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TOMOYO Linux Cross Reference
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/backing-dev.h>
 18 #include <linux/module.h>
 19 #include <linux/blkpg.h>
 20 #include <linux/magic.h>
 21 #include <linux/dax.h>
 22 #include <linux/buffer_head.h>
 23 #include <linux/swap.h>
 24 #include <linux/pagevec.h>
 25 #include <linux/writeback.h>
 26 #include <linux/mpage.h>
 27 #include <linux/mount.h>
 28 #include <linux/uio.h>
 29 #include <linux/namei.h>
 30 #include <linux/log2.h>
 31 #include <linux/cleancache.h>
 32 #include <linux/dax.h>
 33 #include <linux/badblocks.h>
 34 #include <linux/task_io_accounting_ops.h>
 35 #include <linux/falloc.h>
 36 #include <linux/uaccess.h>
 37 #include "internal.h"
 38 
 39 struct bdev_inode {
 40         struct block_device bdev;
 41         struct inode vfs_inode;
 42 };
 43 
 44 static const struct address_space_operations def_blk_aops;
 45 
 46 static inline struct bdev_inode *BDEV_I(struct inode *inode)
 47 {
 48         return container_of(inode, struct bdev_inode, vfs_inode);
 49 }
 50 
 51 struct block_device *I_BDEV(struct inode *inode)
 52 {
 53         return &BDEV_I(inode)->bdev;
 54 }
 55 EXPORT_SYMBOL(I_BDEV);
 56 
 57 static void bdev_write_inode(struct block_device *bdev)
 58 {
 59         struct inode *inode = bdev->bd_inode;
 60         int ret;
 61 
 62         spin_lock(&inode->i_lock);
 63         while (inode->i_state & I_DIRTY) {
 64                 spin_unlock(&inode->i_lock);
 65                 ret = write_inode_now(inode, true);
 66                 if (ret) {
 67                         char name[BDEVNAME_SIZE];
 68                         pr_warn_ratelimited("VFS: Dirty inode writeback failed "
 69                                             "for block device %s (err=%d).\n",
 70                                             bdevname(bdev, name), ret);
 71                 }
 72                 spin_lock(&inode->i_lock);
 73         }
 74         spin_unlock(&inode->i_lock);
 75 }
 76 
 77 /* Kill _all_ buffers and pagecache , dirty or not.. */
 78 void kill_bdev(struct block_device *bdev)
 79 {
 80         struct address_space *mapping = bdev->bd_inode->i_mapping;
 81 
 82         if (mapping->nrpages == 0 && mapping->nrexceptional == 0)
 83                 return;
 84 
 85         invalidate_bh_lrus();
 86         truncate_inode_pages(mapping, 0);
 87 }       
 88 EXPORT_SYMBOL(kill_bdev);
 89 
 90 /* Invalidate clean unused buffers and pagecache. */
 91 void invalidate_bdev(struct block_device *bdev)
 92 {
 93         struct address_space *mapping = bdev->bd_inode->i_mapping;
 94 
 95         if (mapping->nrpages) {
 96                 invalidate_bh_lrus();
 97                 lru_add_drain_all();    /* make sure all lru add caches are flushed */
 98                 invalidate_mapping_pages(mapping, 0, -1);
 99         }
100         /* 99% of the time, we don't need to flush the cleancache on the bdev.
101          * But, for the strange corners, lets be cautious
102          */
103         cleancache_invalidate_inode(mapping);
104 }
105 EXPORT_SYMBOL(invalidate_bdev);
106 
107 int set_blocksize(struct block_device *bdev, int size)
108 {
109         /* Size must be a power of two, and between 512 and PAGE_SIZE */
110         if (size > PAGE_SIZE || size < 512 || !is_power_of_2(size))
111                 return -EINVAL;
112 
113         /* Size cannot be smaller than the size supported by the device */
114         if (size < bdev_logical_block_size(bdev))
115                 return -EINVAL;
116 
117         /* Don't change the size if it is same as current */
118         if (bdev->bd_block_size != size) {
119                 sync_blockdev(bdev);
120                 bdev->bd_block_size = size;
121                 bdev->bd_inode->i_blkbits = blksize_bits(size);
122                 kill_bdev(bdev);
123         }
124         return 0;
125 }
126 
127 EXPORT_SYMBOL(set_blocksize);
128 
129 int sb_set_blocksize(struct super_block *sb, int size)
130 {
131         if (set_blocksize(sb->s_bdev, size))
132                 return 0;
133         /* If we get here, we know size is power of two
134          * and it's value is between 512 and PAGE_SIZE */
135         sb->s_blocksize = size;
136         sb->s_blocksize_bits = blksize_bits(size);
137         return sb->s_blocksize;
138 }
139 
140 EXPORT_SYMBOL(sb_set_blocksize);
141 
142 int sb_min_blocksize(struct super_block *sb, int size)
143 {
144         int minsize = bdev_logical_block_size(sb->s_bdev);
145         if (size < minsize)
146                 size = minsize;
