Minix2.0/src/fs/link.c
/* This file handles the LINK and UNLINK system calls. It also deals with
* deallocating the storage used by a file when the last UNLINK is done to a
* file and the blocks must be returned to the free block pool.
*
* The entry points into this file are
* do_link: perform the LINK system call
* do_unlink: perform the UNLINK and RMDIR system calls
* do_rename: perform the RENAME system call
* truncate: release all the blocks associated with an inode
*/
#include "fs.h"
#include <sys/stat.h>
#include <string.h>
#include <minix/callnr.h>
#include "buf.h"
#include "file.h"
#include "fproc.h"
#include "inode.h"
#include "param.h"
#include "super.h"
#define SAME 1000
FORWARD _PROTOTYPE( int remove_dir, (struct inode *rldirp, struct inode *rip,
char dir_name[NAME_MAX]) );
FORWARD _PROTOTYPE( int unlink_file, (struct inode *dirp, struct inode *rip,
char file_name[NAME_MAX]) );
/*===========================================================================*
* do_link *
*===========================================================================*/
PUBLIC int do_link()
{
/* Perform the link(name1, name2) system call. */
register struct inode *ip, *rip;
register int r;
char string[NAME_MAX];
struct inode *new_ip;
/* See if 'name' (file to be linked) exists. */
if (fetch_name(name1, name1_length, M1) != OK) return(err_code);
if ( (rip = eat_path(user_path)) == NIL_INODE) return(err_code);
/* Check to see if the file has maximum number of links already. */
r = OK;
if ( (rip->i_nlinks & BYTE) >= LINK_MAX) r = EMLINK;
/* Only super_user may link to directories. */
if (r == OK)
if ( (rip->i_mode & I_TYPE) == I_DIRECTORY && !super_user) r = EPERM;
/* If error with 'name', return the inode. */
if (r != OK) {
put_inode(rip);
return(r);
}
/* Does the final directory of 'name2' exist? */
if (fetch_name(name2, name2_length, M1) != OK) {
put_inode(rip);
return(err_code);
}
if ( (ip = last_dir(user_path, string)) == NIL_INODE) r = err_code;
/* If 'name2' exists in full (even if no space) set 'r' to error. */
if (r == OK) {
if ( (new_ip = advance(ip, string)) == NIL_INODE) {
r = err_code;
if (r == ENOENT) r = OK;
} else {
put_inode(new_ip);
r = EEXIST;
}
}
/* Check for links across devices. */
if (r == OK)
if (rip->i_dev != ip->i_dev) r = EXDEV;
/* Try to link. */
if (r == OK)
r = search_dir(ip, string, &rip->i_num, ENTER);
/* If success, register the linking. */
if (r == OK) {
rip->i_nlinks++;
rip->i_update |= CTIME;
rip->i_dirt = DIRTY;
}
/* Done. Release both inodes. */
put_inode(rip);
put_inode(ip);
return(r);
}
/*===========================================================================*
* do_unlink *
*===========================================================================*/
PUBLIC int do_unlink()
{
/* Perform the unlink(name) or rmdir(name) system call. The code for these two
* is almost the same. They differ only in some condition testing. Unlink()
* may be used by the superuser to do dangerous things; rmdir() may not.
