linux/fs/libfs.c
<<
>>
Prefs
   1/*
   2 *      fs/libfs.c
   3 *      Library for filesystems writers.
   4 */
   5
   6#include <linux/export.h>
   7#include <linux/pagemap.h>
   8#include <linux/slab.h>
   9#include <linux/mount.h>
  10#include <linux/vfs.h>
  11#include <linux/quotaops.h>
  12#include <linux/mutex.h>
  13#include <linux/exportfs.h>
  14#include <linux/writeback.h>
  15#include <linux/buffer_head.h> /* sync_mapping_buffers */
  16
  17#include <asm/uaccess.h>
  18
  19#include "internal.h"
  20
  21static inline int simple_positive(struct dentry *dentry)
  22{
  23        return dentry->d_inode && !d_unhashed(dentry);
  24}
  25
  26int simple_getattr(struct vfsmount *mnt, struct dentry *dentry,
  27                   struct kstat *stat)
  28{
  29        struct inode *inode = dentry->d_inode;
  30        generic_fillattr(inode, stat);
  31        stat->blocks = inode->i_mapping->nrpages << (PAGE_CACHE_SHIFT - 9);
  32        return 0;
  33}
  34
  35int simple_statfs(struct dentry *dentry, struct kstatfs *buf)
  36{
  37        buf->f_type = dentry->d_sb->s_magic;
  38        buf->f_bsize = PAGE_CACHE_SIZE;
  39        buf->f_namelen = NAME_MAX;
  40        return 0;
  41}
  42
  43/*
  44 * Retaining negative dentries for an in-memory filesystem just wastes
  45 * memory and lookup time: arrange for them to be deleted immediately.
  46 */
  47static int simple_delete_dentry(const struct dentry *dentry)
  48{
  49        return 1;
  50}
  51
  52/*
  53 * Lookup the data. This is trivial - if the dentry didn't already
  54 * exist, we know it is negative.  Set d_op to delete negative dentries.
  55 */
  56struct dentry *simple_lookup(struct inode *dir, struct dentry *dentry, unsigned int flags)
  57{
  58        static const struct dentry_operations simple_dentry_operations = {
  59                .d_delete = simple_delete_dentry,
  60        };
  61
  62        if (dentry->d_name.len > NAME_MAX)
  63                return ERR_PTR(-ENAMETOOLONG);
  64        if (!dentry->d_sb->s_d_op)
  65                d_set_d_op(dentry, &simple_dentry_operations);
  66        d_add(dentry, NULL);
  67        return NULL;
  68}
  69
  70int dcache_dir_open(struct inode *inode, struct file *file)
  71{
  72        static struct qstr cursor_name = QSTR_INIT(".", 1);
  73
  74        file->private_data = d_alloc(file->f_path.dentry, &cursor_name);
  75
  76        return file->private_data ? 0 : -ENOMEM;
  77}
  78
  79int dcache_dir_close(struct inode *inode, struct file *file)
  80{
  81        dput(file->private_data);
  82        return 0;
  83}
  84
  85loff_t dcache_dir_lseek(struct file *file, loff_t offset, int whence)
  86{
  87        struct dentry *dentry = file->f_path.dentry;
  88        mutex_lock(&dentry->d_inode->i_mutex);
  89        switch (whence) {
  90                case 1:
  91                        offset += file->f_pos;
  92                case 0:
  93                        if (offset >= 0)
  94                                break;
  95                default:
  96                        mutex_unlock(&dentry->d_inode->i_mutex);
  97                        return -EINVAL;
  98        }
  99        if (offset != file->f_pos) {
 100                file->f_pos = offset;
 101                if (file->f_pos >= 2) {
 102                        struct list_head *p;
 103                        struct dentry *cursor = file->private_data;
 104                        loff_t n = file->f_pos - 2;
 105
 106                        spin_lock(&dentry->d_lock);
 107                        /* d_lock not required for cursor */
 108                        list_del(&cursor->d_u.d_child);
 109                        p = dentry->d_subdirs.next;
 110                        while (n && p != &dentry->d_subdirs) {
 111                                struct dentry *next;
 112                                next = list_entry(p, struct dentry, d_u.d_child);
 113                                spin_lock_nested(&next->d_lock, DENTRY_D_LOCK_NESTED);
 114                                if (simple_positive(next))
 115                                        n--;
 116                                spin_unlock(&next->d_lock);
 117                                p = p->next;
 118                        }
 119                        list_add_tail(&cursor->d_u.d_child, p);
 120                        spin_unlock(&dentry->d_lock);
 121                }
 122        }
 123        mutex_unlock(&dentry->d_inode->i_mutex);
 124        return offset;
 125}
 126
 127/* Relationship between i_mode and the DT_xxx types */
 128static inline unsigned char dt_type(struct inode *inode)
 129{
 130        return (inode->i_mode >> 12) & 15;
 131}
 132
 133/*
 134 * Directory is locked and all positive dentries in it are safe, since
 135 * for ramfs-type trees they can't go away without unlink() or rmdir(),
 136 * both impossible due to the lock on directory.
