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,
 163                                             next->d_name.len, filp->f_pos,
 164                                             next->d_inode->i_ino,
 165                                             dt_type(next->d_inode)) < 0)
 166                                         return 0;
 167                                 spin_lock(&dcache_lock);
 168                                 /* next is still alive */
 169                                 list_move(q, p);
 170                                 p = q;
 171                                 filp->f_pos++;
 172                         }
 173                         spin_unlock(&dcache_lock);
 174         }
 175         return 0;
 176 }
 177
 178 ssize_t generic_read_dir(struct file *filp, char __user *buf, size_t siz, loff_t *ppos)
 179 {
 180         return -EISDIR;
 181 }
 182
 183 const struct file_operations simple_dir_operations = {
 184         .open           = dcache_dir_open,
 185         .release        = dcache_dir_close,
 186         .llseek         = dcache_dir_lseek,
 187         .read           = generic_read_dir,
 188         .readdir        = dcache_readdir,
 189         .fsync          = simple_sync_file,
 190 };
 191
 192 const struct inode_operations simple_dir_inode_operations = {
 193         .lookup         = simple_lookup,
 194 };
 195
 196 static const struct super_operations simple_super_operations = {
 197         .statfs         = simple_statfs,
 198 };
 199
 200 /*
 201  * Common helper for pseudo-filesystems (sockfs, pipefs, bdev - stuff that
 202  * will never be mountable)
 203  */
 204 int get_sb_pseudo(struct file_system_type *fs_type, char *name,
 205         const struct super_operations *ops, unsigned long magic,
 206         struct vfsmount *mnt)
 207 {
 208         struct super_block *s = sget(fs_type, NULL, set_anon_super, NULL);
 209         struct dentry *dentry;
 210         struct inode *root;
 211         struct qstr d_name = {.name = name, .len = strlen(name)};
 212
 213         if (IS_ERR(s))
 214                 return PTR_ERR(s);
 215
 216         s->s_flags = MS_NOUSER;
 217         s->s_maxbytes = ~0ULL;
 218         s->s_blocksize = 1024;
 219         s->s_blocksize_bits = 10;
 220         s->s_magic = magic;
 221         s->s_op = ops ? ops : &simple_super_operations;
 222         s->s_time_gran = 1;
 223         root = new_inode(s);
 224         if (!root)
 225                 goto Enomem;
 226         /*
 227          * since this is the first inode, make it number 1. New inodes created
 228          * after this must take care not to collide with it (by passing
 229          * max_reserved of 1 to iunique).
 230          */
 231         root->i_ino = 1;
 232         root->i_mode = S_IFDIR | S_IRUSR | S_IWUSR;
 233         root->i_uid = root->i_gid = 0;
 234         root->i_atime = root->i_mtime = root->i_ctime = CURRENT_TIME;
 235         dentry = d_alloc(NULL, &d_name);
 236         if (!dentry) {
 237                 iput(root);
 238                 goto Enomem;
 239         }
 240         dentry->d_sb = s;
 241         dentry->d_parent = dentry;
 242         d_instantiate(dentry, root);
 243         s->s_root = dentry;
 244         s->s_flags |= MS_ACTIVE;
 245         return simple_set_mnt(mnt, s);
 246
 247 Enomem:
 248         up_write(&s->s_umount);
 249         deactivate_super(s);
 250         return -ENOMEM;
 251 }
 252
 253 int simple_link(struct dentry *old_dentry, struct inode *dir, struct dentry *dentry)
 254 {
 255         struct inode *inode = old_dentry->d_inode;
 256
 257         inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;
 258         inc_nlink(inode);
 259         atomic_inc(&inode->i_count);
 260         dget(dentry);
 261         d_instantiate(dentry, inode);
 262         return 0;
 263 }
 264
 265 static inline int simple_positive(struct dentry *dentry)
 266 {
 267         return dentry->d_inode && !d_unhashed(dentry);
 268 }
 269
 270 int simple_empty(struct dentry *dentry)
 271 {
 272         struct dentry *child;
 273         int ret = 0;
 274
 275         spin_lock(&dcache_lock);
 276         list_for_each_entry(child, &dentry->d_subdirs, d_u.d_child)
 277                 if (simple_positive(child))
 278                         goto out;
 279         ret = 1;
 280 out:
 281         spin_unlock(&dcache_lock);
 282         return ret;
 283 }
 284
 285 int simple_unlink(struct inode *dir, struct dentry *dentry)
 286 {
 287         struct inode *inode = dentry->d_inode;
