linux/fs/libfs.c
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   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        d_set_d_op(dentry, &simple_dentry_operations);
  65        d_add(dentry, NULL);
  66        return NULL;
  67}
  68
  69int dcache_dir_open(struct inode *inode, struct file *file)
  70{
  71        static struct qstr cursor_name = QSTR_INIT(".", 1);
  72
  73        file->private_data = d_alloc(file->f_path.dentry, &cursor_name);
  74
  75        return file->private_data ? 0 : -ENOMEM;
  76}
  77
  78int dcache_dir_close(struct inode *inode, struct file *file)
  79{
  80        dput(file->private_data);
  81        return 0;
  82}
  83
  84loff_t dcache_dir_lseek(struct file *file, loff_t offset, int origin)
  85{
  86        struct dentry *dentry = file->f_path.dentry;
  87        mutex_lock(&dentry->d_inode->i_mutex);
  88        switch (origin) {
  89                case 1:
  90                        offset += file->f_pos;
  91                case 0:
  92                        if (offset >= 0)
  93                                break;
  94                default:
  95                        mutex_unlock(&dentry->d_inode->i_mutex);
  96                        return -EINVAL;
  97        }
  98        if (offset != file->f_pos) {
  99                file->f_pos = offset;
 100                if (file->f_pos >= 2) {
 101                        struct list_head *p;
 102                        struct dentry *cursor = file->private_data;
 103                        loff_t n = file->f_pos - 2;
 104
 105                        spin_lock(&dentry->d_lock);
 106                        /* d_lock not required for cursor */
 107                        list_del(&cursor->d_u.d_child);
 108                        p = dentry->d_subdirs.next;
 109                        while (n && p != &dentry->d_subdirs) {
 110                                struct dentry *next;
 111                                next = list_entry(p, struct dentry, d_u.d_child);
 112                                spin_lock_nested(&next->d_lock, DENTRY_D_LOCK_NESTED);
 113                                if (simple_positive(next))
 114                                        n--;
 115                                spin_unlock(&next->d_lock);
 116                                p = p->next;
 117                        }
 118                        list_add_tail(&cursor->d_u.d_child, p);
 119                        spin_unlock(&dentry->d_lock);
 120                }
 121        }
 122        mutex_unlock(&dentry->d_inode->i_mutex);
 123        return offset;
 124}
 125
 126/* Relationship between i_mode and the DT_xxx types */
 127static inline unsigned char dt_type(struct inode *inode)
 128{
 129        return (inode->i_mode >> 12) & 15;
 130}
 131
 132/*
 133 * Directory is locked and all positive dentries in it are safe, since
 134 * for ramfs-type trees they can't go away without unlink() or rmdir(),
 135 * both impossible due to the lock on directory.
 136 */
 137
 138int dcache_readdir(struct file * filp, void * dirent, filldir_t filldir)
 139{
 140        struct dentry *dentry = filp->f_path.dentry;
 141        struct dentry *cursor = filp->private_data;
 142        struct list_head *p, *q = &cursor->d_u.d_child;
 143        ino_t ino;
 144        int i = filp->f_pos;
 145
 146        switch (i) {
 147                case 0:
 148                        ino = dentry->d_inode->i_ino;
 149                        if (filldir(dirent, ".", 1, i, ino, DT_DIR) < 0)
 150                                break;
 151                        filp->f_pos++;
 152                        i++;
 153                        /* fallthrough */
 154                case 1:
 155                        ino = parent_ino(dentry);
 156                        if (filldir(dirent, "..", 2, i, ino, DT_DIR) < 0)
 157                                break;
 158                        filp->f_pos++;
 159                        i++;
 160                        /* fallthrough */
 161                default:
 162                        spin_lock(&dentry->d_lock);
 163                        if (filp->f_pos == 2)
 164                                list_move(q, &dentry->d_subdirs);
 165
 166                        for (p=q->next; p != &dentry->d_subdirs; p=p->next) {
 167                                struct dentry *next;
 168                                next = list_entry(p, struct dentry, d_u.d_child);
 169                                spin_lock_nested(&next->d_lock, DENTRY_D_LOCK_NESTED);
 170                                if (!simple_positive(next)) {
