453 lines
15 KiB
C
453 lines
15 KiB
C
/* This file handles the LINK and UNLINK system calls. It also deals with
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* deallocating the storage used by a file when the last UNLINK is done to a
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* file and the blocks must be returned to the free block pool.
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*
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* The entry points into this file are
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* do_link: perform the LINK system call
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* do_unlink: perform the UNLINK and RMDIR system calls
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* do_rename: perform the RENAME system call
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* truncate: release all the blocks associated with an inode
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*/
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#include "fs.h"
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#include <sys/stat.h>
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#include <string.h>
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#include <minix/com.h>
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#include <minix/callnr.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 "param.h"
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#include "super.h"
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#define SAME 1000
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FORWARD _PROTOTYPE( int remove_dir, (struct inode *rldirp, struct inode *rip,
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char dir_name[NAME_MAX]) );
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FORWARD _PROTOTYPE( int unlink_file, (struct inode *dirp, struct inode *rip,
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char file_name[NAME_MAX]) );
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/*===========================================================================*
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* do_link *
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*===========================================================================*/
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PUBLIC int do_link()
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{
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/* Perform the link(name1, name2) system call. */
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register struct inode *ip, *rip;
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register int r;
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char string[NAME_MAX];
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struct inode *new_ip;
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/* See if 'name' (file to be linked) exists. */
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if (fetch_name(m_in.name1, m_in.name1_length, M1) != OK) return(err_code);
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if ( (rip = eat_path(user_path)) == NIL_INODE) return(err_code);
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/* Check to see if the file has maximum number of links already. */
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r = OK;
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if (rip->i_nlinks >= (rip->i_sp->s_version == V1 ? CHAR_MAX : SHRT_MAX))
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r = EMLINK;
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/* Only super_user may link to directories. */
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if (r == OK)
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if ( (rip->i_mode & I_TYPE) == I_DIRECTORY && !super_user) r = EPERM;
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/* If error with 'name', return the inode. */
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if (r != OK) {
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put_inode(rip);
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return(r);
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}
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/* Does the final directory of 'name2' exist? */
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if (fetch_name(m_in.name2, m_in.name2_length, M1) != OK) {
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put_inode(rip);
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return(err_code);
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}
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if ( (ip = last_dir(user_path, string)) == NIL_INODE) r = err_code;
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/* If 'name2' exists in full (even if no space) set 'r' to error. */
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if (r == OK) {
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if ( (new_ip = advance(ip, string)) == NIL_INODE) {
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r = err_code;
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if (r == ENOENT) r = OK;
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} else {
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put_inode(new_ip);
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r = EEXIST;
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}
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}
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/* Check for links across devices. */
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if (r == OK)
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if (rip->i_dev != ip->i_dev) r = EXDEV;
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/* Try to link. */
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if (r == OK)
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r = search_dir(ip, string, &rip->i_num, ENTER);
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/* If success, register the linking. */
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if (r == OK) {
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rip->i_nlinks++;
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rip->i_update |= CTIME;
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rip->i_dirt = DIRTY;
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}
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/* Done. Release both inodes. */
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put_inode(rip);
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put_inode(ip);
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return(r);
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}
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/*===========================================================================*
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* do_unlink *
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*===========================================================================*/
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PUBLIC int do_unlink()
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{
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/* Perform the unlink(name) or rmdir(name) system call. The code for these two
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* is almost the same. They differ only in some condition testing. Unlink()
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* may be used by the superuser to do dangerous things; rmdir() may not.
