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 super_block *sb, struct kstatfs *buf)
  24 {
  25         buf->f_type = 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_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_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_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_dentry->d_subdirs.next;
 100                         while (n && p != &file->f_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_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_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_del(q);
 154                                 list_add(q, &dentry->d_subdirs);
 155                         }
 156                         for (p=q->next; p != &dentry->d_subdirs; p=p->next) {
 157                                 struct dentry *next;
 158                                 next = list_entry(p, struct dentry, d_u.d_child);
 159                                 if (d_unhashed(next) || !next->d_inode)
 160                                         continue;
 161
 162                                 spin_unlock(&dcache_lock);
 163                                 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)
 164                                         return 0;
 165                                 spin_lock(&dcache_lock);
 166                                 /* next is still alive */
 167                                 list_del(q);
 168                                 list_add(q, p);
 169                                 p = q;
 170                                 filp->f_pos++;
 171                         }
 172                         spin_unlock(&dcache_lock);
 173         }
 174         return 0;
 175 }
 176
 177 ssize_t generic_read_dir(struct file *filp, char __user *buf, size_t siz, loff_t *ppos)
 178 {
 179         return -EISDIR;
 180 }
 181
 182 struct file_operations simple_dir_operations = {
 183         .open           = dcache_dir_open,
 184         .release        = dcache_dir_close,
 185         .llseek         = dcache_dir_lseek,
 186         .read           = generic_read_dir,
 187         .readdir        = dcache_readdir,
 188         .fsync          = simple_sync_file,
 189 };
 190
 191 struct inode_operations simple_dir_inode_operations = {
 192         .lookup         = simple_lookup,
 193 };
 194
 195 /*
 196  * Common helper for pseudo-filesystems (sockfs, pipefs, bdev - stuff that
 197  * will never be mountable)
 198  */
 199 struct super_block *
 200 get_sb_pseudo(struct file_system_type *fs_type, char *name,
 201         struct super_operations *ops, unsigned long magic)
 202 {
 203         struct super_block *s = sget(fs_type, NULL, set_anon_super, NULL);
 204         static struct super_operations default_ops = {.statfs = simple_statfs};
 205         struct dentry *dentry;
 206         struct inode *root;
 207         struct qstr d_name = {.name = name, .len = strlen(name)};
 208
 209         if (IS_ERR(s))
 210                 return s;
 211
 212         s->s_flags = MS_NOUSER;
 213         s->s_maxbytes = ~0ULL;
 214         s->s_blocksize = 1024;
 215         s->s_blocksize_bits = 10;
 216         s->s_magic = magic;
 217         s->s_op = ops ? ops : &default_ops;
 218         s->s_time_gran = 1;
 219         root = new_inode(s);
 220         if (!root)
 221                 goto Enomem;
 222         root->i_mode = S_IFDIR | S_IRUSR | S_IWUSR;
 223         root->i_uid = root->i_gid = 0;
 224         root->i_atime = root->i_mtime = root->i_ctime = CURRENT_TIME;
 225         dentry = d_alloc(NULL, &d_name);
 226         if (!dentry) {
 227                 iput(root);
 228                 goto Enomem;
 229         }
 230         dentry->d_sb = s;
 231         dentry->d_parent = dentry;
 232         d_instantiate(dentry, root);
 233         s->s_root = dentry;
 234         s->s_flags |= MS_ACTIVE;
 235         return s;
 236
 237 Enomem:
 238         up_write(&s->s_umount);
 239         deactivate_super(s);
 240         return ERR_PTR(-ENOMEM);
 241 }
 242
 243 int simple_link(struct dentry *old_dentry, struct inode *dir, struct dentry *dentry)
 244 {
 245         struct inode *inode = old_dentry->d_inode;
 246
 247         inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;
 248         inode->i_nlink++;
 249         atomic_inc(&inode->i_count);
 250         dget(dentry);
 251         d_instantiate(dentry, inode);
 252         return 0;
 253 }
 254
 255 static inline int simple_positive(struct dentry *dentry)
