482 lines
16 KiB
C
482 lines
16 KiB
C
/* This file contains the procedures for creating, opening, closing, and
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* seeking on files.
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*
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* The entry points into this file are
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* do_creat: perform the CREAT system call
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* do_open: perform the OPEN system call
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* do_mknod: perform the MKNOD system call
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* do_mkdir: perform the MKDIR system call
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* do_close: perform the CLOSE system call
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* do_lseek: perform the LSEEK system call
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*/
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#include "fs.h"
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#include <sys/stat.h>
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#include <fcntl.h>
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#include <minix/callnr.h>
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#include <minix/com.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 "lock.h"
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#include "param.h"
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#include "super.h"
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#define offset m2_l1
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PRIVATE char mode_map[] = {R_BIT, W_BIT, R_BIT|W_BIT, 0};
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FORWARD _PROTOTYPE( int common_open, (int oflags, mode_t omode) );
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FORWARD _PROTOTYPE( int pipe_open, (struct inode *rip,mode_t bits,int oflags));
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FORWARD _PROTOTYPE( struct inode *new_node, (char *path, mode_t bits,
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zone_t z0) );
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/*===========================================================================*
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* do_creat *
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*===========================================================================*/
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PUBLIC int do_creat()
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{
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/* Perform the creat(name, mode) system call. */
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int r;
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if (fetch_name(m_in.name, m_in.name_length, M3) != OK) return(err_code);
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r = common_open(O_WRONLY | O_CREAT | O_TRUNC, (mode_t) m_in.mode);
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return(r);
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}
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/*===========================================================================*
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* do_open *
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*===========================================================================*/
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PUBLIC int do_open()
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{
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/* Perform the open(name, flags,...) system call. */
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int create_mode = 0; /* is really mode_t but this gives problems */
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int r;
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/* If O_CREAT is set, open has three parameters, otherwise two. */
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if (m_in.mode & O_CREAT) {
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create_mode = m_in.c_mode;
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r = fetch_name(m_in.c_name, m_in.name1_length, M1);
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} else {
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r = fetch_name(m_in.name, m_in.name_length, M3);
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}
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if (r != OK) return(err_code); /* name was bad */
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r = common_open(m_in.mode, create_mode);
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return(r);
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}
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/*===========================================================================*
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* common_open *
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*===========================================================================*/
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PRIVATE int common_open(register int oflags, mode_t omode)
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{
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/* Common code from do_creat and do_open. */
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register struct inode *rip;
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int r, b, exist = TRUE;
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dev_t dev;
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mode_t bits;
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off_t pos;
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struct filp *fil_ptr, *filp2;
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/* Remap the bottom two bits of oflags. */
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bits = (mode_t) mode_map[oflags & O_ACCMODE];
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/* See if file descriptor and filp slots are available. */
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if ( (r = get_fd(0, bits, &m_in.fd, &fil_ptr)) != OK) return(r);
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/* If O_CREATE is set, try to make the file. */
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if (oflags & O_CREAT) {
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/* Create a new inode by calling new_node(). */
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omode = I_REGULAR | (omode & ALL_MODES & fp->fp_umask);
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rip = new_node(user_path, omode, NO_ZONE);
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r = err_code;
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if (r == OK) exist = FALSE; /* we just created the file */
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else if (r != EEXIST) return(r); /* other error */
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else exist = !(oflags & O_EXCL); /* file exists, if the O_EXCL
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flag is set this is an error */
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} else {
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/* Scan path name. */
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if ( (rip = eat_path(user_path)) == NIL_INODE) return(err_code);
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}
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/* Claim the file descriptor and filp slot and fill them in. */
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fp->fp_filp[m_in.fd] = fil_ptr;
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fil_ptr->filp_count = 1;
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fil_ptr->filp_ino = rip;
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fil_ptr->filp_flags = oflags;
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/* Only do the normal open code if we didn't just create the file. */
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if (exist) {
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/* Check protections. */
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if ((r = forbidden(rip, bits)) == OK) {
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/* Opening reg. files directories and special files differ. */
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switch (rip->i_mode & I_TYPE) {
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case I_REGULAR:
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/* Truncate regular file if O_TRUNC. */
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if (oflags & O_TRUNC) {
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if ((r = forbidden(rip, W_BIT)) !=OK) break;
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truncate(rip);
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wipe_inode(rip);
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/* Send the inode from the inode cache to the
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* block cache, so it gets written on the next
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* cache flush.