*/
register struct inode *rip;
struct inode *rldirp;
int r;
char string[NAME_MAX];
/* Get the last directory in the path. */
if (fetch_name(name, name_length, M3) != OK) return(err_code);
if ( (rldirp = last_dir(user_path, string)) == NIL_INODE)
return(err_code);
/* The last directory exists. Does the file also exist? */
r = OK;
if ( (rip = advance(rldirp, string)) == NIL_INODE) r = err_code;
/* If error, return inode. */
if (r != OK) {
put_inode(rldirp);
return(r);
}
/* Do not remove a mount point. */
if (rip->i_num == ROOT_INODE) {
put_inode(rldirp);
put_inode(rip);
return(EBUSY);
}
/* Now test if the call is allowed, separately for unlink() and rmdir(). */
if (fs_call == UNLINK) {
/* Only the su may unlink directories, but the su can unlink any dir.*/
if ( (rip->i_mode & I_TYPE) == I_DIRECTORY && !super_user) r = EPERM;
/* Don't unlink a file if it is the root of a mounted file system. */
if (rip->i_num == ROOT_INODE) r = EBUSY;
/* Actually try to unlink the file; fails if parent is mode 0 etc. */
if (r == OK) r = unlink_file(rldirp, rip, string);
} else {
r = remove_dir(rldirp, rip, string); /* call is RMDIR */
}
/* If unlink was possible, it has been done, otherwise it has not. */
put_inode(rip);
put_inode(rldirp);
return(r);
}
/*===========================================================================*
* do_rename *
*===========================================================================*/
PUBLIC int do_rename()
{
/* Perform the rename(name1, name2) system call. */
struct inode *old_dirp, *old_ip; /* ptrs to old dir, file inodes */
struct inode *new_dirp, *new_ip; /* ptrs to new dir, file inodes */
struct inode *new_superdirp, *next_new_superdirp;
int r = OK; /* error flag; initially no error */
int odir, ndir; /* TRUE iff {old|new} file is dir */
int same_pdir; /* TRUE iff parent dirs are the same */
char old_name[NAME_MAX], new_name[NAME_MAX];
ino_t numb;
int r1;
/* See if 'name1' (existing file) exists. Get dir and file inodes. */
if (fetch_name(name1, name1_length, M1) != OK) return(err_code);
if ( (old_dirp = last_dir(user_path, old_name))==NIL_INODE) return(err_code);
if ( (old_ip = advance(old_dirp, old_name)) == NIL_INODE) r = err_code;
/* See if 'name2' (new name) exists. Get dir and file inodes. */
if (fetch_name(name2, name2_length, M1) != OK) r = err_code;
if ( (new_dirp = last_dir(user_path, new_name)) == NIL_INODE) r = err_code;
new_ip = advance(new_dirp, new_name); /* not required to exist */
if (old_ip != NIL_INODE)
odir = ((old_ip->i_mode & I_TYPE) == I_DIRECTORY); /* TRUE iff dir */
/* If it is ok, check for a variety of possible errors. */
if (r == OK) {
same_pdir = (old_dirp == new_dirp);
/* The old inode must not be a superdirectory of the new last dir. */
if (odir && !same_pdir) {
dup_inode(new_superdirp = new_dirp);
while (TRUE) { /* may hang in a file system loop */
if (new_superdirp == old_ip) {
r = EINVAL;
break;
}
next_new_superdirp = advance(new_superdirp, dot2);
put_inode(new_superdirp);
if (next_new_superdirp == new_superdirp)
break; /* back at system root directory */
new_superdirp = next_new_superdirp;
if (new_superdirp == NIL_INODE) {
/* Missing ".." entry. Assume the worst. */
r = EINVAL;
break;
}
}
put_inode(new_superdirp);
}
/* The old or new name must not be . or .. */
if (strcmp(old_name, ".")==0 || strcmp(old_name, "..")==0 ||
strcmp(new_name, ".")==0 || strcmp(new_name, "..")==0) r = EINVAL;
/* Both parent directories must be on the same device. */
if (old_dirp->i_dev != new_dirp->i_dev) r = EXDEV;
/* Parent dirs must be writable, searchable and on a writable device */
if ((r1 = forbidden(old_dirp, W_BIT | X_BIT)) != OK ||
(r1 = forbidden(new_dirp, W_BIT | X_BIT)) != OK) r = r1;
/* Some tests apply only if the new path exists. */
if (new_ip == NIL_INODE) {
/* don't rename a file with a file system mounted on it. */
if (old_ip->i_dev != old_dirp->i_dev) r = EXDEV;
if (odir && (new_dirp->i_nlinks & BYTE) >= LINK_MAX &&
!same_pdir && r == OK) r = EMLINK;
} else {
if (old_ip == new_ip) r = SAME; /* old=new */
/* has the old file or new file a file system mounted on it? */
if (old_ip->i_dev != new_ip->i_dev) r = EXDEV;
ndir = ((new_ip->i_mode & I_TYPE) == I_DIRECTORY); /* dir ? */
if (odir == TRUE && ndir == FALSE) r = ENOTDIR;
if (odir == FALSE && ndir == TRUE) r = EISDIR;
}
}
/* If a process has another root directory than the system root, we might
* "accidently" be moving it's working directory to a place where it's
* root directory isn't a super directory of it anymore. This can make
* the function chroot useless. If chroot will be used often we should
* probably check for it here.