 137 */
 138
 139int dcache_readdir(struct file *file, struct dir_context *ctx)
 140{
 141        struct dentry *dentry = file->f_path.dentry;
 142        struct dentry *cursor = file->private_data;
 143        struct list_head *p, *q = &cursor->d_u.d_child;
 144
 145        if (!dir_emit_dots(file, ctx))
 146                return 0;
 147        spin_lock(&dentry->d_lock);
 148        if (ctx->pos == 2)
 149                list_move(q, &dentry->d_subdirs);
 150
 151        for (p = q->next; p != &dentry->d_subdirs; p = p->next) {
 152                struct dentry *next = list_entry(p, struct dentry, d_u.d_child);
 153                spin_lock_nested(&next->d_lock, DENTRY_D_LOCK_NESTED);
 154                if (!simple_positive(next)) {
 155                        spin_unlock(&next->d_lock);
 156                        continue;
 157                }
 158
 159                spin_unlock(&next->d_lock);
 160                spin_unlock(&dentry->d_lock);
 161                if (!dir_emit(ctx, next->d_name.name, next->d_name.len,
 162                              next->d_inode->i_ino, dt_type(next->d_inode)))
 163                        return 0;
 164                spin_lock(&dentry->d_lock);
 165                spin_lock_nested(&next->d_lock, DENTRY_D_LOCK_NESTED);
 166                /* next is still alive */
 167                list_move(q, p);
 168                spin_unlock(&next->d_lock);
 169                p = q;
 170                ctx->pos++;
 171        }
 172        spin_unlock(&dentry->d_lock);
 173        return 0;
 174}
 175
 176ssize_t generic_read_dir(struct file *filp, char __user *buf, size_t siz, loff_t *ppos)
 177{
 178        return -EISDIR;
 179}
 180
 181const struct file_operations simple_dir_operations = {
 182        .open           = dcache_dir_open,
 183        .release        = dcache_dir_close,
 184        .llseek         = dcache_dir_lseek,
 185        .read           = generic_read_dir,
 186        .iterate        = dcache_readdir,
 187        .fsync          = noop_fsync,
 188};
 189
 190const struct inode_operations simple_dir_inode_operations = {
 191        .lookup         = simple_lookup,
 192};
 193
 194static const struct super_operations simple_super_operations = {
 195        .statfs         = simple_statfs,
 196};
 197
 198/*
 199 * Common helper for pseudo-filesystems (sockfs, pipefs, bdev - stuff that
 200 * will never be mountable)
 201 */
 202struct dentry *mount_pseudo(struct file_system_type *fs_type, char *name,
 203        const struct super_operations *ops,
 204        const struct dentry_operations *dops, unsigned long magic)
 205{
 206        struct super_block *s;
 207        struct dentry *dentry;
 208        struct inode *root;
 209        struct qstr d_name = QSTR_INIT(name, strlen(name));
 210
 211        s = sget(fs_type, NULL, set_anon_super, MS_NOUSER, NULL);
 212        if (IS_ERR(s))
 213                return ERR_CAST(s);
 214
 215        s->s_maxbytes = MAX_LFS_FILESIZE;
 216        s->s_blocksize = PAGE_SIZE;
 217        s->s_blocksize_bits = PAGE_SHIFT;
 218        s->s_magic = magic;
 219        s->s_op = ops ? ops : &simple_super_operations;
 220        s->s_time_gran = 1;
 221        root = new_inode(s);
 222        if (!root)
 223                goto Enomem;
 224        /*
 225         * since this is the first inode, make it number 1. New inodes created
 226         * after this must take care not to collide with it (by passing
 227         * max_reserved of 1 to iunique).