 171                                        spin_unlock(&next->d_lock);
 172                                        continue;
 173                                }
 174
 175                                spin_unlock(&next->d_lock);
 176                                spin_unlock(&dentry->d_lock);
 177                                if (filldir(dirent, next->d_name.name, 
 178                                            next->d_name.len, filp->f_pos, 
 179                                            next->d_inode->i_ino, 
 180                                            dt_type(next->d_inode)) < 0)
 181                                        return 0;
 182                                spin_lock(&dentry->d_lock);
 183                                spin_lock_nested(&next->d_lock, DENTRY_D_LOCK_NESTED);
 184                                /* next is still alive */
 185                                list_move(q, p);
 186                                spin_unlock(&next->d_lock);
 187                                p = q;
 188                                filp->f_pos++;
 189                        }
 190                        spin_unlock(&dentry->d_lock);
 191        }
 192        return 0;
 193}
 194
 195ssize_t generic_read_dir(struct file *filp, char __user *buf, size_t siz, loff_t *ppos)
 196{
 197        return -EISDIR;
 198}
 199
 200const struct file_operations simple_dir_operations = {
 201        .open           = dcache_dir_open,
 202        .release        = dcache_dir_close,
 203        .llseek         = dcache_dir_lseek,
 204        .read           = generic_read_dir,
 205        .readdir        = dcache_readdir,
 206        .fsync          = noop_fsync,
 207};
 208
 209const struct inode_operations simple_dir_inode_operations = {
 210        .lookup         = simple_lookup,
 211};
 212
 213static const struct super_operations simple_super_operations = {
 214        .statfs         = simple_statfs,
 215};
 216
 217/*
 218 * Common helper for pseudo-filesystems (sockfs, pipefs, bdev - stuff that
 219 * will never be mountable)
 220 */
 221struct dentry *mount_pseudo(struct file_system_type *fs_type, char *name,
 222        const struct super_operations *ops,
 223        const struct dentry_operations *dops, unsigned long magic)
 224{
 225        struct super_block *s;
 226        struct dentry *dentry;
 227        struct inode *root;
 228        struct qstr d_name = QSTR_INIT(name, strlen(name));
 229
 230        s = sget(fs_type, NULL, set_anon_super, MS_NOUSER, NULL);
 231        if (IS_ERR(s))
 232                return ERR_CAST(s);
 233
 234        s->s_maxbytes = MAX_LFS_FILESIZE;
 235        s->s_blocksize = PAGE_SIZE;
 236        s->s_blocksize_bits = PAGE_SHIFT;
 237        s->s_magic = magic;
 238        s->s_op = ops ? ops : &simple_super_operations;
 239        s->s_time_gran = 1;
 240        root = new_inode(s);
 241        if (!root)
 242                goto Enomem;
 243        /*
 244         * since this is the first inode, make it number 1. New inodes created
 245         * after this must take care not to collide with it (by passing
 246         * max_reserved of 1 to iunique).
 247         */
 248        root->i_ino = 1;
 249        root->i_mode = S_IFDIR | S_IRUSR | S_IWUSR;
 250        root->i_atime = root->i_mtime = root->i_ctime = CURRENT_TIME;
 251        dentry = __d_alloc(s, &d_name);
 252        if (!dentry) {
 253                iput(root);
 254                goto Enomem;
 255        }
 256        d_instantiate(dentry, root);
 257        s->s_root = dentry;
 258        s->s_d_op = dops;
 259        s->s_flags |= MS_ACTIVE;
 260        return dget(s->s_root);
 261
 262Enomem:
 263        deactivate_locked_super(s);
 264        return ERR_PTR(-ENOMEM);
 265}
 266
 267int simple_open(struct inode *inode, struct file *file)
 268{
 269        if (inode->i_private)
 270                file->private_data = inode->i_private;
 271        return 0;
 272}
 273
 274int simple_link(struct dentry *old_dentry, struct inode *dir, struct dentry *dentry)
 275{
 276        struct inode *inode = old_dentry->d_inode;
 277
 278        inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;
 279        inc_nlink(inode);
 280        ihold(inode);
 281        dget(dentry);
 282        d_instantiate(dentry, inode);
 283        return 0;
 284}
 285
 286int simple_empty(struct dentry *dentry)
 287{
 288        struct dentry *child;
 289        int ret = 0;
 290
 291        spin_lock(&dentry->d_lock);
 292        list_for_each_entry(child, &dentry->d_subdirs, d_u.d_child) {
 293                spin_lock_nested(&child->d_lock, DENTRY_D_LOCK_NESTED);