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*/
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register struct inode *rip;
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struct inode *rldirp;
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int r;
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char string[NAME_MAX];
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/* Get the last directory in the path. */
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if (fetch_name(m_in.name, m_in.name_length, M3) != OK) return(err_code);
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if ( (rldirp = last_dir(user_path, string)) == NIL_INODE)
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return(err_code);
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/* The last directory exists. Does the file also exist? */
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r = OK;
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if ( (rip = advance(rldirp, string)) == NIL_INODE) r = err_code;
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/* If error, return inode. */
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if (r != OK) {
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put_inode(rldirp);
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return(r);
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}
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/* Do not remove a mount point. */
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if (rip->i_num == ROOT_INODE) {
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put_inode(rldirp);
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put_inode(rip);
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return(EBUSY);
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}
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/* Now test if the call is allowed, separately for unlink() and rmdir(). */
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if (call_nr == UNLINK) {
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/* Only the su may unlink directories, but the su can unlink any dir.*/
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if ( (rip->i_mode & I_TYPE) == I_DIRECTORY && !super_user) r = EPERM;
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/* Don't unlink a file if it is the root of a mounted file system. */
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if (rip->i_num == ROOT_INODE) r = EBUSY;
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/* Actually try to unlink the file; fails if parent is mode 0 etc. */
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if (r == OK) r = unlink_file(rldirp, rip, string);
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} else {
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r = remove_dir(rldirp, rip, string); /* call is RMDIR */
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}
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/* If unlink was possible, it has been done, otherwise it has not. */
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put_inode(rip);
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put_inode(rldirp);
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return(r);
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}
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/*===========================================================================*
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* do_rename *
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*===========================================================================*/
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PUBLIC int do_rename()
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{
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/* Perform the rename(name1, name2) system call. */
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struct inode *old_dirp, *old_ip; /* ptrs to old dir, file inodes */
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struct inode *new_dirp, *new_ip; /* ptrs to new dir, file inodes */
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struct inode *new_superdirp, *next_new_superdirp;
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int r = OK; /* error flag; initially no error */
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int odir, ndir; /* TRUE iff {old|new} file is dir */
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int same_pdir; /* TRUE iff parent dirs are the same */
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char old_name[NAME_MAX], new_name[NAME_MAX];
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ino_t numb;
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int r1;
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/* See if 'name1' (existing file) exists. Get dir and file inodes. */
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if (fetch_name(m_in.name1, m_in.name1_length, M1) != OK) return(err_code);
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if ( (old_dirp = last_dir(user_path, old_name))==NIL_INODE) return(err_code);
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if ( (old_ip = advance(old_dirp, old_name)) == NIL_INODE) r = err_code;
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/* See if 'name2' (new name) exists. Get dir and file inodes. */
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if (fetch_name(m_in.name2, m_in.name2_length, M1) != OK) r = err_code;
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if ( (new_dirp = last_dir(user_path, new_name)) == NIL_INODE) r = err_code;
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new_ip = advance(new_dirp, new_name); /* not required to exist */
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if (old_ip != NIL_INODE)
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odir = ((old_ip->i_mode & I_TYPE) == I_DIRECTORY); /* TRUE iff dir */
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/* If it is ok, check for a variety of possible errors. */
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if (r == OK) {
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same_pdir = (old_dirp == new_dirp);
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/* The old inode must not be a superdirectory of the new last dir. */
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if (odir && !same_pdir) {
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dup_inode(new_superdirp = new_dirp);
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while (TRUE) { /* may hang in a file system loop */
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if (new_superdirp == old_ip) {
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r = EINVAL;
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break;
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}
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next_new_superdirp = advance(new_superdirp, dot2);
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put_inode(new_superdirp);
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if (next_new_superdirp == new_superdirp)
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break; /* back at system root directory */
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new_superdirp = next_new_superdirp;
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if (new_superdirp == NIL_INODE) {
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/* Missing ".." entry. Assume the worst. */
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r = EINVAL;
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break;
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}
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}
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put_inode(new_superdirp);
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}
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/* The old or new name must not be . or .. */
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if (strcmp(old_name, ".")==0 || strcmp(old_name, "..")==0 ||
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strcmp(new_name, ".")==0 || strcmp(new_name, "..")==0) r = EINVAL;
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/* Both parent directories must be on the same device. */
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if (old_dirp->i_dev != new_dirp->i_dev) r = EXDEV;
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/* Parent dirs must be writable, searchable and on a writable device */
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if ((r1 = forbidden(old_dirp, W_BIT | X_BIT)) != OK ||
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(r1 = forbidden(new_dirp, W_BIT | X_BIT)) != OK) r = r1;
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/* Some tests apply only if the new path exists. */
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if (new_ip == NIL_INODE) {
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/* don't rename a file with a file system mounted on it. */
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if (old_ip->i_dev != old_dirp->i_dev) r = EXDEV;
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if (odir && new_dirp->i_nlinks >=
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(new_dirp->i_sp->s_version == V1 ? CHAR_MAX : SHRT_MAX) &&
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!same_pdir && r == OK) r = EMLINK;
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} else {
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if (old_ip == new_ip) r = SAME; /* old=new */
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/* has the old file or new file a file system mounted on it? */
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if (old_ip->i_dev != new_ip->i_dev) r = EXDEV;
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ndir = ((new_ip->i_mode & I_TYPE) == I_DIRECTORY); /* dir ? */
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if (odir == TRUE && ndir == FALSE) r = ENOTDIR;
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if (odir == FALSE && ndir == TRUE) r = EISDIR;
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}
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}
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/* If a process has another root directory than the system root, we might
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* "accidently" be moving it's working directory to a place where it's
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* root directory isn't a super directory of it anymore. This can make
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* the function chroot useless. If chroot will be used often we should
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* probably check for it here.
