Minix1.5/fs/open.c
/* This file contains the procedures for creating, opening, closing, and
* seeking on files.
*
* The entry points into this file are
* do_creat: perform the CREAT system call
* do_mknod: perform the MKNOD system call
* do_open: perform the OPEN system call
* do_close: perform the CLOSE system call
* do_lseek: perform the LSEEK system call
* do_mkdir: perform the MKDIR system call
*/
#include "fs.h"
#include <minix/callnr.h>
#include <sys/stat.h>
#include <fcntl.h>
#include "buf.h"
#include "file.h"
#include "fproc.h"
#include "inode.h"
#include "param.h"
PRIVATE char mode_map[] = {R_BIT, W_BIT, R_BIT|W_BIT, 0};
PRIVATE char dot1[NAME_MAX] = ".\0\0\0\0\0\0\0\0\0\0\0\0";
PRIVATE char dot2[NAME_MAX] = "..\0\0\0\0\0\0\0\0\0\0\0";
FORWARD int common_open();
FORWARD struct inode *new_node();
FORWARD int pipe_open();
/*===========================================================================*
* do_creat *
*===========================================================================*/
PUBLIC int do_creat()
{
/* Perform the creat(name, mode) system call. */
/* get name */
if (fetch_name(name, name_length, M3) != OK) return(err_code);
return common_open(O_WRONLY | O_CREAT | O_TRUNC, (mode_t) mode);
}
/*===========================================================================*
* do_mknod *
*===========================================================================*/
PUBLIC int do_mknod()
{
/* Perform the mknod(name, mode, addr) system call. */
register mode_t bits;
unsigned int size;
/* Only the super_user may make nodes other than fifos. */
if (!super_user && ((mode & I_TYPE) != I_NAMED_PIPE)) return(EPERM);
if (fetch_name(name1, name1_length, M1) != OK) return(err_code);
bits = (mode & I_TYPE) | (mode & ALL_MODES & fp->fp_umask);
size = (unsigned int) name2;
put_inode(new_node(user_path, bits, (zone_nr) addr), (off_t)size*BLOCK_SIZE);
return(err_code);
}
/*===========================================================================*
* new_node *
*===========================================================================*/
PRIVATE struct inode *new_node(path, bits, z0, lsize)
char *path; /* pointer to path name */
mode_t bits; /* mode of the new inode */
zone_nr z0; /* zone number 0 for new inode */
off_t lsize; /* size of the special file */
{
/* New_node() is called by common_open(), do_mknod(), and do_mkdir().
* In all cases it allocates a new inode, makes a directory entry for it on
* the path 'path', and initializes it. It returns a pointer to the inode if
* it can do this; otherwise it returns NIL_INODE. It always sets 'err_code'
* to an appropriate value (OK or an error code).
*/
register struct inode *rlast_dir_ptr, *rip;
register int r;
char string[NAME_MAX];
/* See if the path can be opened down to the last directory. */
if ((rlast_dir_ptr = last_dir(path, string)) == NIL_INODE) return(NIL_INODE);
/* The final directory is accessible. Get final component of the path. */
rip = advance(rlast_dir_ptr, string);
if ( rip == NIL_INODE && err_code == ENOENT) {
/* Last path component does not exist. Make new directory entry. */
if ( (rip = alloc_inode(rlast_dir_ptr->i_dev, bits)) == NIL_INODE) {
/* Can't creat new inode: out of inodes. */
put_inode(rlast_dir_ptr);
return(NIL_INODE);
}
/* Force inode to the disk before making directory entry to make
* the system more robust in the face of a crash: an inode with
* no directory entry is much better than the opposite.
