fs/super.c

/* */
This source file includes following definitions.
get_fs_type
__wait_on_super
sync_supers
get_super
put_super
read_super
get_unnamed_dev
put_unnamed_dev
do_umount
sys_umount
do_mount
sys_mount
mount_root
   1 /*
   2  *  linux/fs/super.c
   3  *
   4  *  Copyright (C) 1991, 1992  Linus Torvalds
   5  */
   6 
   7 /*
   8  * super.c contains code to handle the super-block tables.
   9  */
  10 #include <linux/config.h>
  11 #include <linux/sched.h>
  12 #include <linux/kernel.h>
  13 #include <linux/stat.h>
  14 #include <linux/errno.h>
  15 #include <linux/string.h>
  16 #include <linux/locks.h>
  17 
  18 #include <asm/system.h>
  19 #include <asm/segment.h>
  20  
  21 /*
  22  * The definition of file_systems that used to be here is now in
  23  * filesystems.c.  Now super.c contains no fs specific code.  -- jrs
  24  */
  25 
  26 extern struct file_system_type file_systems[];
  27 
  28 extern void wait_for_keypress(void);
  29 extern void fcntl_init_locks(void);
  30 
  31 struct super_block super_block[NR_SUPER];
  32 
  33 /* this is initialized in init/main.c */
  34 dev_t ROOT_DEV = 0;
  35 
  36 struct file_system_type *get_fs_type(char *name)
     /*  */
  37 {
  38         int a;
  39         
  40         if (!name)
  41                 return &file_systems[0];
  42         for(a = 0 ; file_systems[a].read_super ; a++)
  43                 if (!strcmp(name,file_systems[a].name))
  44                         return(&file_systems[a]);
  45         return NULL;
  46 }
  47 
  48 void __wait_on_super(struct super_block * sb)
     /*  */
  49 {
  50         struct wait_queue wait = { current, NULL };
  51 
  52         add_wait_queue(&sb->s_wait, &wait);
  53 repeat:
  54         current->state = TASK_UNINTERRUPTIBLE;
  55         if (sb->s_lock) {
  56                 schedule();
  57                 goto repeat;
  58         }
  59         remove_wait_queue(&sb->s_wait, &wait);
  60         current->state = TASK_RUNNING;
  61 }
  62 
  63 void sync_supers(dev_t dev)
     /*  */
  64 {
  65         struct super_block * sb;
  66 
  67         for (sb = super_block + 0 ; sb < super_block + NR_SUPER ; sb++) {
  68                 if (!sb->s_dev)
  69                         continue;
  70                 wait_on_super(sb);
  71                 if (!sb->s_dev || !sb->s_dirt)
  72                         continue;
  73                 if (dev && (dev != sb->s_dev))
  74                         continue;
  75                 if (sb->s_op && sb->s_op->write_super)
  76                         sb->s_op->write_super(sb);
  77         }
  78 }
  79 
  80 static struct super_block * get_super(dev_t dev)
     /*  */
  81 {
  82         struct super_block * s;
  83 
  84         if (!dev)
  85                 return NULL;
  86         s = 0+super_block;
  87         while (s < NR_SUPER+super_block)
  88                 if (s->s_dev == dev) {
  89                         wait_on_super(s);
  90                         if (s->s_dev == dev)
  91                                 return s;
  92                         s = 0+super_block;
  93                 } else
  94                         s++;
  95         return NULL;
  96 }
  97 
  98 void put_super(dev_t dev)
     /*  */
  99 {
 100         struct super_block * sb;
 101 
 102         if (dev == ROOT_DEV) {
 103                 printk("root diskette changed: prepare for armageddon\n\r");
 104                 return;
 105         }
 106         if (!(sb = get_super(dev)))
 107                 return;
 108         if (sb->s_covered) {
 109                 printk("Mounted disk changed - tssk, tssk\n\r");