 228         */
 229        root->i_ino = 1;
 230        root->i_mode = S_IFDIR | S_IRUSR | S_IWUSR;
 231        root->i_atime = root->i_mtime = root->i_ctime = CURRENT_TIME;
 232        dentry = __d_alloc(s, &d_name);
 233        if (!dentry) {
 234                iput(root);
 235                goto Enomem;
 236        }
 237        d_instantiate(dentry, root);
 238        s->s_root = dentry;
 239        s->s_d_op = dops;
 240        s->s_flags |= MS_ACTIVE;
 241        return dget(s->s_root);
 242
 243Enomem:
 244        deactivate_locked_super(s);
 245        return ERR_PTR(-ENOMEM);
 246}
 247
 248int simple_open(struct inode *inode, struct file *file)
 249{
 250        if (inode->i_private)
 251                file->private_data = inode->i_private;
 252        return 0;
 253}
 254
 255int simple_link(struct dentry *old_dentry, struct inode *dir, struct dentry *dentry)
 256{
 257        struct inode *inode = old_dentry->d_inode;
 258
 259        inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;
 260        inc_nlink(inode);
 261        ihold(inode);
 262        dget(dentry);
 263        d_instantiate(dentry, inode);
 264        return 0;
 265}
 266
 267int simple_empty(struct dentry *dentry)
 268{
 269        struct dentry *child;
 270        int ret = 0;
 271
 272        spin_lock(&dentry->d_lock);
 273        list_for_each_entry(child, &dentry->d_subdirs, d_u.d_child) {
 274                spin_lock_nested(&child->d_lock, DENTRY_D_LOCK_NESTED);
 275                if (simple_positive(child)) {
 276                        spin_unlock(&child->d_lock);
 277                        goto out;
 278                }
 279                spin_unlock(&child->d_lock);
 280        }
 281        ret = 1;
 282out:
 283        spin_unlock(&dentry->d_lock);
 284        return ret;
 285}
 286
 287int simple_unlink(struct inode *dir, struct dentry *dentry)
 288{
 289        struct inode *inode = dentry->d_inode;
 290
 291        inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;
 292        drop_nlink(inode);
 293        dput(dentry);
 294        return 0;
 295}
 296
 297int simple_rmdir(struct inode *dir, struct dentry *dentry)
 298{
 299        if (!simple_empty(dentry))
 300                return -ENOTEMPTY;
 301
 302        drop_nlink(dentry->d_inode);
 303        simple_unlink(dir, dentry);
 304        drop_nlink(dir);
 305        return 0;
 306}
 307
 308int simple_rename(struct inode *old_dir, struct dentry *old_dentry,
 309                struct inode *new_dir, struct dentry *new_dentry)
 310{
 311        struct inode *inode = old_dentry->d_inode;
 312        int they_are_dirs = S_ISDIR(old_dentry->d_inode->i_mode);
 313
 314        if (!simple_empty(new_dentry))
 315                return -ENOTEMPTY;
 316
 317        if (new_dentry->d_inode) {
 318                simple_unlink(new_dir, new_dentry);
 319                if (they_are_dirs) {
 320                        drop_nlink(new_dentry->d_inode);
 321                        drop_nlink(old_dir);
 322                }
 323        } else if (they_are_dirs) {
 324                drop_nlink(old_dir);
 325                inc_nlink(new_dir);
 326        }
 327
 328        old_dir->i_ctime = old_dir->i_mtime = new_dir->i_ctime =
 329                new_dir->i_mtime = inode->i_ctime = CURRENT_TIME;
 330
 331        return 0;
 332}
 333
 334/**
 335 * simple_setattr - setattr for simple filesystem
 336 * @dentry: dentry
 337 * @iattr: iattr structure
 338 *
 339 * Returns 0 on success, -error on failure.
 340 *
 341 * simple_setattr is a simple ->setattr implementation without a proper
 342 * implementation of size changes.
 343 *
 344 * It can either be used for in-memory filesystems or special files
 345 * on simple regular filesystems.  Anything that needs to change on-disk
 346 * or wire state on size changes needs its own setattr method.
