linux/fs/block_dev.c
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   1/*
   2 *  linux/fs/block_dev.c
   3 *
   4 *  Copyright (C) 1991, 1992  Linus Torvalds
   5 *  Copyright (C) 2001  Andrea Arcangeli <andrea@suse.de> SuSE
   6 */
   7
   8#include <linux/init.h>
   9#include <linux/mm.h>
  10#include <linux/fcntl.h>
  11#include <linux/slab.h>
  12#include <linux/kmod.h>
  13#include <linux/major.h>
  14#include <linux/device_cgroup.h>
  15#include <linux/highmem.h>
  16#include <linux/blkdev.h>
  17#include <linux/module.h>
  18#include <linux/blkpg.h>
  19#include <linux/magic.h>
  20#include <linux/buffer_head.h>
  21#include <linux/swap.h>
  22#include <linux/pagevec.h>
  23#include <linux/writeback.h>
  24#include <linux/mpage.h>
  25#include <linux/mount.h>
  26#include <linux/uio.h>
  27#include <linux/namei.h>
  28#include <linux/log2.h>
  29#include <linux/cleancache.h>
  30#include <asm/uaccess.h>
  31#include "internal.h"
  32
  33struct bdev_inode {
  34        struct block_device bdev;
  35        struct inode vfs_inode;
  36};
  37
  38static const struct address_space_operations def_blk_aops;
  39
  40static inline struct bdev_inode *BDEV_I(struct inode *inode)
  41{
  42        return container_of(inode, struct bdev_inode, vfs_inode);
  43}
  44
  45inline struct block_device *I_BDEV(struct inode *inode)
  46{
  47        return &BDEV_I(inode)->bdev;
  48}
  49EXPORT_SYMBOL(I_BDEV);
  50
  51/*
  52 * Move the inode from its current bdi to a new bdi. If the inode is dirty we
  53 * need to move it onto the dirty list of @dst so that the inode is always on
  54 * the right list.
  55 */
  56static void bdev_inode_switch_bdi(struct inode *inode,
  57                        struct backing_dev_info *dst)
  58{
  59        struct backing_dev_info *old = inode->i_data.backing_dev_info;
  60
  61        if (unlikely(dst == old))               /* deadlock avoidance */
  62                return;
  63        bdi_lock_two(&old->wb, &dst->wb);
  64        spin_lock(&inode->i_lock);
  65        inode->i_data.backing_dev_info = dst;
  66        if (inode->i_state & I_DIRTY)
  67                list_move(&inode->i_wb_list, &dst->wb.b_dirty);
  68        spin_unlock(&inode->i_lock);
  69        spin_unlock(&old->wb.list_lock);
  70        spin_unlock(&dst->wb.list_lock);
  71}
  72
  73sector_t blkdev_max_block(struct block_device *bdev)
  74{
  75        sector_t retval = ~((sector_t)0);
  76        loff_t sz = i_size_read(bdev->bd_inode);
  77
  78        if (sz) {
  79                unsigned int size = block_size(bdev);
  80                unsigned int sizebits = blksize_bits(size);
  81                retval = (sz >> sizebits);
  82        }
  83        return retval;
  84}
  85
  86/* Kill _all_ buffers and pagecache , dirty or not.. */
  87void kill_bdev(struct block_device *bdev)
  88{
  89        struct address_space *mapping = bdev->bd_inode->i_mapping;
  90
  91        if (mapping->nrpages == 0)
  92                return;
  93
  94        invalidate_bh_lrus();
  95        truncate_inode_pages(mapping, 0);
  96}       
  97EXPORT_SYMBOL(kill_bdev);
  98
  99/* Invalidate clean unused buffers and pagecache. */
 100void invalidate_bdev(struct block_device *bdev)
 101{
 102        struct address_space *mapping = bdev->bd_inode->i_mapping;
 103
 104        if (mapping->nrpages == 0)
 105                return;
 106
 107        invalidate_bh_lrus();
 108        lru_add_drain_all();    /* make sure all lru add caches are flushed */
 109        invalidate_mapping_pages(mapping, 0, -1);
 110        /* 99% of the time, we don't need to flush the cleancache on the bdev.
 111         * But, for the strange corners, lets be cautious
 112         */
 113        cleancache_invalidate_inode(mapping);
 114}
 115EXPORT_SYMBOL(invalidate_bdev);
 116
 117int set_blocksize(struct block_device *bdev, int size)
 118{
 119        /* Size must be a power of two, and between 512 and PAGE_SIZE */
 120        if (size > PAGE_SIZE || size < 512 || !is_power_of_2(size))
 121                return -EINVAL;
 122
 123        /* Size cannot be smaller than the size supported by the device */
 124        if (size < bdev_logical_block_size(bdev))
 125                return -EINVAL;
 126
 127        /* Don't change the size if it is same as current */
 128        if (bdev->bd_block_size != size) {
 129                sync_blockdev(bdev);
 130                bdev->bd_block_size = size;
 131                bdev->bd_inode->i_blkbits = blksize_bits(size);
 132                kill_bdev(bdev);
 133        }
 134        return 0;
 135}
 136
 137EXPORT_SYMBOL(set_blocksize);
 138
 139int sb_set_blocksize(struct super_block *sb, int size)
 140{
 141        if (set_blocksize(sb->s_bdev, size))
 142                return 0;
 143        /* If we get here, we know size is power of two
 144         * and it's value is between 512 and PAGE_SIZE */
 145        sb->s_blocksize = size;
 146        sb->s_blocksize_bits = blksize_bits(size);
 147        return sb->s_blocksize;
 148}
 149
 150EXPORT_SYMBOL(sb_set_blocksize);
 151
 152int sb_min_blocksize(struct super_block *sb, int size)
 153{
 154        int minsize = bdev_logical_block_size(sb->s_bdev);
 155        if (size < minsize)
 156                size = minsize;
 157        return sb_set_blocksize(sb, size);
 158}
 159
 160EXPORT_SYMBOL(sb_min_blocksize);
 161
 162static int
 163blkdev_get_block(struct inode *inode, sector_t iblock,
 164                struct buffer_head *bh, int create)
 165{
 166        if (iblock >= blkdev_max_block(I_BDEV(inode))) {
 167                if (create)
 168                        return -EIO;
 169
 170                /*
 171                 * for reads, we're just trying to fill a partial page.
 172                 * return a hole, they will have to call get_block again
 173                 * before they can fill it, and they will get -EIO at that
 174                 * time
 175                 */
 176                return 0;
 177        }
 178        bh->b_bdev = I_BDEV(inode);
 179        bh->b_blocknr = iblock;
 180        set_buffer_mapped(bh);
 181        return 0;
 182}
 183
 184static int
 185blkdev_get_blocks(struct inode *inode, sector_t iblock,
 186                struct buffer_head *bh, int create)
 187{
 188        sector_t end_block = blkdev_max_block(I_BDEV(inode));
 189        unsigned long max_blocks = bh->b_size >> inode->i_blkbits;
 190
 191        if ((iblock + max_blocks) > end_block) {
 192                max_blocks = end_block - iblock;
 193                if ((long)max_blocks <= 0) {
 194                        if (create)
 195                                return -EIO;    /* write fully beyond EOF */
 196                        /*
 197                         * It is a read which is fully beyond EOF.  We return
 198                         * a !buffer_mapped buffer
 199                         */
 200                        max_blocks = 0;
 201                }
 202        }
 203
 204        bh->b_bdev = I_BDEV(inode);
 205        bh->b_blocknr = iblock;
 206        bh->b_size = max_blocks << inode->i_blkbits;
 207        if (max_blocks)
 208                set_buffer_mapped(bh);
 209        return 0;
 210}
 211
 212static ssize_t
 213blkdev_direct_IO(int rw, struct kiocb *iocb, const struct iovec *iov,
 214                        loff_t offset, unsigned long nr_segs)
 215{
 216        struct file *file = iocb->ki_filp;
 217        struct inode *inode = file->f_mapping->host;
 218
 219        return __blockdev_direct_IO(rw, iocb, inode, I_BDEV(inode), iov, offset,
 220                                    nr_segs, blkdev_get_blocks, NULL, NULL, 0);
 221}
 222
 223int __sync_blockdev(struct block_device *bdev, int wait)
 224{
 225        if (!bdev)
 226                return 0;
 227        if (!wait)
 228                return filemap_flush(bdev->bd_inode->i_mapping);
 229        return filemap_write_and_wait(bdev->bd_inode->i_mapping);
 230}
 231
 232/*
 233 * Write out and wait upon all the dirty data associated with a block
 234 * device via its mapping.  Does not take the superblock lock.