 110                 return;
 111         }
 112         if (sb->s_op && sb->s_op->put_super)
 113                 sb->s_op->put_super(sb);
 114 }
 115 
 116 static struct super_block * read_super(dev_t dev,char *name,int flags,void *data)
     /*  */
 117 {
 118         struct super_block * s;
 119         struct file_system_type *type;
 120 
 121         if (!dev)
 122                 return NULL;
 123         check_disk_change(dev);
 124         if (s = get_super(dev))
 125                 return s;
 126         if (!(type = get_fs_type(name))) {
 127                 printk("get fs type failed %s\n",name);
 128                 return NULL;
 129         }
 130         for (s = 0+super_block ;; s++) {
 131                 if (s >= NR_SUPER+super_block)
 132                         return NULL;
 133                 if (!s->s_dev)
 134                         break;
 135         }
 136         s->s_dev = dev;
 137         s->s_flags = flags;
 138         if (!type->read_super(s,data)) {
 139                 s->s_dev = 0;
 140                 return NULL;
 141         }
 142         s->s_dev = dev;
 143         s->s_covered = NULL;
 144         s->s_rd_only = 0;
 145         s->s_dirt = 0;
 146         return s;
 147 }
 148 
 149 /*
 150  * Unnamed block devices are dummy devices used by virtual
 151  * filesystems which don't use real block-devices.  -- jrs
 152  */
 153 
 154 static char unnamed_dev_in_use[256];
 155 
 156 static dev_t get_unnamed_dev(void)
     /*  */
 157 {
 158         static int first_use = 0;
 159         int i;
 160 
 161         if (first_use == 0) {
 162                 first_use = 1;
 163                 memset(unnamed_dev_in_use, 0, sizeof(unnamed_dev_in_use));
 164                 unnamed_dev_in_use[0] = 1; /* minor 0 (nodev) is special */
 165         }
 166         for (i = 0; i < 256; i++) {
 167                 if (!unnamed_dev_in_use[i]) {
 168                         unnamed_dev_in_use[i] = 1;
 169                         return (UNNAMED_MAJOR << 8) | i;
 170                 }
 171         }
 172         return 0;
 173 }
 174 
 175 static void put_unnamed_dev(dev_t dev)
     /*  */
 176 {
 177         if (!dev)
 178                 return;
 179         if (!unnamed_dev_in_use[dev]) {
 180                 printk("put_unnamed_dev: trying to free unused device\n");
 181                 return;
 182         }
 183         unnamed_dev_in_use[dev] = 0;
 184 }
 185 
 186 static int do_umount(dev_t dev)
     /*  */
 187 {
 188         struct super_block * sb;
 189 
 190         if (dev==ROOT_DEV)
 191                 return -EBUSY;
 192         if (!(sb=get_super(dev)) || !(sb->s_covered))
 193                 return -ENOENT;
 194         if (!sb->s_covered->i_mount)
 195                 printk("Mounted inode has i_mount=0\n");
 196         if (!fs_may_umount(dev, sb->s_mounted))
 197                 return -EBUSY;
 198         sb->s_covered->i_mount=0;
 199         iput(sb->s_covered);
 200         sb->s_covered = NULL;
 201         iput(sb->s_mounted);
 202         sb->s_mounted = NULL;
 203         if (sb->s_op && sb->s_op->write_super && sb->s_dirt)
 204                 sb->s_op->write_super(sb);
 205         put_super(dev);
 206         return 0;
 207 }
 208 
 209 /*
 210  * Now umount can handle mount points as well as block devices.
 211  * This is important for filesystems which use unnamed block devices.
 212  *
 213  * There is a little kludge here with the dummy_inode.  The current
 214  * vfs release functions only use the r_dev field in the inode so
 215  * we give them the info they need without using a real inode.