 256 {
 257         return dentry->d_inode && !d_unhashed(dentry);
 258 }
 259
 260 int simple_empty(struct dentry *dentry)
 261 {
 262         struct dentry *child;
 263         int ret = 0;
 264
 265         spin_lock(&dcache_lock);
 266         list_for_each_entry(child, &dentry->d_subdirs, d_u.d_child)
 267                 if (simple_positive(child))
 268                         goto out;
 269         ret = 1;
 270 out:
 271         spin_unlock(&dcache_lock);
 272         return ret;
 273 }
 274
 275 int simple_unlink(struct inode *dir, struct dentry *dentry)
 276 {
 277         struct inode *inode = dentry->d_inode;
 278
 279         inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;
 280         inode->i_nlink--;
 281         dput(dentry);
 282         return 0;
 283 }
 284
 285 int simple_rmdir(struct inode *dir, struct dentry *dentry)
 286 {
 287         if (!simple_empty(dentry))
 288                 return -ENOTEMPTY;
 289
 290         dentry->d_inode->i_nlink--;
 291         simple_unlink(dir, dentry);
 292         dir->i_nlink--;
 293         return 0;
 294 }
 295
 296 int simple_rename(struct inode *old_dir, struct dentry *old_dentry,
 297                 struct inode *new_dir, struct dentry *new_dentry)
 298 {
 299         struct inode *inode = old_dentry->d_inode;
 300         int they_are_dirs = S_ISDIR(old_dentry->d_inode->i_mode);
 301
 302         if (!simple_empty(new_dentry))
 303                 return -ENOTEMPTY;
 304
 305         if (new_dentry->d_inode) {
 306                 simple_unlink(new_dir, new_dentry);
 307                 if (they_are_dirs)
 308                         old_dir->i_nlink--;
 309         } else if (they_are_dirs) {
 310                 old_dir->i_nlink--;
 311                 new_dir->i_nlink++;
 312         }
 313
 314         old_dir->i_ctime = old_dir->i_mtime = new_dir->i_ctime =
 315                 new_dir->i_mtime = inode->i_ctime = CURRENT_TIME;
 316
 317         return 0;
 318 }
 319
 320 int simple_readpage(struct file *file, struct page *page)
 321 {
 322         void *kaddr;
 323
 324         if (PageUptodate(page))
 325                 goto out;
 326
 327         kaddr = kmap_atomic(page, KM_USER0);
 328         memset(kaddr, 0, PAGE_CACHE_SIZE);
 329         kunmap_atomic(kaddr, KM_USER0);
 330         flush_dcache_page(page);
 331         SetPageUptodate(page);
 332 out:
 333         unlock_page(page);
 334         return 0;
 335 }
 336
 337 int simple_prepare_write(struct file *file, struct page *page,
 338                         unsigned from, unsigned to)
 339 {
 340         if (!PageUptodate(page)) {
 341                 if (to - from != PAGE_CACHE_SIZE) {
 342                         void *kaddr = kmap_atomic(page, KM_USER0);
 343                         memset(kaddr, 0, from);
 344                         memset(kaddr + to, 0, PAGE_CACHE_SIZE - to);
 345                         flush_dcache_page(page);
 346                         kunmap_atomic(kaddr, KM_USER0);
 347                 }
 348                 SetPageUptodate(page);
 349         }
 350         return 0;
 351 }
 352
 353 int simple_commit_write(struct file *file, struct page *page,
 354                         unsigned offset, unsigned to)
 355 {
 356         struct inode *inode = page->mapping->host;
 357         loff_t pos = ((loff_t)page->index << PAGE_CACHE_SHIFT) + to;
 358
 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 int simple_fill_super(struct super_block *s, int magic, struct tree_descr *files)
 370 {
 371         static struct super_operations s_ops = {.statfs = simple_statfs};
 372         struct inode *inode;
 373         struct dentry *root;
 374         struct dentry *dentry;
 375         int i;
 376
 377         s->s_blocksize = PAGE_CACHE_SIZE;
 378         s->s_blocksize_bits = PAGE_CACHE_SHIFT;
 379         s->s_magic = magic;
 380         s->s_op = &s_ops;
 381         s->s_time_gran = 1;
 382
 383         inode = new_inode(s);
 384         if (!inode)
 385                 return -ENOMEM;
 386         inode->i_mode = S_IFDIR | 0755;
 387         inode->i_uid = inode->i_gid = 0;
 388         inode->i_blksize = PAGE_CACHE_SIZE;
 389         inode->i_blocks = 0;
 390         inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
 391         inode->i_op = &simple_dir_inode_operations;
 392         inode->i_fop = &simple_dir_operations;
 393         inode->i_nlink = 2;
 394         root = d_alloc_root(inode);
 395         if (!root) {
