Root/fs/block_dev.c

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/smp_lock.h>
15#include <linux/device_cgroup.h>
16#include <linux/highmem.h>
17#include <linux/blkdev.h>
18#include <linux/module.h>
19#include <linux/blkpg.h>
20#include <linux/buffer_head.h>
21#include <linux/pagevec.h>
22#include <linux/writeback.h>
23#include <linux/mpage.h>
24#include <linux/mount.h>
25#include <linux/uio.h>
26#include <linux/namei.h>
27#include <linux/log2.h>
28#include <linux/kmemleak.h>
29#include <asm/uaccess.h>
30#include "internal.h"
31
32struct bdev_inode {
33    struct block_device bdev;
34    struct inode vfs_inode;
35};
36
37static const struct address_space_operations def_blk_aops;
38
39static inline struct bdev_inode *BDEV_I(struct inode *inode)
40{
41    return container_of(inode, struct bdev_inode, vfs_inode);
42}
43
44inline struct block_device *I_BDEV(struct inode *inode)
45{
46    return &BDEV_I(inode)->bdev;
47}
48
49EXPORT_SYMBOL(I_BDEV);
50
51static sector_t max_block(struct block_device *bdev)
52{
53    sector_t retval = ~((sector_t)0);
54    loff_t sz = i_size_read(bdev->bd_inode);
55
56    if (sz) {
57        unsigned int size = block_size(bdev);
58        unsigned int sizebits = blksize_bits(size);
59        retval = (sz >> sizebits);
60    }
61    return retval;
62}
63
64/* Kill _all_ buffers and pagecache , dirty or not.. */
65static void kill_bdev(struct block_device *bdev)
66{
67    if (bdev->bd_inode->i_mapping->nrpages == 0)
68        return;
69    invalidate_bh_lrus();
70    truncate_inode_pages(bdev->bd_inode->i_mapping, 0);
71}
72
73int set_blocksize(struct block_device *bdev, int size)
74{
75    /* Size must be a power of two, and between 512 and PAGE_SIZE */
76    if (size > PAGE_SIZE || size < 512 || !is_power_of_2(size))
77        return -EINVAL;
78
79    /* Size cannot be smaller than the size supported by the device */
80    if (size < bdev_logical_block_size(bdev))
81        return -EINVAL;
82
83    /* Don't change the size if it is same as current */
84    if (bdev->bd_block_size != size) {
85        sync_blockdev(bdev);
86        bdev->bd_block_size = size;
87        bdev->bd_inode->i_blkbits = blksize_bits(size);
88        kill_bdev(bdev);
89    }
90    return 0;
91}
92
93EXPORT_SYMBOL(set_blocksize);
94
95int sb_set_blocksize(struct super_block *sb, int size)
96{
97    if (set_blocksize(sb->s_bdev, size))
98        return 0;
99    /* If we get here, we know size is power of two
100     * and it's value is between 512 and PAGE_SIZE */
101    sb->s_blocksize = size;
102    sb->s_blocksize_bits = blksize_bits(size);
103    return sb->s_blocksize;
104}
105
106EXPORT_SYMBOL(sb_set_blocksize);
107
108int sb_min_blocksize(struct super_block *sb, int size)
109{
110    int minsize = bdev_logical_block_size(sb->s_bdev);
111    if (size < minsize)
112        size = minsize;
113    return sb_set_blocksize(sb, size);
114}
115
116EXPORT_SYMBOL(sb_min_blocksize);
117
118static int
119blkdev_get_block(struct inode *inode, sector_t iblock,
120        struct buffer_head *bh, int create)
121{
122    if (iblock >= max_block(I_BDEV(inode))) {
123        if (create)
124            return -EIO;
125
126        /*
127         * for reads, we're just trying to fill a partial page.
128         * return a hole, they will have to call get_block again
129         * before they can fill it, and they will get -EIO at that
130         * time
131         */
132        return 0;
133    }
134    bh->b_bdev = I_BDEV(inode);
135    bh->b_blocknr = iblock;
136    set_buffer_mapped(bh);
137    return 0;
138}
139
140static int
141blkdev_get_blocks(struct inode *inode, sector_t iblock,
142        struct buffer_head *bh, int create)
143{
144    sector_t end_block = max_block(I_BDEV(inode));
145    unsigned long max_blocks = bh->b_size >> inode->i_blkbits;
146
147    if ((iblock + max_blocks) > end_block) {
148        max_blocks = end_block - iblock;
149        if ((long)max_blocks <= 0) {
150            if (create)
151                return -EIO; /* write fully beyond EOF */
152            /*
153             * It is a read which is fully beyond EOF. We return
154             * a !buffer_mapped buffer
155             */
156            max_blocks = 0;
157        }
158    }
159
160    bh->b_bdev = I_BDEV(inode);
161    bh->b_blocknr = iblock;
162    bh->b_size = max_blocks << inode->i_blkbits;
163    if (max_blocks)
164        set_buffer_mapped(bh);
165    return 0;
166}
167
168static ssize_t
169blkdev_direct_IO(int rw, struct kiocb *iocb, const struct iovec *iov,
170            loff_t offset, unsigned long nr_segs)
171{
172    struct file *file = iocb->ki_filp;
173    struct inode *inode = file->f_mapping->host;
174
175    return blockdev_direct_IO_no_locking(rw, iocb, inode, I_BDEV(inode),
176                iov, offset, nr_segs, blkdev_get_blocks, NULL);
177}
178
179int __sync_blockdev(struct block_device *bdev, int wait)
180{
181    if (!bdev)
182        return 0;
183    if (!wait)
184        return filemap_flush(bdev->bd_inode->i_mapping);
185    return filemap_write_and_wait(bdev->bd_inode->i_mapping);
186}
187
188/*
189 * Write out and wait upon all the dirty data associated with a block
190 * device via its mapping. Does not take the superblock lock.
191 */
192int sync_blockdev(struct block_device *bdev)
193{
194    return __sync_blockdev(bdev, 1);
195}
196EXPORT_SYMBOL(sync_blockdev);
197
198/*
199 * Write out and wait upon all dirty data associated with this
200 * device. Filesystem data as well as the underlying block
201 * device. Takes the superblock lock.
202 */
203int fsync_bdev(struct block_device *bdev)
204{
205    struct super_block *sb = get_super(bdev);
206    if (sb) {
207        int res = sync_filesystem(sb);
208        drop_super(sb);
209        return res;
210    }
211    return sync_blockdev(bdev);
212}
213EXPORT_SYMBOL(fsync_bdev);
214
215/**
216 * freeze_bdev -- lock a filesystem and force it into a consistent state
217 * @bdev: blockdevice to lock
218 *
219 * If a superblock is found on this device, we take the s_umount semaphore
220 * on it to make sure nobody unmounts until the snapshot creation is done.