 347 */
 348int simple_setattr(struct dentry *dentry, struct iattr *iattr)
 349{
 350        struct inode *inode = dentry->d_inode;
 351        int error;
 352
 353        error = inode_change_ok(inode, iattr);
 354        if (error)
 355                return error;
 356
 357        if (iattr->ia_valid & ATTR_SIZE)
 358                truncate_setsize(inode, iattr->ia_size);
 359        setattr_copy(inode, iattr);
 360        mark_inode_dirty(inode);
 361        return 0;
 362}
 363EXPORT_SYMBOL(simple_setattr);
 364
 365int simple_readpage(struct file *file, struct page *page)
 366{
 367        clear_highpage(page);
 368        flush_dcache_page(page);
 369        SetPageUptodate(page);
 370        unlock_page(page);
 371        return 0;
 372}
 373
 374int simple_write_begin(struct file *file, struct address_space *mapping,
 375                        loff_t pos, unsigned len, unsigned flags,
 376                        struct page **pagep, void **fsdata)
 377{
 378        struct page *page;
 379        pgoff_t index;
 380
 381        index = pos >> PAGE_CACHE_SHIFT;
 382
 383        page = grab_cache_page_write_begin(mapping, index, flags);
 384        if (!page)
 385                return -ENOMEM;
 386
 387        *pagep = page;
 388
 389        if (!PageUptodate(page) && (len != PAGE_CACHE_SIZE)) {
 390                unsigned from = pos & (PAGE_CACHE_SIZE - 1);
 391
 392                zero_user_segments(page, 0, from, from + len, PAGE_CACHE_SIZE);
 393        }
 394        return 0;
 395}
 396
 397/**
 398 * simple_write_end - .write_end helper for non-block-device FSes
 399 * @available: See .write_end of address_space_operations
 400 * @file:               "
 401 * @mapping:            "
 402 * @pos:                "
 403 * @len:                "
 404 * @copied:             "
 405 * @page:               "
 406 * @fsdata:             "
 407 *
 408 * simple_write_end does the minimum needed for updating a page after writing is
 409 * done. It has the same API signature as the .write_end of
 410 * address_space_operations vector. So it can just be set onto .write_end for
 411 * FSes that don't need any other processing. i_mutex is assumed to be held.
 412 * Block based filesystems should use generic_write_end().
 413 * NOTE: Even though i_size might get updated by this function, mark_inode_dirty
 414 * is not called, so a filesystem that actually does store data in .write_inode
 415 * should extend on what's done here with a call to mark_inode_dirty() in the
 416 * case that i_size has changed.
 417 */
 418int simple_write_end(struct file *file, struct address_space *mapping,
 419                        loff_t pos, unsigned len, unsigned copied,
 420                        struct page *page, void *fsdata)
 421{
 422        struct inode *inode = page->mapping->host;
 423        loff_t last_pos = pos + copied;
 424
 425        /* zero the stale part of the page if we did a short copy */
 426        if (copied < len) {
 427                unsigned from = pos & (PAGE_CACHE_SIZE - 1);
 428
 429                zero_user(page, from + copied, len - copied);
 430        }
 431
 432        if (!PageUptodate(page))
 433                SetPageUptodate(page);
 434        /*
 435         * No need to use i_size_read() here, the i_size
 436         * cannot change under us because we hold the i_mutex.
 437         */
 438        if (last_pos > inode->i_size)
 439                i_size_write(inode, last_pos);
 440
 441        set_page_dirty(page);
 442        unlock_page(page);
 443        page_cache_release(page);
 444
 445        return copied;
 446}
 447
 448/*
 449 * the inodes created here are not hashed. If you use iunique to generate
 450 * unique inode values later for this filesystem, then you must take care
 451 * to pass it an appropriate max_reserved value to avoid collisions.
 452 */
 453int simple_fill_super(struct super_block *s, unsigned long magic,
 454                      struct tree_descr *files)
 455{
 456        struct inode *inode;
 457        struct dentry *root;
 458        struct dentry *dentry;
 459        int i;
 460
 461        s->s_blocksize = PAGE_CACHE_SIZE;
 462        s->s_blocksize_bits = PAGE_CACHE_SHIFT;
 463        s->s_magic = magic;
 464        s->s_op = &simple_super_operations;
 465        s->s_time_gran = 1;
 466
 467        inode = new_inode(s);
 468        if (!inode)
 469                return -ENOMEM;
 470        /*
 471         * because the root inode is 1, the files array must not contain an
 472         * entry at index 1
 473         */
 474        inode->i_ino = 1;
 475        inode->i_mode = S_IFDIR | 0755;
 476        inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
 477        inode->i_op = &simple_dir_inode_operations;
 478        inode->i_fop = &simple_dir_operations;
 479        set_nlink(inode, 2);
 480        root = d_make_root(inode);
 481        if (!root)
 482                return -ENOMEM;
 483        for (i = 0; !files->name || files->name[0]; i++, files++) {
 484                if (!files->name)
 485                        continue;
 486
 487                /* warn if it tries to conflict with the root inode */
 488                if (unlikely(i == 1))
