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phunix/servers/fs/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
*
*/
#include "fs.h"
#include <string.h>
#include <minix/callnr.h>
#include <sys/stat.h>
#include "buf.h"
#include "file.h"
#include "fproc.h"
#include "inode.h"
#include "super.h"
PUBLIC char dot1[2] = "."; /* used for search_dir to bypass the access */
PUBLIC char dot2[3] = ".."; /* permissions for . and .. */
FORWARD _PROTOTYPE( char *get_name, (char *old_name, char string [NAME_MAX]) );
FORWARD _PROTOTYPE( struct inode *ltraverse, (struct inode *rip,
char *path, char *suffix, struct inode *ldip) );
/*===========================================================================*
* parse_path *
*===========================================================================*/
PUBLIC struct inode *parse_path(path, string, action)
char *path; /* the path name to be parsed */
char string[NAME_MAX]; /* the final component is returned here */
int action; /* action on last part of path */
{
/* This is the actual code for last_dir and eat_path. Return the inode of
* the last directory and the name of object within that directory, or the
* inode of the last object (an empty name will be returned). Names are
* returned in string. If string is null the name is discarded. The action
* code determines how "last" is defined. If an error occurs, NIL_INODE
* will be returned with an error code in err_code.
*/
struct inode *rip, *dir_ip;
char *new_name;
int symloop;
char lstring[NAME_MAX];
/* 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 */
symloop = 0; /* symbolic link traversal count */
if (string == (char *) 0) string = lstring;
/* 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' && (action & PATH_PENULTIMATE)) {
if ( (rip->i_mode & I_TYPE) == I_DIRECTORY) {
return(rip); /* normal exit */
} else {
/* last file of path prefix is not a directory */
put_inode(rip);
err_code = ENOTDIR;
return(NIL_INODE);
}
}
/* There is more path. Keep parsing. */
dir_ip = rip;
rip = advance(&dir_ip, string);
if (rip == NIL_INODE) {
if (*new_name == '\0' && (action & PATH_NONSYMBOLIC) != 0)
return(dir_ip);
else {
put_inode(dir_ip);
return(NIL_INODE);
}
}
/* The call to advance() succeeded. Fetch next component. */
if (S_ISLNK(rip->i_mode)) {
if (*new_name != '\0' || (action & PATH_OPAQUE) == 0) {
if (*new_name != '\0') new_name--;
rip = ltraverse(rip, path, new_name, dir_ip);
put_inode(dir_ip);
if (++symloop > SYMLOOP) {
err_code = ELOOP;
put_inode(rip);
rip = NIL_INODE;
}
if (rip == NIL_INODE) return(NIL_INODE);
continue;
}
} else if (*new_name != '\0') {
put_inode(dir_ip);
path = new_name;
continue;
}
/* Either last name reached or symbolic link is opaque */
if ((action & PATH_NONSYMBOLIC) != 0) {
put_inode(rip);
return(dir_ip);
} else {
put_inode(dir_ip);
return(rip);
}
}
}
/*===========================================================================*
* 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'.
*/
return parse_path(path, (char *) 0, EAT_PATH);
}
/*===========================================================================*
* 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'.
*/
return parse_path(path, string, LAST_DIR);
}
/*===========================================================================*
* ltraverse *
*===========================================================================*/
PRIVATE struct inode *ltraverse(rip, path, suffix, ldip)
register struct inode *rip; /* symbolic link */
char *path; /* path containing link */
char *suffix; /* suffix following link within path */
register struct inode *ldip; /* directory containing link */
{
/* Traverse a symbolic link. Copy the link text from the inode and insert
* the text into the path. Return the inode of base directory and the
* ammended path. The symbolic link inode is always freed. The inode
* returned is already duplicated. NIL_INODE is returned on error.