221 * The reference counter (bd_fsfreeze_count) guarantees that only the last
222 * unfreeze process can unfreeze the frozen filesystem actually when multiple
223 * freeze requests arrive simultaneously. It counts up in freeze_bdev() and
224 * count down in thaw_bdev(). When it becomes 0, thaw_bdev() will unfreeze
225 * actually.
226 */
227struct super_block *freeze_bdev(struct block_device *bdev)
228{
229    struct super_block *sb;
230    int error = 0;
231
232    mutex_lock(&bdev->bd_fsfreeze_mutex);
233    if (++bdev->bd_fsfreeze_count > 1) {
234        /*
235         * We don't even need to grab a reference - the first call
236         * to freeze_bdev grab an active reference and only the last
237         * thaw_bdev drops it.
238         */
239        sb = get_super(bdev);
240        drop_super(sb);
241        mutex_unlock(&bdev->bd_fsfreeze_mutex);
242        return sb;
243    }
244
245    sb = get_active_super(bdev);
246    if (!sb)
247        goto out;
248    if (sb->s_flags & MS_RDONLY) {
249        sb->s_frozen = SB_FREEZE_TRANS;
250        up_write(&sb->s_umount);
251        mutex_unlock(&bdev->bd_fsfreeze_mutex);
252        return sb;
253    }
254
255    sb->s_frozen = SB_FREEZE_WRITE;
256    smp_wmb();
257
258    sync_filesystem(sb);
259
260    sb->s_frozen = SB_FREEZE_TRANS;
261    smp_wmb();
262
263    sync_blockdev(sb->s_bdev);
264
265    if (sb->s_op->freeze_fs) {
266        error = sb->s_op->freeze_fs(sb);
267        if (error) {
268            printk(KERN_ERR
269                "VFS:Filesystem freeze failed\n");
270            sb->s_frozen = SB_UNFROZEN;
271            deactivate_locked_super(sb);
272            bdev->bd_fsfreeze_count--;
273            mutex_unlock(&bdev->bd_fsfreeze_mutex);
274            return ERR_PTR(error);
275        }
276    }
277    up_write(&sb->s_umount);
278
279 out:
280    sync_blockdev(bdev);
281    mutex_unlock(&bdev->bd_fsfreeze_mutex);
282    return sb; /* thaw_bdev releases s->s_umount */
283}
284EXPORT_SYMBOL(freeze_bdev);
285
286/**
287 * thaw_bdev -- unlock filesystem
288 * @bdev: blockdevice to unlock
289 * @sb: associated superblock
290 *
291 * Unlocks the filesystem and marks it writeable again after freeze_bdev().
292 */
293int thaw_bdev(struct block_device *bdev, struct super_block *sb)
294{
295    int error = -EINVAL;
296
297    mutex_lock(&bdev->bd_fsfreeze_mutex);
298    if (!bdev->bd_fsfreeze_count)
299        goto out_unlock;
300
301    error = 0;
302    if (--bdev->bd_fsfreeze_count > 0)
303        goto out_unlock;
304
305    if (!sb)
306        goto out_unlock;
307
308    BUG_ON(sb->s_bdev != bdev);
309    down_write(&sb->s_umount);
310    if (sb->s_flags & MS_RDONLY)
311        goto out_unfrozen;
312
313    if (sb->s_op->unfreeze_fs) {
314        error = sb->s_op->unfreeze_fs(sb);
315        if (error) {
316            printk(KERN_ERR
317                "VFS:Filesystem thaw failed\n");
318            sb->s_frozen = SB_FREEZE_TRANS;
319            bdev->bd_fsfreeze_count++;
320            mutex_unlock(&bdev->bd_fsfreeze_mutex);
321            return error;
322        }
323    }
324
325out_unfrozen:
326    sb->s_frozen = SB_UNFROZEN;
327    smp_wmb();
328    wake_up(&sb->s_wait_unfrozen);
329
330    if (sb)
331        deactivate_locked_super(sb);
332out_unlock:
333    mutex_unlock(&bdev->bd_fsfreeze_mutex);
334    return 0;
335}
336EXPORT_SYMBOL(thaw_bdev);
337
338static int blkdev_writepage(struct page *page, struct writeback_control *wbc)
339{
340    return block_write_full_page(page, blkdev_get_block, wbc);
341}
342
343static int blkdev_readpage(struct file * file, struct page * page)
344{
345    return block_read_full_page(page, blkdev_get_block);
346}
347
348static int blkdev_write_begin(struct file *file, struct address_space *mapping,
349            loff_t pos, unsigned len, unsigned flags,
350            struct page **pagep, void **fsdata)
351{
352    *pagep = NULL;
353    return block_write_begin(file, mapping, pos, len, flags, pagep, fsdata,
354                blkdev_get_block);
355}
356
357static int blkdev_write_end(struct file *file, struct address_space *mapping,
358            loff_t pos, unsigned len, unsigned copied,
359            struct page *page, void *fsdata)
360{
361    int ret;
362    ret = block_write_end(file, mapping, pos, len, copied, page, fsdata);
363
364    unlock_page(page);
365    page_cache_release(page);
366
367    return ret;
368}
369
370/*
371 * private llseek:
372 * for a block special file file->f_path.dentry->d_inode->i_size is zero
373 * so we compute the size by hand (just as in block_read/write above)
374 */
375static loff_t block_llseek(struct file *file, loff_t offset, int origin)
376{
377    struct inode *bd_inode = file->f_mapping->host;
378    loff_t size;
379    loff_t retval;
380
381    mutex_lock(&bd_inode->i_mutex);
382    size = i_size_read(bd_inode);
383
384    switch (origin) {
385        case 2:
386            offset += size;
387            break;
388        case 1:
389            offset += file->f_pos;
390    }
391    retval = -EINVAL;
392    if (offset >= 0 && offset <= size) {
393        if (offset != file->f_pos) {
394            file->f_pos = offset;
395        }
396        retval = offset;
397    }
398    mutex_unlock(&bd_inode->i_mutex);
399    return retval;
400}
401    
402/*
403 * Filp is never NULL; the only case when ->fsync() is called with
404 * NULL first argument is nfsd_sync_dir() and that's not a directory.
405 */
406 
407int blkdev_fsync(struct file *filp, struct dentry *dentry, int datasync)
408{
409    struct inode *bd_inode = filp->f_mapping->host;
410    struct block_device *bdev = I_BDEV(bd_inode);
411    int error;
412
413    /*
414     * There is no need to serialise calls to blkdev_issue_flush with
415     * i_mutex and doing so causes performance issues with concurrent
416     * O_SYNC writers to a block device.
