minix/servers/fs/mount.c
2005-08-22 15:23:47 +00:00

218 lines
6.3 KiB
C

/* This file performs the MOUNT and UMOUNT system calls.
*
* The entry points into this file are
* do_mount: perform the MOUNT system call
* do_umount: perform the UMOUNT system call
*/
#include "fs.h"
#include <fcntl.h>
#include <minix/com.h>
#include <sys/stat.h>
#include "buf.h"
#include "file.h"
#include "fproc.h"
#include "inode.h"
#include "param.h"
#include "super.h"
FORWARD _PROTOTYPE( dev_t name_to_dev, (char *path) );
/*===========================================================================*
* do_mount *
*===========================================================================*/
PUBLIC int do_mount()
{
/* Perform the mount(name, mfile, rd_only) system call. */
register struct inode *rip, *root_ip;
struct super_block *xp, *sp;
dev_t dev;
mode_t bits;
int rdir, mdir; /* TRUE iff {root|mount} file is dir */
int r, found;
/* Only the super-user may do MOUNT. */
if (!super_user) return(EPERM);
/* If 'name' is not for a block special file, return error. */
if (fetch_name(m_in.name1, m_in.name1_length, M1) != OK) return(err_code);
if ( (dev = name_to_dev(user_path)) == NO_DEV) return(err_code);
/* Scan super block table to see if dev already mounted & find a free slot.*/
sp = NIL_SUPER;
found = FALSE;
for (xp = &super_block[0]; xp < &super_block[NR_SUPERS]; xp++) {
if (xp->s_dev == dev) found = TRUE; /* is it mounted already? */
if (xp->s_dev == NO_DEV) sp = xp; /* record free slot */
}
if (found) return(EBUSY); /* already mounted */
if (sp == NIL_SUPER) return(ENFILE); /* no super block available */
/* Open the device the file system lives on. */
if (dev_open(dev, who, m_in.rd_only ? R_BIT : (R_BIT|W_BIT)) != OK)
return(EINVAL);
/* Make the cache forget about blocks it has open on the filesystem */
(void) do_sync();
invalidate(dev);
/* Fill in the super block. */
sp->s_dev = dev; /* read_super() needs to know which dev */
r = read_super(sp);
/* Is it recognized as a Minix filesystem? */
if (r != OK) {
dev_close(dev);
sp->s_dev = NO_DEV;
return(r);
}
/* Now get the inode of the file to be mounted on. */
if (fetch_name(m_in.name2, m_in.name2_length, M1) != OK) {
dev_close(dev);
sp->s_dev = NO_DEV;
return(err_code);
}
if ( (rip = eat_path(user_path)) == NIL_INODE) {
dev_close(dev);
sp->s_dev = NO_DEV;
return(err_code);
}
/* It may not be busy. */
r = OK;
if (rip->i_count > 1) r = EBUSY;
/* It may not be special. */
bits = rip->i_mode & I_TYPE;
if (bits == I_BLOCK_SPECIAL || bits == I_CHAR_SPECIAL) r = ENOTDIR;
/* Get the root inode of the mounted file system. */
root_ip = NIL_INODE; /* if 'r' not OK, make sure this is defined */
if (r == OK) {
if ( (root_ip = get_inode(dev, ROOT_INODE)) == NIL_INODE) r = err_code;
}
if (root_ip != NIL_INODE && root_ip->i_mode == 0) {
r = EINVAL;
}
/* File types of 'rip' and 'root_ip' may not conflict. */
if (r == OK) {
mdir = ((rip->i_mode & I_TYPE) == I_DIRECTORY); /* TRUE iff dir */
rdir = ((root_ip->i_mode & I_TYPE) == I_DIRECTORY);
if (!mdir && rdir) r = EISDIR;
}
/* If error, return the super block and both inodes; release the maps. */
if (r != OK) {
put_inode(rip);
put_inode(root_ip);
(void) do_sync();
invalidate(dev);
dev_close(dev);
sp->s_dev = NO_DEV;
return(r);
}
/* Nothing else can go wrong. Perform the mount. */
rip->i_mount = I_MOUNT; /* this bit says the inode is mounted on */
sp->s_imount = rip;
sp->s_isup = root_ip;
sp->s_rd_only = m_in.rd_only;
return(OK);
}
/*===========================================================================*
* do_umount *
*===========================================================================*/
PUBLIC int do_umount()
{
/* Perform the umount(name) system call. */
dev_t dev;
/* Only the super-user may do UMOUNT. */
if (!super_user) return(EPERM);
/* If 'name' is not for a block special file, return error. */
if (fetch_name(m_in.name, m_in.name_length, M3) != OK) return(err_code);
if ( (dev = name_to_dev(user_path)) == NO_DEV) return(err_code);
return(unmount(dev));
}
/*===========================================================================*
* unmount *
*===========================================================================*/
PUBLIC int unmount(dev)
Dev_t dev;
{
/* Unmount a file system by device number. */
register struct inode *rip;
struct super_block *sp, *sp1;
int count;
/* See if the mounted device is busy. Only 1 inode using it should be
* open -- the root inode -- and that inode only 1 time.
*/
count = 0;
for (rip = &inode[0]; rip< &inode[NR_INODES]; rip++)
if (rip->i_count > 0 && rip->i_dev == dev) count += rip->i_count;
if (count > 1) return(EBUSY); /* can't umount a busy file system */
/* Find the super block. */
sp = NIL_SUPER;
for (sp1 = &super_block[0]; sp1 < &super_block[NR_SUPERS]; sp1++) {
if (sp1->s_dev == dev) {
sp = sp1;
break;
}
}
/* Sync the disk, and invalidate cache. */
(void) do_sync(); /* force any cached blocks out of memory */
invalidate(dev); /* invalidate cache entries for this dev */
if (sp == NIL_SUPER) {
return(EINVAL);
}
/* Close the device the file system lives on. */
dev_close(dev);
/* Finish off the unmount. */
sp->s_imount->i_mount = NO_MOUNT; /* inode returns to normal */
put_inode(sp->s_imount); /* release the inode mounted on */
put_inode(sp->s_isup); /* release the root inode of the mounted fs */
sp->s_imount = NIL_INODE;
sp->s_dev = NO_DEV;
return(OK);
}
/*===========================================================================*
* name_to_dev *
*===========================================================================*/
PRIVATE dev_t name_to_dev(path)
char *path; /* pointer to path name */
{
/* Convert the block special file 'path' to a device number. If 'path'
* is not a block special file, return error code in 'err_code'.
*/
register struct inode *rip;
register dev_t dev;
/* If 'path' can't be opened, give up immediately. */
if ( (rip = eat_path(path)) == NIL_INODE) return(NO_DEV);
/* If 'path' is not a block special file, return error. */
if ( (rip->i_mode & I_TYPE) != I_BLOCK_SPECIAL) {
err_code = ENOTBLK;
put_inode(rip);
return(NO_DEV);
}
/* Extract the device number. */
dev = (dev_t) rip->i_zone[0];
put_inode(rip);
return(dev);
}