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*/
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rw_inode(rip, WRITING);
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}
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break;
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case I_DIRECTORY:
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/* Directories may be read but not written. */
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r = (bits & W_BIT ? EISDIR : OK);
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break;
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case I_CHAR_SPECIAL:
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case I_BLOCK_SPECIAL:
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/* Invoke the driver for special processing. */
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dev = (dev_t) rip->i_zone[0];
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r = dev_open(dev, who, bits | (oflags & ~O_ACCMODE));
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break;
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case I_NAMED_PIPE:
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oflags |= O_APPEND; /* force append mode */
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fil_ptr->filp_flags = oflags;
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r = pipe_open(rip, bits, oflags);
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if (r != ENXIO) {
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/* See if someone else is doing a rd or wt on
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* the FIFO. If so, use its filp entry so the
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* file position will be automatically shared.
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*/
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b = (bits & R_BIT ? R_BIT : W_BIT);
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fil_ptr->filp_count = 0; /* don't find self */
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if ((filp2 = find_filp(rip, b)) != NIL_FILP) {
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/* Co-reader or writer found. Use it.*/
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fp->fp_filp[m_in.fd] = filp2;
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filp2->filp_count++;
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filp2->filp_ino = rip;
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filp2->filp_flags = oflags;
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/* i_count was incremented incorrectly
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* by eatpath above, not knowing that
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* we were going to use an existing
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* filp entry. Correct this error.
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*/
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rip->i_count--;
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} else {
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/* Nobody else found. Restore filp. */
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fil_ptr->filp_count = 1;
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if (b == R_BIT)
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pos = rip->i_zone[V2_NR_DZONES+0];
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else
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pos = rip->i_zone[V2_NR_DZONES+1];
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fil_ptr->filp_pos = pos;
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}
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}
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break;
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}
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}
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}
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/* If error, release inode. */
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if (r != OK) {
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if (r == SUSPEND) return(r); /* Oops, just suspended */
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fp->fp_filp[m_in.fd] = NIL_FILP;
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fil_ptr->filp_count= 0;
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put_inode(rip);
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return(r);
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}
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return(m_in.fd);
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}
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/*===========================================================================*
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* new_node *
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*===========================================================================*/
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PRIVATE struct inode *new_node(char *path, mode_t bits, zone_t z0)
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{
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/* New_node() is called by common_open(), do_mknod(), and do_mkdir().
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* In all cases it allocates a new inode, makes a directory entry for it on
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* the path 'path', and initializes it. It returns a pointer to the inode if
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* it can do this; otherwise it returns NIL_INODE. It always sets 'err_code'
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* to an appropriate value (OK or an error code).
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*/
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register struct inode *rlast_dir_ptr, *rip;
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register int r;
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char string[NAME_MAX];
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/* See if the path can be opened down to the last directory. */
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if ((rlast_dir_ptr = last_dir(path, string)) == NIL_INODE) return(NIL_INODE);
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/* The final directory is accessible. Get final component of the path. */
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rip = advance(rlast_dir_ptr, string);
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if ( rip == NIL_INODE && err_code == ENOENT) {
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/* Last path component does not exist. Make new directory entry. */
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if ( (rip = alloc_inode(rlast_dir_ptr->i_dev, bits)) == NIL_INODE) {
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/* Can't creat new inode: out of inodes. */
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put_inode(rlast_dir_ptr);
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return(NIL_INODE);
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}
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/* Force inode to the disk before making directory entry to make
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* the system more robust in the face of a crash: an inode with
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* no directory entry is much better than the opposite.
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*/
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rip->i_nlinks++;
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rip->i_zone[0] = z0; /* major/minor device numbers */
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rw_inode(rip, WRITING); /* force inode to disk now */
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/* New inode acquired. Try to make directory entry. */
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if ((r = search_dir(rlast_dir_ptr, string, &rip->i_num,ENTER)) != OK) {
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put_inode(rlast_dir_ptr);
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rip->i_nlinks--; /* pity, have to free disk inode */
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rip->i_dirt = DIRTY; /* dirty inodes are written out */
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put_inode(rip); /* this call frees the inode */
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err_code = r;
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return(NIL_INODE);
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}
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} else {
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/* Either last component exists, or there is some problem. */
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if (rip != NIL_INODE)
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r = EEXIST;
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else
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r = err_code;
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}
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/* Return the directory inode and exit. */
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put_inode(rlast_dir_ptr);
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err_code = r;
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return(rip);
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}
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/*===========================================================================*
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* pipe_open *
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*===========================================================================*/
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PRIVATE int pipe_open(register struct inode *rip, register mode_t bits,
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register int oflags)
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{
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/* This function is called from common_open. It checks if
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* there is at least one reader/writer pair for the pipe, if not
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* it suspends the caller, otherwise it revives all other blocked
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* processes hanging on the pipe.
