sanchayanmaity/minix
1
0
Fork 0
Code Issues Pull requests Projects Releases Packages Wiki Activity
minix/servers/fs/open.c

563 lines
18 KiB
C
Raw Blame History

/* 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_open: perform the OPEN system call
* do_mknod: perform the MKNOD system call
* do_mkdir: perform the MKDIR system call
* do_close: perform the CLOSE system call
* do_lseek: perform the LSEEK system call
*/
#include "fs.h"
#include <sys/stat.h>
#include <fcntl.h>
#include <string.h>
#include <unistd.h>
#include <minix/callnr.h>
#include <minix/com.h>
#include "buf.h"
#include "file.h"
#include "fproc.h"
#include "inode.h"
#include "lock.h"
#include "param.h"
#include "super.h"
#define offset m2_l1
PRIVATE char mode_map[] = {R_BIT, W_BIT, R_BIT|W_BIT, 0};
FORWARD _PROTOTYPE( int common_open, (int oflags, mode_t omode) );
FORWARD _PROTOTYPE( int pipe_open, (struct inode *rip,mode_t bits,int oflags));
FORWARD _PROTOTYPE( struct inode *new_node, (struct inode **ldirp,
char *path, mode_t bits, zone_t z0, int opaque, char *string));
/*===========================================================================*
* do_creat *
*===========================================================================*/
PUBLIC int do_creat()
{
/* Perform the creat(name, mode) system call. */
int r;
if (fetch_name(m_in.name, m_in.name_length, M3) != OK) return(err_code);
r = common_open(O_WRONLY | O_CREAT | O_TRUNC, (mode_t) m_in.mode);
return(r);
}
/*===========================================================================*
* do_open *
*===========================================================================*/
PUBLIC int do_open()
{
/* Perform the open(name, flags,...) system call. */
int create_mode = 0; /* is really mode_t but this gives problems */
int r;
/* If O_CREAT is set, open has three parameters, otherwise two. */
if (m_in.mode & O_CREAT) {
create_mode = m_in.c_mode;
r = fetch_name(m_in.c_name, m_in.name1_length, M1);
} else {
r = fetch_name(m_in.name, m_in.name_length, M3);
}
if (r != OK) return(err_code); /* name was bad */
r = common_open(m_in.mode, create_mode);
return(r);
}
/*===========================================================================*
* common_open *
*===========================================================================*/
PRIVATE int common_open(register int oflags, mode_t omode)
{
/* Common code from do_creat and do_open. */
struct inode *rip, *ldirp;
int r, b, exist = TRUE;
dev_t dev;
mode_t bits;
off_t pos;
struct filp *fil_ptr, *filp2;
/* 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, &m_in.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(&ldirp, user_path, omode, NO_ZONE, oflags&O_EXCL, NULL);
r = err_code;
put_inode(ldirp);
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);
}
/* Claim the file descriptor and filp slot and fill them in. */
fp->fp_filp[m_in.fd] = fil_ptr;
FD_SET(m_in.fd, &fp->fp_filp_inuse);
fil_ptr->filp_count = 1;
fil_ptr->filp_ino = rip;
fil_ptr->filp_flags = oflags;
/* Only do the normal open code if we didn't just create the file. */
if (exist) {
/* Check protections. */
if ((r = forbidden(rip, bits)) == 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) {
if ((r = forbidden(rip, W_BIT)) !=OK) break;
truncate_inode(rip, 0);
wipe_inode(rip);
/* Send the inode from the inode cache to the
* block cache, so it gets written on the next
* cache flush.
*/
rw_inode(rip, WRITING);
}
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];
r = dev_open(dev, who_e, bits | (oflags & ~O_ACCMODE));
break;
case I_NAMED_PIPE:
oflags |= O_APPEND; /* force append mode */
fil_ptr->filp_flags = oflags;
r = pipe_open(rip, bits, oflags);
if (r != ENXIO) {
/* See if someone else is doing a rd or wt on
* the FIFO. If so, use its filp entry so the
* file position will be automatically shared.
*/
b = (bits & R_BIT ? R_BIT : W_BIT);
fil_ptr->filp_count = 0; /* don't find self */
if ((filp2 = find_filp(rip, b)) != NIL_FILP) {
/* Co-reader or writer found. Use it.*/
fp->fp_filp[m_in.fd] = filp2;
filp2->filp_count++;
filp2->filp_ino = rip;
filp2->filp_flags = oflags;
/* i_count was incremented incorrectly
* by eatpath above, not knowing that
* we were going to use an existing
* filp entry. Correct this error.
