SAFE public projects git trees. - safe/jmp/linux-2.6/blob - fs/libfs.c

   1 /*
   2  *      fs/libfs.c
   3  *      Library for filesystems writers.
   4  */
   5
   6 #include <linux/module.h>
   7 #include <linux/pagemap.h>
   8 #include <linux/mount.h>
   9 #include <linux/vfs.h>
  10 #include <linux/mutex.h>
  11
  12 #include <asm/uaccess.h>
  13
  14 int simple_getattr(struct vfsmount *mnt, struct dentry *dentry,
  15                    struct kstat *stat)
  16 {
  17         struct inode *inode = dentry->d_inode;
  18         generic_fillattr(inode, stat);
  19         stat->blocks = inode->i_mapping->nrpages << (PAGE_CACHE_SHIFT - 9);
  20         return 0;
  21 }
  22
  23 int simple_statfs(struct dentry *dentry, struct kstatfs *buf)
  24 {
  25         buf->f_type = dentry->d_sb->s_magic;
  26         buf->f_bsize = PAGE_CACHE_SIZE;
  27         buf->f_namelen = NAME_MAX;
  28         return 0;
  29 }
  30
  31 /*
  32  * Retaining negative dentries for an in-memory filesystem just wastes
  33  * memory and lookup time: arrange for them to be deleted immediately.
  34  */
  35 static int simple_delete_dentry(struct dentry *dentry)
  36 {
  37         return 1;
  38 }
  39
  40 /*
  41  * Lookup the data. This is trivial - if the dentry didn't already
  42  * exist, we know it is negative.  Set d_op to delete negative dentries.
  43  */
  44 struct dentry *simple_lookup(struct inode *dir, struct dentry *dentry, struct nameidata *nd)
  45 {
  46         static struct dentry_operations simple_dentry_operations = {
  47                 .d_delete = simple_delete_dentry,
  48         };
  49
  50         if (dentry->d_name.len > NAME_MAX)
  51                 return ERR_PTR(-ENAMETOOLONG);
  52         dentry->d_op = &simple_dentry_operations;
  53         d_add(dentry, NULL);
  54         return NULL;
  55 }
  56
  57 int simple_sync_file(struct file * file, struct dentry *dentry, int datasync)
  58 {
  59         return 0;
  60 }
  61
  62 int dcache_dir_open(struct inode *inode, struct file *file)
  63 {
  64         static struct qstr cursor_name = {.len = 1, .name = "."};
  65
  66         file->private_data = d_alloc(file->f_path.dentry, &cursor_name);
  67
  68         return file->private_data ? 0 : -ENOMEM;
  69 }
  70
  71 int dcache_dir_close(struct inode *inode, struct file *file)
  72 {
  73         dput(file->private_data);
  74         return 0;
  75 }
  76
  77 loff_t dcache_dir_lseek(struct file *file, loff_t offset, int origin)
  78 {
  79         mutex_lock(&file->f_path.dentry->d_inode->i_mutex);
  80         switch (origin) {
  81                 case 1:
  82                         offset += file->f_pos;
  83                 case 0:
  84                         if (offset >= 0)
  85                                 break;
  86                 default:
  87                         mutex_unlock(&file->f_path.dentry->d_inode->i_mutex);
  88                         return -EINVAL;
  89         }
  90         if (offset != file->f_pos) {
  91                 file->f_pos = offset;
  92                 if (file->f_pos >= 2) {
  93                         struct list_head *p;
  94                         struct dentry *cursor = file->private_data;
  95                         loff_t n = file->f_pos - 2;
  96
  97                         spin_lock(&dcache_lock);
  98                         list_del(&cursor->d_u.d_child);
  99                         p = file->f_path.dentry->d_subdirs.next;
 100                         while (n && p != &file->f_path.dentry->d_subdirs) {
 101                                 struct dentry *next;
 102                                 next = list_entry(p, struct dentry, d_u.d_child);
 103                                 if (!d_unhashed(next) && next->d_inode)
 104                                         n--;
 105                                 p = p->next;
 106                         }
 107                         list_add_tail(&cursor->d_u.d_child, p);
 108                         spin_unlock(&dcache_lock);
 109                 }
 110         }
 111         mutex_unlock(&file->f_path.dentry->d_inode->i_mutex);
 112         return offset;
 113 }
 114
 115 /* Relationship between i_mode and the DT_xxx types */
 116 static inline unsigned char dt_type(struct inode *inode)
 117 {
 118         return (inode->i_mode >> 12) & 15;
 119 }
 120
 121 /*
 122  * Directory is locked and all positive dentries in it are safe, since
 123  * for ramfs-type trees they can't go away without unlink() or rmdir(),
 124  * both impossible due to the lock on directory.