*/
rip->i_nlinks++;
rip->i_zone[0] = z0; /* major/minor device numbers */
rip->i_size = lsize; /* size (needed for block specials) */
rw_inode(rip, WRITING); /* force inode to disk now */
/* New inode acquired. Try to make directory entry. */
if ((r = search_dir(rlast_dir_ptr, string, &rip->i_num,ENTER)) != OK) {
put_inode(rlast_dir_ptr);
rip->i_nlinks--; /* pity, have to free disk inode */
rip->i_dirt = DIRTY; /* dirty inodes are written out */
put_inode(rip); /* this call frees the inode */
err_code = r;
return(NIL_INODE);
}
} else {
/* Either last component exists, or there is some problem. */
if (rip != NIL_INODE)
r = EEXIST;
else
r = err_code;
}
/* Return the directory inode and exit. */
put_inode(rlast_dir_ptr);
err_code = r;
return(rip);
}
/*===========================================================================*
* do_open *
*===========================================================================*/
PUBLIC int do_open()
{
/* Perform the open(name, flags,...) system call. */
int create_mode = 0;
int r;
/* If O_CREAT is set, open has three parameters, otherwise two. */
if (mode & O_CREAT) {
create_mode = c_mode;
r = fetch_name(c_name, name1_length, M1);
} else {
r = fetch_name(name, name_length, M3);
}
if (r != OK) return(err_code); /* name was bad */
return common_open(mode, (mode_t) create_mode);
}
/*===========================================================================*
* common_open *
*===========================================================================*/
PRIVATE int common_open(oflags, omode)
register int oflags;
mode_t omode;
{
/* Common code from do_creat and do_open. */
register struct inode *rip;
register int r;
register mode_t bits;
struct filp *fil_ptr;
dev_t dev;
int nonblocking, exist = TRUE;
/* Remap the bottom two bits of oflags. */
bits = (mode_t) mode_map[oflags & O_ACCMODE];
/* See if file descriptor and filp slots are available. */
if ( (r = get_fd(0, bits, &fd, &fil_ptr)) != OK) return(r);
/* If O_CREATE is set, try to make the file. */
if (oflags & O_CREAT) {
/* Create a new inode by calling new_node(). */
omode = I_REGULAR | (omode & ALL_MODES & fp->fp_umask);
rip = new_node(user_path, omode, NO_ZONE, (off_t) 0);
r = err_code;
if (r == OK) exist = FALSE; /* we just created the file */
else if (r != EEXIST) return(r); /* other error */
else exist = !(oflags & O_EXCL); /* file exists, if the O_EXCL
flag is set this is an error */
} else {
/* Scan path name. */
if ( (rip = eat_path(user_path)) == NIL_INODE) return(err_code);
}
/* Only do the normal open code if we didn't just create the file. */
if (exist) {
#if 0 /* I doubt this, but what does POSIX say?
* I fixed the test anyway, to go with fixing the O_TRUNC test.
* BDE
*/
/* O_TRUNC and O_CREAT implies W_BIT */
if ((oflags & (O_TRUNC | O_CREAT)) == (O_CREAT | O_TRUNC))
bits |= W_BIT;
#endif
/* Check protections. */
if ((r = forbidden(rip, bits, 0)) == OK) {
/* Opening reg. files directories and special files differ. */
switch (rip->i_mode & I_TYPE) {
case I_REGULAR:
/* Truncate regular file if O_TRUNC. */
if (oflags & O_TRUNC) {
truncate(rip);
wipe_inode(rip);
}
break;
case I_DIRECTORY:
/* Directories may be read but not written. */
r = (bits & W_BIT ? EISDIR : OK);
break;
case I_CHAR_SPECIAL:
case I_BLOCK_SPECIAL:
/* Invoke the driver for special processing. */
dev = (dev_t) rip->i_zone[0];
nonblocking = oflags & O_NONBLOCK;
r = dev_open(rip, (int) bits, nonblocking);
break;
case I_NAMED_PIPE:
r = pipe_open(rip, bits, oflags);
break;
}
}
}
/* If error, release inode. */
if (r != OK) {
put_inode(rip);
return(r);
}
/* Claim the file descriptor and filp slot and fill them in. */
fp->fp_filp[fd] = fil_ptr;
fil_ptr->filp_count = 1;
fil_ptr->filp_ino = rip;
fil_ptr->filp_flags = oflags;
return(fd);
}
/*===========================================================================*
* pipe_open *
*===========================================================================*/
PRIVATE int pipe_open(rip, bits, oflags)
register struct inode *rip;
register mode_t bits;
register int oflags;
{
/* This function is called from do_creat and do_open, it checks if
* there is at least one reader/writer pair for the pipe, if not
* it suspends the caller, otherwise it revives all other blocked
* processes hanging on the pipe.