 489                        printk(KERN_WARNING "%s: %s passed in a files array"
 490                                "with an index of 1!\n", __func__,
 491                                s->s_type->name);
 492
 493                dentry = d_alloc_name(root, files->name);
 494                if (!dentry)
 495                        goto out;
 496                inode = new_inode(s);
 497                if (!inode) {
 498                        dput(dentry);
 499                        goto out;
 500                }
 501                inode->i_mode = S_IFREG | files->mode;
 502                inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
 503                inode->i_fop = files->ops;
 504                inode->i_ino = i;
 505                d_add(dentry, inode);
 506        }
 507        s->s_root = root;
 508        return 0;
 509out:
 510        d_genocide(root);
 511        shrink_dcache_parent(root);
 512        dput(root);
 513        return -ENOMEM;
 514}
 515
 516static DEFINE_SPINLOCK(pin_fs_lock);
 517
 518int simple_pin_fs(struct file_system_type *type, struct vfsmount **mount, int *count)
 519{
 520        struct vfsmount *mnt = NULL;
 521        spin_lock(&pin_fs_lock);
 522        if (unlikely(!*mount)) {
 523                spin_unlock(&pin_fs_lock);
 524                mnt = vfs_kern_mount(type, MS_KERNMOUNT, type->name, NULL);
 525                if (IS_ERR(mnt))
 526                        return PTR_ERR(mnt);
 527                spin_lock(&pin_fs_lock);
 528                if (!*mount)
 529                        *mount = mnt;
 530        }
 531        mntget(*mount);
 532        ++*count;
 533        spin_unlock(&pin_fs_lock);
 534        mntput(mnt);
 535        return 0;
 536}
 537
 538void simple_release_fs(struct vfsmount **mount, int *count)
 539{
 540        struct vfsmount *mnt;
 541        spin_lock(&pin_fs_lock);
 542        mnt = *mount;
 543        if (!--*count)
 544                *mount = NULL;
 545        spin_unlock(&pin_fs_lock);
 546        mntput(mnt);
 547}
 548
 549/**
 550 * simple_read_from_buffer - copy data from the buffer to user space
 551 * @to: the user space buffer to read to
 552 * @count: the maximum number of bytes to read
 553 * @ppos: the current position in the buffer
 554 * @from: the buffer to read from
 555 * @available: the size of the buffer
 556 *
 557 * The simple_read_from_buffer() function reads up to @count bytes from the
 558 * buffer @from at offset @ppos into the user space address starting at @to.
 559 *
 560 * On success, the number of bytes read is returned and the offset @ppos is
 561 * advanced by this number, or negative value is returned on error.
 562 **/
 563ssize_t simple_read_from_buffer(void __user *to, size_t count, loff_t *ppos,
 564                                const void *from, size_t available)
 565{
 566        loff_t pos = *ppos;
 567        size_t ret;
 568
 569        if (pos < 0)
 570                return -EINVAL;
 571        if (pos >= available || !count)
 572                return 0;
 573        if (count > available - pos)
 574                count = available - pos;
 575        ret = copy_to_user(to, from + pos, count);
 576        if (ret == count)
 577                return -EFAULT;
 578        count -= ret;
 579        *ppos = pos + count;
 580        return count;
 581}
 582
 583/**
 584 * simple_write_to_buffer - copy data from user space to the buffer
 585 * @to: the buffer to write to
 586 * @available: the size of the buffer
 587 * @ppos: the current position in the buffer
 588 * @from: the user space buffer to read from
 589 * @count: the maximum number of bytes to read
 590 *
 591 * The simple_write_to_buffer() function reads up to @count bytes from the user
 592 * space address starting at @from into the buffer @to at offset @ppos.
 593 *
 594 * On success, the number of bytes written is returned and the offset @ppos is
 595 * advanced by this number, or negative value is returned on error.
 596 **/
 597ssize_t simple_write_to_buffer(void *to, size_t available, loff_t *ppos,
 598                const void __user *from, size_t count)
 599{
 600        loff_t pos = *ppos;
 601        size_t res;
 602
 603        if (pos < 0)
 604                return -EINVAL;
 605        if (pos >= available || !count)
 606                return 0;
 607        if (count > available - pos)
 608                count = available - pos;
 609        res = copy_from_user(to + pos, from, count);
 610        if (res == count)
 611                return -EFAULT;
 612        count -= res;
 613        *ppos = pos + count;
 614        return count;
 615}
 616
 617/**
 618 * memory_read_from_buffer - copy data from the buffer
 619 * @to: the kernel space buffer to read to
 620 * @count: the maximum number of bytes to read
 621 * @ppos: the current position in the buffer
 622 * @from: the buffer to read from
 623 * @available: the size of the buffer
 624 *
 625 * The memory_read_from_buffer() function reads up to @count bytes from the
 626 * buffer @from at offset @ppos into the kernel space address starting at @to.
 627 *
 628 * On success, the number of bytes read is returned and the offset @ppos is
 629 * advanced by this number, or negative value is returned on error.