*/
rip->i_count--;
} else {
/* Nobody else found. Restore filp. */
fil_ptr->filp_count = 1;
if (b == R_BIT)
pos = rip->i_zone[V2_NR_DZONES+0];
else
pos = rip->i_zone[V2_NR_DZONES+1];
fil_ptr->filp_pos = pos;
}
}
break;
}
}
}
/* If error, release inode. */
if (r != OK) {
if (r == SUSPEND) return(r); /* Oops, just suspended */
fp->fp_filp[m_in.fd] = NIL_FILP;
FD_CLR(m_in.fd, &fp->fp_filp_inuse);
fil_ptr->filp_count= 0;
put_inode(rip);
return(r);
}
return(m_in.fd);
}
/*===========================================================================*
* new_node *
*===========================================================================*/
PRIVATE struct inode *new_node(struct inode **ldirp,
char *path, mode_t bits, zone_t z0, int opaque, char *parsed)
{
/* 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).
*
* The parsed path rest is returned in 'parsed' if parsed is nonzero. It
* has to hold at least NAME_MAX bytes.
*/
register struct inode *rip;
register int r;
char string[NAME_MAX];
*ldirp = parse_path(path, string, opaque ? LAST_DIR : LAST_DIR_EATSYM);
if (*ldirp == NIL_INODE) return(NIL_INODE);
/* The final directory is accessible. Get final component of the path. */
rip = advance(ldirp, string);
if (S_ISDIR(bits) &&
(*ldirp)->i_nlinks >= ((*ldirp)->i_sp->s_version == V1 ?
CHAR_MAX : SHRT_MAX)) {
/* New entry is a directory, alas we can't give it a ".." */
put_inode(rip);
err_code = EMLINK;
return(NIL_INODE);
}
if ( rip == NIL_INODE && err_code == ENOENT) {
/* Last path component does not exist. Make new directory entry. */
if ( (rip = alloc_inode((*ldirp)->i_dev, bits)) == NIL_INODE) {
/* Can't creat new inode: out of inodes. */
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 */
rw_inode(rip, WRITING); /* force inode to disk now */
/* New inode acquired. Try to make directory entry. */
if ((r = search_dir(*ldirp, string, &rip->i_num,ENTER)) != OK) {
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;
}
if(parsed) { /* Give the caller the parsed string if requested. */
strncpy(parsed, string, NAME_MAX-1);
parsed[NAME_MAX-1] = '\0';
}
/* The caller has to return the directory inode (*ldirp). */
err_code = r;
return(rip);
}
/*===========================================================================*
* pipe_open *
*===========================================================================*/
PRIVATE int pipe_open(register struct inode *rip, register mode_t bits,
register int oflags)
{
/* This function is called from common_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.
*/
rip->i_pipe = I_PIPE;
if((bits & (R_BIT|W_BIT)) == (R_BIT|W_BIT)) {
printf("pipe opened RW.\n");
return ENXIO;
}
if (find_filp(rip, bits & W_BIT ? R_BIT : W_BIT) == NIL_FILP) {
if (oflags & O_NONBLOCK) {
if (bits & W_BIT) return(ENXIO);
} else {
suspend(XPOPEN); /* suspend caller */
return(SUSPEND);
}
} else if (susp_count > 0) {/* revive blocked processes */
release(rip, OPEN, susp_count);
release(rip, CREAT, susp_count);
}
return(OK);
}
/*===========================================================================*
* do_mknod *
*===========================================================================*/
PUBLIC int do_mknod()
{
/* Perform the mknod(name, mode, addr) system call. */
register mode_t bits, mode_bits;
struct inode *ip, *ldirp;
/* Only the super_user may make nodes other than fifos. */
mode_bits = (mode_t) m_in.mk_mode; /* mode of the inode */
if (!super_user && ((mode_bits & I_TYPE) != I_NAMED_PIPE)) return(EPERM);
if (fetch_name(m_in.name1, m_in.name1_length, M1) != OK) return(err_code);
bits = (mode_bits & I_TYPE) | (mode_bits & ALL_MODES & fp->fp_umask);
ip = new_node(&ldirp, user_path, bits, (zone_t) m_in.mk_z0, TRUE, NULL);
put_inode(ip);
put_inode(ldirp);
return(err_code);
}
/*===========================================================================*
* 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 */
struct inode *rip, *ldirp;
if (fetch_name(m_in.name1, m_in.name1_length, M1) != OK) return(err_code);
/* Next make the inode. If that fails, return error code. */
bits = I_DIRECTORY | (m_in.mode & RWX_MODES & fp->fp_umask);
rip = new_node(&ldirp, user_path, bits, (zone_t) 0, TRUE, string);
if (rip == NIL_INODE || err_code == EEXIST) {
put_inode(rip); /* can't make dir: it already exists */
put_inode(ldirp);
return(err_code);
}
/* Get the inode numbers for . and .. to enter in the directory. */
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. */
/* Use dot1 and dot2, so the mode of the directory isn't important. */
rip->i_mode = bits; /* set mode */
r1 = search_dir(rip, dot1, &dot, ENTER); /* enter . in the new dir */
r2 = search_dir(rip, dot2, &dotdot, ENTER); /* enter .. in the new dir */
/* 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 -
* links counts haven't been touched.