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*/
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/* The rename will probably work. Only two things can go wrong now:
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* 1. being unable to remove the new file. (when new file already exists)
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* 2. being unable to make the new directory entry. (new file doesn't exists)
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* [directory has to grow by one block and cannot because the disk
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* is completely full].
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*/
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if (r == OK) {
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if (new_ip != NIL_INODE) {
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/* There is already an entry for 'new'. Try to remove it. */
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if (odir)
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r = remove_dir(new_dirp, new_ip, new_name);
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else
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r = unlink_file(new_dirp, new_ip, new_name);
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}
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/* if r is OK, the rename will succeed, while there is now an
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* unused entry in the new parent directory.
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*/
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}
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if (r == OK) {
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/* If the new name will be in the same parent directory as the old one,
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* first remove the old name to free an entry for the new name,
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* otherwise first try to create the new name entry to make sure
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* the rename will succeed.
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*/
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numb = old_ip->i_num; /* inode number of old file */
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if (same_pdir) {
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r = search_dir(old_dirp, old_name, (ino_t *) 0, DELETE);
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/* shouldn't go wrong. */
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if (r==OK) (void) search_dir(old_dirp, new_name, &numb, ENTER);
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} else {
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r = search_dir(new_dirp, new_name, &numb, ENTER);
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if (r == OK)
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(void) search_dir(old_dirp, old_name, (ino_t *) 0, DELETE);
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}
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}
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/* If r is OK, the ctime and mtime of old_dirp and new_dirp have been marked
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* for update in search_dir.
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*/
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if (r == OK && odir && !same_pdir) {
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/* Update the .. entry in the directory (still points to old_dirp). */
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numb = new_dirp->i_num;
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(void) unlink_file(old_ip, NIL_INODE, dot2);
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if (search_dir(old_ip, dot2, &numb, ENTER) == OK) {
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/* New link created. */
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new_dirp->i_nlinks++;
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new_dirp->i_dirt = DIRTY;
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}
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}
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/* Release the inodes. */
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put_inode(old_dirp);
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put_inode(old_ip);
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put_inode(new_dirp);
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put_inode(new_ip);
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return(r == SAME ? OK : r);
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}
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/*===========================================================================*
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* truncate *
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*===========================================================================*/
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PUBLIC void truncate(rip)
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register struct inode *rip; /* pointer to inode to be truncated */
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{
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/* Remove all the zones from the inode 'rip' and mark it dirty. */
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register block_t b;
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zone_t z, zone_size, z1;
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off_t position;
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int i, scale, file_type, waspipe, single, nr_indirects;
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struct buf *bp;
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dev_t dev;
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file_type = rip->i_mode & I_TYPE; /* check to see if file is special */
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if (file_type == I_CHAR_SPECIAL || file_type == I_BLOCK_SPECIAL) return;
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dev = rip->i_dev; /* device on which inode resides */
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scale = rip->i_sp->s_log_zone_size;
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zone_size = (zone_t) rip->i_sp->s_block_size << scale;
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nr_indirects = rip->i_nindirs;
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/* Pipes can shrink, so adjust size to make sure all zones are removed. */
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waspipe = rip->i_pipe == I_PIPE; /* TRUE is this was a pipe */
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if (waspipe) rip->i_size = PIPE_SIZE(rip->i_sp->s_block_size);
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/* Step through the file a zone at a time, finding and freeing the zones. */
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for (position = 0; position < rip->i_size; position += zone_size) {
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if ( (b = read_map(rip, position)) != NO_BLOCK) {
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z = (zone_t) b >> scale;
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free_zone(dev, z);
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}
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}
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/* All the data zones have been freed. Now free the indirect zones. */
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rip->i_dirt = DIRTY;