 294                if (simple_positive(child)) {
 295                        spin_unlock(&child->d_lock);
 296                        goto out;
 297                }
 298                spin_unlock(&child->d_lock);
 299        }
 300        ret = 1;
 301out:
 302        spin_unlock(&dentry->d_lock);
 303        return ret;
 304}
 305
 306int simple_unlink(struct inode *dir, struct dentry *dentry)
 307{
 308        struct inode *inode = dentry->d_inode;
 309
 310        inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;
 311        drop_nlink(inode);
 312        dput(dentry);
 313        return 0;
 314}
 315
 316int simple_rmdir(struct inode *dir, struct dentry *dentry)
 317{
 318        if (!simple_empty(dentry))
 319                return -ENOTEMPTY;
 320
 321        drop_nlink(dentry->d_inode);
 322        simple_unlink(dir, dentry);
 323        drop_nlink(dir);
 324        return 0;
 325}
 326
 327int simple_rename(struct inode *old_dir, struct dentry *old_dentry,
 328                struct inode *new_dir, struct dentry *new_dentry)
 329{
 330        struct inode *inode = old_dentry->d_inode;
 331        int they_are_dirs = S_ISDIR(old_dentry->d_inode->i_mode);
 332
 333        if (!simple_empty(new_dentry))
 334                return -ENOTEMPTY;
 335
 336        if (new_dentry->d_inode) {
 337                simple_unlink(new_dir, new_dentry);
 338                if (they_are_dirs) {
 339                        drop_nlink(new_dentry->d_inode);
 340                        drop_nlink(old_dir);
 341                }
 342        } else if (they_are_dirs) {
 343                drop_nlink(old_dir);
 344                inc_nlink(new_dir);
 345        }
 346
 347        old_dir->i_ctime = old_dir->i_mtime = new_dir->i_ctime =
 348                new_dir->i_mtime = inode->i_ctime = CURRENT_TIME;
 349
 350        return 0;
 351}
 352
 353/**
 354 * simple_setattr - setattr for simple filesystem
 355 * @dentry: dentry
 356 * @iattr: iattr structure
 357 *
 358 * Returns 0 on success, -error on failure.
 359 *
 360 * simple_setattr is a simple ->setattr implementation without a proper
 361 * implementation of size changes.
 362 *
 363 * It can either be used for in-memory filesystems or special files
 364 * on simple regular filesystems.  Anything that needs to change on-disk
 365 * or wire state on size changes needs its own setattr method.
 366 */
 367int simple_setattr(struct dentry *dentry, struct iattr *iattr)
 368{
 369        struct inode *inode = dentry->d_inode;
 370        int error;
 371
 372        WARN_ON_ONCE(inode->i_op->truncate);
 373
 374        error = inode_change_ok(inode, iattr);
 375        if (error)
 376                return error;
 377
 378        if (iattr->ia_valid & ATTR_SIZE)
 379                truncate_setsize(inode, iattr->ia_size);
 380        setattr_copy(inode, iattr);
 381        mark_inode_dirty(inode);
 382        return 0;
 383}
 384EXPORT_SYMBOL(simple_setattr);
 385
 386int simple_readpage(struct file *file, struct page *page)
 387{
 388        clear_highpage(page);
 389        flush_dcache_page(page);
 390        SetPageUptodate(page);
 391        unlock_page(page);
 392        return 0;
 393}
 394
 395int simple_write_begin(struct file *file, struct address_space *mapping,
 396                        loff_t pos, unsigned len, unsigned flags,
 397                        struct page **pagep, void **fsdata)
 398{
 399        struct page *page;
 400        pgoff_t index;
 401
 402        index = pos >> PAGE_CACHE_SHIFT;
 403
 404        page = grab_cache_page_write_begin(mapping, index, flags);
 405        if (!page)
 406                return -ENOMEM;
 407
 408        *pagep = page;
 409
 410        if (!PageUptodate(page) && (len != PAGE_CACHE_SIZE)) {
 411                unsigned from = pos & (PAGE_CACHE_SIZE - 1);
 412
 413                zero_user_segments(page, 0, from, from + len, PAGE_CACHE_SIZE);
 414        }
 415        return 0;
 416}
 417
 418/**
 419 * simple_write_end - .write_end helper for non-block-device FSes
 420 * @available: See .write_end of address_space_operations
 421 * @file:               "
 422 * @mapping:            "
 423 * @pos:                "
 424 * @len:                "
 425 * @copied:             "
 426 * @page:               "
 427 * @fsdata:             "
 428 *
 429 * simple_write_end does the minimum needed for updating a page after writing is
 430 * done. It has the same API signature as the .write_end of
 431 * address_space_operations vector. So it can just be set onto .write_end for
 432 * FSes that don't need any other processing. i_mutex is assumed to be held.