147         return sb_set_blocksize(sb, size);
148 }
149 
150 EXPORT_SYMBOL(sb_min_blocksize);
151 
152 static int
153 blkdev_get_block(struct inode *inode, sector_t iblock,
154                 struct buffer_head *bh, int create)
155 {
156         bh->b_bdev = I_BDEV(inode);
157         bh->b_blocknr = iblock;
158         set_buffer_mapped(bh);
159         return 0;
160 }
161 
162 static struct inode *bdev_file_inode(struct file *file)
163 {
164         return file->f_mapping->host;
165 }
166 
167 static unsigned int dio_bio_write_op(struct kiocb *iocb)
168 {
169         unsigned int op = REQ_OP_WRITE | REQ_SYNC | REQ_IDLE;
170 
171         /* avoid the need for a I/O completion work item */
172         if (iocb->ki_flags & IOCB_DSYNC)
173                 op |= REQ_FUA;
174         return op;
175 }
176 
177 #define DIO_INLINE_BIO_VECS 4
178 
179 static void blkdev_bio_end_io_simple(struct bio *bio)
180 {
181         struct task_struct *waiter = bio->bi_private;
182 
183         WRITE_ONCE(bio->bi_private, NULL);
184         wake_up_process(waiter);
185 }
186 
187 static ssize_t
188 __blkdev_direct_IO_simple(struct kiocb *iocb, struct iov_iter *iter,
189                 int nr_pages)
190 {
191         struct file *file = iocb->ki_filp;
192         struct block_device *bdev = I_BDEV(bdev_file_inode(file));
193         struct bio_vec inline_vecs[DIO_INLINE_BIO_VECS], *vecs, *bvec;
194         loff_t pos = iocb->ki_pos;
195         bool should_dirty = false;
196         struct bio bio;
197         ssize_t ret;
198         blk_qc_t qc;
199         int i;
200 
201         if ((pos | iov_iter_alignment(iter)) &
202             (bdev_logical_block_size(bdev) - 1))
203                 return -EINVAL;
204 
205         if (nr_pages <= DIO_INLINE_BIO_VECS)
206                 vecs = inline_vecs;
207         else {
208                 vecs = kmalloc(nr_pages * sizeof(struct bio_vec), GFP_KERNEL);
209                 if (!vecs)
210                         return -ENOMEM;
211         }
212 
213         bio_init(&bio, vecs, nr_pages);
214         bio_set_dev(&bio, bdev);
215         bio.bi_iter.bi_sector = pos >> 9;
216         bio.bi_write_hint = iocb->ki_hint;
217         bio.bi_private = current;
218         bio.bi_end_io = blkdev_bio_end_io_simple;
219 
220         ret = bio_iov_iter_get_pages(&bio, iter);
221         if (unlikely(ret))
222                 return ret;
223         ret = bio.bi_iter.bi_size;
224 
225         if (iov_iter_rw(iter) == READ) {
226                 bio.bi_opf = REQ_OP_READ;
227                 if (iter_is_iovec(iter))
228                         should_dirty = true;
229         } else {
230                 bio.bi_opf = dio_bio_write_op(iocb);
231                 task_io_account_write(ret);
232         }
233 
234         qc = submit_bio(&bio);
235         for (;;) {
236                 set_current_state(TASK_UNINTERRUPTIBLE);
237                 if (!READ_ONCE(bio.bi_private))
238                         break;
239                 if (!(iocb->ki_flags & IOCB_HIPRI) ||
240                     !blk_poll(bdev_get_queue(bdev), qc))
241                         io_schedule();
242         }
243         __set_current_state(TASK_RUNNING);
244 
245         bio_for_each_segment_all(bvec, &bio, i) {
246                 if (should_dirty && !PageCompound(bvec->bv_page))
247                         set_page_dirty_lock(bvec->bv_page);
248                 put_page(bvec->bv_page);
249         }
250 
251         if (vecs != inline_vecs)
252                 kfree(vecs);
253 
254         if (unlikely(bio.bi_status))
255                 ret = blk_status_to_errno(bio.bi_status);
256 
257         bio_uninit(&bio);
258 
259         return ret;
260 }
261 
262 struct blkdev_dio {
263         union {
264                 struct kiocb            *iocb;
265                 struct task_struct      *waiter;
266         };
267         size_t                  size;
268         atomic_t                ref;
269         bool                    multi_bio : 1;
270         bool                    should_dirty : 1;
271         bool                    is_sync : 1;
272         struct bio              bio;
273 };
274 
275 static struct bio_set *blkdev_dio_pool __read_mostly;
276 
277 static void blkdev_bio_end_io(struct bio *bio)
278 {
279         struct blkdev_dio *dio = bio->bi_private;
280         bool should_dirty = dio->should_dirty;
281 
282         if (dio->multi_bio && !atomic_dec_and_test(&dio->ref)) {
283                 if (bio->bi_status && !dio->bio.bi_status)
284                         dio->bio.bi_status = bio->bi_status;
285         } else {