 216  * If any other fields are ever needed by any block device release
 217  * functions, they should be faked here.  -- jrs
 218  */
 219 
 220 int sys_umount(char * name)
     /*  */
 221 {
 222         struct inode * inode;
 223         dev_t dev;
 224         int retval;
 225         struct inode dummy_inode;
 226         struct file_operations * fops;
 227 
 228         if (!suser())
 229                 return -EPERM;
 230         retval = namei(name,&inode);
 231         if (retval)
 232                 return retval;
 233         if (S_ISBLK(inode->i_mode)) {
 234                 dev = inode->i_rdev;
 235                 if (IS_NODEV(inode)) {
 236                         iput(inode);
 237                         return -EACCES;
 238                 }
 239         } else if (S_ISDIR(inode->i_mode)) {
 240                 if (!inode || !inode->i_sb || inode != inode->i_sb->s_mounted) {
 241                         iput(inode);
 242                         return -EINVAL;
 243                 }
 244                 dev = inode->i_sb->s_dev;
 245                 iput(inode);
 246                 memset(&dummy_inode, 0, sizeof(dummy_inode));
 247                 dummy_inode.i_rdev = dev;
 248                 inode = &dummy_inode;
 249         } else {
 250                 iput(inode);
 251                 return -EINVAL;
 252         }
 253         if (MAJOR(dev) >= MAX_BLKDEV) {
 254                 iput(inode);
 255                 return -ENXIO;
 256         }
 257         if (!(retval = do_umount(dev))) {
 258                 fops = blkdev_fops[MAJOR(dev)];
 259                 if (fops && fops->release)
 260                         fops->release(inode,NULL);
 261                 if (MAJOR(dev) == UNNAMED_MAJOR)
 262                         put_unnamed_dev(dev);
 263         }
 264         if (inode != &dummy_inode)
 265                 iput(inode);
 266         if (retval)
 267                 return retval;
 268         sync_dev(dev);
 269         return 0;
 270 }
 271 
 272 /*
 273  * do_mount() does the actual mounting after sys_mount has done the ugly
 274  * parameter parsing. When enough time has gone by, and everything uses the
 275  * new mount() parameters, sys_mount() can then be cleaned up.
 276  *
 277  * We cannot mount a filesystem if it has active, used, or dirty inodes.
 278  * We also have to flush all inode-data for this device, as the new mount
 279  * might need new info.
 280  */
 281 static int do_mount(dev_t dev, const char * dir, char * type, int flags, void * data)
     /*  */
 282 {
 283         struct inode * dir_i;
 284         struct super_block * sb;
 285         int error;
 286 
 287         error = namei(dir,&dir_i);
 288         if (error)
 289                 return error;
 290         if (dir_i->i_count != 1 || dir_i->i_mount) {
 291                 iput(dir_i);
 292                 return -EBUSY;
 293         }
 294         if (!S_ISDIR(dir_i->i_mode)) {
 295                 iput(dir_i);
 296                 return -EPERM;
 297         }
 298         if (!fs_may_mount(dev)) {
 299                 iput(dir_i);
 300                 return -EBUSY;
 301         }
 302         sb = read_super(dev,type,flags,data);
 303         if (!sb || sb->s_covered) {
 304                 iput(dir_i);
 305                 return -EBUSY;
 306         }
 307         sb->s_flags = flags;
 308         sb->s_covered = dir_i;
 309         dir_i->i_mount = 1;
 310         return 0;               /* we don't iput(dir_i) - see umount */
 311 }
 312 
 313 /*
 314  * Flags is a 16-bit value that allows up to 16 non-fs dependent flags to
 315  * be given to the mount() call (ie: read-only, no-dev, no-suid etc).
 316  *
 317  * data is a (void *) that can point to any structure up to 4095 bytes, which
 318  * can contain arbitrary fs-dependent information (or be NULL).
 319  *
 320  * NOTE! As old versions of mount() didn't use this setup, the flags has to have
 321  * a special 16-bit magic number in the hight word: 0xC0ED. If this magic word
 322  * isn't present, the flags and data info isn't used, as the syscall assumes we
 323  * are talking to an older version that didn't understand them.