 396                 iput(inode);
 397                 return -ENOMEM;
 398         }
 399         for (i = 0; !files->name || files->name[0]; i++, files++) {
 400                 if (!files->name)
 401                         continue;
 402                 dentry = d_alloc_name(root, files->name);
 403                 if (!dentry)
 404                         goto out;
 405                 inode = new_inode(s);
 406                 if (!inode)
 407                         goto out;
 408                 inode->i_mode = S_IFREG | files->mode;
 409                 inode->i_uid = inode->i_gid = 0;
 410                 inode->i_blksize = PAGE_CACHE_SIZE;
 411                 inode->i_blocks = 0;
 412                 inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
 413                 inode->i_fop = files->ops;
 414                 inode->i_ino = i;
 415                 d_add(dentry, inode);
 416         }
 417         s->s_root = root;
 418         return 0;
 419 out:
 420         d_genocide(root);
 421         dput(root);
 422         return -ENOMEM;
 423 }
 424
 425 static DEFINE_SPINLOCK(pin_fs_lock);
 426
 427 int simple_pin_fs(char *name, struct vfsmount **mount, int *count)
 428 {
 429         struct vfsmount *mnt = NULL;
 430         spin_lock(&pin_fs_lock);
 431         if (unlikely(!*mount)) {
 432                 spin_unlock(&pin_fs_lock);
 433                 mnt = do_kern_mount(name, 0, name, NULL);
 434                 if (IS_ERR(mnt))
 435                         return PTR_ERR(mnt);
 436                 spin_lock(&pin_fs_lock);
 437                 if (!*mount)
 438                         *mount = mnt;
 439         }
 440         mntget(*mount);
 441         ++*count;
 442         spin_unlock(&pin_fs_lock);
 443         mntput(mnt);
 444         return 0;
 445 }
 446
 447 void simple_release_fs(struct vfsmount **mount, int *count)
 448 {
 449         struct vfsmount *mnt;
 450         spin_lock(&pin_fs_lock);
 451         mnt = *mount;
 452         if (!--*count)
 453                 *mount = NULL;
 454         spin_unlock(&pin_fs_lock);
 455         mntput(mnt);
 456 }
 457
 458 ssize_t simple_read_from_buffer(void __user *to, size_t count, loff_t *ppos,
 459                                 const void *from, size_t available)
 460 {
 461         loff_t pos = *ppos;
 462         if (pos < 0)
 463                 return -EINVAL;
 464         if (pos >= available)
 465                 return 0;
 466         if (count > available - pos)
 467                 count = available - pos;
 468         if (copy_to_user(to, from + pos, count))
 469                 return -EFAULT;
 470         *ppos = pos + count;
 471         return count;
 472 }
 473
 474 /*
 475  * Transaction based IO.
 476  * The file expects a single write which triggers the transaction, and then
 477  * possibly a read which collects the result - which is stored in a
 478  * file-local buffer.
 479  */
 480 char *simple_transaction_get(struct file *file, const char __user *buf, size_t size)
 481 {
 482         struct simple_transaction_argresp *ar;
 483         static DEFINE_SPINLOCK(simple_transaction_lock);
 484
 485         if (size > SIMPLE_TRANSACTION_LIMIT - 1)
 486                 return ERR_PTR(-EFBIG);
 487
 488         ar = (struct simple_transaction_argresp *)get_zeroed_page(GFP_KERNEL);
 489         if (!ar)
 490                 return ERR_PTR(-ENOMEM);
 491
 492         spin_lock(&simple_transaction_lock);
 493
 494         /* only one write allowed per open */
 495         if (file->private_data) {
 496                 spin_unlock(&simple_transaction_lock);
 497                 free_page((unsigned long)ar);
 498                 return ERR_PTR(-EBUSY);
 499         }
 500
 501         file->private_data = ar;
 502
 503         spin_unlock(&simple_transaction_lock);
 504
 505         if (copy_from_user(ar->data, buf, size))
 506                 return ERR_PTR(-EFAULT);
 507
 508         return ar->data;
 509 }
 510
 511 ssize_t simple_transaction_read(struct file *file, char __user *buf, size_t size, loff_t *pos)
 512 {
 513         struct simple_transaction_argresp *ar = file->private_data;
 514
 515         if (!ar)
 516                 return 0;
 517         return simple_read_from_buffer(buf, size, pos, ar->data, ar->size);
 518 }
 519
 520 int simple_transaction_release(struct inode *inode, struct file *file)
 521 {
 522         free_page((unsigned long)file->private_data);
 523         return 0;
 524 }
 525