*/
if(search_dir(ldirp, string, (ino_t *) 0, DELETE) != OK)
panic(__FILE__, "Dir disappeared ", rip->i_num);
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' */
}
/*===========================================================================*
* do_close *
*===========================================================================*/
PUBLIC int do_close()
{
/* Perform the close(fd) system call. */
register struct filp *rfilp;
register struct inode *rip;
struct file_lock *flp;
int rw, mode_word, lock_count;
dev_t dev;
/* First locate the inode that belongs to the file descriptor. */
if ( (rfilp = get_filp(m_in.fd)) == NIL_FILP) return(err_code);
rip = rfilp->filp_ino; /* 'rip' points to the inode */
if (rfilp->filp_count - 1 == 0 && rfilp->filp_mode != FILP_CLOSED) {
/* 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) {
dev = (dev_t) rip->i_zone[0];
if (mode_word == I_BLOCK_SPECIAL) {
/* Invalidate cache entries unless special is mounted
* or ROOT
*/
if (!mounted(rip)) {
(void) do_sync(); /* purge cache */
invalidate(dev);
}
}
/* Do any special processing on device close. */
dev_close(dev);
}
}
/* If the inode being closed is a pipe, release everyone hanging on it. */
if (rip->i_pipe == 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) {
if (rip->i_pipe == I_PIPE && rip->i_count > 1) {
/* Save the file position in the i-node in case needed later.
* The read and write positions are saved separately. The
* last 3 zones in the i-node are not used for (named) pipes.
*/
if (rfilp->filp_mode == R_BIT)
rip->i_zone[V2_NR_DZONES+0] = (zone_t) rfilp->filp_pos;
else
rip->i_zone[V2_NR_DZONES+1] = (zone_t) rfilp->filp_pos;
}
put_inode(rip);
}
fp->fp_cloexec &= ~(1L << m_in.fd); /* turn off close-on-exec bit */
fp->fp_filp[m_in.fd] = NIL_FILP;
FD_CLR(m_in.fd, &fp->fp_filp_inuse);
/* Check to see if the file is locked. If so, release all locks. */
if (nr_locks == 0) return(OK);
lock_count = nr_locks; /* save count of locks */
for (flp = &file_lock[0]; flp < &file_lock[NR_LOCKS]; flp++) {
if (flp->lock_type == 0) continue; /* slot not in use */
if (flp->lock_inode == rip && flp->lock_pid == fp->fp_pid) {
flp->lock_type = 0;
nr_locks--;
}
}
if (nr_locks < lock_count) lock_revive(); /* lock released */
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(m_in.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 start position to use. */
switch(m_in.whence) {
case SEEK_SET: pos = 0; break;
case SEEK_CUR: pos = rfilp->filp_pos; break;
case SEEK_END: pos = rfilp->filp_ino->i_size; break;
default: return(EINVAL);
}
/* Check for overflow. */
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);
}
/*===========================================================================*
* do_slink *
*===========================================================================*/
PUBLIC int do_slink()
{
/* Perform the symlink(name1, name2) system call. */
register int r; /* error code */
char string[NAME_MAX]; /* last component of the new dir's path name */
struct inode *sip; /* inode containing symbolic link */
struct buf *bp; /* disk buffer for link */
struct inode *ldirp; /* directory containing link */
if (fetch_name(m_in.name2, m_in.name2_length, M1) != OK)
return(err_code);
if (m_in.name1_length <= 1 || m_in.name1_length >= _MIN_BLOCK_SIZE)
return(ENAMETOOLONG);
/* Create the inode for the symlink. */
sip = new_node(&ldirp, user_path, (mode_t) (I_SYMBOLIC_LINK | RWX_MODES),
(zone_t) 0, TRUE, string);
/* Allocate a disk block for the contents of the symlink.
* Copy contents of symlink (the name pointed to) into first disk block.
*/
if ((r = err_code) == OK) {
r = (bp = new_block(sip, (off_t) 0)) == NIL_BUF
? err_code
: sys_vircopy(who_e, D, (vir_bytes) m_in.name1,
SELF, D, (vir_bytes) bp->b_data,
(vir_bytes) m_in.name1_length-1);
if(r == OK) {
bp->b_data[_MIN_BLOCK_SIZE-1] = '\0';
sip->i_size = strlen(bp->b_data);
if(sip->i_size != m_in.name1_length-1) {
/* This can happen if the user provides a buffer
* with a \0 in it. This can cause a lot of trouble
* when the symlink is used later. We could just use
* the strlen() value, but we want to let the user
* know he did something wrong. ENAMETOOLONG doesn't
* exactly describe the error, but there is no
* ENAMETOOWRONG.
*/
r = ENAMETOOLONG;
}
}
put_block(bp, DIRECTORY_BLOCK); /* put_block() accepts NIL_BUF. */
if (r != OK) {
sip->i_nlinks = 0;
if (search_dir(ldirp, string, (ino_t *) 0, DELETE) != OK)
panic(__FILE__, "Symbolic link vanished", NO_NUM);
}
}
/* put_inode() accepts NIL_INODE as a noop, so the below are safe. */
put_inode(sip);
put_inode(ldirp);
return(r);
}
Reference in a new issue View git blame Copy permalink