 235 */
 236int sync_blockdev(struct block_device *bdev)
 237{
 238        return __sync_blockdev(bdev, 1);
 239}
 240EXPORT_SYMBOL(sync_blockdev);
 241
 242/*
 243 * Write out and wait upon all dirty data associated with this
 244 * device.   Filesystem data as well as the underlying block
 245 * device.  Takes the superblock lock.
 246 */
 247int fsync_bdev(struct block_device *bdev)
 248{
 249        struct super_block *sb = get_super(bdev);
 250        if (sb) {
 251                int res = sync_filesystem(sb);
 252                drop_super(sb);
 253                return res;
 254        }
 255        return sync_blockdev(bdev);
 256}
 257EXPORT_SYMBOL(fsync_bdev);
 258
 259/**
 260 * freeze_bdev  --  lock a filesystem and force it into a consistent state
 261 * @bdev:       blockdevice to lock
 262 *
 263 * If a superblock is found on this device, we take the s_umount semaphore
 264 * on it to make sure nobody unmounts until the snapshot creation is done.
 265 * The reference counter (bd_fsfreeze_count) guarantees that only the last
 266 * unfreeze process can unfreeze the frozen filesystem actually when multiple
 267 * freeze requests arrive simultaneously. It counts up in freeze_bdev() and
 268 * count down in thaw_bdev(). When it becomes 0, thaw_bdev() will unfreeze
 269 * actually.
 270 */
 271struct super_block *freeze_bdev(struct block_device *bdev)
 272{
 273        struct super_block *sb;
 274        int error = 0;
 275
 276        mutex_lock(&bdev->bd_fsfreeze_mutex);
 277        if (++bdev->bd_fsfreeze_count > 1) {
 278                /*
 279                 * We don't even need to grab a reference - the first call
 280                 * to freeze_bdev grab an active reference and only the last
 281                 * thaw_bdev drops it.
 282                 */
 283                sb = get_super(bdev);
 284                drop_super(sb);
 285                mutex_unlock(&bdev->bd_fsfreeze_mutex);
 286                return sb;
 287        }
 288
 289        sb = get_active_super(bdev);
 290        if (!sb)
 291                goto out;
 292        error = freeze_super(sb);
 293        if (error) {
 294                deactivate_super(sb);
 295                bdev->bd_fsfreeze_count--;
 296                mutex_unlock(&bdev->bd_fsfreeze_mutex);
 297                return ERR_PTR(error);
 298        }
 299        deactivate_super(sb);
 300 out:
 301        sync_blockdev(bdev);
 302        mutex_unlock(&bdev->bd_fsfreeze_mutex);
 303        return sb;      /* thaw_bdev releases s->s_umount */
 304}
 305EXPORT_SYMBOL(freeze_bdev);
 306
 307/**
 308 * thaw_bdev  -- unlock filesystem
 309 * @bdev:       blockdevice to unlock
 310 * @sb:         associated superblock
 311 *
 312 * Unlocks the filesystem and marks it writeable again after freeze_bdev().
 313 */
 314int thaw_bdev(struct block_device *bdev, struct super_block *sb)
 315{
 316        int error = -EINVAL;
 317
 318        mutex_lock(&bdev->bd_fsfreeze_mutex);
 319        if (!bdev->bd_fsfreeze_count)
 320                goto out;
 321
 322        error = 0;
 323        if (--bdev->bd_fsfreeze_count > 0)
 324                goto out;
 325
 326        if (!sb)
 327                goto out;
 328
 329        error = thaw_super(sb);
 330        if (error) {
 331                bdev->bd_fsfreeze_count++;
 332                mutex_unlock(&bdev->bd_fsfreeze_mutex);
 333                return error;
 334        }
 335out:
 336        mutex_unlock(&bdev->bd_fsfreeze_mutex);
 337        return 0;
 338}
 339EXPORT_SYMBOL(thaw_bdev);
 340
 341static int blkdev_writepage(struct page *page, struct writeback_control *wbc)
 342{
 343        return block_write_full_page(page, blkdev_get_block, wbc);
 344}
 345
 346static int blkdev_readpage(struct file * file, struct page * page)
 347{
 348        return block_read_full_page(page, blkdev_get_block);
 349}
 350
 351static int blkdev_write_begin(struct file *file, struct address_space *mapping,
 352                        loff_t pos, unsigned len, unsigned flags,
 353                        struct page **pagep, void **fsdata)
 354{
 355        return block_write_begin(mapping, pos, len, flags, pagep,
 356                                 blkdev_get_block);
 357}
 358
 359static int blkdev_write_end(struct file *file, struct address_space *mapping,
 360                        loff_t pos, unsigned len, unsigned copied,
 361                        struct page *page, void *fsdata)
 362{
 363        int ret;
 364        ret = block_write_end(file, mapping, pos, len, copied, page, fsdata);
 365
 366        unlock_page(page);
 367        page_cache_release(page);
 368
 369        return ret;
 370}
 371
 372/*
 373 * private llseek:
 374 * for a block special file file->f_path.dentry->d_inode->i_size is zero
 375 * so we compute the size by hand (just as in block_read/write above)
 376 */
 377static loff_t block_llseek(struct file *file, loff_t offset, int origin)
 378{
 379        struct inode *bd_inode = file->f_mapping->host;
 380        loff_t size;
 381        loff_t retval;
 382
 383        mutex_lock(&bd_inode->i_mutex);
 384        size = i_size_read(bd_inode);
 385
 386        retval = -EINVAL;
 387        switch (origin) {
 388                case SEEK_END:
 389                        offset += size;
 390                        break;
 391                case SEEK_CUR:
 392                        offset += file->f_pos;
 393                case SEEK_SET:
 394                        break;
 395                default:
 396                        goto out;
 397        }
 398        if (offset >= 0 && offset <= size) {
 399                if (offset != file->f_pos) {
 400                        file->f_pos = offset;
 401                }
 402                retval = offset;
 403        }
 404out:
 405        mutex_unlock(&bd_inode->i_mutex);
 406        return retval;
 407}
 408        
 409int blkdev_fsync(struct file *filp, loff_t start, loff_t end, int datasync)
 410{
 411        struct inode *bd_inode = filp->f_mapping->host;
 412        struct block_device *bdev = I_BDEV(bd_inode);
 413        int error;
 414        
 415        error = filemap_write_and_wait_range(filp->f_mapping, start, end);
 416        if (error)
 417                return error;
 418
 419        /*
 420         * There is no need to serialise calls to blkdev_issue_flush with
 421         * i_mutex and doing so causes performance issues with concurrent
 422         * O_SYNC writers to a block device.