417     */
418    mutex_unlock(&bd_inode->i_mutex);
419
420    error = blkdev_issue_flush(bdev, NULL);
421    if (error == -EOPNOTSUPP)
422        error = 0;
423
424    mutex_lock(&bd_inode->i_mutex);
425
426    return error;
427}
428EXPORT_SYMBOL(blkdev_fsync);
429
430/*
431 * pseudo-fs
432 */
433
434static __cacheline_aligned_in_smp DEFINE_SPINLOCK(bdev_lock);
435static struct kmem_cache * bdev_cachep __read_mostly;
436
437static struct inode *bdev_alloc_inode(struct super_block *sb)
438{
439    struct bdev_inode *ei = kmem_cache_alloc(bdev_cachep, GFP_KERNEL);
440    if (!ei)
441        return NULL;
442    return &ei->vfs_inode;
443}
444
445static void bdev_destroy_inode(struct inode *inode)
446{
447    struct bdev_inode *bdi = BDEV_I(inode);
448
449    kmem_cache_free(bdev_cachep, bdi);
450}
451
452static void init_once(void *foo)
453{
454    struct bdev_inode *ei = (struct bdev_inode *) foo;
455    struct block_device *bdev = &ei->bdev;
456
457    memset(bdev, 0, sizeof(*bdev));
458    mutex_init(&bdev->bd_mutex);
459    INIT_LIST_HEAD(&bdev->bd_inodes);
460    INIT_LIST_HEAD(&bdev->bd_list);
461#ifdef CONFIG_SYSFS
462    INIT_LIST_HEAD(&bdev->bd_holder_list);
463#endif
464    inode_init_once(&ei->vfs_inode);
465    /* Initialize mutex for freeze. */
466    mutex_init(&bdev->bd_fsfreeze_mutex);
467}
468
469static inline void __bd_forget(struct inode *inode)
470{
471    list_del_init(&inode->i_devices);
472    inode->i_bdev = NULL;
473    inode->i_mapping = &inode->i_data;
474}
475
476static void bdev_clear_inode(struct inode *inode)
477{
478    struct block_device *bdev = &BDEV_I(inode)->bdev;
479    struct list_head *p;
480    spin_lock(&bdev_lock);
481    while ( (p = bdev->bd_inodes.next) != &bdev->bd_inodes ) {
482        __bd_forget(list_entry(p, struct inode, i_devices));
483    }
484    list_del_init(&bdev->bd_list);
485    spin_unlock(&bdev_lock);
486}
487
488static const struct super_operations bdev_sops = {
489    .statfs = simple_statfs,
490    .alloc_inode = bdev_alloc_inode,
491    .destroy_inode = bdev_destroy_inode,
492    .drop_inode = generic_delete_inode,
493    .clear_inode = bdev_clear_inode,
494};
495
496static int bd_get_sb(struct file_system_type *fs_type,
497    int flags, const char *dev_name, void *data, struct vfsmount *mnt)
498{
499    return get_sb_pseudo(fs_type, "bdev:", &bdev_sops, 0x62646576, mnt);
500}
501
502static struct file_system_type bd_type = {
503    .name = "bdev",
504    .get_sb = bd_get_sb,
505    .kill_sb = kill_anon_super,
506};
507
508struct super_block *blockdev_superblock __read_mostly;
509
510void __init bdev_cache_init(void)
511{
512    int err;
513    struct vfsmount *bd_mnt;
514
515    bdev_cachep = kmem_cache_create("bdev_cache", sizeof(struct bdev_inode),
516            0, (SLAB_HWCACHE_ALIGN|SLAB_RECLAIM_ACCOUNT|
517                SLAB_MEM_SPREAD|SLAB_PANIC),
518            init_once);
519    err = register_filesystem(&bd_type);
520    if (err)
521        panic("Cannot register bdev pseudo-fs");
522    bd_mnt = kern_mount(&bd_type);
523    if (IS_ERR(bd_mnt))
524        panic("Cannot create bdev pseudo-fs");
525    /*
526     * This vfsmount structure is only used to obtain the
527     * blockdev_superblock, so tell kmemleak not to report it.
528     */
529    kmemleak_not_leak(bd_mnt);
530    blockdev_superblock = bd_mnt->mnt_sb; /* For writeback */
531}
532
533/*
534 * Most likely _very_ bad one - but then it's hardly critical for small
535 * /dev and can be fixed when somebody will need really large one.
536 * Keep in mind that it will be fed through icache hash function too.
537 */
538static inline unsigned long hash(dev_t dev)
539{
540    return MAJOR(dev)+MINOR(dev);
541}
542
543static int bdev_test(struct inode *inode, void *data)
544{
545    return BDEV_I(inode)->bdev.bd_dev == *(dev_t *)data;
546}
547
548static int bdev_set(struct inode *inode, void *data)
549{
550    BDEV_I(inode)->bdev.bd_dev = *(dev_t *)data;
551    return 0;
552}
553
554static LIST_HEAD(all_bdevs);
555
556struct block_device *bdget(dev_t dev)
557{
558    struct block_device *bdev;
559    struct inode *inode;
560
561    inode = iget5_locked(blockdev_superblock, hash(dev),
562            bdev_test, bdev_set, &dev);
563
564    if (!inode)
565        return NULL;
566
567    bdev = &BDEV_I(inode)->bdev;
568
569    if (inode->i_state & I_NEW) {
570        bdev->bd_contains = NULL;
571        bdev->bd_inode = inode;
572        bdev->bd_block_size = (1 << inode->i_blkbits);
573        bdev->bd_part_count = 0;
574        bdev->bd_invalidated = 0;
575        inode->i_mode = S_IFBLK;
576        inode->i_rdev = dev;
577        inode->i_bdev = bdev;
578        inode->i_data.a_ops = &def_blk_aops;
579        mapping_set_gfp_mask(&inode->i_data, GFP_USER);
580        inode->i_data.backing_dev_info = &default_backing_dev_info;
581        spin_lock(&bdev_lock);
582        list_add(&bdev->bd_list, &all_bdevs);
583        spin_unlock(&bdev_lock);
584        unlock_new_inode(inode);
585    }
586    return bdev;
587}
588
589EXPORT_SYMBOL(bdget);
590
591/**
592 * bdgrab -- Grab a reference to an already referenced block device
593 * @bdev: Block device to grab a reference to.
594 */
595struct block_device *bdgrab(struct block_device *bdev)
596{
597    atomic_inc(&bdev->bd_inode->i_count);
598    return bdev;
599}
600
601long nr_blockdev_pages(void)
602{
603    struct block_device *bdev;
604    long ret = 0;
605    spin_lock(&bdev_lock);
606    list_for_each_entry(bdev, &all_bdevs, bd_list) {
607        ret += bdev->bd_inode->i_mapping->nrpages;
608    }
609    spin_unlock(&bdev_lock);
610    return ret;
611}
612
613void bdput(struct block_device *bdev)
614{
615    iput(bdev->bd_inode);
616}
617
618EXPORT_SYMBOL(bdput);
619 
620static struct block_device *bd_acquire(struct inode *inode)
621{
622    struct block_device *bdev;
623
624    spin_lock(&bdev_lock);
625    bdev = inode->i_bdev;
626    if (bdev) {
627        atomic_inc(&bdev->bd_inode->i_count);
628        spin_unlock(&bdev_lock);
629        return bdev;
630    }
631    spin_unlock(&bdev_lock);
632
633    bdev = bdget(inode->i_rdev);
634    if (bdev) {
635        spin_lock(&bdev_lock);
636        if (!inode->i_bdev) {
637            /*
638             * We take an additional bd_inode->i_count for inode,
639             * and it's released in clear_inode() of inode.