 288
 289         inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;
 290         drop_nlink(inode);
 291         dput(dentry);
 292         return 0;
 293 }
 294
 295 int simple_rmdir(struct inode *dir, struct dentry *dentry)
 296 {
 297         if (!simple_empty(dentry))
 298                 return -ENOTEMPTY;
 299
 300         drop_nlink(dentry->d_inode);
 301         simple_unlink(dir, dentry);
 302         drop_nlink(dir);
 303         return 0;
 304 }
 305
 306 int simple_rename(struct inode *old_dir, struct dentry *old_dentry,
 307                 struct inode *new_dir, struct dentry *new_dentry)
 308 {
 309         struct inode *inode = old_dentry->d_inode;
 310         int they_are_dirs = S_ISDIR(old_dentry->d_inode->i_mode);
 311
 312         if (!simple_empty(new_dentry))
 313                 return -ENOTEMPTY;
 314
 315         if (new_dentry->d_inode) {
 316                 simple_unlink(new_dir, new_dentry);
 317                 if (they_are_dirs)
 318                         drop_nlink(old_dir);
 319         } else if (they_are_dirs) {
 320                 drop_nlink(old_dir);
 321                 inc_nlink(new_dir);
 322         }
 323
 324         old_dir->i_ctime = old_dir->i_mtime = new_dir->i_ctime =
 325                 new_dir->i_mtime = inode->i_ctime = CURRENT_TIME;
 326
 327         return 0;
 328 }
 329
 330 int simple_readpage(struct file *file, struct page *page)
 331 {
 332         clear_highpage(page);
 333         flush_dcache_page(page);
 334         SetPageUptodate(page);
 335         unlock_page(page);
 336         return 0;
 337 }
 338
 339 int simple_prepare_write(struct file *file, struct page *page,
 340                         unsigned from, unsigned to)
 341 {
 342         if (!PageUptodate(page)) {
 343                 if (to - from != PAGE_CACHE_SIZE) {
 344                         void *kaddr = kmap_atomic(page, KM_USER0);
 345                         memset(kaddr, 0, from);
 346                         memset(kaddr + to, 0, PAGE_CACHE_SIZE - to);
 347                         flush_dcache_page(page);
 348                         kunmap_atomic(kaddr, KM_USER0);
 349                 }
 350         }
 351         return 0;
 352 }
 353
 354 int simple_commit_write(struct file *file, struct page *page,
 355                         unsigned from, unsigned to)
 356 {
 357         struct inode *inode = page->mapping->host;
 358         loff_t pos = ((loff_t)page->index << PAGE_CACHE_SHIFT) + to;
 359
 360         if (!PageUptodate(page))
 361                 SetPageUptodate(page);
 362         /*
 363          * No need to use i_size_read() here, the i_size
 364          * cannot change under us because we hold the i_mutex.
 365          */
 366         if (pos > inode->i_size)
 367                 i_size_write(inode, pos);
 368         set_page_dirty(page);
 369         return 0;
 370 }
 371
 372 /*
 373  * the inodes created here are not hashed. If you use iunique to generate
 374  * unique inode values later for this filesystem, then you must take care
 375  * to pass it an appropriate max_reserved value to avoid collisions.
 376  */
 377 int simple_fill_super(struct super_block *s, int magic, struct tree_descr *files)
 378 {
 379         struct inode *inode;
 380         struct dentry *root;
 381         struct dentry *dentry;
 382         int i;
 383
 384         s->s_blocksize = PAGE_CACHE_SIZE;
 385         s->s_blocksize_bits = PAGE_CACHE_SHIFT;
 386         s->s_magic = magic;
 387         s->s_op = &simple_super_operations;
 388         s->s_time_gran = 1;
 389
 390         inode = new_inode(s);
 391         if (!inode)
 392                 return -ENOMEM;
 393         /*
 394          * because the root inode is 1, the files array must not contain an
 395          * entry at index 1
 396          */
 397         inode->i_ino = 1;
 398         inode->i_mode = S_IFDIR | 0755;
 399         inode->i_uid = inode->i_gid = 0;
 400         inode->i_blocks = 0;
 401         inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
 402         inode->i_op = &simple_dir_inode_operations;
 403         inode->i_fop = &simple_dir_operations;
 404         inode->i_nlink = 2;
 405         root = d_alloc_root(inode);
 406         if (!root) {
 407                 iput(inode);
 408                 return -ENOMEM;
 409         }
 410         for (i = 0; !files->name || files->name[0]; i++, files++) {
 411                 if (!files->name)
 412                         continue;
 413
