Minix1.5/fs/path.c
/* 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
*/
#include "fs.h"
#include <string.h>
#include <minix/callnr.h>
#include "buf.h"
#include "file.h"
#include "fproc.h"
#include "inode.h"
#include "super.h"
FORWARD char *get_name();
/*===========================================================================*
* eat_path *
*===========================================================================*/
PUBLIC struct inode *eat_path(path)
char *path; /* the path name to be parsed */
{
/* Parse the path 'path' and put its inode in the inode table. If not possible,
* return NIL_INODE as function value and an error code in 'err_code'.
*/
register struct inode *ldip, *rip;
char string[NAME_MAX]; /* hold 1 path component name here */
/* First open the path down to the final directory. */
if ( (ldip = last_dir(path, string)) == NIL_INODE)
return(NIL_INODE); /* we couldn't open final directory */
/* The path consisting only of "/" is a special case, check for it. */
if (string[0] == '\0') return(ldip);
/* Get final component of the path. */
rip = advance(ldip, string);
put_inode(ldip);
return(rip);
}
/*===========================================================================*
* last_dir *
*===========================================================================*/
PUBLIC struct inode *last_dir(path, string)
char *path; /* the path name to be parsed */
char string[NAME_MAX]; /* the final component is returned here */
{
/* Given a path, 'path', located in the fs address space, parse it as
* far as the last directory, fetch the inode for the last directory into
* the inode table, and return a pointer to the inode. In
* addition, return the final component of the path in 'string'.
* If the last directory can't be opened, return NIL_INODE and
* the reason for failure in 'err_code'.
*/
register struct inode *rip;
register char *new_name;
register struct inode *new_ip;
char *p;
/* Is the path absolute or relative? Initialize 'rip' accordingly. */
rip = (*path == '/' ? fp->fp_rootdir : fp->fp_workdir);
/* If dir has been removed or path is empty, return ENOENT. */
if (rip->i_nlinks == 0 || *path == '\0') {
err_code = ENOENT;
return(NIL_INODE);
}
dup_inode(rip); /* inode will be returned with put_inode */
/* Remove trailing "/." from paths (e.g., "/usr/ast/." becomes "/usr/ast") */
if (fs_call == UNLINK || fs_call == RMDIR) {
while (1) {
p = path + strlen(path) - 2; /* pts to next-to-last char */
if (p > path && *p == '/' && *(p + 1) == '.')
*p = '\0';
else
break;
}
}
/* Scan the path component by component. */
while (TRUE) {
/* Extract one component. */
if ( (new_name = get_name(path, string)) == (char*) 0) {
put_inode(rip); /* bad path in user space */
return(NIL_INODE);
}
if (*new_name == '\0') return(rip); /* normal exit */
/* There is more path. Keep parsing. */
new_ip = advance(rip, string);
put_inode(rip); /* rip either obsolete or irrelevant */
if (new_ip == NIL_INODE) return(NIL_INODE);
/* The call to advance() succeeded. Fetch next component. */
path = new_name;
rip = new_ip;
}
}
/*===========================================================================*
* get_name *
*===========================================================================*/
PRIVATE char *get_name(old_name, string)
char *old_name; /* path name to parse */
char string[NAME_MAX]; /* component extracted from 'old_name' */
{
/* Given a pointer to a path name in fs space, 'old_name', copy the next
* component to 'string' and pad with zeros. A pointer to that part of
* the name as yet unparsed is returned. Roughly speaking,
* 'get_name' = 'old_name' - 'string'.
*
* This routine follows the standard convention that /usr/ast, /usr//ast,
* //usr///ast and /usr/ast/ are all equivalent.
*/
register int c;
register char *np, *rnp;
np = string; /* 'np' points to current position */
rnp = old_name; /* 'rnp' points to unparsed string */
while ( (c = *rnp) == '/') rnp++; /* skip leading slashes */
/* Copy the unparsed path, 'old_name', to the array, 'string'. */
while ( rnp < &old_name[PATH_MAX] && c != '/' && c != '\0') {
if (np < &string[NAME_MAX]) *np++ = c;
c = *++rnp; /* advance to next character */
}
/* To make /usr/ast/ equivalent to /usr/ast, skip trailing slashes. */
while (c == '/' && rnp < &old_name[PATH_MAX]) c = *++rnp;
/* Pad the component name out to NAME_MAX chars, using 0 as filler. */
while (np < &string[NAME_MAX]) *np++ = '\0';
if (rnp >= &old_name[PATH_MAX]) {
err_code = ENAMETOOLONG;
return((char *) 0);
}
return(rnp);
}
/*===========================================================================*
* advance *
*===========================================================================*/
PUBLIC struct inode *advance(dirp, string)
struct inode *dirp; /* inode for directory to be searched */
char string[NAME_MAX]; /* component name to look for */
{
/* 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. If it can't be done, return NIL_INODE.