 433 * Block based filesystems should use generic_write_end().
 434 * NOTE: Even though i_size might get updated by this function, mark_inode_dirty
 435 * is not called, so a filesystem that actually does store data in .write_inode
 436 * should extend on what's done here with a call to mark_inode_dirty() in the
 437 * case that i_size has changed.
 438 */
 439int simple_write_end(struct file *file, struct address_space *mapping,
 440                        loff_t pos, unsigned len, unsigned copied,
 441                        struct page *page, void *fsdata)
 442{
 443        struct inode *inode = page->mapping->host;
 444        loff_t last_pos = pos + copied;
 445
 446        /* zero the stale part of the page if we did a short copy */
 447        if (copied < len) {
 448                unsigned from = pos & (PAGE_CACHE_SIZE - 1);
 449
 450                zero_user(page, from + copied, len - copied);
 451        }
 452
 453        if (!PageUptodate(page))
 454                SetPageUptodate(page);
 455        /*
 456         * No need to use i_size_read() here, the i_size
 457         * cannot change under us because we hold the i_mutex.
 458         */
 459        if (last_pos > inode->i_size)
 460                i_size_write(inode, last_pos);
 461
 462        set_page_dirty(page);
 463        unlock_page(page);
 464        page_cache_release(page);
 465
 466        return copied;
 467}
 468
 469/*
 470 * the inodes created here are not hashed. If you use iunique to generate
 471 * unique inode values later for this filesystem, then you must take care
 472 * to pass it an appropriate max_reserved value to avoid collisions.
 473 */
 474int simple_fill_super(struct super_block *s, unsigned long magic,
 475                      struct tree_descr *files)
 476{
 477        struct inode *inode;
 478        struct dentry *root;
 479        struct dentry *dentry;
 480        int i;
 481
 482        s->s_blocksize = PAGE_CACHE_SIZE;
 483        s->s_blocksize_bits = PAGE_CACHE_SHIFT;
 484        s->s_magic = magic;
 485        s->s_op = &simple_super_operations;
 486        s->s_time_gran = 1;
 487
 488        inode = new_inode(s);
 489        if (!inode)
 490                return -ENOMEM;
 491        /*
 492         * because the root inode is 1, the files array must not contain an
 493         * entry at index 1
 494         */
 495        inode->i_ino = 1;
 496        inode->i_mode = S_IFDIR | 0755;
 497        inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
 498        inode->i_op = &simple_dir_inode_operations;
 499        inode->i_fop = &simple_dir_operations;
 500        set_nlink(inode, 2);
 501        root = d_make_root(inode);
 502        if (!root)
 503                return -ENOMEM;
 504        for (i = 0; !files->name || files->name[0]; i++, files++) {
 505                if (!files->name)
 506                        continue;
 507
 508                /* warn if it tries to conflict with the root inode */
 509                if (unlikely(i == 1))
 510                        printk(KERN_WARNING "%s: %s passed in a files array"
 511                                "with an index of 1!\n", __func__,
 512                                s->s_type->name);
 513
 514                dentry = d_alloc_name(root, files->name);
 515                if (!dentry)
 516                        goto out;
 517                inode = new_inode(s);
 518                if (!inode) {
 519                        dput(dentry);
 520                        goto out;
 521                }
 522                inode->i_mode = S_IFREG | files->mode;
 523                inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
 524                inode->i_fop = files->ops;
 525                inode->i_ino = i;
 526                d_add(dentry, inode);
 527        }
 528        s->s_root = root;
 529        return 0;
 530out:
 531        d_genocide(root);
 532        shrink_dcache_parent(root);
 533        dput(root);
 534        return -ENOMEM;
 535}
 536
 537static DEFINE_SPINLOCK(pin_fs_lock);
 538
 539int simple_pin_fs(struct file_system_type *type, struct vfsmount **mount, int *count)
 540{
 541        struct vfsmount *mnt = NULL;
 542        spin_lock(&pin_fs_lock);
 543        if (unlikely(!*mount)) {
 544                spin_unlock(&pin_fs_lock);
 545                mnt = vfs_kern_mount(type, MS_KERNMOUNT, type->name, NULL);
 546                if (IS_ERR(mnt))
 547                        return PTR_ERR(mnt);
 548                spin_lock(&pin_fs_lock);
 549                if (!*mount)
 550                        *mount = mnt;
 551        }
 552        mntget(*mount);
 553        ++*count;
 554        spin_unlock(&pin_fs_lock);
 555        mntput(mnt);
 556        return 0;
 557}
 558
 559void simple_release_fs(struct vfsmount **mount, int *count)
 560{
 561        struct vfsmount *mnt;
 562        spin_lock(&pin_fs_lock);
 563        mnt = *mount;
 564        if (!--*count)
 565                *mount = NULL;
 566        spin_unlock(&pin_fs_lock);
 567        mntput(mnt);
 568}
 569
 570/**
 571 * simple_read_from_buffer - copy data from the buffer to user space
 572 * @to: the user space buffer to read to
 573 * @count: the maximum number of bytes to read
 574 * @ppos: the current position in the buffer
 575 * @from: the buffer to read from
 576 * @available: the size of the buffer
 577 *
 578 * The simple_read_from_buffer() function reads up to @count bytes from the
 579 * buffer @from at offset @ppos into the user space address starting at @to.