 414                 /* warn if it tries to conflict with the root inode */
 415                 if (unlikely(i == 1))
 416                         printk(KERN_WARNING "%s: %s passed in a files array"
 417                                 "with an index of 1!\n", __func__,
 418                                 s->s_type->name);
 419
 420                 dentry = d_alloc_name(root, files->name);
 421                 if (!dentry)
 422                         goto out;
 423                 inode = new_inode(s);
 424                 if (!inode)
 425                         goto out;
 426                 inode->i_mode = S_IFREG | files->mode;
 427                 inode->i_uid = inode->i_gid = 0;
 428                 inode->i_blocks = 0;
 429                 inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
 430                 inode->i_fop = files->ops;
 431                 inode->i_ino = i;
 432                 d_add(dentry, inode);
 433         }
 434         s->s_root = root;
 435         return 0;
 436 out:
 437         d_genocide(root);
 438         dput(root);
 439         return -ENOMEM;
 440 }
 441
 442 static DEFINE_SPINLOCK(pin_fs_lock);
 443
 444 int simple_pin_fs(struct file_system_type *type, struct vfsmount **mount, int *count)
 445 {
 446         struct vfsmount *mnt = NULL;
 447         spin_lock(&pin_fs_lock);
 448         if (unlikely(!*mount)) {
 449                 spin_unlock(&pin_fs_lock);
 450                 mnt = vfs_kern_mount(type, 0, type->name, NULL);
 451                 if (IS_ERR(mnt))
 452                         return PTR_ERR(mnt);
 453                 spin_lock(&pin_fs_lock);
 454                 if (!*mount)
 455                         *mount = mnt;
 456         }
 457         mntget(*mount);
 458         ++*count;
 459         spin_unlock(&pin_fs_lock);
 460         mntput(mnt);
 461         return 0;
 462 }
 463
 464 void simple_release_fs(struct vfsmount **mount, int *count)
 465 {
 466         struct vfsmount *mnt;
 467         spin_lock(&pin_fs_lock);
 468         mnt = *mount;
 469         if (!--*count)
 470                 *mount = NULL;
 471         spin_unlock(&pin_fs_lock);
 472         mntput(mnt);
 473 }
 474
 475 ssize_t simple_read_from_buffer(void __user *to, size_t count, loff_t *ppos,
 476                                 const void *from, size_t available)
 477 {
 478         loff_t pos = *ppos;
 479         if (pos < 0)
 480                 return -EINVAL;
 481         if (pos >= available)
 482                 return 0;
 483         if (count > available - pos)
 484                 count = available - pos;
 485         if (copy_to_user(to, from + pos, count))
 486                 return -EFAULT;
 487         *ppos = pos + count;
 488         return count;
 489 }
 490
 491 /*
 492  * Transaction based IO.
 493  * The file expects a single write which triggers the transaction, and then
 494  * possibly a read which collects the result - which is stored in a
 495  * file-local buffer.
 496  */
 497 char *simple_transaction_get(struct file *file, const char __user *buf, size_t size)
 498 {
 499         struct simple_transaction_argresp *ar;
 500         static DEFINE_SPINLOCK(simple_transaction_lock);
 501
 502         if (size > SIMPLE_TRANSACTION_LIMIT - 1)
 503                 return ERR_PTR(-EFBIG);
 504
 505         ar = (struct simple_transaction_argresp *)get_zeroed_page(GFP_KERNEL);
 506         if (!ar)
 507                 return ERR_PTR(-ENOMEM);
 508
 509         spin_lock(&simple_transaction_lock);
 510
 511         /* only one write allowed per open */
 512         if (file->private_data) {
 513                 spin_unlock(&simple_transaction_lock);
 514                 free_page((unsigned long)ar);
 515                 return ERR_PTR(-EBUSY);
 516         }
 517
 518         file->private_data = ar;
 519
 520         spin_unlock(&simple_transaction_lock);
 521
 522         if (copy_from_user(ar->data, buf, size))
 523                 return ERR_PTR(-EFAULT);
 524
 525         return ar->data;
 526 }
 527
 528 ssize_t simple_transaction_read(struct file *file, char __user *buf, size_t size, loff_t *pos)
 529 {
 530         struct simple_transaction_argresp *ar = file->private_data;
 531
 532         if (!ar)
 533                 return 0;
 534         return simple_read_from_buffer(buf, size, pos, ar->data, ar->size);
 535 }
 536
 537 int simple_transaction_release(struct inode *inode, struct file *file)
 538 {
 539         free_page((unsigned long)file->private_data);
 540         return 0;