 125  */
 126
 127 int dcache_readdir(struct file * filp, void * dirent, filldir_t filldir)
 128 {
 129         struct dentry *dentry = filp->f_path.dentry;
 130         struct dentry *cursor = filp->private_data;
 131         struct list_head *p, *q = &cursor->d_u.d_child;
 132         ino_t ino;
 133         int i = filp->f_pos;
 134
 135         switch (i) {
 136                 case 0:
 137                         ino = dentry->d_inode->i_ino;
 138                         if (filldir(dirent, ".", 1, i, ino, DT_DIR) < 0)
 139                                 break;
 140                         filp->f_pos++;
 141                         i++;
 142                         /* fallthrough */
 143                 case 1:
 144                         ino = parent_ino(dentry);
 145                         if (filldir(dirent, "..", 2, i, ino, DT_DIR) < 0)
 146                                 break;
 147                         filp->f_pos++;
 148                         i++;
 149                         /* fallthrough */
 150                 default:
 151                         spin_lock(&dcache_lock);
 152                         if (filp->f_pos == 2)
 153                                 list_move(q, &dentry->d_subdirs);
 154
 155                         for (p=q->next; p != &dentry->d_subdirs; p=p->next) {
 156                                 struct dentry *next;
 157                                 next = list_entry(p, struct dentry, d_u.d_child);
 158                                 if (d_unhashed(next) || !next->d_inode)
 159                                         continue;
 160
 161                                 spin_unlock(&dcache_lock);
 162                                 if (filldir(dirent, next->d_name.name, next->d_name.len, filp->f_pos, next->d_inode->i_ino, dt_type(next->d_inode)) < 0)
 163                                         return 0;
 164                                 spin_lock(&dcache_lock);
 165                                 /* next is still alive */
 166                                 list_move(q, p);
 167                                 p = q;
 168                                 filp->f_pos++;
 169                         }
 170                         spin_unlock(&dcache_lock);
 171         }
 172         return 0;
 173 }
 174
 175 ssize_t generic_read_dir(struct file *filp, char __user *buf, size_t siz, loff_t *ppos)
 176 {
 177         return -EISDIR;
 178 }
 179
 180 const struct file_operations simple_dir_operations = {
 181         .open           = dcache_dir_open,
 182         .release        = dcache_dir_close,
 183         .llseek         = dcache_dir_lseek,
 184         .read           = generic_read_dir,
 185         .readdir        = dcache_readdir,
 186         .fsync          = simple_sync_file,
 187 };
 188
 189 const struct inode_operations simple_dir_inode_operations = {
 190         .lookup         = simple_lookup,
 191 };
 192
 193 static const struct super_operations simple_super_operations = {
 194         .statfs         = simple_statfs,
 195 };
 196
 197 /*
 198  * Common helper for pseudo-filesystems (sockfs, pipefs, bdev - stuff that
 199  * will never be mountable)
 200  */
 201 int get_sb_pseudo(struct file_system_type *fs_type, char *name,
 202         const struct super_operations *ops, unsigned long magic,
 203         struct vfsmount *mnt)
 204 {
 205         struct super_block *s = sget(fs_type, NULL, set_anon_super, NULL);
 206         struct dentry *dentry;
 207         struct inode *root;
 208         struct qstr d_name = {.name = name, .len = strlen(name)};
 209
 210         if (IS_ERR(s))
 211                 return PTR_ERR(s);
 212
 213         s->s_flags = MS_NOUSER;
 214         s->s_maxbytes = ~0ULL;
 215         s->s_blocksize = 1024;
 216         s->s_blocksize_bits = 10;
 217         s->s_magic = magic;
 218         s->s_op = ops ? ops : &simple_super_operations;
 219         s->s_time_gran = 1;
 220         root = new_inode(s);
 221         if (!root)
 222                 goto Enomem;
 223         /*
 224          * since this is the first inode, make it number 1. New inodes created
 225          * after this must take care not to collide with it (by passing
 226          * max_reserved of 1 to iunique).