 580 *
 581 * On success, the number of bytes read is returned and the offset @ppos is
 582 * advanced by this number, or negative value is returned on error.
 583 **/
 584ssize_t simple_read_from_buffer(void __user *to, size_t count, loff_t *ppos,
 585                                const void *from, size_t available)
 586{
 587        loff_t pos = *ppos;
 588        size_t ret;
 589
 590        if (pos < 0)
 591                return -EINVAL;
 592        if (pos >= available || !count)
 593                return 0;
 594        if (count > available - pos)
 595                count = available - pos;
 596        ret = copy_to_user(to, from + pos, count);
 597        if (ret == count)
 598                return -EFAULT;
 599        count -= ret;
 600        *ppos = pos + count;
 601        return count;
 602}
 603
 604/**
 605 * simple_write_to_buffer - copy data from user space to the buffer
 606 * @to: the buffer to write to
 607 * @available: the size of the buffer
 608 * @ppos: the current position in the buffer
 609 * @from: the user space buffer to read from
 610 * @count: the maximum number of bytes to read
 611 *
 612 * The simple_write_to_buffer() function reads up to @count bytes from the user
 613 * space address starting at @from into the buffer @to at offset @ppos.
 614 *
 615 * On success, the number of bytes written is returned and the offset @ppos is
 616 * advanced by this number, or negative value is returned on error.
 617 **/
 618ssize_t simple_write_to_buffer(void *to, size_t available, loff_t *ppos,
 619                const void __user *from, size_t count)
 620{
 621        loff_t pos = *ppos;
 622        size_t res;
 623
 624        if (pos < 0)
 625                return -EINVAL;
 626        if (pos >= available || !count)
 627                return 0;
 628        if (count > available - pos)
 629                count = available - pos;
 630        res = copy_from_user(to + pos, from, count);
 631        if (res == count)
 632                return -EFAULT;
 633        count -= res;
 634        *ppos = pos + count;
 635        return count;
 636}
 637
 638/**
 639 * memory_read_from_buffer - copy data from the buffer
 640 * @to: the kernel space buffer to read to
 641 * @count: the maximum number of bytes to read
 642 * @ppos: the current position in the buffer
 643 * @from: the buffer to read from
 644 * @available: the size of the buffer
 645 *
 646 * The memory_read_from_buffer() function reads up to @count bytes from the
 647 * buffer @from at offset @ppos into the kernel space address starting at @to.
 648 *
 649 * On success, the number of bytes read is returned and the offset @ppos is
 650 * advanced by this number, or negative value is returned on error.
 651 **/
 652ssize_t memory_read_from_buffer(void *to, size_t count, loff_t *ppos,
 653                                const void *from, size_t available)
 654{
 655        loff_t pos = *ppos;
 656
 657        if (pos < 0)
 658                return -EINVAL;
 659        if (pos >= available)
 660                return 0;
 661        if (count > available - pos)
 662                count = available - pos;
 663        memcpy(to, from + pos, count);
 664        *ppos = pos + count;
 665
 666        return count;
 667}
 668
 669/*
 670 * Transaction based IO.
 671 * The file expects a single write which triggers the transaction, and then
 672 * possibly a read which collects the result - which is stored in a
 673 * file-local buffer.