640             * So, we can access it via ->i_mapping always
641             * without igrab().
642             */
643            atomic_inc(&bdev->bd_inode->i_count);
644            inode->i_bdev = bdev;
645            inode->i_mapping = bdev->bd_inode->i_mapping;
646            list_add(&inode->i_devices, &bdev->bd_inodes);
647        }
648        spin_unlock(&bdev_lock);
649    }
650    return bdev;
651}
652
653/* Call when you free inode */
654
655void bd_forget(struct inode *inode)
656{
657    struct block_device *bdev = NULL;
658
659    spin_lock(&bdev_lock);
660    if (inode->i_bdev) {
661        if (!sb_is_blkdev_sb(inode->i_sb))
662            bdev = inode->i_bdev;
663        __bd_forget(inode);
664    }
665    spin_unlock(&bdev_lock);
666
667    if (bdev)
668        iput(bdev->bd_inode);
669}
670
671int bd_claim(struct block_device *bdev, void *holder)
672{
673    int res;
674    spin_lock(&bdev_lock);
675
676    /* first decide result */
677    if (bdev->bd_holder == holder)
678        res = 0; /* already a holder */
679    else if (bdev->bd_holder != NULL)
680        res = -EBUSY; /* held by someone else */
681    else if (bdev->bd_contains == bdev)
682        res = 0; /* is a whole device which isn't held */
683
684    else if (bdev->bd_contains->bd_holder == bd_claim)
685        res = 0; /* is a partition of a device that is being partitioned */
686    else if (bdev->bd_contains->bd_holder != NULL)
687        res = -EBUSY; /* is a partition of a held device */
688    else
689        res = 0; /* is a partition of an un-held device */
690
691    /* now impose change */
692    if (res==0) {
693        /* note that for a whole device bd_holders
694         * will be incremented twice, and bd_holder will
695         * be set to bd_claim before being set to holder
696         */
697        bdev->bd_contains->bd_holders ++;
698        bdev->bd_contains->bd_holder = bd_claim;
699        bdev->bd_holders++;
700        bdev->bd_holder = holder;
701    }
702    spin_unlock(&bdev_lock);
703    return res;
704}
705
706EXPORT_SYMBOL(bd_claim);
707
708void bd_release(struct block_device *bdev)
709{
710    spin_lock(&bdev_lock);
711    if (!--bdev->bd_contains->bd_holders)
712        bdev->bd_contains->bd_holder = NULL;
713    if (!--bdev->bd_holders)
714        bdev->bd_holder = NULL;
715    spin_unlock(&bdev_lock);
716}
717
718EXPORT_SYMBOL(bd_release);
719
720#ifdef CONFIG_SYSFS
721/*
722 * Functions for bd_claim_by_kobject / bd_release_from_kobject
723 *
724 * If a kobject is passed to bd_claim_by_kobject()
725 * and the kobject has a parent directory,
726 * following symlinks are created:
727 * o from the kobject to the claimed bdev
728 * o from "holders" directory of the bdev to the parent of the kobject
729 * bd_release_from_kobject() removes these symlinks.
730 *
731 * Example:
732 * If /dev/dm-0 maps to /dev/sda, kobject corresponding to
733 * /sys/block/dm-0/slaves is passed to bd_claim_by_kobject(), then:
734 * /sys/block/dm-0/slaves/sda --> /sys/block/sda
735 * /sys/block/sda/holders/dm-0 --> /sys/block/dm-0
736 */
737
738static int add_symlink(struct kobject *from, struct kobject *to)
739{
740    if (!from || !to)
741        return 0;
742    return sysfs_create_link(from, to, kobject_name(to));
743}
744
745static void del_symlink(struct kobject *from, struct kobject *to)
746{
747    if (!from || !to)
748        return;
749    sysfs_remove_link(from, kobject_name(to));
750}
751
752/*
753 * 'struct bd_holder' contains pointers to kobjects symlinked by
754 * bd_claim_by_kobject.
755 * It's connected to bd_holder_list which is protected by bdev->bd_sem.
756 */
757struct bd_holder {
758    struct list_head list; /* chain of holders of the bdev */
759    int count; /* references from the holder */
760    struct kobject *sdir; /* holder object, e.g. "/block/dm-0/slaves" */
761    struct kobject *hdev; /* e.g. "/block/dm-0" */
762    struct kobject *hdir; /* e.g. "/block/sda/holders" */
763    struct kobject *sdev; /* e.g. "/block/sda" */
764};
765
766/*
767 * Get references of related kobjects at once.
768 * Returns 1 on success. 0 on failure.
769 *
770 * Should call bd_holder_release_dirs() after successful use.
771 */
772static int bd_holder_grab_dirs(struct block_device *bdev,
773            struct bd_holder *bo)
774{
775    if (!bdev || !bo)
776        return 0;
777
778    bo->sdir = kobject_get(bo->sdir);
779    if (!bo->sdir)
780        return 0;
781
782    bo->hdev = kobject_get(bo->sdir->parent);
783    if (!bo->hdev)
784        goto fail_put_sdir;
785
786    bo->sdev = kobject_get(&part_to_dev(bdev->bd_part)->kobj);
787    if (!bo->sdev)
788        goto fail_put_hdev;
789
790    bo->hdir = kobject_get(bdev->bd_part->holder_dir);
791    if (!bo->hdir)
792        goto fail_put_sdev;
793
794    return 1;
795
796fail_put_sdev:
797    kobject_put(bo->sdev);
798fail_put_hdev:
799    kobject_put(bo->hdev);
800fail_put_sdir:
801    kobject_put(bo->sdir);
802
803    return 0;
804}
805
806/* Put references of related kobjects at once. */
807static void bd_holder_release_dirs(struct bd_holder *bo)
808{
809    kobject_put(bo->hdir);
810    kobject_put(bo->sdev);
811    kobject_put(bo->hdev);
812    kobject_put(bo->sdir);
813}
814
815static struct bd_holder *alloc_bd_holder(struct kobject *kobj)
816{
817    struct bd_holder *bo;
818
819    bo = kzalloc(sizeof(*bo), GFP_KERNEL);
820    if (!bo)
821        return NULL;
822
823    bo->count = 1;
824    bo->sdir = kobj;
825
826    return bo;
827}
828
829static void free_bd_holder(struct bd_holder *bo)
830{
831    kfree(bo);
832}
833
834/**
835 * find_bd_holder - find matching struct bd_holder from the block device
836 *
837 * @bdev: struct block device to be searched
838 * @bo: target struct bd_holder
839 *
840 * Returns matching entry with @bo in @bdev->bd_holder_list.