 630 **/
 631ssize_t memory_read_from_buffer(void *to, size_t count, loff_t *ppos,
 632                                const void *from, size_t available)
 633{
 634        loff_t pos = *ppos;
 635
 636        if (pos < 0)
 637                return -EINVAL;
 638        if (pos >= available)
 639                return 0;
 640        if (count > available - pos)
 641                count = available - pos;
 642        memcpy(to, from + pos, count);
 643        *ppos = pos + count;
 644
 645        return count;
 646}
 647
 648/*
 649 * Transaction based IO.
 650 * The file expects a single write which triggers the transaction, and then
 651 * possibly a read which collects the result - which is stored in a
 652 * file-local buffer.
 653 */
 654
 655void simple_transaction_set(struct file *file, size_t n)
 656{
 657        struct simple_transaction_argresp *ar = file->private_data;
 658
 659        BUG_ON(n > SIMPLE_TRANSACTION_LIMIT);
 660
 661        /*
 662         * The barrier ensures that ar->size will really remain zero until
 663         * ar->data is ready for reading.
 664         */
 665        smp_mb();
 666        ar->size = n;
 667}
 668
 669char *simple_transaction_get(struct file *file, const char __user *buf, size_t size)
 670{
 671        struct simple_transaction_argresp *ar;
 672        static DEFINE_SPINLOCK(simple_transaction_lock);
 673
 674        if (size > SIMPLE_TRANSACTION_LIMIT - 1)
 675                return ERR_PTR(-EFBIG);
 676
 677        ar = (struct simple_transaction_argresp *)get_zeroed_page(GFP_KERNEL);
 678        if (!ar)
 679                return ERR_PTR(-ENOMEM);
 680
 681        spin_lock(&simple_transaction_lock);
 682
 683        /* only one write allowed per open */
 684        if (file->private_data) {
 685                spin_unlock(&simple_transaction_lock);
 686                free_page((unsigned long)ar);
 687                return ERR_PTR(-EBUSY);
 688        }
 689
 690        file->private_data = ar;
 691
 692        spin_unlock(&simple_transaction_lock);
 693
 694        if (copy_from_user(ar->data, buf, size))
 695                return ERR_PTR(-EFAULT);
 696
 697        return ar->data;
 698}
 699
 700ssize_t simple_transaction_read(struct file *file, char __user *buf, size_t size, loff_t *pos)
 701{
 702        struct simple_transaction_argresp *ar = file->private_data;
 703
 704        if (!ar)
 705                return 0;
 706        return simple_read_from_buffer(buf, size, pos, ar->data, ar->size);
 707}
 708
 709int simple_transaction_release(struct inode *inode, struct file *file)
 710{
 711        free_page((unsigned long)file->private_data);
 712        return 0;
 713}
 714
 715/* Simple attribute files */
 716
 717struct simple_attr {
 718        int (*get)(void *, u64 *);
 719        int (*set)(void *, u64);
 720        char get_buf[24];       /* enough to store a u64 and "\n\0" */
 721        char set_buf[24];
 722        void *data;
 723        const char *fmt;        /* format for read operation */
 724        struct mutex mutex;     /* protects access to these buffers */
 725};
 726
 727/* simple_attr_open is called by an actual attribute open file operation
 728 * to set the attribute specific access operations. */
 729int simple_attr_open(struct inode *inode, struct file *file,
 730                     int (*get)(void *, u64 *), int (*set)(void *, u64),
 731                     const char *fmt)
 732{
 733        struct simple_attr *attr;
 734
 735        attr = kmalloc(sizeof(*attr), GFP_KERNEL);
 736        if (!attr)
 737                return -ENOMEM;
 738
 739        attr->get = get;
 740        attr->set = set;
 741        attr->data = inode->i_private;
 742        attr->fmt = fmt;
 743        mutex_init(&attr->mutex);
 744
 745        file->private_data = attr;
 746
 747        return nonseekable_open(inode, file);
 748}
 749
 750int simple_attr_release(struct inode *inode, struct file *file)
 751{
 752        kfree(file->private_data);
 753        return 0;
 754}
 755
 756/* read from the buffer that is filled with the get function */
 757ssize_t simple_attr_read(struct file *file, char __user *buf,
 758                         size_t len, loff_t *ppos)
 759{
 760        struct simple_attr *attr;
 761        size_t size;
 762        ssize_t ret;
 763
 764        attr = file->private_data;
 765
 766        if (!attr->get)
 767                return -EACCES;
 768
 769        ret = mutex_lock_interruptible(&attr->mutex);
 770        if (ret)
 771                return ret;
 772
 773        if (*ppos) {            /* continued read */