*/
/* The rename will probably work. Only two things can go wrong now:
* 1. being unable to remove the new file. (when new file already exists)
* 2. being unable to make the new directory entry. (new file doesn't exists)
* [directory has to grow by one block and cannot because the disk
* is completely full].
*/
if (r == OK) {
if (new_ip != NIL_INODE) {
/* There is already an entry for 'new'. Try to remove it. */
if (odir)
r = remove_dir(new_dirp, new_ip, new_name);
else
r = unlink_file(new_dirp, new_ip, new_name);
}
/* if r is OK, the rename will succeed, while there is now an
* unused entry in the new parent directory.
*/
}
if (r == OK) {
/* If the new name will be in the same parent directory as the old one,
* first remove the old name to free an entry for the new name,
* otherwise first try to create the new name entry to make sure
* the rename will succeed.
*/
numb = old_ip->i_num; /* inode number of old file */
if (same_pdir) {
r = search_dir(old_dirp, old_name, (ino_t *) 0, DELETE);
/* shouldn't go wrong. */
if (r==OK) (void) search_dir(old_dirp, new_name, &numb, ENTER);
} else {
r = search_dir(new_dirp, new_name, &numb, ENTER);
if (r == OK)
(void) search_dir(old_dirp, old_name, (ino_t *) 0, DELETE);
}
}
/* If r is OK, the ctime and mtime of old_dirp and new_dirp have been marked
* for update in search_dir.
*/
if (r == OK && odir && !same_pdir) {
/* Update the .. entry in the directory (still points to old_dirp). */
numb = new_dirp->i_num;
(void) unlink_file(old_ip, NIL_INODE, dot2);
if (search_dir(old_ip, dot2, &numb, ENTER) == OK) {
/* New link created. */
new_dirp->i_nlinks++;
new_dirp->i_dirt = DIRTY;
}
}
/* Release the inodes. */
put_inode(old_dirp);
put_inode(old_ip);
put_inode(new_dirp);
put_inode(new_ip);
return(r == SAME ? OK : r);
}
/*===========================================================================*
* truncate *
*===========================================================================*/
PUBLIC void truncate(rip)
register struct inode *rip; /* pointer to inode to be truncated */
{
/* Remove all the zones from the inode 'rip' and mark it dirty. */
register block_t b;
zone_t z, zone_size, z1;
off_t position;
int i, scale, file_type, waspipe, single, nr_indirects;
struct buf *bp;
dev_t dev;
file_type = rip->i_mode & I_TYPE; /* check to see if file is special */
if (file_type == I_CHAR_SPECIAL || file_type == I_BLOCK_SPECIAL) return;
dev = rip->i_dev; /* device on which inode resides */
scale = rip->i_sp->s_log_zone_size;
zone_size = (zone_t) BLOCK_SIZE << scale;
nr_indirects = rip->i_nindirs;
/* Pipes can shrink, so adjust size to make sure all zones are removed. */
waspipe = rip->i_pipe == I_PIPE; /* TRUE is this was a pipe */
if (waspipe) rip->i_size = PIPE_SIZE;
/* Step through the file a zone at a time, finding and freeing the zones. */
for (position = 0; position < rip->i_size; position += zone_size) {
if ( (b = read_map(rip, position)) != NO_BLOCK) {
z = (zone_t) b >> scale;
free_zone(dev, z);
}
}
/* All the data zones have been freed. Now free the indirect zones. */
rip->i_dirt = DIRTY;
if (waspipe) {
wipe_inode(rip); /* clear out inode for pipes */
return; /* indirect slots contain file positions */
}
single = rip->i_ndzones;