*/
register struct inode *rip;
struct inode *rip2;
register struct super_block *sp;
int r;
dev_t mnt_dev;
ino_t numb;
/* If 'string' is empty, yield same inode straight away. */
if (string[0] == '\0') return(get_inode(dirp->i_dev, dirp->i_num));
/* Check for NIL_INODE. */
if (dirp == NIL_INODE) return(NIL_INODE);
/* If 'string' is not present in the directory, signal error. */
if ( (r = search_dir(dirp, string, &numb, LOOK_UP)) != OK) {
err_code = r;
return(NIL_INODE);
}
/* The component has been found in the directory. Get inode. */
if ( (rip = get_inode(dirp->i_dev, numb)) == NIL_INODE) return(NIL_INODE);
if (rip->i_num == ROOT_INODE)
if (dirp->i_num == ROOT_INODE) {
if (string[1] == '.') {
for (sp = &super_block[1]; sp < &super_block[NR_SUPERS]; sp++){
if (sp->s_dev == rip->i_dev) {
/* Release the root inode. Replace by the
* inode mounted on.
*/
put_inode(rip);
mnt_dev = sp->s_imount->i_dev;
rip2 = get_inode(mnt_dev, sp->s_imount->i_num);
rip = advance(rip2, string);
put_inode(rip2);
break;
}
}
}
}
if (rip == NIL_INODE) return(NIL_INODE);
/* 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.
*/
while (rip != NIL_INODE && rip->i_mount == I_MOUNT) {
/* The inode is indeed mounted on. */
for (sp = &super_block[0]; sp < &super_block[NR_SUPERS]; sp++) {
if (sp->s_imount == rip) {
/* Release the inode mounted on. Replace by the
* inode of the root inode of the mounted device.
*/
put_inode(rip);
rip = get_inode(sp->s_dev, ROOT_INODE);
break;
}
}
}
return(rip); /* return pointer to inode's component */
}
/*===========================================================================*
* search_dir *
*===========================================================================*/
PUBLIC int search_dir(ldir_ptr, string, numb, flag)
register struct inode *ldir_ptr; /* ptr to inode for dir to search */
char string[NAME_MAX]; /* component to search for */
ino_t *numb; /* pointer to inode number */
int flag; /* LOOK_UP, ENTER, or DELETE */
{
/* 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 'string' is "", return success on any entry except . and ..
*/
register dir_struct *dp;
register struct buf *bp;
register struct inode *rip;
int r, e_hit, t, match, huntany;
mode_t bits;
off_t pos;
unsigned new_slots, old_slots;
block_nr b;
/* If 'ldir_ptr' is not a pointer to a searchable dir inode, error. */
if ( (ldir_ptr->i_mode & I_TYPE) != I_DIRECTORY) return(ENOTDIR);
bits = (flag == LOOK_UP ? X_BIT : W_BIT|X_BIT);
if ( (r = forbidden(ldir_ptr, bits, 0)) != OK) return(r);
/* Step through the directory one block at a time. */
old_slots = ldir_ptr->i_size/DIR_ENTRY_SIZE;
new_slots = 0;
e_hit = FALSE;
match = 0; /* set when a string match occurs */
huntany = (*string == '\0' ? 1 : 0); /* set iff looking up "" */
for (pos = 0; pos < ldir_ptr->i_size; pos += 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 */
/* Search a directory block. */
for (dp = &bp->b_dir[0]; dp < &bp->b_dir[NR_DIR_ENTRIES]; dp++) {
if (++new_slots > old_slots) { /* not found, but room left */
if (flag == ENTER) e_hit = TRUE;
break;
}
/* Match occurs if string found; "" matches all exc . and .. */
if (flag != ENTER && dp->d_inum != 0) {
if (huntany) {
/* If this test succeeds, dir is not empty. */
if (strcmp(dp->d_name, "." ) != 0 &&
strcmp(dp->d_name, "..") != 0) match = 1;
} else {
if (strncmp(dp->d_name, string, NAME_MAX) == 0)
match = 1;
}
}
if (match) {
/* LOOK_UP or DELETE found what it wanted. */
r = OK;
if (flag == DELETE) {
/* Save d_inum for recovery. */
rip = get_inode(ldir_ptr->i_dev, dp->d_inum);
t = NAME_MAX - sizeof(ino_t);
*((ino_t *) &dp->d_name[t])=dp->d_inum;
dp->d_inum = 0; /* erase entry */
bp->b_dirt = DIRTY;
ldir_ptr->i_update = MTIME;
put_inode(rip);
} else
*numb = dp->d_inum; /* 'flag' is LOOK_UP */
put_block(bp, DIRECTORY_BLOCK);
return(r);
}
/* Check for free slot for the benefit of ENTER. */
if (flag == ENTER && dp->d_inum == 0) {
e_hit = TRUE; /* we found a free slot */
break;
}
}
/* 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(ENOENT);
/* 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 (new_slots == 0) return(EFBIG); /* dir size limited by slot count */
if ( (bp = new_block(ldir_ptr, ldir_ptr->i_size)) == NIL_BUF)
return(err_code);
dp = &bp->b_dir[0];
}
/* 'bp' now points to a directory block with space. 'dp' points to slot. */
copy(dp->d_name, string, NAME_MAX);
dp->d_inum = *numb;
bp->b_dirt = DIRTY;
put_block(bp, DIRECTORY_BLOCK);
ldir_ptr->i_update = 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;
return(OK);
}