 227          */
 228         root->i_ino = 1;
 229         root->i_mode = S_IFDIR | S_IRUSR | S_IWUSR;
 230         root->i_uid = root->i_gid = 0;
 231         root->i_atime = root->i_mtime = root->i_ctime = CURRENT_TIME;
 232         dentry = d_alloc(NULL, &d_name);
 233         if (!dentry) {
 234                 iput(root);
 235                 goto Enomem;
 236         }
 237         dentry->d_sb = s;
 238         dentry->d_parent = dentry;
 239         d_instantiate(dentry, root);
 240         s->s_root = dentry;
 241         s->s_flags |= MS_ACTIVE;
 242         return simple_set_mnt(mnt, s);
 243
 244 Enomem:
 245         up_write(&s->s_umount);
 246         deactivate_super(s);
 247         return -ENOMEM;
 248 }
 249
 250 int simple_link(struct dentry *old_dentry, struct inode *dir, struct dentry *dentry)
 251 {
 252         struct inode *inode = old_dentry->d_inode;
 253
 254         inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;
 255         inc_nlink(inode);
 256         atomic_inc(&inode->i_count);
 257         dget(dentry);
 258         d_instantiate(dentry, inode);
 259         return 0;
 260 }
 261
 262 static inline int simple_positive(struct dentry *dentry)
 263 {
 264         return dentry->d_inode && !d_unhashed(dentry);
 265 }
 266
 267 int simple_empty(struct dentry *dentry)
 268 {
 269         struct dentry *child;
 270         int ret = 0;
 271
 272         spin_lock(&dcache_lock);
 273         list_for_each_entry(child, &dentry->d_subdirs, d_u.d_child)
 274                 if (simple_positive(child))
 275                         goto out;
 276         ret = 1;
 277 out:
 278         spin_unlock(&dcache_lock);
 279         return ret;
 280 }
 281
 282 int simple_unlink(struct inode *dir, struct dentry *dentry)
 283 {
 284         struct inode *inode = dentry->d_inode;
 285
 286         inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;
 287         drop_nlink(inode);
 288         dput(dentry);
 289         return 0;
 290 }
 291
 292 int simple_rmdir(struct inode *dir, struct dentry *dentry)
 293 {
 294         if (!simple_empty(dentry))
 295                 return -ENOTEMPTY;
 296
 297         drop_nlink(dentry->d_inode);
 298         simple_unlink(dir, dentry);
 299         drop_nlink(dir);
 300         return 0;
 301 }
 302
 303 int simple_rename(struct inode *old_dir, struct dentry *old_dentry,
 304                 struct inode *new_dir, struct dentry *new_dentry)
 305 {
 306         struct inode *inode = old_dentry->d_inode;
 307         int they_are_dirs = S_ISDIR(old_dentry->d_inode->i_mode);
 308
 309         if (!simple_empty(new_dentry))
 310                 return -ENOTEMPTY;
 311
 312         if (new_dentry->d_inode) {
 313                 simple_unlink(new_dir, new_dentry);
 314                 if (they_are_dirs)
 315                         drop_nlink(old_dir);
 316         } else if (they_are_dirs) {
 317                 drop_nlink(old_dir);
 318                 inc_nlink(new_dir);
 319         }
 320
 321         old_dir->i_ctime = old_dir->i_mtime = new_dir->i_ctime =
 322                 new_dir->i_mtime = inode->i_ctime = CURRENT_TIME;
 323
 324         return 0;
 325 }
 326
 327 int simple_readpage(struct file *file, struct page *page)
 328 {
 329         clear_highpage(page);
 330         flush_dcache_page(page);
 331         SetPageUptodate(page);
 332         unlock_page(page);
 333         return 0;
 334 }
 335
 336 int simple_prepare_write(struct file *file, struct page *page,
 337                         unsigned from, unsigned to)
 338 {
 339         if (!PageUptodate(page)) {
 340                 if (to - from != PAGE_CACHE_SIZE) {
 341                         void *kaddr = kmap_atomic(page, KM_USER0);
 342                         memset(kaddr, 0, from);
 343                         memset(kaddr + to, 0, PAGE_CACHE_SIZE - to);
 344                         flush_dcache_page(page);
 345                         kunmap_atomic(kaddr, KM_USER0);
 346                 }
 347         }
 348         return 0;
 349 }
 350
 351 int simple_commit_write(struct file *file, struct page *page,
 352                         unsigned from, unsigned to)
 353 {
 354         struct inode *inode = page->mapping->host;
 355         loff_t pos = ((loff_t)page->index << PAGE_CACHE_SHIFT) + to;
 356
 357         if (!PageUptodate(page))
 358                 SetPageUptodate(page);
 359         /*
 360          * No need to use i_size_read() here, the i_size
 361          * cannot change under us because we hold the i_mutex.