 774                size = strlen(attr->get_buf);
 775        } else {                /* first read */
 776                u64 val;
 777                ret = attr->get(attr->data, &val);
 778                if (ret)
 779                        goto out;
 780
 781                size = scnprintf(attr->get_buf, sizeof(attr->get_buf),
 782                                 attr->fmt, (unsigned long long)val);
 783        }
 784
 785        ret = simple_read_from_buffer(buf, len, ppos, attr->get_buf, size);
 786out:
 787        mutex_unlock(&attr->mutex);
 788        return ret;
 789}
 790
 791/* interpret the buffer as a number to call the set function with */
 792ssize_t simple_attr_write(struct file *file, const char __user *buf,
 793                          size_t len, loff_t *ppos)
 794{
 795        struct simple_attr *attr;
 796        u64 val;
 797        size_t size;
 798        ssize_t ret;
 799
 800        attr = file->private_data;
 801        if (!attr->set)
 802                return -EACCES;
 803
 804        ret = mutex_lock_interruptible(&attr->mutex);
 805        if (ret)
 806                return ret;
 807
 808        ret = -EFAULT;
 809        size = min(sizeof(attr->set_buf) - 1, len);
 810        if (copy_from_user(attr->set_buf, buf, size))
 811                goto out;
 812
 813        attr->set_buf[size] = '\0';
 814        val = simple_strtoll(attr->set_buf, NULL, 0);
 815        ret = attr->set(attr->data, val);
 816        if (ret == 0)
 817                ret = len; /* on success, claim we got the whole input */
 818out:
 819        mutex_unlock(&attr->mutex);
 820        return ret;
 821}
 822
 823/**
 824 * generic_fh_to_dentry - generic helper for the fh_to_dentry export operation
 825 * @sb:         filesystem to do the file handle conversion on
 826 * @fid:        file handle to convert
 827 * @fh_len:     length of the file handle in bytes
 828 * @fh_type:    type of file handle
 829 * @get_inode:  filesystem callback to retrieve inode
 830 *
 831 * This function decodes @fid as long as it has one of the well-known
 832 * Linux filehandle types and calls @get_inode on it to retrieve the
 833 * inode for the object specified in the file handle.
 834 */
 835struct dentry *generic_fh_to_dentry(struct super_block *sb, struct fid *fid,
 836                int fh_len, int fh_type, struct inode *(*get_inode)
 837                        (struct super_block *sb, u64 ino, u32 gen))
 838{
 839        struct inode *inode = NULL;
 840
 841        if (fh_len < 2)
 842                return NULL;
 843
 844        switch (fh_type) {
 845        case FILEID_INO32_GEN:
 846        case FILEID_INO32_GEN_PARENT:
 847                inode = get_inode(sb, fid->i32.ino, fid->i32.gen);
 848                break;
 849        }
 850
 851        return d_obtain_alias(inode);
 852}
 853EXPORT_SYMBOL_GPL(generic_fh_to_dentry);
 854
 855/**
 856 * generic_fh_to_parent - generic helper for the fh_to_parent export operation
 857 * @sb:         filesystem to do the file handle conversion on
 858 * @fid:        file handle to convert
 859 * @fh_len:     length of the file handle in bytes
 860 * @fh_type:    type of file handle
 861 * @get_inode:  filesystem callback to retrieve inode
 862 *
 863 * This function decodes @fid as long as it has one of the well-known
 864 * Linux filehandle types and calls @get_inode on it to retrieve the
 865 * inode for the _parent_ object specified in the file handle if it
 866 * is specified in the file handle, or NULL otherwise.
 867 */
 868struct dentry *generic_fh_to_parent(struct super_block *sb, struct fid *fid,
 869                int fh_len, int fh_type, struct inode *(*get_inode)
 870                        (struct super_block *sb, u64 ino, u32 gen))
 871{
 872        struct inode *inode = NULL;
 873
 874        if (fh_len <= 2)
 875                return NULL;
 876
 877        switch (fh_type) {
 878        case FILEID_INO32_GEN_PARENT:
 879                inode = get_inode(sb, fid->i32.parent_ino,
 880                                  (fh_len > 3 ? fid->i32.parent_gen : 0));
 881                break;
 882        }
 883
 884        return d_obtain_alias(inode);
 885}
 886EXPORT_SYMBOL_GPL(generic_fh_to_parent);
 887
 888/**
 889 * generic_file_fsync - generic fsync implementation for simple filesystems
 890 * @file:       file to synchronize
 891 * @datasync:   only synchronize essential metadata if true
 892 *
 893 * This is a generic implementation of the fsync method for simple
 894 * filesystems which track all non-inode metadata in the buffers list
 895 * hanging off the address_space structure.