841 * If found, increment the reference count and return the pointer.
842 * If not found, returns NULL.
843 */
844static struct bd_holder *find_bd_holder(struct block_device *bdev,
845                    struct bd_holder *bo)
846{
847    struct bd_holder *tmp;
848
849    list_for_each_entry(tmp, &bdev->bd_holder_list, list)
850        if (tmp->sdir == bo->sdir) {
851            tmp->count++;
852            return tmp;
853        }
854
855    return NULL;
856}
857
858/**
859 * add_bd_holder - create sysfs symlinks for bd_claim() relationship
860 *
861 * @bdev: block device to be bd_claimed
862 * @bo: preallocated and initialized by alloc_bd_holder()
863 *
864 * Add @bo to @bdev->bd_holder_list, create symlinks.
865 *
866 * Returns 0 if symlinks are created.
867 * Returns -ve if something fails.
868 */
869static int add_bd_holder(struct block_device *bdev, struct bd_holder *bo)
870{
871    int err;
872
873    if (!bo)
874        return -EINVAL;
875
876    if (!bd_holder_grab_dirs(bdev, bo))
877        return -EBUSY;
878
879    err = add_symlink(bo->sdir, bo->sdev);
880    if (err)
881        return err;
882
883    err = add_symlink(bo->hdir, bo->hdev);
884    if (err) {
885        del_symlink(bo->sdir, bo->sdev);
886        return err;
887    }
888
889    list_add_tail(&bo->list, &bdev->bd_holder_list);
890    return 0;
891}
892
893/**
894 * del_bd_holder - delete sysfs symlinks for bd_claim() relationship
895 *
896 * @bdev: block device to be bd_claimed
897 * @kobj: holder's kobject
898 *
899 * If there is matching entry with @kobj in @bdev->bd_holder_list
900 * and no other bd_claim() from the same kobject,
901 * remove the struct bd_holder from the list, delete symlinks for it.
902 *
903 * Returns a pointer to the struct bd_holder when it's removed from the list
904 * and ready to be freed.
905 * Returns NULL if matching claim isn't found or there is other bd_claim()
906 * by the same kobject.
907 */
908static struct bd_holder *del_bd_holder(struct block_device *bdev,
909                    struct kobject *kobj)
910{
911    struct bd_holder *bo;
912
913    list_for_each_entry(bo, &bdev->bd_holder_list, list) {
914        if (bo->sdir == kobj) {
915            bo->count--;
916            BUG_ON(bo->count < 0);
917            if (!bo->count) {
918                list_del(&bo->list);
919                del_symlink(bo->sdir, bo->sdev);
920                del_symlink(bo->hdir, bo->hdev);
921                bd_holder_release_dirs(bo);
922                return bo;
923            }
924            break;
925        }
926    }
927
928    return NULL;
929}
930
931/**
932 * bd_claim_by_kobject - bd_claim() with additional kobject signature
933 *
934 * @bdev: block device to be claimed
935 * @holder: holder's signature
936 * @kobj: holder's kobject
937 *
938 * Do bd_claim() and if it succeeds, create sysfs symlinks between
939 * the bdev and the holder's kobject.
940 * Use bd_release_from_kobject() when relesing the claimed bdev.
941 *
942 * Returns 0 on success. (same as bd_claim())
943 * Returns errno on failure.
944 */
945static int bd_claim_by_kobject(struct block_device *bdev, void *holder,
946                struct kobject *kobj)
947{
948    int err;
949    struct bd_holder *bo, *found;
950
951    if (!kobj)
952        return -EINVAL;
953
954    bo = alloc_bd_holder(kobj);
955    if (!bo)
956        return -ENOMEM;
957
958    mutex_lock(&bdev->bd_mutex);
959
960    err = bd_claim(bdev, holder);
961    if (err)
962        goto fail;
963
964    found = find_bd_holder(bdev, bo);
965    if (found)
966        goto fail;
967
968    err = add_bd_holder(bdev, bo);
969    if (err)
970        bd_release(bdev);
971    else
972        bo = NULL;
973fail:
974    mutex_unlock(&bdev->bd_mutex);
975    free_bd_holder(bo);
976    return err;
977}
978
979/**
980 * bd_release_from_kobject - bd_release() with additional kobject signature
981 *
982 * @bdev: block device to be released
983 * @kobj: holder's kobject
984 *
985 * Do bd_release() and remove sysfs symlinks created by bd_claim_by_kobject().
986 */
987static void bd_release_from_kobject(struct block_device *bdev,
988                    struct kobject *kobj)
989{
990    if (!kobj)
991        return;
992
993    mutex_lock(&bdev->bd_mutex);
994    bd_release(bdev);
995    free_bd_holder(del_bd_holder(bdev, kobj));
996    mutex_unlock(&bdev->bd_mutex);
997}
998
999/**
1000 * bd_claim_by_disk - wrapper function for bd_claim_by_kobject()
1001 *
1002 * @bdev: block device to be claimed
1003 * @holder: holder's signature
1004 * @disk: holder's gendisk
1005 *
1006 * Call bd_claim_by_kobject() with getting @disk->slave_dir.
1007 */
1008int bd_claim_by_disk(struct block_device *bdev, void *holder,
1009            struct gendisk *disk)
1010{
1011    return bd_claim_by_kobject(bdev, holder, kobject_get(disk->slave_dir));
1012}
1013EXPORT_SYMBOL_GPL(bd_claim_by_disk);
1014
1015/**
1016 * bd_release_from_disk - wrapper function for bd_release_from_kobject()
1017 *
1018 * @bdev: block device to be claimed
1019 * @disk: holder's gendisk
1020 *
1021 * Call bd_release_from_kobject() and put @disk->slave_dir.
1022 */
1023void bd_release_from_disk(struct block_device *bdev, struct gendisk *disk)
1024{
1025    bd_release_from_kobject(bdev, disk->slave_dir);
1026    kobject_put(disk->slave_dir);
1027}
1028EXPORT_SYMBOL_GPL(bd_release_from_disk);
1029#endif
1030
1031/*
1032 * Tries to open block device by device number. Use it ONLY if you
1033 * really do not have anything better - i.e. when you are behind a
1034 * truly sucky interface and all you are given is a device number. _Never_
1035 * to be used for internal purposes. If you ever need it - reconsider
1036 * your API.
1037 */
1038struct block_device *open_by_devnum(dev_t dev, fmode_t mode)
1039{
1040    struct block_device *bdev = bdget(dev);
1041    int err = -ENOMEM;
1042    if (bdev)
1043        err = blkdev_get(bdev, mode);
1044    return err ? ERR_PTR(err) : bdev;
1045}
1046
1047EXPORT_SYMBOL(open_by_devnum);
1048
1049/**
1050 * flush_disk - invalidates all buffer-cache entries on a disk
1051 *
1052 * @bdev: struct block device to be flushed
1053 *
1054 * Invalidates all buffer-cache entries on a disk. It should be called
1055 * when a disk has been changed -- either by a media change or online
1056 * resize.