*/
if (find_filp(rip, bits & W_BIT ? R_BIT : W_BIT) == NIL_FILP) {
if (oflags & O_NONBLOCK) return(bits & W_BIT ? ENXIO : OK);
suspend(XOPEN); /* suspend caller */
} else if (susp_count > 0) {/* revive blocked processes */
release(rip, OPEN, susp_count);
release(rip, CREAT, susp_count);
}
rip->i_pipe = I_PIPE;
return OK ;
}
/*===========================================================================*
* do_close *
*===========================================================================*/
PUBLIC int do_close()
{
/* Perform the close(fd) system call. */
register struct filp *rfilp;
register struct inode *rip;
int rw;
int mode_word;
/* First locate the inode that belongs to the file descriptor. */
if ( (rfilp = get_filp(fd)) == NIL_FILP) return(err_code);
rip = rfilp->filp_ino; /* 'rip' points to the inode */
/* Check to see if the file is special. */
mode_word = rip->i_mode & I_TYPE;
if (mode_word == I_CHAR_SPECIAL || mode_word == I_BLOCK_SPECIAL) {
if (mode_word == I_BLOCK_SPECIAL) {
/* Invalidate cache entries unless special is mounted or ROOT*/
do_sync(); /* purge cache */
if (mounted(rip) == FALSE) invalidate((dev_t) rip->i_zone[0]);
}
if (rfilp->filp_count == 1) dev_close(rip); /* about to become 0 */
}
/* If the inode being closed is a pipe, release everyone hanging on it. */
if (rip->i_pipe) {
rw = (rfilp->filp_mode & R_BIT ? WRITE : READ);
release(rip, rw, NR_PROCS);
}
/* If a write has been done, the inode is already marked as DIRTY. */
if (--rfilp->filp_count == 0) put_inode(rip);
fp->fp_filp[fd] = NIL_FILP;
return(OK);
}
/*===========================================================================*
* do_lseek *
*===========================================================================*/
PUBLIC int do_lseek()
{
/* Perform the lseek(ls_fd, offset, whence) system call. */
register struct filp *rfilp;
register off_t pos;
/* Check to see if the file descriptor is valid. */
if ( (rfilp = get_filp(ls_fd)) == NIL_FILP) return(err_code);
/* No lseek on pipes. */
if (rfilp->filp_ino->i_pipe == I_PIPE) return(ESPIPE);
/* The value of 'whence' determines the algorithm to use. */
switch(whence) {
case 0: pos = offset; break;
case 1: pos = rfilp->filp_pos + offset; break;
case 2: pos = rfilp->filp_ino->i_size + offset; break;
default: return(EINVAL);
}
/* Check if pos is invalid. */
if (pos < 0 || pos > MAX_FILE_POS) return(EINVAL);
if (pos != rfilp->filp_pos)
rfilp->filp_ino->i_seek = ISEEK; /* inhibit read ahead */
rfilp->filp_pos = pos;
reply_l1 = pos; /* insert the long into the output message */
return(OK);
}
/*===========================================================================*
* do_mkdir *
*===========================================================================*/
PUBLIC int do_mkdir()
{
/* Perform the mkdir(name, mode) system call. */
int r1, r2; /* status codes */
ino_t dot, dotdot; /* inode numbers for . and .. */
mode_t bits; /* mode bits for the new inode */
char string[NAME_MAX]; /* last component of the new dir's path name */
register struct inode *rip, *ldirp;
/* First make the inode. If that fails, return error code. */
if (fetch_name(name1, name1_length, M1) != OK) return(err_code);
bits = S_IFDIR | (mode & RWX_MODES & fp->fp_umask);
rip = new_node(user_path, bits, (zone_nr) 0, (off_t) 0);
if (rip == NIL_INODE) return(err_code);
if (err_code == EEXIST) {
put_inode(rip); /* can't make dir: it already exists */
return(err_code);
}
/* Get the inode numbers for . and .. to enter in the directory. */
ldirp = last_dir(user_path, string); /* pointer to new dir's parent */
dotdot = ldirp->i_num; /* parent's inode number */
dot = rip->i_num; /* inode number of the new dir itself */
/* Now make dir entries for . and .. unless the disk is completely full. */
rip->i_mode |= S_IRWXU; /* make sure . and .. can be entered */
r1 = search_dir(rip, dot1, &dot, ENTER); /* enter . in the new dir */
r2 = search_dir(rip, dot2, &dotdot, ENTER); /* enter .. in the new dir */
rip->i_mode = bits; /* now set mode correctly */
/* If both . and .. were successfully entered, increment the link counts. */
if (r1 == OK && r2 == OK) {
/* Normal case. It was possible to enter . and .. in the new dir. */
rip->i_nlinks++; /* this accounts for . */
ldirp->i_nlinks++; /* this accounts for .. */
ldirp->i_dirt = DIRTY; /* mark parent's inode as dirty */
} else {
/* It was not possible to enter . or .. probably disk was full. */
(void) search_dir(rip, ".", (ino_t *) 0, DELETE);
(void) search_dir(rip, "..", (ino_t *) 0, DELETE);
(void) search_dir(ldirp, string, (ino_t *) 0, DELETE);
rip->i_nlinks--; /* undo the increment done in new_node() */
}
rip->i_dirt = DIRTY; /* either way, i_nlinks has changed */
put_inode(ldirp); /* return the inode of the parent dir */
put_inode(rip); /* return the inode of the newly made dir */
return(err_code); /* new_node() always sets 'err_code' */
}