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*/
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rip->i_pipe = I_PIPE;
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if (find_filp(rip, bits & W_BIT ? R_BIT : W_BIT) == NIL_FILP) {
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if (oflags & O_NONBLOCK) {
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if (bits & W_BIT) return(ENXIO);
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} else {
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suspend(XPOPEN); /* suspend caller */
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return(SUSPEND);
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}
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} else if (susp_count > 0) {/* revive blocked processes */
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release(rip, OPEN, susp_count);
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release(rip, CREAT, susp_count);
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}
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return(OK);
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}
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/*===========================================================================*
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* do_mknod *
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*===========================================================================*/
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PUBLIC int do_mknod()
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{
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/* Perform the mknod(name, mode, addr) system call. */
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register mode_t bits, mode_bits;
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struct inode *ip;
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/* Only the super_user may make nodes other than fifos. */
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mode_bits = (mode_t) m_in.mk_mode; /* mode of the inode */
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if (!super_user && ((mode_bits & I_TYPE) != I_NAMED_PIPE)) return(EPERM);
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if (fetch_name(m_in.name1, m_in.name1_length, M1) != OK) return(err_code);
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bits = (mode_bits & I_TYPE) | (mode_bits & ALL_MODES & fp->fp_umask);
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ip = new_node(user_path, bits, (zone_t) m_in.mk_z0);
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put_inode(ip);
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return(err_code);
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}
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/*===========================================================================*
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* do_mkdir *
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*===========================================================================*/
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PUBLIC int do_mkdir()
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{
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/* Perform the mkdir(name, mode) system call. */
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int r1, r2; /* status codes */
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ino_t dot, dotdot; /* inode numbers for . and .. */
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mode_t bits; /* mode bits for the new inode */
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char string[NAME_MAX]; /* last component of the new dir's path name */
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register struct inode *rip, *ldirp;
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/* Check to see if it is possible to make another link in the parent dir. */
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if (fetch_name(m_in.name1, m_in.name1_length, M1) != OK) return(err_code);
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ldirp = last_dir(user_path, string); /* pointer to new dir's parent */
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if (ldirp == NIL_INODE) return(err_code);
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if (ldirp->i_nlinks >= (ldirp->i_sp->s_version == V1 ? CHAR_MAX : SHRT_MAX)) {
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put_inode(ldirp); /* return parent */
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return(EMLINK);
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}
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/* Next make the inode. If that fails, return error code. */
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bits = I_DIRECTORY | (m_in.mode & RWX_MODES & fp->fp_umask);
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rip = new_node(user_path, bits, (zone_t) 0);
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if (rip == NIL_INODE || err_code == EEXIST) {
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put_inode(rip); /* can't make dir: it already exists */
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put_inode(ldirp); /* return parent too */
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return(err_code);
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}
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/* Get the inode numbers for . and .. to enter in the directory. */
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dotdot = ldirp->i_num; /* parent's inode number */
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dot = rip->i_num; /* inode number of the new dir itself */
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/* Now make dir entries for . and .. unless the disk is completely full. */
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/* Use dot1 and dot2, so the mode of the directory isn't important. */
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rip->i_mode = bits; /* set mode */
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r1 = search_dir(rip, dot1, &dot, ENTER); /* enter . in the new dir */
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r2 = search_dir(rip, dot2, &dotdot, ENTER); /* enter .. in the new dir */
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/* If both . and .. were successfully entered, increment the link counts. */
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if (r1 == OK && r2 == OK) {
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/* Normal case. It was possible to enter . and .. in the new dir. */
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rip->i_nlinks++; /* this accounts for . */
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ldirp->i_nlinks++; /* this accounts for .. */
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ldirp->i_dirt = DIRTY; /* mark parent's inode as dirty */
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} else {
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/* It was not possible to enter . or .. probably disk was full. */
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(void) search_dir(ldirp, string, (ino_t *) 0, DELETE);
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rip->i_nlinks--; /* undo the increment done in new_node() */
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}
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rip->i_dirt = DIRTY; /* either way, i_nlinks has changed */
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put_inode(ldirp); /* return the inode of the parent dir */
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put_inode(rip); /* return the inode of the newly made dir */
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return(err_code); /* new_node() always sets 'err_code' */
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}