1057 */
1058static void flush_disk(struct block_device *bdev)
1059{
1060    if (__invalidate_device(bdev)) {
1061        char name[BDEVNAME_SIZE] = "";
1062
1063        if (bdev->bd_disk)
1064            disk_name(bdev->bd_disk, 0, name);
1065        printk(KERN_WARNING "VFS: busy inodes on changed media or "
1066               "resized disk %s\n", name);
1067    }
1068
1069    if (!bdev->bd_disk)
1070        return;
1071    if (disk_partitionable(bdev->bd_disk))
1072        bdev->bd_invalidated = 1;
1073}
1074
1075/**
1076 * check_disk_size_change - checks for disk size change and adjusts bdev size.
1077 * @disk: struct gendisk to check
1078 * @bdev: struct bdev to adjust.
1079 *
1080 * This routine checks to see if the bdev size does not match the disk size
1081 * and adjusts it if it differs.
1082 */
1083void check_disk_size_change(struct gendisk *disk, struct block_device *bdev)
1084{
1085    loff_t disk_size, bdev_size;
1086
1087    disk_size = (loff_t)get_capacity(disk) << 9;
1088    bdev_size = i_size_read(bdev->bd_inode);
1089    if (disk_size != bdev_size) {
1090        char name[BDEVNAME_SIZE];
1091
1092        disk_name(disk, 0, name);
1093        printk(KERN_INFO
1094               "%s: detected capacity change from %lld to %lld\n",
1095               name, bdev_size, disk_size);
1096        i_size_write(bdev->bd_inode, disk_size);
1097        flush_disk(bdev);
1098    }
1099}
1100EXPORT_SYMBOL(check_disk_size_change);
1101
1102/**
1103 * revalidate_disk - wrapper for lower-level driver's revalidate_disk call-back
1104 * @disk: struct gendisk to be revalidated
1105 *
1106 * This routine is a wrapper for lower-level driver's revalidate_disk
1107 * call-backs. It is used to do common pre and post operations needed
1108 * for all revalidate_disk operations.
1109 */
1110int revalidate_disk(struct gendisk *disk)
1111{
1112    struct block_device *bdev;
1113    int ret = 0;
1114
1115    if (disk->fops->revalidate_disk)
1116        ret = disk->fops->revalidate_disk(disk);
1117
1118    bdev = bdget_disk(disk, 0);
1119    if (!bdev)
1120        return ret;
1121
1122    mutex_lock(&bdev->bd_mutex);
1123    check_disk_size_change(disk, bdev);
1124    mutex_unlock(&bdev->bd_mutex);
1125    bdput(bdev);
1126    return ret;
1127}
1128EXPORT_SYMBOL(revalidate_disk);
1129
1130/*
1131 * This routine checks whether a removable media has been changed,
1132 * and invalidates all buffer-cache-entries in that case. This
1133 * is a relatively slow routine, so we have to try to minimize using
1134 * it. Thus it is called only upon a 'mount' or 'open'. This
1135 * is the best way of combining speed and utility, I think.
1136 * People changing diskettes in the middle of an operation deserve
1137 * to lose :-)
1138 */
1139int check_disk_change(struct block_device *bdev)
1140{
1141    struct gendisk *disk = bdev->bd_disk;
1142    const struct block_device_operations *bdops = disk->fops;
1143
1144    if (!bdops->media_changed)
1145        return 0;
1146    if (!bdops->media_changed(bdev->bd_disk))
1147        return 0;
1148
1149    flush_disk(bdev);
1150    if (bdops->revalidate_disk)
1151        bdops->revalidate_disk(bdev->bd_disk);
1152    return 1;
1153}
1154
1155EXPORT_SYMBOL(check_disk_change);
1156
1157void bd_set_size(struct block_device *bdev, loff_t size)
1158{
1159    unsigned bsize = bdev_logical_block_size(bdev);
1160
1161    bdev->bd_inode->i_size = size;
1162    while (bsize < PAGE_CACHE_SIZE) {
1163        if (size & bsize)
1164            break;
1165        bsize <<= 1;
1166    }
1167    bdev->bd_block_size = bsize;
1168    bdev->bd_inode->i_blkbits = blksize_bits(bsize);
1169}
1170EXPORT_SYMBOL(bd_set_size);
1171
1172static int __blkdev_put(struct block_device *bdev, fmode_t mode, int for_part);
1173
1174/*
1175 * bd_mutex locking:
1176 *
1177 * mutex_lock(part->bd_mutex)
1178 * mutex_lock_nested(whole->bd_mutex, 1)
1179 */
1180
1181static int __blkdev_get(struct block_device *bdev, fmode_t mode, int for_part)
1182{
1183    struct gendisk *disk;
1184    int ret;
1185    int partno;
1186    int perm = 0;
1187
1188    if (mode & FMODE_READ)
1189        perm |= MAY_READ;
1190    if (mode & FMODE_WRITE)
1191        perm |= MAY_WRITE;
1192    /*
1193     * hooks: /n/, see "layering violations".
1194     */
1195    ret = devcgroup_inode_permission(bdev->bd_inode, perm);
1196    if (ret != 0) {
1197        bdput(bdev);
1198        return ret;
1199    }
1200
1201    lock_kernel();
1202 restart:
1203
1204    ret = -ENXIO;
1205    disk = get_gendisk(bdev->bd_dev, &partno);
1206    if (!disk)
1207        goto out_unlock_kernel;
1208
1209    mutex_lock_nested(&bdev->bd_mutex, for_part);
1210    if (!bdev->bd_openers) {
1211        bdev->bd_disk = disk;
1212        bdev->bd_contains = bdev;
1213        if (!partno) {
1214            struct backing_dev_info *bdi;
1215
1216            ret = -ENXIO;
1217            bdev->bd_part = disk_get_part(disk, partno);
1218            if (!bdev->bd_part)
1219                goto out_clear;
1220
1221            if (disk->fops->open) {
1222                ret = disk->fops->open(bdev, mode);
1223                if (ret == -ERESTARTSYS) {
1224                    /* Lost a race with 'disk' being
1225                     * deleted, try again.