 526 /* Simple attribute files */
 527
 528 struct simple_attr {
 529         u64 (*get)(void *);
 530         void (*set)(void *, u64);
 531         char get_buf[24];       /* enough to store a u64 and "\n\0" */
 532         char set_buf[24];
 533         void *data;
 534         const char *fmt;        /* format for read operation */
 535         struct mutex mutex;     /* protects access to these buffers */
 536 };
 537
 538 /* simple_attr_open is called by an actual attribute open file operation
 539  * to set the attribute specific access operations. */
 540 int simple_attr_open(struct inode *inode, struct file *file,
 541                      u64 (*get)(void *), void (*set)(void *, u64),
 542                      const char *fmt)
 543 {
 544         struct simple_attr *attr;
 545
 546         attr = kmalloc(sizeof(*attr), GFP_KERNEL);
 547         if (!attr)
 548                 return -ENOMEM;
 549
 550         attr->get = get;
 551         attr->set = set;
 552         attr->data = inode->u.generic_ip;
 553         attr->fmt = fmt;
 554         mutex_init(&attr->mutex);
 555
 556         file->private_data = attr;
 557
 558         return nonseekable_open(inode, file);
 559 }
 560
 561 int simple_attr_close(struct inode *inode, struct file *file)
 562 {
 563         kfree(file->private_data);
 564         return 0;
 565 }
 566
 567 /* read from the buffer that is filled with the get function */
 568 ssize_t simple_attr_read(struct file *file, char __user *buf,
 569                          size_t len, loff_t *ppos)
 570 {
 571         struct simple_attr *attr;
 572         size_t size;
 573         ssize_t ret;
 574
 575         attr = file->private_data;
 576
 577         if (!attr->get)
 578                 return -EACCES;
 579
 580         mutex_lock(&attr->mutex);
 581         if (*ppos) /* continued read */
 582                 size = strlen(attr->get_buf);
 583         else      /* first read */
 584                 size = scnprintf(attr->get_buf, sizeof(attr->get_buf),
 585                                  attr->fmt,
 586                                  (unsigned long long)attr->get(attr->data));
 587
 588         ret = simple_read_from_buffer(buf, len, ppos, attr->get_buf, size);
 589         mutex_unlock(&attr->mutex);
 590         return ret;
 591 }
 592
 593 /* interpret the buffer as a number to call the set function with */
 594 ssize_t simple_attr_write(struct file *file, const char __user *buf,
 595                           size_t len, loff_t *ppos)
 596 {
 597         struct simple_attr *attr;
 598         u64 val;
 599         size_t size;
 600         ssize_t ret;
 601
 602         attr = file->private_data;
 603
 604         if (!attr->set)
 605                 return -EACCES;
 606
 607         mutex_lock(&attr->mutex);
 608         ret = -EFAULT;
 609         size = min(sizeof(attr->set_buf) - 1, len);
 610         if (copy_from_user(attr->set_buf, buf, size))
 611                 goto out;
 612
 613         ret = len; /* claim we got the whole input */
 614         attr->set_buf[size] = '\0';
 615         val = simple_strtol(attr->set_buf, NULL, 0);
 616         attr->set(attr->data, val);
 617 out:
 618         mutex_unlock(&attr->mutex);
 619         return ret;
 620 }
 621
 622 EXPORT_SYMBOL(dcache_dir_close);
 623 EXPORT_SYMBOL(dcache_dir_lseek);
 624 EXPORT_SYMBOL(dcache_dir_open);
 625 EXPORT_SYMBOL(dcache_readdir);
 626 EXPORT_SYMBOL(generic_read_dir);
 627 EXPORT_SYMBOL(get_sb_pseudo);
 628 EXPORT_SYMBOL(simple_commit_write);
 629 EXPORT_SYMBOL(simple_dir_inode_operations);
 630 EXPORT_SYMBOL(simple_dir_operations);
 631 EXPORT_SYMBOL(simple_empty);
 632 EXPORT_SYMBOL(d_alloc_name);
 633 EXPORT_SYMBOL(simple_fill_super);
 634 EXPORT_SYMBOL(simple_getattr);
 635 EXPORT_SYMBOL(simple_link);
 636 EXPORT_SYMBOL(simple_lookup);
 637 EXPORT_SYMBOL(simple_pin_fs);
 638 EXPORT_SYMBOL(simple_prepare_write);
 639 EXPORT_SYMBOL(simple_readpage);
 640 EXPORT_SYMBOL(simple_release_fs);
 641 EXPORT_SYMBOL(simple_rename);
 642 EXPORT_SYMBOL(simple_rmdir);
 643 EXPORT_SYMBOL(simple_statfs);
 644 EXPORT_SYMBOL(simple_sync_file);
 645 EXPORT_SYMBOL(simple_unlink);
 646 EXPORT_SYMBOL(simple_read_from_buffer);
 647 EXPORT_SYMBOL(simple_transaction_get);
 648 EXPORT_SYMBOL(simple_transaction_read);
 649 EXPORT_SYMBOL(simple_transaction_release);
 650 EXPORT_SYMBOL_GPL(simple_attr_open);
 651 EXPORT_SYMBOL_GPL(simple_attr_close);
 652 EXPORT_SYMBOL_GPL(simple_attr_read);
 653 EXPORT_SYMBOL_GPL(simple_attr_write);