 362          */
 363         if (pos > inode->i_size)
 364                 i_size_write(inode, pos);
 365         set_page_dirty(page);
 366         return 0;
 367 }
 368
 369 /*
 370  * the inodes created here are not hashed. If you use iunique to generate
 371  * unique inode values later for this filesystem, then you must take care
 372  * to pass it an appropriate max_reserved value to avoid collisions.
 373  */
 374 int simple_fill_super(struct super_block *s, int magic, struct tree_descr *files)
 375 {
 376         struct inode *inode;
 377         struct dentry *root;
 378         struct dentry *dentry;
 379         int i;
 380
 381         s->s_blocksize = PAGE_CACHE_SIZE;
 382         s->s_blocksize_bits = PAGE_CACHE_SHIFT;
 383         s->s_magic = magic;
 384         s->s_op = &simple_super_operations;
 385         s->s_time_gran = 1;
 386
 387         inode = new_inode(s);
 388         if (!inode)
 389                 return -ENOMEM;
 390         /*
 391          * because the root inode is 1, the files array must not contain an
 392          * entry at index 1
 393          */
 394         inode->i_ino = 1;
 395         inode->i_mode = S_IFDIR | 0755;
 396         inode->i_uid = inode->i_gid = 0;
 397         inode->i_blocks = 0;
 398         inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
 399         inode->i_op = &simple_dir_inode_operations;
 400         inode->i_fop = &simple_dir_operations;
 401         inode->i_nlink = 2;
 402         root = d_alloc_root(inode);
 403         if (!root) {
 404                 iput(inode);
 405                 return -ENOMEM;
 406         }
 407         for (i = 0; !files->name || files->name[0]; i++, files++) {
 408                 if (!files->name)
 409                         continue;
 410
 411                 /* warn if it tries to conflict with the root inode */
 412                 if (unlikely(i == 1))
 413                         printk(KERN_WARNING "%s: %s passed in a files array"
 414                                 "with an index of 1!\n", __func__,
 415                                 s->s_type->name);
 416
 417                 dentry = d_alloc_name(root, files->name);
 418                 if (!dentry)
 419                         goto out;
 420                 inode = new_inode(s);
 421                 if (!inode)
 422                         goto out;
 423                 inode->i_mode = S_IFREG | files->mode;
 424                 inode->i_uid = inode->i_gid = 0;
 425                 inode->i_blocks = 0;
 426                 inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
 427                 inode->i_fop = files->ops;
 428                 inode->i_ino = i;
 429                 d_add(dentry, inode);
 430         }
 431         s->s_root = root;
 432         return 0;
 433 out:
 434         d_genocide(root);
 435         dput(root);
 436         return -ENOMEM;
 437 }
 438
 439 static DEFINE_SPINLOCK(pin_fs_lock);
 440
 441 int simple_pin_fs(struct file_system_type *type, struct vfsmount **mount, int *count)
 442 {
 443         struct vfsmount *mnt = NULL;
 444         spin_lock(&pin_fs_lock);
 445         if (unlikely(!*mount)) {
 446                 spin_unlock(&pin_fs_lock);
 447                 mnt = vfs_kern_mount(type, 0, type->name, NULL);
 448                 if (IS_ERR(mnt))
 449                         return PTR_ERR(mnt);
 450                 spin_lock(&pin_fs_lock);
 451                 if (!*mount)
 452                         *mount = mnt;
 453         }
 454         mntget(*mount);
 455         ++*count;
 456         spin_unlock(&pin_fs_lock);
 457         mntput(mnt);
 458         return 0;
 459 }
 460
 461 void simple_release_fs(struct vfsmount **mount, int *count)
 462 {
 463         struct vfsmount *mnt;
 464         spin_lock(&pin_fs_lock);
 465         mnt = *mount;
 466         if (!--*count)
 467                 *mount = NULL;
 468         spin_unlock(&pin_fs_lock);
 469         mntput(mnt);
 470 }
 471
 472 ssize_t simple_read_from_buffer(void __user *to, size_t count, loff_t *ppos,
 473                                 const void *from, size_t available)
 474 {
 475         loff_t pos = *ppos;
 476         if (pos < 0)
 477                 return -EINVAL;
 478         if (pos >= available)
 479                 return 0;
 480         if (count > available - pos)
 481                 count = available - pos;
 482         if (copy_to_user(to, from + pos, count))
 483                 return -EFAULT;
 484         *ppos = pos + count;
 485         return count;
 486 }
 487
 488 /*
 489  * Transaction based IO.