 423         */
 424        error = blkdev_issue_flush(bdev, GFP_KERNEL, NULL);
 425        if (error == -EOPNOTSUPP)
 426                error = 0;
 427
 428        return error;
 429}
 430EXPORT_SYMBOL(blkdev_fsync);
 431
 432/*
 433 * pseudo-fs
 434 */
 435
 436static  __cacheline_aligned_in_smp DEFINE_SPINLOCK(bdev_lock);
 437static struct kmem_cache * bdev_cachep __read_mostly;
 438
 439static struct inode *bdev_alloc_inode(struct super_block *sb)
 440{
 441        struct bdev_inode *ei = kmem_cache_alloc(bdev_cachep, GFP_KERNEL);
 442        if (!ei)
 443                return NULL;
 444        return &ei->vfs_inode;
 445}
 446
 447static void bdev_i_callback(struct rcu_head *head)
 448{
 449        struct inode *inode = container_of(head, struct inode, i_rcu);
 450        struct bdev_inode *bdi = BDEV_I(inode);
 451
 452        kmem_cache_free(bdev_cachep, bdi);
 453}
 454
 455static void bdev_destroy_inode(struct inode *inode)
 456{
 457        call_rcu(&inode->i_rcu, bdev_i_callback);
 458}
 459
 460static void init_once(void *foo)
 461{
 462        struct bdev_inode *ei = (struct bdev_inode *) foo;
 463        struct block_device *bdev = &ei->bdev;
 464
 465        memset(bdev, 0, sizeof(*bdev));
 466        mutex_init(&bdev->bd_mutex);
 467        INIT_LIST_HEAD(&bdev->bd_inodes);
 468        INIT_LIST_HEAD(&bdev->bd_list);
 469#ifdef CONFIG_SYSFS
 470        INIT_LIST_HEAD(&bdev->bd_holder_disks);
 471#endif
 472        inode_init_once(&ei->vfs_inode);
 473        /* Initialize mutex for freeze. */
 474        mutex_init(&bdev->bd_fsfreeze_mutex);
 475}
 476
 477static inline void __bd_forget(struct inode *inode)
 478{
 479        list_del_init(&inode->i_devices);
 480        inode->i_bdev = NULL;
 481        inode->i_mapping = &inode->i_data;
 482}
 483
 484static void bdev_evict_inode(struct inode *inode)
 485{
 486        struct block_device *bdev = &BDEV_I(inode)->bdev;
 487        struct list_head *p;
 488        truncate_inode_pages(&inode->i_data, 0);
 489        invalidate_inode_buffers(inode); /* is it needed here? */
 490        clear_inode(inode);
 491        spin_lock(&bdev_lock);
 492        while ( (p = bdev->bd_inodes.next) != &bdev->bd_inodes ) {
 493                __bd_forget(list_entry(p, struct inode, i_devices));
 494        }
 495        list_del_init(&bdev->bd_list);
 496        spin_unlock(&bdev_lock);
 497}
 498
 499static const struct super_operations bdev_sops = {
 500        .statfs = simple_statfs,
 501        .alloc_inode = bdev_alloc_inode,
 502        .destroy_inode = bdev_destroy_inode,
 503        .drop_inode = generic_delete_inode,
 504        .evict_inode = bdev_evict_inode,
 505};
 506
 507static struct dentry *bd_mount(struct file_system_type *fs_type,
 508        int flags, const char *dev_name, void *data)
 509{
 510        return mount_pseudo(fs_type, "bdev:", &bdev_sops, NULL, BDEVFS_MAGIC);
 511}
 512
 513static struct file_system_type bd_type = {
 514        .name           = "bdev",
 515        .mount          = bd_mount,
 516        .kill_sb        = kill_anon_super,
 517};
 518
 519static struct super_block *blockdev_superblock __read_mostly;
 520
 521void __init bdev_cache_init(void)
 522{
 523        int err;
 524        static struct vfsmount *bd_mnt;
 525
 526        bdev_cachep = kmem_cache_create("bdev_cache", sizeof(struct bdev_inode),
 527                        0, (SLAB_HWCACHE_ALIGN|SLAB_RECLAIM_ACCOUNT|
 528                                SLAB_MEM_SPREAD|SLAB_PANIC),
 529                        init_once);
 530        err = register_filesystem(&bd_type);
 531        if (err)
 532                panic("Cannot register bdev pseudo-fs");
 533        bd_mnt = kern_mount(&bd_type);
 534        if (IS_ERR(bd_mnt))
 535                panic("Cannot create bdev pseudo-fs");
 536        blockdev_superblock = bd_mnt->mnt_sb;   /* For writeback */
 537}
 538
 539/*
 540 * Most likely _very_ bad one - but then it's hardly critical for small
 541 * /dev and can be fixed when somebody will need really large one.
 542 * Keep in mind that it will be fed through icache hash function too.
 543 */
 544static inline unsigned long hash(dev_t dev)
 545{
 546        return MAJOR(dev)+MINOR(dev);
 547}
 548
 549static int bdev_test(struct inode *inode, void *data)
 550{
 551        return BDEV_I(inode)->bdev.bd_dev == *(dev_t *)data;
 552}
 553
 554static int bdev_set(struct inode *inode, void *data)
 555{
 556        BDEV_I(inode)->bdev.bd_dev = *(dev_t *)data;
 557        return 0;
 558}
 559
 560static LIST_HEAD(all_bdevs);
 561
 562struct block_device *bdget(dev_t dev)
 563{
 564        struct block_device *bdev;
 565        struct inode *inode;
 566
 567        inode = iget5_locked(blockdev_superblock, hash(dev),
 568                        bdev_test, bdev_set, &dev);
 569
 570        if (!inode)
 571                return NULL;
 572
 573        bdev = &BDEV_I(inode)->bdev;
 574
 575        if (inode->i_state & I_NEW) {
 576                bdev->bd_contains = NULL;
 577                bdev->bd_super = NULL;
 578                bdev->bd_inode = inode;
 579                bdev->bd_block_size = (1 << inode->i_blkbits);
 580                bdev->bd_part_count = 0;
 581                bdev->bd_invalidated = 0;
 582                inode->i_mode = S_IFBLK;
 583                inode->i_rdev = dev;
 584                inode->i_bdev = bdev;
 585                inode->i_data.a_ops = &def_blk_aops;
 586                mapping_set_gfp_mask(&inode->i_data, GFP_USER);
 587                inode->i_data.backing_dev_info = &default_backing_dev_info;
 588                spin_lock(&bdev_lock);
 589                list_add(&bdev->bd_list, &all_bdevs);
 590                spin_unlock(&bdev_lock);
 591                unlock_new_inode(inode);
 592        }
 593        return bdev;
 594}
 595
 596EXPORT_SYMBOL(bdget);
 597
 598/**
 599 * bdgrab -- Grab a reference to an already referenced block device
 600 * @bdev:       Block device to grab a reference to.
 601 */
 602struct block_device *bdgrab(struct block_device *bdev)
 603{
 604        ihold(bdev->bd_inode);
 605        return bdev;
 606}
 607
 608long nr_blockdev_pages(void)
 609{
 610        struct block_device *bdev;
 611        long ret = 0;
 612        spin_lock(&bdev_lock);
 613        list_for_each_entry(bdev, &all_bdevs, bd_list) {
 614                ret += bdev->bd_inode->i_mapping->nrpages;
 615        }
 616        spin_unlock(&bdev_lock);
 617        return ret;
 618}
 619
 620void bdput(struct block_device *bdev)
 621{
 622        iput(bdev->bd_inode);
 623}
 624
 625EXPORT_SYMBOL(bdput);
 626 
 627static struct block_device *bd_acquire(struct inode *inode)
 628{
 629        struct block_device *bdev;
 630
 631        spin_lock(&bdev_lock);
 632        bdev = inode->i_bdev;
 633        if (bdev) {
 634                ihold(bdev->bd_inode);
 635                spin_unlock(&bdev_lock);
 636                return bdev;
 637        }
 638        spin_unlock(&bdev_lock);
 639
 640        bdev = bdget(inode->i_rdev);
 641        if (bdev) {
 642                spin_lock(&bdev_lock);
 643                if (!inode->i_bdev) {
 644                        /*
 645                         * We take an additional reference to bd_inode,
 646                         * and it's released in clear_inode() of inode.