 674 */
 675
 676void simple_transaction_set(struct file *file, size_t n)
 677{
 678        struct simple_transaction_argresp *ar = file->private_data;
 679
 680        BUG_ON(n > SIMPLE_TRANSACTION_LIMIT);
 681
 682        /*
 683         * The barrier ensures that ar->size will really remain zero until
 684         * ar->data is ready for reading.
 685         */
 686        smp_mb();
 687        ar->size = n;
 688}
 689
 690char *simple_transaction_get(struct file *file, const char __user *buf, size_t size)
 691{
 692        struct simple_transaction_argresp *ar;
 693        static DEFINE_SPINLOCK(simple_transaction_lock);
 694
 695        if (size > SIMPLE_TRANSACTION_LIMIT - 1)
 696                return ERR_PTR(-EFBIG);
 697
 698        ar = (struct simple_transaction_argresp *)get_zeroed_page(GFP_KERNEL);
 699        if (!ar)
 700                return ERR_PTR(-ENOMEM);
 701
 702        spin_lock(&simple_transaction_lock);
 703
 704        /* only one write allowed per open */
 705        if (file->private_data) {
 706                spin_unlock(&simple_transaction_lock);
 707                free_page((unsigned long)ar);
 708                return ERR_PTR(-EBUSY);
 709        }
 710
 711        file->private_data = ar;
 712
 713        spin_unlock(&simple_transaction_lock);
 714
 715        if (copy_from_user(ar->data, buf, size))
 716                return ERR_PTR(-EFAULT);
 717
 718        return ar->data;
 719}
 720
 721ssize_t simple_transaction_read(struct file *file, char __user *buf, size_t size, loff_t *pos)
 722{
 723        struct simple_transaction_argresp *ar = file->private_data;
 724
 725        if (!ar)
 726                return 0;
 727        return simple_read_from_buffer(buf, size, pos, ar->data, ar->size);
 728}
 729
 730int simple_transaction_release(struct inode *inode, struct file *file)
 731{
 732        free_page((unsigned long)file->private_data);
 733        return 0;
 734}
 735
 736/* Simple attribute files */
 737
 738struct simple_attr {
 739        int (*get)(void *, u64 *);
 740        int (*set)(void *, u64);
 741        char get_buf[24];       /* enough to store a u64 and "\n\0" */
 742        char set_buf[24];
 743        void *data;
 744        const char *fmt;        /* format for read operation */
 745        struct mutex mutex;     /* protects access to these buffers */
 746};
 747
 748/* simple_attr_open is called by an actual attribute open file operation
 749 * to set the attribute specific access operations. */
 750int simple_attr_open(struct inode *inode, struct file *file,
 751                     int (*get)(void *, u64 *), int (*set)(void *, u64),
 752                     const char *fmt)
 753{
 754        struct simple_attr *attr;
 755
 756        attr = kmalloc(sizeof(*attr), GFP_KERNEL);
 757        if (!attr)
 758                return -ENOMEM;
 759
 760        attr->get = get;
 761        attr->set = set;
 762        attr->data = inode->i_private;
 763        attr->fmt = fmt;
 764        mutex_init(&attr->mutex);
 765
 766        file->private_data = attr;
 767
 768        return nonseekable_open(inode, file);
 769}
 770
 771int simple_attr_release(struct inode *inode, struct file *file)
 772{
 773        kfree(file->private_data);
 774        return 0;
 775}
 776
 777/* read from the buffer that is filled with the get function */
 778ssize_t simple_attr_read(struct file *file, char __user *buf,
 779                         size_t len, loff_t *ppos)
 780{
 781        struct simple_attr *attr;
 782        size_t size;
 783        ssize_t ret;
 784
 785        attr = file->private_data;
 786
 787        if (!attr->get)
 788                return -EACCES;
 789
 790        ret = mutex_lock_interruptible(&attr->mutex);
 791        if (ret)
 792                return ret;
 793
 794        if (*ppos) {            /* continued read */
 795                size = strlen(attr->get_buf);
 796        } else {                /* first read */
 797                u64 val;
 798                ret = attr->get(attr->data, &val);
 799                if (ret)
 800                        goto out;
 801
 802                size = scnprintf(attr->get_buf, sizeof(attr->get_buf),
 803                                 attr->fmt, (unsigned long long)val);