1226                     * See md.c
1227                     */
1228                    disk_put_part(bdev->bd_part);
1229                    bdev->bd_part = NULL;
1230                    module_put(disk->fops->owner);
1231                    put_disk(disk);
1232                    bdev->bd_disk = NULL;
1233                    mutex_unlock(&bdev->bd_mutex);
1234                    goto restart;
1235                }
1236                if (ret)
1237                    goto out_clear;
1238            }
1239            if (!bdev->bd_openers) {
1240                bd_set_size(bdev,(loff_t)get_capacity(disk)<<9);
1241                bdi = blk_get_backing_dev_info(bdev);
1242                if (bdi == NULL)
1243                    bdi = &default_backing_dev_info;
1244                bdev->bd_inode->i_data.backing_dev_info = bdi;
1245            }
1246            if (bdev->bd_invalidated)
1247                rescan_partitions(disk, bdev);
1248        } else {
1249            struct block_device *whole;
1250            whole = bdget_disk(disk, 0);
1251            ret = -ENOMEM;
1252            if (!whole)
1253                goto out_clear;
1254            BUG_ON(for_part);
1255            ret = __blkdev_get(whole, mode, 1);
1256            if (ret)
1257                goto out_clear;
1258            bdev->bd_contains = whole;
1259            bdev->bd_inode->i_data.backing_dev_info =
1260               whole->bd_inode->i_data.backing_dev_info;
1261            bdev->bd_part = disk_get_part(disk, partno);
1262            if (!(disk->flags & GENHD_FL_UP) ||
1263                !bdev->bd_part || !bdev->bd_part->nr_sects) {
1264                ret = -ENXIO;
1265                goto out_clear;
1266            }
1267            bd_set_size(bdev, (loff_t)bdev->bd_part->nr_sects << 9);
1268        }
1269    } else {
1270        module_put(disk->fops->owner);
1271        put_disk(disk);
1272        disk = NULL;
1273        if (bdev->bd_contains == bdev) {
1274            if (bdev->bd_disk->fops->open) {
1275                ret = bdev->bd_disk->fops->open(bdev, mode);
1276                if (ret)
1277                    goto out_unlock_bdev;
1278            }
1279            if (bdev->bd_invalidated)
1280                rescan_partitions(bdev->bd_disk, bdev);
1281        }
1282    }
1283    bdev->bd_openers++;
1284    if (for_part)
1285        bdev->bd_part_count++;
1286    mutex_unlock(&bdev->bd_mutex);
1287    unlock_kernel();
1288    return 0;
1289
1290 out_clear:
1291    disk_put_part(bdev->bd_part);
1292    bdev->bd_disk = NULL;
1293    bdev->bd_part = NULL;
1294    bdev->bd_inode->i_data.backing_dev_info = &default_backing_dev_info;
1295    if (bdev != bdev->bd_contains)
1296        __blkdev_put(bdev->bd_contains, mode, 1);
1297    bdev->bd_contains = NULL;
1298 out_unlock_bdev:
1299    mutex_unlock(&bdev->bd_mutex);
1300 out_unlock_kernel:
1301    unlock_kernel();
1302
1303    if (disk)
1304        module_put(disk->fops->owner);
1305    put_disk(disk);
1306    bdput(bdev);
1307
1308    return ret;
1309}
1310
1311int blkdev_get(struct block_device *bdev, fmode_t mode)
1312{
1313    return __blkdev_get(bdev, mode, 0);
1314}
1315EXPORT_SYMBOL(blkdev_get);
1316
1317static int blkdev_open(struct inode * inode, struct file * filp)
1318{
1319    struct block_device *bdev;
1320    int res;
1321
1322    /*
1323     * Preserve backwards compatibility and allow large file access
1324     * even if userspace doesn't ask for it explicitly. Some mkfs
1325     * binary needs it. We might want to drop this workaround
1326     * during an unstable branch.
1327     */
1328    filp->f_flags |= O_LARGEFILE;
1329
1330    if (filp->f_flags & O_NDELAY)
1331        filp->f_mode |= FMODE_NDELAY;
1332    if (filp->f_flags & O_EXCL)
1333        filp->f_mode |= FMODE_EXCL;
1334    if ((filp->f_flags & O_ACCMODE) == 3)
1335        filp->f_mode |= FMODE_WRITE_IOCTL;
1336
1337    bdev = bd_acquire(inode);
1338    if (bdev == NULL)
1339        return -ENOMEM;
1340
1341    filp->f_mapping = bdev->bd_inode->i_mapping;
1342
1343    res = blkdev_get(bdev, filp->f_mode);
1344    if (res)
1345        return res;
1346
1347    if (filp->f_mode & FMODE_EXCL) {
1348        res = bd_claim(bdev, filp);
1349        if (res)
1350            goto out_blkdev_put;
1351    }
1352
1353    return 0;
1354
1355 out_blkdev_put:
1356    blkdev_put(bdev, filp->f_mode);
1357    return res;
1358}
1359
1360static int __blkdev_put(struct block_device *bdev, fmode_t mode, int for_part)
1361{
1362    int ret = 0;
1363    struct gendisk *disk = bdev->bd_disk;
1364    struct block_device *victim = NULL;
1365
1366    mutex_lock_nested(&bdev->bd_mutex, for_part);
1367    lock_kernel();
1368    if (for_part)
1369        bdev->bd_part_count--;
1370
1371    if (!--bdev->bd_openers) {
1372        sync_blockdev(bdev);
1373        kill_bdev(bdev);
1374    }
1375    if (bdev->bd_contains == bdev) {
1376        if (disk->fops->release)
1377            ret = disk->fops->release(disk, mode);
1378    }
1379    if (!bdev->bd_openers) {
1380        struct module *owner = disk->fops->owner;
1381
1382        put_disk(disk);
1383        module_put(owner);
1384        disk_put_part(bdev->bd_part);
1385        bdev->bd_part = NULL;
1386        bdev->bd_disk = NULL;
1387        bdev->bd_inode->i_data.backing_dev_info = &default_backing_dev_info;
1388        if (bdev != bdev->bd_contains)
1389            victim = bdev->bd_contains;
1390        bdev->bd_contains = NULL;
1391    }
1392    unlock_kernel();
1393    mutex_unlock(&bdev->bd_mutex);
1394    bdput(bdev);
1395    if (victim)
1396        __blkdev_put(victim, mode, 1);
1397    return ret;
1398}
1399
1400int blkdev_put(struct block_device *bdev, fmode_t mode)
1401{
1402    return __blkdev_put(bdev, mode, 0);
1403}
1404EXPORT_SYMBOL(blkdev_put);
1405
1406static int blkdev_close(struct inode * inode, struct file * filp)
1407{
1408    struct block_device *bdev = I_BDEV(filp->f_mapping->host);
1409    if (bdev->bd_holder == filp)
1410        bd_release(bdev);
1411    return blkdev_put(bdev, filp->f_mode);
1412}
1413
1414static long block_ioctl(struct file *file, unsigned cmd, unsigned long arg)
1415{
1416    struct block_device *bdev = I_BDEV(file->f_mapping->host);
1417    fmode_t mode = file->f_mode;
1418
1419    /*
1420     * O_NDELAY can be altered using fcntl(.., F_SETFL, ..), so we have
1421     * to updated it before every ioctl.
1422     */
1423    if (file->f_flags & O_NDELAY)
1424        mode |= FMODE_NDELAY;
1425    else
1426        mode &= ~FMODE_NDELAY;
1427
1428    return blkdev_ioctl(bdev, mode, cmd, arg);
1429}
1430
1431/*
1432 * Write data to the block device. Only intended for the block device itself
1433 * and the raw driver which basically is a fake block device.