 647                         * So, we can access it via ->i_mapping always
 648                         * without igrab().
 649                         */
 650                        ihold(bdev->bd_inode);
 651                        inode->i_bdev = bdev;
 652                        inode->i_mapping = bdev->bd_inode->i_mapping;
 653                        list_add(&inode->i_devices, &bdev->bd_inodes);
 654                }
 655                spin_unlock(&bdev_lock);
 656        }
 657        return bdev;
 658}
 659
 660static inline int sb_is_blkdev_sb(struct super_block *sb)
 661{
 662        return sb == blockdev_superblock;
 663}
 664
 665/* Call when you free inode */
 666
 667void bd_forget(struct inode *inode)
 668{
 669        struct block_device *bdev = NULL;
 670
 671        spin_lock(&bdev_lock);
 672        if (inode->i_bdev) {
 673                if (!sb_is_blkdev_sb(inode->i_sb))
 674                        bdev = inode->i_bdev;
 675                __bd_forget(inode);
 676        }
 677        spin_unlock(&bdev_lock);
 678
 679        if (bdev)
 680                iput(bdev->bd_inode);
 681}
 682
 683/**
 684 * bd_may_claim - test whether a block device can be claimed
 685 * @bdev: block device of interest
 686 * @whole: whole block device containing @bdev, may equal @bdev
 687 * @holder: holder trying to claim @bdev
 688 *
 689 * Test whether @bdev can be claimed by @holder.
 690 *
 691 * CONTEXT:
 692 * spin_lock(&bdev_lock).
 693 *
 694 * RETURNS:
 695 * %true if @bdev can be claimed, %false otherwise.
 696 */
 697static bool bd_may_claim(struct block_device *bdev, struct block_device *whole,
 698                         void *holder)
 699{
 700        if (bdev->bd_holder == holder)
 701                return true;     /* already a holder */
 702        else if (bdev->bd_holder != NULL)
 703                return false;    /* held by someone else */
 704        else if (bdev->bd_contains == bdev)
 705                return true;     /* is a whole device which isn't held */
 706
 707        else if (whole->bd_holder == bd_may_claim)
 708                return true;     /* is a partition of a device that is being partitioned */
 709        else if (whole->bd_holder != NULL)
 710                return false;    /* is a partition of a held device */
 711        else
 712                return true;     /* is a partition of an un-held device */
 713}
 714
 715/**
 716 * bd_prepare_to_claim - prepare to claim a block device
 717 * @bdev: block device of interest
 718 * @whole: the whole device containing @bdev, may equal @bdev
 719 * @holder: holder trying to claim @bdev
 720 *
 721 * Prepare to claim @bdev.  This function fails if @bdev is already
 722 * claimed by another holder and waits if another claiming is in
 723 * progress.  This function doesn't actually claim.  On successful
 724 * return, the caller has ownership of bd_claiming and bd_holder[s].
 725 *
 726 * CONTEXT:
 727 * spin_lock(&bdev_lock).  Might release bdev_lock, sleep and regrab
 728 * it multiple times.
 729 *
 730 * RETURNS:
 731 * 0 if @bdev can be claimed, -EBUSY otherwise.
 732 */
 733static int bd_prepare_to_claim(struct block_device *bdev,
 734                               struct block_device *whole, void *holder)
 735{
 736retry:
 737        /* if someone else claimed, fail */
 738        if (!bd_may_claim(bdev, whole, holder))
 739                return -EBUSY;
 740
 741        /* if claiming is already in progress, wait for it to finish */
 742        if (whole->bd_claiming) {
 743                wait_queue_head_t *wq = bit_waitqueue(&whole->bd_claiming, 0);
 744                DEFINE_WAIT(wait);
 745
 746                prepare_to_wait(wq, &wait, TASK_UNINTERRUPTIBLE);
 747                spin_unlock(&bdev_lock);
 748                schedule();
 749                finish_wait(wq, &wait);
 750                spin_lock(&bdev_lock);
 751                goto retry;
 752        }
 753
 754        /* yay, all mine */
 755        return 0;
 756}
 757
 758/**
 759 * bd_start_claiming - start claiming a block device
 760 * @bdev: block device of interest
 761 * @holder: holder trying to claim @bdev
 762 *
 763 * @bdev is about to be opened exclusively.  Check @bdev can be opened
 764 * exclusively and mark that an exclusive open is in progress.  Each
 765 * successful call to this function must be matched with a call to
 766 * either bd_finish_claiming() or bd_abort_claiming() (which do not
 767 * fail).
 768 *
 769 * This function is used to gain exclusive access to the block device
 770 * without actually causing other exclusive open attempts to fail. It
 771 * should be used when the open sequence itself requires exclusive
 772 * access but may subsequently fail.
 773 *
 774 * CONTEXT:
 775 * Might sleep.
 776 *
 777 * RETURNS:
 778 * Pointer to the block device containing @bdev on success, ERR_PTR()
 779 * value on failure.
 780 */
 781static struct block_device *bd_start_claiming(struct block_device *bdev,
 782                                              void *holder)
 783{
 784        struct gendisk *disk;
 785        struct block_device *whole;
 786        int partno, err;
 787
 788        might_sleep();
 789
 790        /*
 791         * @bdev might not have been initialized properly yet, look up
 792         * and grab the outer block device the hard way.
 793         */
 794        disk = get_gendisk(bdev->bd_dev, &partno);
 795        if (!disk)
 796                return ERR_PTR(-ENXIO);
 797
 798        /*
 799         * Normally, @bdev should equal what's returned from bdget_disk()
 800         * if partno is 0; however, some drivers (floppy) use multiple
 801         * bdev's for the same physical device and @bdev may be one of the
 802         * aliases.  Keep @bdev if partno is 0.  This means claimer
 803         * tracking is broken for those devices but it has always been that
 804         * way.
 805         */
 806        if (partno)
 807                whole = bdget_disk(disk, 0);
 808        else
 809                whole = bdgrab(bdev);
 810
 811        module_put(disk->fops->owner);
 812        put_disk(disk);
 813        if (!whole)
 814                return ERR_PTR(-ENOMEM);
 815
 816        /* prepare to claim, if successful, mark claiming in progress */
 817        spin_lock(&bdev_lock);
 818
 819        err = bd_prepare_to_claim(bdev, whole, holder);
 820        if (err == 0) {
 821                whole->bd_claiming = holder;
 822                spin_unlock(&bdev_lock);
 823                return whole;
 824        } else {
 825                spin_unlock(&bdev_lock);
 826                bdput(whole);
 827                return ERR_PTR(err);
 828        }
 829}
 830
 831#ifdef CONFIG_SYSFS
 832struct bd_holder_disk {
 833        struct list_head        list;
 834        struct gendisk          *disk;
 835        int                     refcnt;
 836};
 837
 838static struct bd_holder_disk *bd_find_holder_disk(struct block_device *bdev,
 839                                                  struct gendisk *disk)
 840{
 841        struct bd_holder_disk *holder;
 842
 843        list_for_each_entry(holder, &bdev->bd_holder_disks, list)
 844                if (holder->disk == disk)
 845                        return holder;
 846        return NULL;
 847}
 848
 849static int add_symlink(struct kobject *from, struct kobject *to)
 850{
 851        return sysfs_create_link(from, to, kobject_name(to));
 852}
 853
 854static void del_symlink(struct kobject *from, struct kobject *to)
 855{
 856        sysfs_remove_link(from, kobject_name(to));
 857}
 858
 859/**
 860 * bd_link_disk_holder - create symlinks between holding disk and slave bdev
 861 * @bdev: the claimed slave bdev
 862 * @disk: the holding disk
 863 *
 864 * DON'T USE THIS UNLESS YOU'RE ALREADY USING IT.
 865 *
 866 * This functions creates the following sysfs symlinks.