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if (waspipe) {
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wipe_inode(rip); /* clear out inode for pipes */
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return; /* indirect slots contain file positions */
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}
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single = rip->i_ndzones;
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free_zone(dev, rip->i_zone[single]); /* single indirect zone */
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if ( (z = rip->i_zone[single+1]) != NO_ZONE) {
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/* Free all the single indirect zones pointed to by the double. */
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b = (block_t) z << scale;
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bp = get_block(dev, b, NORMAL); /* get double indirect zone */
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for (i = 0; i < nr_indirects; i++) {
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z1 = rd_indir(bp, i);
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free_zone(dev, z1);
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}
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/* Now free the double indirect zone itself. */
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put_block(bp, INDIRECT_BLOCK);
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free_zone(dev, z);
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}
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/* Leave zone numbers for de(1) to recover file after an unlink(2). */
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}
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/*===========================================================================*
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* remove_dir *
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*===========================================================================*/
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PRIVATE int remove_dir(rldirp, rip, dir_name)
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struct inode *rldirp; /* parent directory */
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struct inode *rip; /* directory to be removed */
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char dir_name[NAME_MAX]; /* name of directory to be removed */
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{
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/* A directory file has to be removed. Five conditions have to met:
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* - The file must be a directory
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* - The directory must be empty (except for . and ..)
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* - The final component of the path must not be . or ..
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* - The directory must not be the root of a mounted file system
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* - The directory must not be anybody's root/working directory
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*/
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int r;
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register struct fproc *rfp;
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/* search_dir checks that rip is a directory too. */
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if ((r = search_dir(rip, "", (ino_t *) 0, IS_EMPTY)) != OK) return r;
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if (strcmp(dir_name, ".") == 0 || strcmp(dir_name, "..") == 0)return(EINVAL);
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if (rip->i_num == ROOT_INODE) return(EBUSY); /* can't remove 'root' */
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for (rfp = &fproc[INIT_PROC_NR + 1]; rfp < &fproc[NR_PROCS]; rfp++)
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if (rfp->fp_workdir == rip || rfp->fp_rootdir == rip) return(EBUSY);
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/* can't remove anybody's working dir */
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/* Actually try to unlink the file; fails if parent is mode 0 etc. */
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if ((r = unlink_file(rldirp, rip, dir_name)) != OK) return r;
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/* Unlink . and .. from the dir. The super user can link and unlink any dir,
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* so don't make too many assumptions about them.
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*/
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(void) unlink_file(rip, NIL_INODE, dot1);
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(void) unlink_file(rip, NIL_INODE, dot2);
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return(OK);
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}
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/*===========================================================================*
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* unlink_file *
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*===========================================================================*/
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PRIVATE int unlink_file(dirp, rip, file_name)
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struct inode *dirp; /* parent directory of file */
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struct inode *rip; /* inode of file, may be NIL_INODE too. */
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char file_name[NAME_MAX]; /* name of file to be removed */
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{
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/* Unlink 'file_name'; rip must be the inode of 'file_name' or NIL_INODE. */
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ino_t numb; /* inode number */
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int r;
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/* If rip is not NIL_INODE, it is used to get faster access to the inode. */
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if (rip == NIL_INODE) {
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/* Search for file in directory and try to get its inode. */
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err_code = search_dir(dirp, file_name, &numb, LOOK_UP);
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if (err_code == OK) rip = get_inode(dirp->i_dev, (int) numb);
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if (err_code != OK || rip == NIL_INODE) return(err_code);
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} else {
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dup_inode(rip); /* inode will be returned with put_inode */
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}
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r = search_dir(dirp, file_name, (ino_t *) 0, DELETE);
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if (r == OK) {
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rip->i_nlinks--; /* entry deleted from parent's dir */
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rip->i_update |= CTIME;
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rip->i_dirt = DIRTY;
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}
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put_inode(rip);
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return(r);
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}
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