 804        }
 805
 806        ret = simple_read_from_buffer(buf, len, ppos, attr->get_buf, size);
 807out:
 808        mutex_unlock(&attr->mutex);
 809        return ret;
 810}
 811
 812/* interpret the buffer as a number to call the set function with */
 813ssize_t simple_attr_write(struct file *file, const char __user *buf,
 814                          size_t len, loff_t *ppos)
 815{
 816        struct simple_attr *attr;
 817        u64 val;
 818        size_t size;
 819        ssize_t ret;
 820
 821        attr = file->private_data;
 822        if (!attr->set)
 823                return -EACCES;
 824
 825        ret = mutex_lock_interruptible(&attr->mutex);
 826        if (ret)
 827                return ret;
 828
 829        ret = -EFAULT;
 830        size = min(sizeof(attr->set_buf) - 1, len);
 831        if (copy_from_user(attr->set_buf, buf, size))
 832                goto out;
 833
 834        attr->set_buf[size] = '\0';
 835        val = simple_strtoll(attr->set_buf, NULL, 0);
 836        ret = attr->set(attr->data, val);
 837        if (ret == 0)
 838                ret = len; /* on success, claim we got the whole input */
 839out:
 840        mutex_unlock(&attr->mutex);
 841        return ret;
 842}
 843
 844/**
 845 * generic_fh_to_dentry - generic helper for the fh_to_dentry export operation
 846 * @sb:         filesystem to do the file handle conversion on
 847 * @fid:        file handle to convert
 848 * @fh_len:     length of the file handle in bytes
 849 * @fh_type:    type of file handle
 850 * @get_inode:  filesystem callback to retrieve inode
 851 *
 852 * This function decodes @fid as long as it has one of the well-known
 853 * Linux filehandle types and calls @get_inode on it to retrieve the
 854 * inode for the object specified in the file handle.
 855 */
 856struct dentry *generic_fh_to_dentry(struct super_block *sb, struct fid *fid,
 857                int fh_len, int fh_type, struct inode *(*get_inode)
 858                        (struct super_block *sb, u64 ino, u32 gen))
 859{
 860        struct inode *inode = NULL;
 861
 862        if (fh_len < 2)
 863                return NULL;
 864
 865        switch (fh_type) {
 866        case FILEID_INO32_GEN:
 867        case FILEID_INO32_GEN_PARENT:
 868                inode = get_inode(sb, fid->i32.ino, fid->i32.gen);
 869                break;
 870        }
 871
 872        return d_obtain_alias(inode);
 873}
 874EXPORT_SYMBOL_GPL(generic_fh_to_dentry);
 875
 876/**
 877 * generic_fh_to_parent - generic helper for the fh_to_parent export operation
 878 * @sb:         filesystem to do the file handle conversion on
 879 * @fid:        file handle to convert
 880 * @fh_len:     length of the file handle in bytes
 881 * @fh_type:    type of file handle
 882 * @get_inode:  filesystem callback to retrieve inode
 883 *
 884 * This function decodes @fid as long as it has one of the well-known
 885 * Linux filehandle types and calls @get_inode on it to retrieve the
 886 * inode for the _parent_ object specified in the file handle if it
 887 * is specified in the file handle, or NULL otherwise.
 888 */
 889struct dentry *generic_fh_to_parent(struct super_block *sb, struct fid *fid,
 890                int fh_len, int fh_type, struct inode *(*get_inode)
 891                        (struct super_block *sb, u64 ino, u32 gen))
 892{
 893        struct inode *inode = NULL;
 894
 895        if (fh_len <= 2)
 896                return NULL;
 897
 898        switch (fh_type) {
 899        case FILEID_INO32_GEN_PARENT:
 900                inode = get_inode(sb, fid->i32.parent_ino,
 901                                  (fh_len > 3 ? fid->i32.parent_gen : 0));
 902                break;
 903        }
 904
 905        return d_obtain_alias(inode);
 906}
 907EXPORT_SYMBOL_GPL(generic_fh_to_parent);
 908
 909/**
 910 * generic_file_fsync - generic fsync implementation for simple filesystems
 911 * @file:       file to synchronize
 912 * @datasync:   only synchronize essential metadata if true
 913 *
 914 * This is a generic implementation of the fsync method for simple
 915 * filesystems which track all non-inode metadata in the buffers list
 916 * hanging off the address_space structure.