 490  * The file expects a single write which triggers the transaction, and then
 491  * possibly a read which collects the result - which is stored in a
 492  * file-local buffer.
 493  */
 494 char *simple_transaction_get(struct file *file, const char __user *buf, size_t size)
 495 {
 496         struct simple_transaction_argresp *ar;
 497         static DEFINE_SPINLOCK(simple_transaction_lock);
 498
 499         if (size > SIMPLE_TRANSACTION_LIMIT - 1)
 500                 return ERR_PTR(-EFBIG);
 501
 502         ar = (struct simple_transaction_argresp *)get_zeroed_page(GFP_KERNEL);
 503         if (!ar)
 504                 return ERR_PTR(-ENOMEM);
 505
 506         spin_lock(&simple_transaction_lock);
 507
 508         /* only one write allowed per open */
 509         if (file->private_data) {
 510                 spin_unlock(&simple_transaction_lock);
 511                 free_page((unsigned long)ar);
 512                 return ERR_PTR(-EBUSY);
 513         }
 514
 515         file->private_data = ar;
 516
 517         spin_unlock(&simple_transaction_lock);
 518
 519         if (copy_from_user(ar->data, buf, size))
 520                 return ERR_PTR(-EFAULT);
 521
 522         return ar->data;
 523 }
 524
 525 ssize_t simple_transaction_read(struct file *file, char __user *buf, size_t size, loff_t *pos)
 526 {
 527         struct simple_transaction_argresp *ar = file->private_data;
 528
 529         if (!ar)
 530                 return 0;
 531         return simple_read_from_buffer(buf, size, pos, ar->data, ar->size);
 532 }
 533
 534 int simple_transaction_release(struct inode *inode, struct file *file)
 535 {
 536         free_page((unsigned long)file->private_data);
 537         return 0;
 538 }
 539
 540 /* Simple attribute files */
 541
 542 struct simple_attr {
 543         u64 (*get)(void *);
 544         void (*set)(void *, u64);
 545         char get_buf[24];       /* enough to store a u64 and "\n\0" */
 546         char set_buf[24];
 547         void *data;
 548         const char *fmt;        /* format for read operation */
 549         struct mutex mutex;     /* protects access to these buffers */
 550 };
 551
 552 /* simple_attr_open is called by an actual attribute open file operation
 553  * to set the attribute specific access operations. */
 554 int simple_attr_open(struct inode *inode, struct file *file,
 555                      u64 (*get)(void *), void (*set)(void *, u64),
 556                      const char *fmt)
 557 {
 558         struct simple_attr *attr;
 559
 560         attr = kmalloc(sizeof(*attr), GFP_KERNEL);
 561         if (!attr)
 562                 return -ENOMEM;
 563
 564         attr->get = get;
 565         attr->set = set;
 566         attr->data = inode->i_private;
 567         attr->fmt = fmt;
 568         mutex_init(&attr->mutex);
 569
 570         file->private_data = attr;
 571
 572         return nonseekable_open(inode, file);
 573 }
 574
 575 int simple_attr_close(struct inode *inode, struct file *file)
 576 {
 577         kfree(file->private_data);
 578         return 0;
 579 }
 580