 867 *
 868 * - from "slaves" directory of the holder @disk to the claimed @bdev
 869 * - from "holders" directory of the @bdev to the holder @disk
 870 *
 871 * For example, if /dev/dm-0 maps to /dev/sda and disk for dm-0 is
 872 * passed to bd_link_disk_holder(), then:
 873 *
 874 *   /sys/block/dm-0/slaves/sda --> /sys/block/sda
 875 *   /sys/block/sda/holders/dm-0 --> /sys/block/dm-0
 876 *
 877 * The caller must have claimed @bdev before calling this function and
 878 * ensure that both @bdev and @disk are valid during the creation and
 879 * lifetime of these symlinks.
 880 *
 881 * CONTEXT:
 882 * Might sleep.
 883 *
 884 * RETURNS:
 885 * 0 on success, -errno on failure.
 886 */
 887int bd_link_disk_holder(struct block_device *bdev, struct gendisk *disk)
 888{
 889        struct bd_holder_disk *holder;
 890        int ret = 0;
 891
 892        mutex_lock(&bdev->bd_mutex);
 893
 894        WARN_ON_ONCE(!bdev->bd_holder);
 895
 896        /* FIXME: remove the following once add_disk() handles errors */
 897        if (WARN_ON(!disk->slave_dir || !bdev->bd_part->holder_dir))
 898                goto out_unlock;
 899
 900        holder = bd_find_holder_disk(bdev, disk);
 901        if (holder) {
 902                holder->refcnt++;
 903                goto out_unlock;
 904        }
 905
 906        holder = kzalloc(sizeof(*holder), GFP_KERNEL);
 907        if (!holder) {
 908                ret = -ENOMEM;
 909                goto out_unlock;
 910        }
 911
 912        INIT_LIST_HEAD(&holder->list);
 913        holder->disk = disk;
 914        holder->refcnt = 1;
 915
 916        ret = add_symlink(disk->slave_dir, &part_to_dev(bdev->bd_part)->kobj);
 917        if (ret)
 918                goto out_free;
 919
 920        ret = add_symlink(bdev->bd_part->holder_dir, &disk_to_dev(disk)->kobj);
 921        if (ret)
 922                goto out_del;
 923        /*
 924         * bdev could be deleted beneath us which would implicitly destroy
 925         * the holder directory.  Hold on to it.
 926         */
 927        kobject_get(bdev->bd_part->holder_dir);
 928
 929        list_add(&holder->list, &bdev->bd_holder_disks);
 930        goto out_unlock;
 931
 932out_del:
 933        del_symlink(disk->slave_dir, &part_to_dev(bdev->bd_part)->kobj);
 934out_free:
 935        kfree(holder);
 936out_unlock:
 937        mutex_unlock(&bdev->bd_mutex);
 938        return ret;
 939}
 940EXPORT_SYMBOL_GPL(bd_link_disk_holder);
 941
 942/**
 943 * bd_unlink_disk_holder - destroy symlinks created by bd_link_disk_holder()
 944 * @bdev: the calimed slave bdev
 945 * @disk: the holding disk
 946 *
 947 * DON'T USE THIS UNLESS YOU'RE ALREADY USING IT.
 948 *
 949 * CONTEXT:
 950 * Might sleep.
 951 */
 952void bd_unlink_disk_holder(struct block_device *bdev, struct gendisk *disk)
 953{
 954        struct bd_holder_disk *holder;
 955
 956        mutex_lock(&bdev->bd_mutex);
 957
 958        holder = bd_find_holder_disk(bdev, disk);
 959
 960        if (!WARN_ON_ONCE(holder == NULL) && !--holder->refcnt) {
 961                del_symlink(disk->slave_dir, &part_to_dev(bdev->bd_part)->kobj);
 962                del_symlink(bdev->bd_part->holder_dir,
 963                            &disk_to_dev(disk)->kobj);
 964                kobject_put(bdev->bd_part->holder_dir);
 965                list_del_init(&holder->list);
 966                kfree(holder);
 967        }
 968
 969        mutex_unlock(&bdev->bd_mutex);
 970}
 971EXPORT_SYMBOL_GPL(bd_unlink_disk_holder);
 972#endif
 973
 974/**
 975 * flush_disk - invalidates all buffer-cache entries on a disk
 976 *
 977 * @bdev:      struct block device to be flushed
 978 * @kill_dirty: flag to guide handling of dirty inodes
 979 *
 980 * Invalidates all buffer-cache entries on a disk. It should be called
 981 * when a disk has been changed -- either by a media change or online
 982 * resize.
 983 */
 984static void flush_disk(struct block_device *bdev, bool kill_dirty)
 985{
 986        if (__invalidate_device(bdev, kill_dirty)) {
 987                char name[BDEVNAME_SIZE] = "";
 988
 989                if (bdev->bd_disk)
 990                        disk_name(bdev->bd_disk, 0, name);
 991                printk(KERN_WARNING "VFS: busy inodes on changed media or "
 992                       "resized disk %s\n", name);
 993        }
 994
 995        if (!bdev->bd_disk)
 996                return;
 997        if (disk_part_scan_enabled(bdev->bd_disk))
 998                bdev->bd_invalidated = 1;
 999}
1000
1001/**
1002 * check_disk_size_change - checks for disk size change and adjusts bdev size.
1003 * @disk: struct gendisk to check
1004 * @bdev: struct bdev to adjust.
1005 *
1006 * This routine checks to see if the bdev size does not match the disk size
1007 * and adjusts it if it differs.
1008 */
1009void check_disk_size_change(struct gendisk *disk, struct block_device *bdev)
1010{
1011        loff_t disk_size, bdev_size;
1012
1013        disk_size = (loff_t)get_capacity(disk) << 9;
1014        bdev_size = i_size_read(bdev->bd_inode);
1015        if (disk_size != bdev_size) {
1016                char name[BDEVNAME_SIZE];
1017
1018                disk_name(disk, 0, name);
1019                printk(KERN_INFO
1020                       "%s: detected capacity change from %lld to %lld\n",
1021                       name, bdev_size, disk_size);
1022                i_size_write(bdev->bd_inode, disk_size);
1023                flush_disk(bdev, false);
1024        }
1025}
1026EXPORT_SYMBOL(check_disk_size_change);
1027
1028/**
1029 * revalidate_disk - wrapper for lower-level driver's revalidate_disk call-back
1030 * @disk: struct gendisk to be revalidated
1031 *
1032 * This routine is a wrapper for lower-level driver's revalidate_disk
1033 * call-backs.  It is used to do common pre and post operations needed
1034 * for all revalidate_disk operations.
1035 */
1036int revalidate_disk(struct gendisk *disk)
1037{
1038        struct block_device *bdev;
1039        int ret = 0;
1040
1041        if (disk->fops->revalidate_disk)
1042                ret = disk->fops->revalidate_disk(disk);
1043
1044        bdev = bdget_disk(disk, 0);
1045        if (!bdev)
1046                return ret;
1047
1048        mutex_lock(&bdev->bd_mutex);
1049        check_disk_size_change(disk, bdev);
1050        mutex_unlock(&bdev->bd_mutex);
1051        bdput(bdev);
1052        return ret;
1053}
1054EXPORT_SYMBOL(revalidate_disk);
1055
1056/*
1057 * This routine checks whether a removable media has been changed,
1058 * and invalidates all buffer-cache-entries in that case. This
1059 * is a relatively slow routine, so we have to try to minimize using
1060 * it. Thus it is called only upon a 'mount' or 'open'. This
1061 * is the best way of combining speed and utility, I think.