 917 */
 918int generic_file_fsync(struct file *file, loff_t start, loff_t end,
 919                       int datasync)
 920{
 921        struct inode *inode = file->f_mapping->host;
 922        int err;
 923        int ret;
 924
 925        err = filemap_write_and_wait_range(inode->i_mapping, start, end);
 926        if (err)
 927                return err;
 928
 929        mutex_lock(&inode->i_mutex);
 930        ret = sync_mapping_buffers(inode->i_mapping);
 931        if (!(inode->i_state & I_DIRTY))
 932                goto out;
 933        if (datasync && !(inode->i_state & I_DIRTY_DATASYNC))
 934                goto out;
 935
 936        err = sync_inode_metadata(inode, 1);
 937        if (ret == 0)
 938                ret = err;
 939out:
 940        mutex_unlock(&inode->i_mutex);
 941        return ret;
 942}
 943EXPORT_SYMBOL(generic_file_fsync);
 944
 945/**
 946 * generic_check_addressable - Check addressability of file system
 947 * @blocksize_bits:     log of file system block size
 948 * @num_blocks:         number of blocks in file system
 949 *
 950 * Determine whether a file system with @num_blocks blocks (and a
 951 * block size of 2**@blocksize_bits) is addressable by the sector_t
 952 * and page cache of the system.  Return 0 if so and -EFBIG otherwise.
 953 */
 954int generic_check_addressable(unsigned blocksize_bits, u64 num_blocks)
 955{
 956        u64 last_fs_block = num_blocks - 1;
 957        u64 last_fs_page =
 958                last_fs_block >> (PAGE_CACHE_SHIFT - blocksize_bits);
 959
 960        if (unlikely(num_blocks == 0))
 961                return 0;
 962
 963        if ((blocksize_bits < 9) || (blocksize_bits > PAGE_CACHE_SHIFT))
 964                return -EINVAL;
 965
 966        if ((last_fs_block > (sector_t)(~0ULL) >> (blocksize_bits - 9)) ||
 967            (last_fs_page > (pgoff_t)(~0ULL))) {
 968                return -EFBIG;
 969        }
 970        return 0;
 971}
 972EXPORT_SYMBOL(generic_check_addressable);
 973
 974/*
 975 * No-op implementation of ->fsync for in-memory filesystems.
 976 */
 977int noop_fsync(struct file *file, loff_t start, loff_t end, int datasync)
 978{
 979        return 0;
 980}
 981
 982EXPORT_SYMBOL(dcache_dir_close);
 983EXPORT_SYMBOL(dcache_dir_lseek);
 984EXPORT_SYMBOL(dcache_dir_open);
 985EXPORT_SYMBOL(dcache_readdir);
 986EXPORT_SYMBOL(generic_read_dir);
 987EXPORT_SYMBOL(mount_pseudo);
 988EXPORT_SYMBOL(simple_write_begin);
 989EXPORT_SYMBOL(simple_write_end);
 990EXPORT_SYMBOL(simple_dir_inode_operations);
 991EXPORT_SYMBOL(simple_dir_operations);
 992EXPORT_SYMBOL(simple_empty);
 993EXPORT_SYMBOL(simple_fill_super);
 994EXPORT_SYMBOL(simple_getattr);
 995EXPORT_SYMBOL(simple_open);
 996EXPORT_SYMBOL(simple_link);
 997EXPORT_SYMBOL(simple_lookup);
 998EXPORT_SYMBOL(simple_pin_fs);
 999EXPORT_SYMBOL(simple_readpage);
1000EXPORT_SYMBOL(simple_release_fs);
1001EXPORT_SYMBOL(simple_rename);
1002EXPORT_SYMBOL(simple_rmdir);
1003EXPORT_SYMBOL(simple_statfs);
1004EXPORT_SYMBOL(noop_fsync);
1005EXPORT_SYMBOL(simple_unlink);
1006EXPORT_SYMBOL(simple_read_from_buffer);
1007EXPORT_SYMBOL(simple_write_to_buffer);
1008EXPORT_SYMBOL(memory_read_from_buffer);
1009EXPORT_SYMBOL(simple_transaction_set);
1010EXPORT_SYMBOL(simple_transaction_get);
1011EXPORT_SYMBOL(simple_transaction_read);
1012EXPORT_SYMBOL(simple_transaction_release);
1013EXPORT_SYMBOL_GPL(simple_attr_open);
1014EXPORT_SYMBOL_GPL(simple_attr_release);
1015EXPORT_SYMBOL_GPL(simple_attr_read);
1016EXPORT_SYMBOL_GPL(simple_attr_write);
1017
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