 541 }
 542
 543 /* Simple attribute files */
 544
 545 struct simple_attr {
 546         u64 (*get)(void *);
 547         void (*set)(void *, u64);
 548         char get_buf[24];       /* enough to store a u64 and "\n\0" */
 549         char set_buf[24];
 550         void *data;
 551         const char *fmt;        /* format for read operation */
 552         struct mutex mutex;     /* protects access to these buffers */
 553 };
 554
 555 /* simple_attr_open is called by an actual attribute open file operation
 556  * to set the attribute specific access operations. */
 557 int simple_attr_open(struct inode *inode, struct file *file,
 558                      u64 (*get)(void *), void (*set)(void *, u64),
 559                      const char *fmt)
 560 {
 561         struct simple_attr *attr;
 562
 563         attr = kmalloc(sizeof(*attr), GFP_KERNEL);
 564         if (!attr)
 565                 return -ENOMEM;
 566
 567         attr->get = get;
 568         attr->set = set;
 569         attr->data = inode->i_private;
 570         attr->fmt = fmt;
 571         mutex_init(&attr->mutex);
 572
 573         file->private_data = attr;
 574
 575         return nonseekable_open(inode, file);
 576 }
 577
 578 int simple_attr_close(struct inode *inode, struct file *file)
 579 {
 580         kfree(file->private_data);
 581         return 0;
 582 }
 583
 584 /* read from the buffer that is filled with the get function */
 585 ssize_t simple_attr_read(struct file *file, char __user *buf,
 586                          size_t len, loff_t *ppos)
 587 {
 588         struct simple_attr *attr;
 589         size_t size;
 590         ssize_t ret;
 591
 592         attr = file->private_data;
 593
 594         if (!attr->get)
 595                 return -EACCES;
 596
 597         mutex_lock(&attr->mutex);
 598         if (*ppos) /* continued read */
 599                 size = strlen(attr->get_buf);
 600         else      /* first read */
 601                 size = scnprintf(attr->get_buf, sizeof(attr->get_buf),
 602                                  attr->fmt,
 603                                  (unsigned long long)attr->get(attr->data));
 604
 605         ret = simple_read_from_buffer(buf, len, ppos, attr->get_buf, size);
 606         mutex_unlock(&attr->mutex);
 607         return ret;
 608 }
 609
 610 /* interpret the buffer as a number to call the set function with */
 611 ssize_t simple_attr_write(struct file *file, const char __user *buf,
 612                           size_t len, loff_t *ppos)
 613 {
 614         struct simple_attr *attr;
 615         u64 val;
 616         size_t size;
 617         ssize_t ret;
 618
 619         attr = file->private_data;
 620
 621         if (!attr->set)
 622                 return -EACCES;
 623
 624         mutex_lock(&attr->mutex);
 625         ret = -EFAULT;
 626         size = min(sizeof(attr->set_buf) - 1, len);
 627         if (copy_from_user(attr->set_buf, buf, size))
 628                 goto out;
 629
 630         ret = len; /* claim we got the whole input */
 631         attr->set_buf[size] = '\0';
 632         val = simple_strtol(attr->set_buf, NULL, 0);
 633         attr->set(attr->data, val);
 634 out:
 635         mutex_unlock(&attr->mutex);
 636         return ret;
 637 }
 638
 639 EXPORT_SYMBOL(dcache_dir_close);
 640 EXPORT_SYMBOL(dcache_dir_lseek);
 641 EXPORT_SYMBOL(dcache_dir_open);
 642 EXPORT_SYMBOL(dcache_readdir);
 643 EXPORT_SYMBOL(generic_read_dir);
 644 EXPORT_SYMBOL(get_sb_pseudo);
 645 EXPORT_SYMBOL(simple_commit_write);
 646 EXPORT_SYMBOL(simple_dir_inode_operations);
 647 EXPORT_SYMBOL(simple_dir_operations);
 648 EXPORT_SYMBOL(simple_empty);
 649 EXPORT_SYMBOL(d_alloc_name);
 650 EXPORT_SYMBOL(simple_fill_super);
 651 EXPORT_SYMBOL(simple_getattr);
 652 EXPORT_SYMBOL(simple_link);
 653 EXPORT_SYMBOL(simple_lookup);
 654 EXPORT_SYMBOL(simple_pin_fs);
 655 EXPORT_SYMBOL(simple_prepare_write);
 656 EXPORT_SYMBOL(simple_readpage);
 657 EXPORT_SYMBOL(simple_release_fs);
 658 EXPORT_SYMBOL(simple_rename);
 659 EXPORT_SYMBOL(simple_rmdir);
 660 EXPORT_SYMBOL(simple_statfs);
 661 EXPORT_SYMBOL(simple_sync_file);
 662 EXPORT_SYMBOL(simple_unlink);
 663 EXPORT_SYMBOL(simple_read_from_buffer);
 664 EXPORT_SYMBOL(simple_transaction_get);
 665 EXPORT_SYMBOL(simple_transaction_read);
 666 EXPORT_SYMBOL(simple_transaction_release);
 667 EXPORT_SYMBOL_GPL(simple_attr_open);
 668 EXPORT_SYMBOL_GPL(simple_attr_close);
 669 EXPORT_SYMBOL_GPL(simple_attr_read);
 670 EXPORT_SYMBOL_GPL(simple_attr_write);