1062 * People changing diskettes in the middle of an operation deserve
1063 * to lose :-)
1064 */
1065int check_disk_change(struct block_device *bdev)
1066{
1067        struct gendisk *disk = bdev->bd_disk;
1068        const struct block_device_operations *bdops = disk->fops;
1069        unsigned int events;
1070
1071        events = disk_clear_events(disk, DISK_EVENT_MEDIA_CHANGE |
1072                                   DISK_EVENT_EJECT_REQUEST);
1073        if (!(events & DISK_EVENT_MEDIA_CHANGE))
1074                return 0;
1075
1076        flush_disk(bdev, true);
1077        if (bdops->revalidate_disk)
1078                bdops->revalidate_disk(bdev->bd_disk);
1079        return 1;
1080}
1081
1082EXPORT_SYMBOL(check_disk_change);
1083
1084void bd_set_size(struct block_device *bdev, loff_t size)
1085{
1086        unsigned bsize = bdev_logical_block_size(bdev);
1087
1088        bdev->bd_inode->i_size = size;
1089        while (bsize < PAGE_CACHE_SIZE) {
1090                if (size & bsize)
1091                        break;
1092                bsize <<= 1;
1093        }
1094        bdev->bd_block_size = bsize;
1095        bdev->bd_inode->i_blkbits = blksize_bits(bsize);
1096}
1097EXPORT_SYMBOL(bd_set_size);
1098
1099static int __blkdev_put(struct block_device *bdev, fmode_t mode, int for_part);
1100
1101/*
1102 * bd_mutex locking:
1103 *
1104 *  mutex_lock(part->bd_mutex)
1105 *    mutex_lock_nested(whole->bd_mutex, 1)
1106 */
1107
1108static int __blkdev_get(struct block_device *bdev, fmode_t mode, int for_part)
1109{
1110        struct gendisk *disk;
1111        struct module *owner;
1112        int ret;
1113        int partno;
1114        int perm = 0;
1115
1116        if (mode & FMODE_READ)
1117                perm |= MAY_READ;
1118        if (mode & FMODE_WRITE)
1119                perm |= MAY_WRITE;
1120        /*
1121         * hooks: /n/, see "layering violations".
1122         */
1123        if (!for_part) {
1124                ret = devcgroup_inode_permission(bdev->bd_inode, perm);
1125                if (ret != 0) {
1126                        bdput(bdev);
1127                        return ret;
1128                }
1129        }
1130
1131 restart:
1132
1133        ret = -ENXIO;
1134        disk = get_gendisk(bdev->bd_dev, &partno);
1135        if (!disk)
1136                goto out;
1137        owner = disk->fops->owner;
1138
1139        disk_block_events(disk);
1140        mutex_lock_nested(&bdev->bd_mutex, for_part);
1141        if (!bdev->bd_openers) {
1142                bdev->bd_disk = disk;
1143                bdev->bd_queue = disk->queue;
1144                bdev->bd_contains = bdev;
1145                if (!partno) {
1146                        struct backing_dev_info *bdi;
1147
1148                        ret = -ENXIO;
1149                        bdev->bd_part = disk_get_part(disk, partno);
1150                        if (!bdev->bd_part)
1151                                goto out_clear;
1152
1153                        ret = 0;
1154                        if (disk->fops->open) {
1155                                ret = disk->fops->open(bdev, mode);
1156                                if (ret == -ERESTARTSYS) {
1157                                        /* Lost a race with 'disk' being
1158                                         * deleted, try again.
1159                                         * See md.c
1160                                         */
1161                                        disk_put_part(bdev->bd_part);
1162                                        bdev->bd_part = NULL;
1163                                        bdev->bd_disk = NULL;
1164                                        bdev->bd_queue = NULL;
1165                                        mutex_unlock(&bdev->bd_mutex);
1166                                        disk_unblock_events(disk);
1167                                        put_disk(disk);
1168                                        module_put(owner);
1169                                        goto restart;
1170                                }
1171                        }
1172
1173                        if (!ret && !bdev->bd_openers) {
1174                                bd_set_size(bdev,(loff_t)get_capacity(disk)<<9);
1175                                bdi = blk_get_backing_dev_info(bdev);
1176                                if (bdi == NULL)
1177                                        bdi = &default_backing_dev_info;
1178                                bdev_inode_switch_bdi(bdev->bd_inode, bdi);
1179                        }
1180
1181                        /*
1182                         * If the device is invalidated, rescan partition
1183                         * if open succeeded or failed with -ENOMEDIUM.
1184                         * The latter is necessary to prevent ghost
1185                         * partitions on a removed medium.
1186                         */
1187                        if (bdev->bd_invalidated) {
1188                                if (!ret)
1189                                        rescan_partitions(disk, bdev);
1190                                else if (ret == -ENOMEDIUM)
1191                                        invalidate_partitions(disk, bdev);
1192                        }
1193                        if (ret)
1194                                goto out_clear;
1195                } else {
1196                        struct block_device *whole;
1197                        whole = bdget_disk(disk, 0);
1198                        ret = -ENOMEM;
1199                        if (!whole)
1200                                goto out_clear;
1201                        BUG_ON(for_part);
1202                        ret = __blkdev_get(whole, mode, 1);
1203                        if (ret)
1204                                goto out_clear;
1205                        bdev->bd_contains = whole;
1206                        bdev_inode_switch_bdi(bdev->bd_inode,
1207                                whole->bd_inode->i_data.backing_dev_info);
1208                        bdev->bd_part = disk_get_part(disk, partno);
1209                        if (!(disk->flags & GENHD_FL_UP) ||
1210                            !bdev->bd_part || !bdev->bd_part->nr_sects) {
1211                                ret = -ENXIO;
1212                                goto out_clear;
1213                        }
1214                        bd_set_size(bdev, (loff_t)bdev->bd_part->nr_sects << 9);
1215                }
1216        } else {
1217                if (bdev->bd_contains == bdev) {
1218                        ret = 0;
1219                        if (bdev->bd_disk->fops->open)
1220                                ret = bdev->bd_disk->fops->open(bdev, mode);
1221                        /* the same as first opener case, read comment there */
1222                        if (bdev->bd_invalidated) {
1223                                if (!ret)
1224                                        rescan_partitions(bdev->bd_disk, bdev);
1225                                else if (ret == -ENOMEDIUM)
1226                                        invalidate_partitions(bdev->bd_disk, bdev);
1227                        }
1228                        if (ret)
1229                                goto out_unlock_bdev;
1230                }
1231                /* only one opener holds refs to the module and disk */
1232                put_disk(disk);
1233                module_put(owner);
1234        }
1235        bdev->bd_openers++;
1236        if (for_part)
1237                bdev->bd_part_count++;
1238        mutex_unlock(&bdev->bd_mutex);
1239        disk_unblock_events(disk);
1240        return 0;
1241
1242 out_clear:
1243        disk_put_part(bdev->bd_part);
1244        bdev->bd_disk = NULL;
1245        bdev->bd_part = NULL;
1246        bdev->bd_queue = NULL;
1247        bdev_inode_switch_bdi(bdev->bd_inode, &default_backing_dev_info);
1248        if (bdev != bdev->bd_contains)
1249                __blkdev_put(bdev->bd_contains, mode, 1);
1250        bdev->bd_contains = NULL;
1251 out_unlock_bdev:
1252        mutex_unlock(&bdev->bd_mutex);
1253        disk_unblock_events(disk);
1254        put_disk(disk);
1255        module_put(owner);
1256 out:
1257        bdput(bdev);
1258
1259        return ret;
1260}
1261
1262/**
1263 * blkdev_get - open a block device
1264 * @bdev: block_device to open
1265 * @mode: FMODE_* mask
1266 * @holder: exclusive holder identifier
1267 *
1268 * Open @bdev with @mode.  If @mode includes %FMODE_EXCL, @bdev is
1269 * open with exclusive access.  Specifying %FMODE_EXCL with %NULL
1270 * @holder is invalid.  Exclusive opens may nest for the same @holder.
1271 *
1272 * On success, the reference count of @bdev is unchanged.  On failure,
1273 * @bdev is put.
1274 *
1275 * CONTEXT:
1276 * Might sleep.