free_zone(dev, rip->i_zone[single]); /* single indirect zone */
if ( (z = rip->i_zone[single+1]) != NO_ZONE) {
/* Free all the single indirect zones pointed to by the double. */
b = (block_t) z << scale;
bp = get_block(dev, b, NORMAL); /* get double indirect zone */
for (i = 0; i < nr_indirects; i++) {
z1 = rd_indir(bp, i);
free_zone(dev, z1);
}
/* Now free the double indirect zone itself. */
put_block(bp, INDIRECT_BLOCK);
free_zone(dev, z);
}
/* Leave zone numbers for de(1) to recover file after an unlink(2). */
}
/*===========================================================================*
* remove_dir *
*===========================================================================*/
PRIVATE int remove_dir(rldirp, rip, dir_name)
struct inode *rldirp; /* parent directory */
struct inode *rip; /* directory to be removed */
char dir_name[NAME_MAX]; /* name of directory to be removed */
{
/* A directory file has to be removed. Five conditions have to met:
* - The file must be a directory
* - The directory must be empty (except for . and ..)
* - The final component of the path must not be . or ..
* - The directory must not be the root of a mounted file system
* - The directory must not be anybody's root/working directory
*/
int r;
register struct fproc *rfp;
/* search_dir checks that rip is a directory too. */
if ((r = search_dir(rip, "", (ino_t *) 0, IS_EMPTY)) != OK) return r;
if (strcmp(dir_name, ".") == 0 || strcmp(dir_name, "..") == 0)return(EINVAL);
if (rip->i_num == ROOT_INODE) return(EBUSY); /* can't remove 'root' */
for (rfp = &fproc[INIT_PROC_NR + 1]; rfp < &fproc[NR_PROCS]; rfp++)
if (rfp->fp_workdir == rip || rfp->fp_rootdir == rip) return(EBUSY);
/* can't remove anybody's working dir */
/* Actually try to unlink the file; fails if parent is mode 0 etc. */
if ((r = unlink_file(rldirp, rip, dir_name)) != OK) return r;
/* Unlink . and .. from the dir. The super user can link and unlink any dir,
* so don't make too many assumptions about them.
*/
(void) unlink_file(rip, NIL_INODE, dot1);
(void) unlink_file(rip, NIL_INODE, dot2);
return(OK);
}
/*===========================================================================*
* unlink_file *
*===========================================================================*/
PRIVATE int unlink_file(dirp, rip, file_name)
struct inode *dirp; /* parent directory of file */
struct inode *rip; /* inode of file, may be NIL_INODE too. */
char file_name[NAME_MAX]; /* name of file to be removed */
{
/* Unlink 'file_name'; rip must be the inode of 'file_name' or NIL_INODE. */
ino_t numb; /* inode number */
int r;
/* If rip is not NIL_INODE, it is used to get faster access to the inode. */
if (rip == NIL_INODE) {
/* Search for file in directory and try to get its inode. */
err_code = search_dir(dirp, file_name, &numb, LOOK_UP);
if (err_code == OK) rip = get_inode(dirp->i_dev, (int) numb);
if (err_code != OK || rip == NIL_INODE) return(err_code);
} else {
dup_inode(rip); /* inode will be returned with put_inode */
}
r = search_dir(dirp, file_name, (ino_t *) 0, DELETE);
if (r == OK) {
rip->i_nlinks--; /* entry deleted from parent's dir */
rip->i_update |= CTIME;
rip->i_dirt = DIRTY;
}
put_inode(rip);
return(r);
}