 324  */
 325 int sys_mount(char * dev_name, char * dir_name, char * type,
     /*  */
 326         unsigned long new_flags, void * data)
 327 {
 328         struct file_system_type * fstype;
 329         struct inode * inode;
 330         struct file_operations * fops;
 331         dev_t dev;
 332         int retval;
 333         char tmp[100], * t;
 334         int i;
 335         unsigned long flags = 0;
 336         unsigned long page = 0;
 337 
 338         if (!suser())
 339                 return -EPERM;
 340         if (type) {
 341                 for (i = 0 ; i < 100 ; i++)
 342                         if (!(tmp[i] = get_fs_byte(type++)))
 343                                 break;
 344                 t = tmp;
 345         } else
 346                 t = NULL;
 347         if (!(fstype = get_fs_type(t)))
 348                 return -ENODEV;
 349         t = fstype->name;
 350         if (fstype->requires_dev) {
 351                 if (retval = namei(dev_name,&inode))
 352                         return retval;
 353                 if (!S_ISBLK(inode->i_mode)) {
 354                         iput(inode);
 355                         return -ENOTBLK;
 356                 }
 357                 if (IS_NODEV(inode)) {
 358                         iput(inode);
 359                         return -EACCES;
 360                 }
 361                 dev = inode->i_rdev;
 362                 if (MAJOR(dev) >= MAX_BLKDEV) {
 363                         iput(inode);
 364                         return -ENXIO;
 365                 }
 366         }
 367         else {
 368                 if (!(dev = get_unnamed_dev()))
 369                         return -EMFILE;
 370                 inode = NULL;
 371         }
 372         fops = blkdev_fops[MAJOR(dev)];
 373         if (fops && fops->open) {
 374                 if (retval = fops->open(inode,NULL)) {
 375                         iput(inode);
 376                         return retval;
 377                 }
 378         }
 379         if ((new_flags & 0xffff0000) == 0xC0ED0000) {
 380                 flags = new_flags & 0xffff;
 381                 if (data) {
 382                         if ((unsigned long) data >= TASK_SIZE) {
 383                                 iput(inode);
 384                                 return -EFAULT;
 385                         }
 386                         page = get_free_page(GFP_KERNEL);
 387                         i = TASK_SIZE - (unsigned long) data;
 388                         if (i < 0 || i > 4095)
 389                                 i = 4095;
 390                         memcpy_fromfs((void *) page,data,i);
 391                 }
 392         }
 393         retval = do_mount(dev,dir_name,t,flags,(void *) page);
 394         free_page(page);
 395         if (retval && fops && fops->release)
 396                 fops->release(inode,NULL);
 397         iput(inode);
 398         return retval;
 399 }
 400 
 401 void mount_root(void)
     /*  */
 402 {
 403         struct file_system_type * fs_type;
 404         struct super_block * sb;
 405         struct inode * inode;
 406 
 407         memset(file_table, 0, sizeof(file_table));
 408         memset(super_block, 0, sizeof(super_block));
 409         fcntl_init_locks();
 410         if (MAJOR(ROOT_DEV) == 2) {
 411                 printk("Insert root floppy and press ENTER");
 412                 wait_for_keypress();
 413         }
 414         for (fs_type = file_systems; fs_type->read_super; fs_type++) {
 415                 if (!fs_type->requires_dev)
 416                         continue;
 417                 sb = read_super(ROOT_DEV,fs_type->name,0,NULL);
 418                 if (sb) {
 419                         inode = sb->s_mounted;
 420                         inode->i_count += 3 ;   /* NOTE! it is logically used 4 times, not 1 */
 421                         sb->s_covered = inode;
 422                         sb->s_flags = 0;
 423                         current->pwd = inode;
 424                         current->root = inode;
 425                         return;
 426                 }
 427         }
 428         panic("Unable to mount root");
 429 }
/* */
root/fs/super.c

DEFINITIONS