1277 *
1278 * RETURNS:
1279 * 0 on success, -errno on failure.
1280 */
1281int blkdev_get(struct block_device *bdev, fmode_t mode, void *holder)
1282{
1283        struct block_device *whole = NULL;
1284        int res;
1285
1286        WARN_ON_ONCE((mode & FMODE_EXCL) && !holder);
1287
1288        if ((mode & FMODE_EXCL) && holder) {
1289                whole = bd_start_claiming(bdev, holder);
1290                if (IS_ERR(whole)) {
1291                        bdput(bdev);
1292                        return PTR_ERR(whole);
1293                }
1294        }
1295
1296        res = __blkdev_get(bdev, mode, 0);
1297
1298        if (whole) {
1299                struct gendisk *disk = whole->bd_disk;
1300
1301                /* finish claiming */
1302                mutex_lock(&bdev->bd_mutex);
1303                spin_lock(&bdev_lock);
1304
1305                if (!res) {
1306                        BUG_ON(!bd_may_claim(bdev, whole, holder));
1307                        /*
1308                         * Note that for a whole device bd_holders
1309                         * will be incremented twice, and bd_holder
1310                         * will be set to bd_may_claim before being
1311                         * set to holder
1312                         */
1313                        whole->bd_holders++;
1314                        whole->bd_holder = bd_may_claim;
1315                        bdev->bd_holders++;
1316                        bdev->bd_holder = holder;
1317                }
1318
1319                /* tell others that we're done */
1320                BUG_ON(whole->bd_claiming != holder);
1321                whole->bd_claiming = NULL;
1322                wake_up_bit(&whole->bd_claiming, 0);
1323
1324                spin_unlock(&bdev_lock);
1325
1326                /*
1327                 * Block event polling for write claims if requested.  Any
1328                 * write holder makes the write_holder state stick until
1329                 * all are released.  This is good enough and tracking
1330                 * individual writeable reference is too fragile given the
1331                 * way @mode is used in blkdev_get/put().
1332                 */
1333                if (!res && (mode & FMODE_WRITE) && !bdev->bd_write_holder &&
1334                    (disk->flags & GENHD_FL_BLOCK_EVENTS_ON_EXCL_WRITE)) {
1335                        bdev->bd_write_holder = true;
1336                        disk_block_events(disk);
1337                }
1338
1339                mutex_unlock(&bdev->bd_mutex);
1340                bdput(whole);
1341        }
1342
1343        return res;
1344}
1345EXPORT_SYMBOL(blkdev_get);
1346
1347/**
1348 * blkdev_get_by_path - open a block device by name
1349 * @path: path to the block device to open
1350 * @mode: FMODE_* mask
1351 * @holder: exclusive holder identifier
1352 *
1353 * Open the blockdevice described by the device file at @path.  @mode
1354 * and @holder are identical to blkdev_get().
1355 *
1356 * On success, the returned block_device has reference count of one.
1357 *
1358 * CONTEXT:
1359 * Might sleep.
1360 *
1361 * RETURNS:
1362 * Pointer to block_device on success, ERR_PTR(-errno) on failure.
1363 */
1364struct block_device *blkdev_get_by_path(const char *path, fmode_t mode,
1365                                        void *holder)
1366{
1367        struct block_device *bdev;
1368        int err;
1369
1370        bdev = lookup_bdev(path);
1371        if (IS_ERR(bdev))
1372                return bdev;
1373
1374        err = blkdev_get(bdev, mode, holder);
1375        if (err)
1376                return ERR_PTR(err);
1377
1378        if ((mode & FMODE_WRITE) && bdev_read_only(bdev)) {
1379                blkdev_put(bdev, mode);
1380                return ERR_PTR(-EACCES);
1381        }
1382
1383        return bdev;
1384}
1385EXPORT_SYMBOL(blkdev_get_by_path);
1386
1387/**
1388 * blkdev_get_by_dev - open a block device by device number
1389 * @dev: device number of block device to open
1390 * @mode: FMODE_* mask
1391 * @holder: exclusive holder identifier
1392 *
1393 * Open the blockdevice described by device number @dev.  @mode and
1394 * @holder are identical to blkdev_get().
1395 *
1396 * Use it ONLY if you really do not have anything better - i.e. when
1397 * you are behind a truly sucky interface and all you are given is a
1398 * device number.  _Never_ to be used for internal purposes.  If you
1399 * ever need it - reconsider your API.
1400 *
1401 * On success, the returned block_device has reference count of one.
1402 *
1403 * CONTEXT:
1404 * Might sleep.
1405 *
1406 * RETURNS:
1407 * Pointer to block_device on success, ERR_PTR(-errno) on failure.
1408 */
1409struct block_device *blkdev_get_by_dev(dev_t dev, fmode_t mode, void *holder)
1410{
1411        struct block_device *bdev;
1412        int err;
1413
1414        bdev = bdget(dev);
1415        if (!bdev)
1416                return ERR_PTR(-ENOMEM);
1417
1418        err = blkdev_get(bdev, mode, holder);
1419        if (err)
1420                return ERR_PTR(err);
1421
1422        return bdev;
1423}
1424EXPORT_SYMBOL(blkdev_get_by_dev);
1425
1426static int blkdev_open(struct inode * inode, struct file * filp)
1427{
1428        struct block_device *bdev;
1429
1430        /*
1431         * Preserve backwards compatibility and allow large file access
1432         * even if userspace doesn't ask for it explicitly. Some mkfs
1433         * binary needs it. We might want to drop this workaround
1434         * during an unstable branch.
1435         */
1436        filp->f_flags |= O_LARGEFILE;
1437
1438        if (filp->f_flags & O_NDELAY)
1439                filp->f_mode |= FMODE_NDELAY;
1440        if (filp->f_flags & O_EXCL)
1441                filp->f_mode |= FMODE_EXCL;
1442        if ((filp->f_flags & O_ACCMODE) == 3)
1443                filp->f_mode |= FMODE_WRITE_IOCTL;
1444
1445        bdev = bd_acquire(inode);
1446        if (bdev == NULL)
1447                return -ENOMEM;
1448
1449        filp->f_mapping = bdev->bd_inode->i_mapping;
1450
1451        return blkdev_get(bdev, filp->f_mode, filp);
1452}
1453
1454static int __blkdev_put(struct block_device *bdev, fmode_t mode, int for_part)
1455{
1456        int ret = 0;
1457        struct gendisk *disk = bdev->bd_disk;
1458        struct block_device *victim = NULL;
1459
1460        mutex_lock_nested(&bdev->bd_mutex, for_part);
1461        if (for_part)
1462                bdev->bd_part_count--;
1463
1464        if (!--bdev->bd_openers) {
1465                WARN_ON_ONCE(bdev->bd_holders);
1466                sync_blockdev(bdev);
1467                kill_bdev(bdev);
1468                /* ->release can cause the old bdi to disappear,
1469                 * so must switch it out first
1470                 */
1471                bdev_inode_switch_bdi(bdev->bd_inode,
1472                                        &default_backing_dev_info);
1473        }
1474        if (bdev->bd_contains == bdev) {
1475                if (disk->fops->release)
1476                        ret = disk->fops->release(disk, mode);
1477        }
1478        if (!bdev->bd_openers) {
1479                struct module *owner = disk->fops->owner;
1480
1481                disk_put_part(bdev->bd_part);
1482                bdev->bd_part = NULL;
1483                bdev->bd_disk = NULL;
1484                if (bdev != bdev->bd_contains)
1485                        victim = bdev->bd_contains;
1486                bdev->bd_contains = NULL;
1487
1488                put_disk(disk);
1489                module_put(owner);
1490        }
1491        mutex_unlock(&bdev->bd_mutex);
1492        bdput(bdev);
1493        if (victim)
1494                __blkdev_put(victim, mode, 1);
1495        return ret;
1496}
1497
1498int blkdev_put(struct block_device *bdev, fmode_t mode)
1499{
1500        mutex_lock(&bdev->bd_mutex);
1501
1502        if (mode & FMODE_EXCL) {
1503                bool bdev_free;
1504
1505                /*
1506                 * Release a claim on the device.  The holder fields
1507                 * are protected with bdev_lock.  bd_mutex is to
1508                 * synchronize disk_holder unlinking.
