[0];
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extended = 1;
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}
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/* 'bp' now points to a directory block with space. 'dp' points to slot. */
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(void) memset(dp->d_name, 0, (size_t) NAME_MAX); /* clear entry */
|
|
for (i = 0; string[i] && i < NAME_MAX; i++) dp->d_name[i] = string[i];
|
|
sp = ldir_ptr->i_sp;
|
|
dp->d_ino = conv4(sp->s_native, (int) *numb);
|
|
bp->b_dirt = DIRTY;
|
|
put_block(bp, DIRECTORY_BLOCK);
|
|
ldir_ptr->i_update |= CTIME | MTIME; /* mark mtime for update later */
|
|
ldir_ptr->i_dirt = DIRTY;
|
|
if (new_slots > old_slots) {
|
|
ldir_ptr->i_size = (off_t) new_slots * DIR_ENTRY_SIZE;
|
|
/* Send the change to disk if the directory is extended. */
|
|
if (extended) rw_inode(ldir_ptr, WRITING);
|
|
}
|
|
return(OK);
|
|
}
|