 581 /* read from the buffer that is filled with the get function */
 582 ssize_t simple_attr_read(struct file *file, char __user *buf,
 583                          size_t len, loff_t *ppos)
 584 {
 585         struct simple_attr *attr;
 586         size_t size;
 587         ssize_t ret;
 588
 589         attr = file->private_data;
 590
 591         if (!attr->get)
 592                 return -EACCES;
 593
 594         mutex_lock(&attr->mutex);
 595         if (*ppos) /* continued read */
 596                 size = strlen(attr->get_buf);
 597         else      /* first read */
 598                 size = scnprintf(attr->get_buf, sizeof(attr->get_buf),
 599                                  attr->fmt,
 600                                  (unsigned long long)attr->get(attr->data));
 601
 602         ret = simple_read_from_buffer(buf, len, ppos, attr->get_buf, size);
 603         mutex_unlock(&attr->mutex);
 604         return ret;
 605 }
 606
 607 /* interpret the buffer as a number to call the set function with */
 608 ssize_t simple_attr_write(struct file *file, const char __user *buf,
 609                           size_t len, loff_t *ppos)
 610 {
 611         struct simple_attr *attr;
 612         u64 val;
 613         size_t size;
 614         ssize_t ret;
 615
 616         attr = file->private_data;
 617
 618         if (!attr->set)
 619                 return -EACCES;
 620
 621         mutex_lock(&attr->mutex);
 622         ret = -EFAULT;
 623         size = min(sizeof(attr->set_buf) - 1, len);
 624         if (copy_from_user(attr->set_buf, buf, size))
 625                 goto out;
 626
 627         ret = len; /* claim we got the whole input */
 628         attr->set_buf[size] = '\0';
 629         val = simple_strtol(attr->set_buf, NULL, 0);
 630         attr->set(attr->data, val);
 631 out:
 632         mutex_unlock(&attr->mutex);
 633         return ret;
 634 }
 635
 636 EXPORT_SYMBOL(dcache_dir_close);
 637 EXPORT_SYMBOL(dcache_dir_lseek);
 638 EXPORT_SYMBOL(dcache_dir_open);
 639 EXPORT_SYMBOL(dcache_readdir);
 640 EXPORT_SYMBOL(generic_read_dir);
 641 EXPORT_SYMBOL(get_sb_pseudo);
 642 EXPORT_SYMBOL(simple_commit_write);
 643 EXPORT_SYMBOL(simple_dir_inode_operations);
 644 EXPORT_SYMBOL(simple_dir_operations);
 645 EXPORT_SYMBOL(simple_empty);
 646 EXPORT_SYMBOL(d_alloc_name);
 647 EXPORT_SYMBOL(simple_fill_super);
 648 EXPORT_SYMBOL(simple_getattr);
 649 EXPORT_SYMBOL(simple_link);
 650 EXPORT_SYMBOL(simple_lookup);
 651 EXPORT_SYMBOL(simple_pin_fs);
 652 EXPORT_SYMBOL(simple_prepare_write);
 653 EXPORT_SYMBOL(simple_readpage);
 654 EXPORT_SYMBOL(simple_release_fs);
 655 EXPORT_SYMBOL(simple_rename);
 656 EXPORT_SYMBOL(simple_rmdir);
 657 EXPORT_SYMBOL(simple_statfs);
 658 EXPORT_SYMBOL(simple_sync_file);
 659 EXPORT_SYMBOL(simple_unlink);
 660 EXPORT_SYMBOL(simple_read_from_buffer);
 661 EXPORT_SYMBOL(simple_transaction_get);
 662 EXPORT_SYMBOL(simple_transaction_read);
 663 EXPORT_SYMBOL(simple_transaction_release);
 664 EXPORT_SYMBOL_GPL(simple_attr_open);
 665 EXPORT_SYMBOL_GPL(simple_attr_close);
 666 EXPORT_SYMBOL_GPL(simple_attr_read);
 667 EXPORT_SYMBOL_GPL(simple_attr_write);