 896 */
 897int generic_file_fsync(struct file *file, loff_t start, loff_t end,
 898                       int datasync)
 899{
 900        struct inode *inode = file->f_mapping->host;
 901        int err;
 902        int ret;
 903
 904        err = filemap_write_and_wait_range(inode->i_mapping, start, end);
 905        if (err)
 906                return err;
 907
 908        mutex_lock(&inode->i_mutex);
 909        ret = sync_mapping_buffers(inode->i_mapping);
 910        if (!(inode->i_state & I_DIRTY))
 911                goto out;
 912        if (datasync && !(inode->i_state & I_DIRTY_DATASYNC))
 913                goto out;
 914
 915        err = sync_inode_metadata(inode, 1);
 916        if (ret == 0)
 917                ret = err;
 918out:
 919        mutex_unlock(&inode->i_mutex);
 920        return ret;
 921}
 922EXPORT_SYMBOL(generic_file_fsync);
 923
 924/**
 925 * generic_check_addressable - Check addressability of file system
 926 * @blocksize_bits:     log of file system block size
 927 * @num_blocks:         number of blocks in file system
 928 *
 929 * Determine whether a file system with @num_blocks blocks (and a
 930 * block size of 2**@blocksize_bits) is addressable by the sector_t
 931 * and page cache of the system.  Return 0 if so and -EFBIG otherwise.
 932 */
 933int generic_check_addressable(unsigned blocksize_bits, u64 num_blocks)
 934{
 935        u64 last_fs_block = num_blocks - 1;
 936        u64 last_fs_page =
 937                last_fs_block >> (PAGE_CACHE_SHIFT - blocksize_bits);
 938
 939        if (unlikely(num_blocks == 0))
 940                return 0;
 941
 942        if ((blocksize_bits < 9) || (blocksize_bits > PAGE_CACHE_SHIFT))
 943                return -EINVAL;
 944
 945        if ((last_fs_block > (sector_t)(~0ULL) >> (blocksize_bits - 9)) ||
 946            (last_fs_page > (pgoff_t)(~0ULL))) {
 947                return -EFBIG;
 948        }
 949        return 0;
 950}
 951EXPORT_SYMBOL(generic_check_addressable);
 952
 953/*
 954 * No-op implementation of ->fsync for in-memory filesystems.
 955 */
 956int noop_fsync(struct file *file, loff_t start, loff_t end, int datasync)
 957{
 958        return 0;
 959}
 960
 961EXPORT_SYMBOL(dcache_dir_close);
 962EXPORT_SYMBOL(dcache_dir_lseek);
 963EXPORT_SYMBOL(dcache_dir_open);
 964EXPORT_SYMBOL(dcache_readdir);
 965EXPORT_SYMBOL(generic_read_dir);
 966EXPORT_SYMBOL(mount_pseudo);
 967EXPORT_SYMBOL(simple_write_begin);
 968EXPORT_SYMBOL(simple_write_end);
 969EXPORT_SYMBOL(simple_dir_inode_operations);
 970EXPORT_SYMBOL(simple_dir_operations);
 971EXPORT_SYMBOL(simple_empty);
 972EXPORT_SYMBOL(simple_fill_super);
 973EXPORT_SYMBOL(simple_getattr);
 974EXPORT_SYMBOL(simple_open);
 975EXPORT_SYMBOL(simple_link);
 976EXPORT_SYMBOL(simple_lookup);
 977EXPORT_SYMBOL(simple_pin_fs);
 978EXPORT_SYMBOL(simple_readpage);
 979EXPORT_SYMBOL(simple_release_fs);
 980EXPORT_SYMBOL(simple_rename);
 981EXPORT_SYMBOL(simple_rmdir);
 982EXPORT_SYMBOL(simple_statfs);
 983EXPORT_SYMBOL(noop_fsync);
 984EXPORT_SYMBOL(simple_unlink);
 985EXPORT_SYMBOL(simple_read_from_buffer);
 986EXPORT_SYMBOL(simple_write_to_buffer);
 987EXPORT_SYMBOL(memory_read_from_buffer);
 988EXPORT_SYMBOL(simple_transaction_set);
 989EXPORT_SYMBOL(simple_transaction_get);
 990EXPORT_SYMBOL(simple_transaction_read);
 991EXPORT_SYMBOL(simple_transaction_release);
 992EXPORT_SYMBOL_GPL(simple_attr_open);
 993EXPORT_SYMBOL_GPL(simple_attr_release);
 994EXPORT_SYMBOL_GPL(simple_attr_read);
 995EXPORT_SYMBOL_GPL(simple_attr_write);
 996
lxr.linux.no kindly hosted by Redpill Linpro AS, provider of Linux consulting and operations services since 1995.