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/*===========================================================================*
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* do_close *
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*===========================================================================*/
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PUBLIC int do_close()
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{
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/* Perform the close(fd) system call. */
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register struct filp *rfilp;
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register struct inode *rip;
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struct file_lock *flp;
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int rw, mode_word, lock_count;
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dev_t dev;
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/* First locate the inode that belongs to the file descriptor. */
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if ( (rfilp = get_filp(m_in.fd)) == NIL_FILP) return(err_code);
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rip = rfilp->filp_ino; /* 'rip' points to the inode */
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if (rfilp->filp_count - 1 == 0 && rfilp->filp_mode != FILP_CLOSED) {
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/* Check to see if the file is special. */
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mode_word = rip->i_mode & I_TYPE;
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if (mode_word == I_CHAR_SPECIAL || mode_word == I_BLOCK_SPECIAL) {
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dev = (dev_t) rip->i_zone[0];
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if (mode_word == I_BLOCK_SPECIAL) {
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/* Invalidate cache entries unless special is mounted
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* or ROOT
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*/
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if (!mounted(rip)) {
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(void) do_sync(); /* purge cache */
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invalidate(dev);
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}
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}
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/* Do any special processing on device close. */
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dev_close(dev);
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}
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}
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/* If the inode being closed is a pipe, release everyone hanging on it. */
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if (rip->i_pipe == I_PIPE) {
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rw = (rfilp->filp_mode & R_BIT ? WRITE : READ);
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release(rip, rw, NR_PROCS);
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}
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/* If a write has been done, the inode is already marked as DIRTY. */
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if (--rfilp->filp_count == 0) {
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if (rip->i_pipe == I_PIPE && rip->i_count > 1) {
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/* Save the file position in the i-node in case needed later.
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* The read and write positions are saved separately. The
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* last 3 zones in the i-node are not used for (named) pipes.
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*/
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if (rfilp->filp_mode == R_BIT)
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rip->i_zone[V2_NR_DZONES+0] = (zone_t) rfilp->filp_pos;
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else
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rip->i_zone[V2_NR_DZONES+1] = (zone_t) rfilp->filp_pos;
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}
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put_inode(rip);
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}
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fp->fp_cloexec &= ~(1L << m_in.fd); /* turn off close-on-exec bit */
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fp->fp_filp[m_in.fd] = NIL_FILP;
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/* Check to see if the file is locked. If so, release all locks. */
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if (nr_locks == 0) return(OK);
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lock_count = nr_locks; /* save count of locks */
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for (flp = &file_lock[0]; flp < &file_lock[NR_LOCKS]; flp++) {
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if (flp->lock_type == 0) continue; /* slot not in use */
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if (flp->lock_inode == rip && flp->lock_pid == fp->fp_pid) {
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flp->lock_type = 0;
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nr_locks--;
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}
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}
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if (nr_locks < lock_count) lock_revive(); /* lock released */
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return(OK);
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}
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/*===========================================================================*
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* do_lseek *
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*===========================================================================*/
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PUBLIC int do_lseek()
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{
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/* Perform the lseek(ls_fd, offset, whence) system call. */
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register struct filp *rfilp;
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register off_t pos;
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/* Check to see if the file descriptor is valid. */
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if ( (rfilp = get_filp(m_in.ls_fd)) == NIL_FILP) return(err_code);
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/* No lseek on pipes. */
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if (rfilp->filp_ino->i_pipe == I_PIPE) return(ESPIPE);
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/* The value of 'whence' determines the start position to use. */
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switch(m_in.whence) {
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case 0: pos = 0; break;
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case 1: pos = rfilp->filp_pos; break;
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case 2: pos = rfilp->filp_ino->i_size; break;
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default: return(EINVAL);
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}
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/* Check for overflow. */
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if (((long)m_in.offset > 0) && ((long)(pos + m_in.offset) < (long)pos))
|
|
return(EINVAL);
|
|
if (((long)m_in.offset < 0) && ((long)(pos + m_in.offset) > (long)pos))
|
|
return(EINVAL);
|
|
pos = pos + m_in.offset;
|
|
|
|
if (pos != rfilp->filp_pos)
|
|
rfilp->filp_ino->i_seek = ISEEK; /* inhibit read ahead */
|
|
rfilp->filp_pos = pos;
|
|
m_out.reply_l1 = pos; /* insert the long into the output message */
|
|
return(OK);
|
|
}
|