1509                 */
1510                spin_lock(&bdev_lock);
1511
1512                WARN_ON_ONCE(--bdev->bd_holders < 0);
1513                WARN_ON_ONCE(--bdev->bd_contains->bd_holders < 0);
1514
1515                /* bd_contains might point to self, check in a separate step */
1516                if ((bdev_free = !bdev->bd_holders))
1517                        bdev->bd_holder = NULL;
1518                if (!bdev->bd_contains->bd_holders)
1519                        bdev->bd_contains->bd_holder = NULL;
1520
1521                spin_unlock(&bdev_lock);
1522
1523                /*
1524                 * If this was the last claim, remove holder link and
1525                 * unblock evpoll if it was a write holder.
1526                 */
1527                if (bdev_free && bdev->bd_write_holder) {
1528                        disk_unblock_events(bdev->bd_disk);
1529                        bdev->bd_write_holder = false;
1530                }
1531        }
1532
1533        /*
1534         * Trigger event checking and tell drivers to flush MEDIA_CHANGE
1535         * event.  This is to ensure detection of media removal commanded
1536         * from userland - e.g. eject(1).
1537         */
1538        disk_flush_events(bdev->bd_disk, DISK_EVENT_MEDIA_CHANGE);
1539
1540        mutex_unlock(&bdev->bd_mutex);
1541
1542        return __blkdev_put(bdev, mode, 0);
1543}
1544EXPORT_SYMBOL(blkdev_put);
1545
1546static int blkdev_close(struct inode * inode, struct file * filp)
1547{
1548        struct block_device *bdev = I_BDEV(filp->f_mapping->host);
1549
1550        return blkdev_put(bdev, filp->f_mode);
1551}
1552
1553static long block_ioctl(struct file *file, unsigned cmd, unsigned long arg)
1554{
1555        struct block_device *bdev = I_BDEV(file->f_mapping->host);
1556        fmode_t mode = file->f_mode;
1557
1558        /*
1559         * O_NDELAY can be altered using fcntl(.., F_SETFL, ..), so we have
1560         * to updated it before every ioctl.
1561         */
1562        if (file->f_flags & O_NDELAY)
1563                mode |= FMODE_NDELAY;
1564        else
1565                mode &= ~FMODE_NDELAY;
1566
1567        return blkdev_ioctl(bdev, mode, cmd, arg);
1568}
1569
1570/*
1571 * Write data to the block device.  Only intended for the block device itself
1572 * and the raw driver which basically is a fake block device.
1573 *
1574 * Does not take i_mutex for the write and thus is not for general purpose
1575 * use.
1576 */
1577ssize_t blkdev_aio_write(struct kiocb *iocb, const struct iovec *iov,
1578                         unsigned long nr_segs, loff_t pos)
1579{
1580        struct file *file = iocb->ki_filp;
1581        ssize_t ret;
1582
1583        BUG_ON(iocb->ki_pos != pos);
1584
1585        ret = __generic_file_aio_write(iocb, iov, nr_segs, &iocb->ki_pos);
1586        if (ret > 0 || ret == -EIOCBQUEUED) {
1587                ssize_t err;
1588
1589                err = generic_write_sync(file, pos, ret);
1590                if (err < 0 && ret > 0)
1591                        ret = err;
1592        }
1593        return ret;
1594}
1595EXPORT_SYMBOL_GPL(blkdev_aio_write);
1596
1597/*
1598 * Try to release a page associated with block device when the system
1599 * is under memory pressure.
1600 */
1601static int blkdev_releasepage(struct page *page, gfp_t wait)
1602{
1603        struct super_block *super = BDEV_I(page->mapping->host)->bdev.bd_super;
1604
1605        if (super && super->s_op->bdev_try_to_free_page)
1606                return super->s_op->bdev_try_to_free_page(super, page, wait);
1607
1608        return try_to_free_buffers(page);
1609}
1610
1611static const struct address_space_operations def_blk_aops = {
1612        .readpage       = blkdev_readpage,
1613        .writepage      = blkdev_writepage,
1614        .write_begin    = blkdev_write_begin,
1615        .write_end      = blkdev_write_end,
1616        .writepages     = generic_writepages,
1617        .releasepage    = blkdev_releasepage,
1618        .direct_IO      = blkdev_direct_IO,
1619};
1620
1621const struct file_operations def_blk_fops = {
1622        .open           = blkdev_open,
1623        .release        = blkdev_close,
1624        .llseek         = block_llseek,
1625        .read           = do_sync_read,
1626        .write          = do_sync_write,
1627        .aio_read       = generic_file_aio_read,
1628        .aio_write      = blkdev_aio_write,
1629        .mmap           = generic_file_mmap,
1630        .fsync          = blkdev_fsync,
1631        .unlocked_ioctl = block_ioctl,
1632#ifdef CONFIG_COMPAT
1633        .compat_ioctl   = compat_blkdev_ioctl,
1634#endif
1635        .splice_read    = generic_file_splice_read,
1636        .splice_write   = generic_file_splice_write,
1637};
1638
1639int ioctl_by_bdev(struct block_device *bdev, unsigned cmd, unsigned long arg)
1640{
1641        int res;
1642        mm_segment_t old_fs = get_fs();
1643        set_fs(KERNEL_DS);
1644        res = blkdev_ioctl(bdev, 0, cmd, arg);
1645        set_fs(old_fs);
1646        return res;
1647}
1648
1649EXPORT_SYMBOL(ioctl_by_bdev);
1650
1651/**
1652 * lookup_bdev  - lookup a struct block_device by name
1653 * @pathname:   special file representing the block device
1654 *
1655 * Get a reference to the blockdevice at @pathname in the current
1656 * namespace if possible and return it.  Return ERR_PTR(error)
1657 * otherwise.
1658 */
1659struct block_device *lookup_bdev(const char *pathname)
1660{
1661        struct block_device *bdev;
1662        struct inode *inode;
1663        struct path path;
1664        int error;
1665
1666        if (!pathname || !*pathname)
1667                return ERR_PTR(-EINVAL);
1668
1669        error = kern_path(pathname, LOOKUP_FOLLOW, &path);
1670        if (error)
1671                return ERR_PTR(error);
1672
1673        inode = path.dentry->d_inode;
1674        error = -ENOTBLK;
1675        if (!S_ISBLK(inode->i_mode))
1676                goto fail;
1677        error = -EACCES;
1678        if (path.mnt->mnt_flags & MNT_NODEV)
1679                goto fail;
1680        error = -ENOMEM;
1681        bdev = bd_acquire(inode);
1682        if (!bdev)
1683                goto fail;
1684out:
1685        path_put(&path);
1686        return bdev;
1687fail:
1688        bdev = ERR_PTR(error);
1689        goto out;
1690}
1691EXPORT_SYMBOL(lookup_bdev);
1692
1693int __invalidate_device(struct block_device *bdev, bool kill_dirty)
1694{
1695        struct super_block *sb = get_super(bdev);
1696        int res = 0;
1697
1698        if (sb) {
1699                /*
1700                 * no need to lock the super, get_super holds the
1701                 * read mutex so the filesystem cannot go away
1702                 * under us (->put_super runs with the write lock
1703                 * hold).
1704                 */
1705                shrink_dcache_sb(sb);
1706                res = invalidate_inodes(sb, kill_dirty);
1707                drop_super(sb);
1708        }
1709        invalidate_bdev(bdev);
1710        return res;
1711}
1712EXPORT_SYMBOL(__invalidate_device);
1713
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