1434 *
1435 * Does not take i_mutex for the write and thus is not for general purpose
1436 * use.
1437 */
1438ssize_t blkdev_aio_write(struct kiocb *iocb, const struct iovec *iov,
1439             unsigned long nr_segs, loff_t pos)
1440{
1441    struct file *file = iocb->ki_filp;
1442    ssize_t ret;
1443
1444    BUG_ON(iocb->ki_pos != pos);
1445
1446    ret = __generic_file_aio_write(iocb, iov, nr_segs, &iocb->ki_pos);
1447    if (ret > 0 || ret == -EIOCBQUEUED) {
1448        ssize_t err;
1449
1450        err = generic_write_sync(file, pos, ret);
1451        if (err < 0 && ret > 0)
1452            ret = err;
1453    }
1454    return ret;
1455}
1456EXPORT_SYMBOL_GPL(blkdev_aio_write);
1457
1458/*
1459 * Try to release a page associated with block device when the system
1460 * is under memory pressure.
1461 */
1462static int blkdev_releasepage(struct page *page, gfp_t wait)
1463{
1464    struct super_block *super = BDEV_I(page->mapping->host)->bdev.bd_super;
1465
1466    if (super && super->s_op->bdev_try_to_free_page)
1467        return super->s_op->bdev_try_to_free_page(super, page, wait);
1468
1469    return try_to_free_buffers(page);
1470}
1471
1472static const struct address_space_operations def_blk_aops = {
1473    .readpage = blkdev_readpage,
1474    .writepage = blkdev_writepage,
1475    .sync_page = block_sync_page,
1476    .write_begin = blkdev_write_begin,
1477    .write_end = blkdev_write_end,
1478    .writepages = generic_writepages,
1479    .releasepage = blkdev_releasepage,
1480    .direct_IO = blkdev_direct_IO,
1481};
1482
1483const struct file_operations def_blk_fops = {
1484    .open = blkdev_open,
1485    .release = blkdev_close,
1486    .llseek = block_llseek,
1487    .read = do_sync_read,
1488    .write = do_sync_write,
1489      .aio_read = generic_file_aio_read,
1490    .aio_write = blkdev_aio_write,
1491    .mmap = generic_file_mmap,
1492    .fsync = blkdev_fsync,
1493    .unlocked_ioctl = block_ioctl,
1494#ifdef CONFIG_COMPAT
1495    .compat_ioctl = compat_blkdev_ioctl,
1496#endif
1497    .splice_read = generic_file_splice_read,
1498    .splice_write = generic_file_splice_write,
1499};
1500
1501int ioctl_by_bdev(struct block_device *bdev, unsigned cmd, unsigned long arg)
1502{
1503    int res;
1504    mm_segment_t old_fs = get_fs();
1505    set_fs(KERNEL_DS);
1506    res = blkdev_ioctl(bdev, 0, cmd, arg);
1507    set_fs(old_fs);
1508    return res;
1509}
1510
1511EXPORT_SYMBOL(ioctl_by_bdev);
1512
1513/**
1514 * lookup_bdev - lookup a struct block_device by name
1515 * @pathname: special file representing the block device
1516 *
1517 * Get a reference to the blockdevice at @pathname in the current
1518 * namespace if possible and return it. Return ERR_PTR(error)
1519 * otherwise.
1520 */
1521struct block_device *lookup_bdev(const char *pathname)
1522{
1523    struct block_device *bdev;
1524    struct inode *inode;
1525    struct path path;
1526    int error;
1527
1528    if (!pathname || !*pathname)
1529        return ERR_PTR(-EINVAL);
1530
1531    error = kern_path(pathname, LOOKUP_FOLLOW, &path);
1532    if (error)
1533        return ERR_PTR(error);
1534
1535    inode = path.dentry->d_inode;
1536    error = -ENOTBLK;
1537    if (!S_ISBLK(inode->i_mode))
1538        goto fail;
1539    error = -EACCES;
1540    if (path.mnt->mnt_flags & MNT_NODEV)
1541        goto fail;
1542    error = -ENOMEM;
1543    bdev = bd_acquire(inode);
1544    if (!bdev)
1545        goto fail;
1546out:
1547    path_put(&path);
1548    return bdev;
1549fail:
1550    bdev = ERR_PTR(error);
1551    goto out;
1552}
1553EXPORT_SYMBOL(lookup_bdev);
1554
1555/**
1556 * open_bdev_exclusive - open a block device by name and set it up for use
1557 *
1558 * @path: special file representing the block device
1559 * @mode: FMODE_... combination to pass be used
1560 * @holder: owner for exclusion
1561 *
1562 * Open the blockdevice described by the special file at @path, claim it
1563 * for the @holder.
1564 */
1565struct block_device *open_bdev_exclusive(const char *path, fmode_t mode, void *holder)
1566{
1567    struct block_device *bdev;
1568    int error = 0;
1569
1570    bdev = lookup_bdev(path);
1571    if (IS_ERR(bdev))
1572        return bdev;
1573
1574    error = blkdev_get(bdev, mode);
1575    if (error)
1576        return ERR_PTR(error);
1577    error = -EACCES;
1578    if ((mode & FMODE_WRITE) && bdev_read_only(bdev))
1579        goto blkdev_put;
1580    error = bd_claim(bdev, holder);
1581    if (error)
1582        goto blkdev_put;
1583
1584    return bdev;
1585    
1586blkdev_put:
1587    blkdev_put(bdev, mode);
1588    return ERR_PTR(error);
1589}
1590
1591EXPORT_SYMBOL(open_bdev_exclusive);
1592
1593/**
1594 * close_bdev_exclusive - close a blockdevice opened by open_bdev_exclusive()
1595 *
1596 * @bdev: blockdevice to close
1597 * @mode: mode, must match that used to open.
1598 *
1599 * This is the counterpart to open_bdev_exclusive().
1600 */
1601void close_bdev_exclusive(struct block_device *bdev, fmode_t mode)
1602{
1603    bd_release(bdev);
1604    blkdev_put(bdev, mode);
1605}
1606
1607EXPORT_SYMBOL(close_bdev_exclusive);
1608
1609int __invalidate_device(struct block_device *bdev)
1610{
1611    struct super_block *sb = get_super(bdev);
1612    int res = 0;
1613
1614    if (sb) {
1615        /*
1616         * no need to lock the super, get_super holds the
1617         * read mutex so the filesystem cannot go away
1618         * under us (->put_super runs with the write lock
1619         * hold).
1620         */
1621        shrink_dcache_sb(sb);
1622        res = invalidate_inodes(sb);
1623        drop_super(sb);
1624    }
1625    invalidate_bdev(bdev);
1626    return res;
1627}
1628EXPORT_SYMBOL(__invalidate_device);
1629

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