*/
block_t b; /* block containing link text */
struct inode *bip; /* inode of base directory */
struct buf *bp; /* buffer containing link text */
size_t sl; /* length of link */
size_t tl; /* length of suffix */
char *sp; /* start of link text */
bip = NIL_INODE;
bp = NIL_BUF;
if ((b = read_map(rip, (off_t) 0)) != NO_BLOCK) {
bp = get_block(rip->i_dev, b, NORMAL);
sl = rip->i_size;
sp = bp->b_data;
/* Insert symbolic text into path name. */
tl = strlen(suffix);
if (sl > 0 && sl + tl <= PATH_MAX-1) {
memmove(path+sl, suffix, tl);
memmove(path, sp, sl);
path[sl+tl] = 0;
dup_inode(bip = path[0] == '/' ? fp->fp_rootdir : ldip);
}
}
put_block(bp, DIRECTORY_BLOCK);
put_inode(rip);
if (bip == NIL_INODE)
{
err_code = ENOENT;
}
return (bip);
}
/*===========================================================================*
* 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;
if (np < &string[NAME_MAX]) *np = '\0'; /* Terminate string */
if (rnp >= &old_name[PATH_MAX]) {
err_code = ENAMETOOLONG;
return((char *) 0);
}
return(rnp);
}
/*===========================================================================*
* advance *
*===========================================================================*/
PUBLIC struct inode *advance(pdirp, string)
struct inode **pdirp; /* 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, *dirp;
register struct super_block *sp;
int r, inumb;
dev_t mnt_dev;
ino_t numb;
dirp = *pdirp;
/* If 'string' is empty, yield same inode straight away. */
if (string[0] == '\0') { return(get_inode(dirp->i_dev, (int) 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);
}
/* Don't go beyond the current root directory, unless the string is dot2. */
if (dirp == fp->fp_rootdir && strcmp(string, "..") == 0 && string != dot2)
return(get_inode(dirp->i_dev, (int) dirp->i_num));
/* The component has been found in the directory. Get inode. */
if ( (rip = get_inode(dirp->i_dev, (int) numb)) == NIL_INODE) {
return(NIL_INODE);
}
/* 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] == '.') {
sp= rip->i_sp;
if (sp->s_imount != sp->s_isup)
{
/* Release the root inode. Replace by the
* inode mounted on. Update parent.
*/
put_inode(rip);
put_inode(dirp);
mnt_dev = sp->s_imount->i_dev;
inumb = (int) sp->s_imount->i_num;
dirp = *pdirp = get_inode(mnt_dev, inumb);
rip = advance(pdirp, string);
}
}
}
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, DELETE or IS_EMPTY */
{
/* 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 direct *dp = NULL;
register struct buf *bp = NULL;
int i, r, e_hit, t, match;
mode_t bits;
off_t pos;
unsigned new_slots, old_slots;
block_t b;
struct super_block *sp;
int extended = 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 r = forbidden(ldir_ptr, bits); /* check access permissions */
}
if (r != OK) return(r);
/* Step through the directory one block at a time. */
old_slots = (unsigned) (ldir_ptr->i_size/DIR_ENTRY_SIZE);
new_slots = 0;
e_hit = FALSE;
match = 0; /* set when a string match occurs */
for (pos = 0; 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 */
if (bp == NO_BLOCK)
panic(__FILE__,"get_block returned NO_BLOCK", NO_NUM);
/* Search a directory block. */
for (dp = &bp->b_dir[0];
dp < &bp->b_dir[NR_DIR_ENTRIES(ldir_ptr->i_sp->s_block_size)];
dp++) {
if (++new_slots > old_slots) { /* not found, but room left */
if (flag == ENTER) e_hit = TRUE;
break;
}
/* Match occurs if string found. */
if (flag != ENTER && dp->d_ino != 0) {
if (flag == IS_EMPTY) {
/* 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 == IS_EMPTY) r = ENOTEMPTY;
else if (flag == DELETE) {
/* Save d_ino for recovery. */
t = NAME_MAX - sizeof(ino_t);
*((ino_t *) &dp->d_name[t]) = dp->d_ino;
dp->d_ino = 0; /* erase entry */
bp->b_dirt = DIRTY;
ldir_ptr->i_update |= CTIME | MTIME;
ldir_ptr->i_dirt = DIRTY;
} else {
sp = ldir_ptr->i_sp; /* 'flag' is LOOK_UP */
*numb = conv4(sp->s_native, (int) 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 == 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(flag == IS_EMPTY ? OK : 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];
extended = 1;
}
/* 'bp' now points to a directory block with space. 'dp' points to slot. */
(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);
}
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