286                 if (!dio->is_sync) {
287                         struct kiocb *iocb = dio->iocb;
288                         ssize_t ret;
289 
290                         if (likely(!dio->bio.bi_status)) {
291                                 ret = dio->size;
292                                 iocb->ki_pos += ret;
293                         } else {
294                                 ret = blk_status_to_errno(dio->bio.bi_status);
295                         }
296 
297                         dio->iocb->ki_complete(iocb, ret, 0);
298                         bio_put(&dio->bio);
299                 } else {
300                         struct task_struct *waiter = dio->waiter;
301 
302                         WRITE_ONCE(dio->waiter, NULL);
303                         wake_up_process(waiter);
304                 }
305         }
306 
307         if (should_dirty) {
308                 bio_check_pages_dirty(bio);
309         } else {
310                 struct bio_vec *bvec;
311                 int i;
312 
313                 bio_for_each_segment_all(bvec, bio, i)
314                         put_page(bvec->bv_page);
315                 bio_put(bio);
316         }
317 }
318 
319 static ssize_t
320 __blkdev_direct_IO(struct kiocb *iocb, struct iov_iter *iter, int nr_pages)
321 {
322         struct file *file = iocb->ki_filp;
323         struct inode *inode = bdev_file_inode(file);
324         struct block_device *bdev = I_BDEV(inode);
325         struct blk_plug plug;
326         struct blkdev_dio *dio;
327         struct bio *bio;
328         bool is_read = (iov_iter_rw(iter) == READ), is_sync;
329         loff_t pos = iocb->ki_pos;
330         blk_qc_t qc = BLK_QC_T_NONE;
331         int ret = 0;
332 
333         if ((pos | iov_iter_alignment(iter)) &
334             (bdev_logical_block_size(bdev) - 1))
335                 return -EINVAL;
336 
337         bio = bio_alloc_bioset(GFP_KERNEL, nr_pages, blkdev_dio_pool);
338         bio_get(bio); /* extra ref for the completion handler */
339 
340         dio = container_of(bio, struct blkdev_dio, bio);
341         dio->is_sync = is_sync = is_sync_kiocb(iocb);
342         if (dio->is_sync)
343                 dio->waiter = current;
344         else
345                 dio->iocb = iocb;
346 
347         dio->size = 0;
348         dio->multi_bio = false;
349         dio->should_dirty = is_read && (iter->type == ITER_IOVEC);
350 
351         blk_start_plug(&plug);
352         for (;;) {
353                 bio_set_dev(bio, bdev);
354                 bio->bi_iter.bi_sector = pos >> 9;
355                 bio->bi_write_hint = iocb->ki_hint;
356                 bio->bi_private = dio;
357                 bio->bi_end_io = blkdev_bio_end_io;
358 
359                 ret = bio_iov_iter_get_pages(bio, iter);
360                 if (unlikely(ret)) {
361                         bio->bi_status = BLK_STS_IOERR;
362                         bio_endio(bio);
363                         break;
364                 }
365 
366                 if (is_read) {
367                         bio->bi_opf = REQ_OP_READ;
368                         if (dio->should_dirty)
369                                 bio_set_pages_dirty(bio);
370                 } else {
371                         bio->bi_opf = dio_bio_write_op(iocb);
372                         task_io_account_write(bio->bi_iter.bi_size);
373                 }
374 
375                 dio->size += bio->bi_iter.bi_size;
376                 pos += bio->bi_iter.bi_size;
377 
378                 nr_pages = iov_iter_npages(iter, BIO_MAX_PAGES);
379                 if (!nr_pages) {
380                         qc = submit_bio(bio);
381                         break;
382                 }
383 
384                 if (!dio->multi_bio) {
385                         dio->multi_bio = true;
386                         atomic_set(&dio->ref, 2);
387                 } else {
388                         atomic_inc(&dio->ref);
389                 }
390 
391                 submit_bio(bio);
392                 bio = bio_alloc(GFP_KERNEL, nr_pages);
393         }
394         blk_finish_plug(&plug);
395 
396         if (!is_sync)
397                 return -EIOCBQUEUED;
398 
399         for (;;) {
400                 set_current_state(TASK_UNINTERRUPTIBLE);
401                 if (!READ_ONCE(dio->waiter))
402                         break;
403 
404                 if (!(iocb->ki_flags & IOCB_HIPRI) ||
405                     !blk_poll(bdev_get_queue(bdev), qc))
406                         io_schedule();
407         }
408         __set_current_state(TASK_RUNNING);
409 
410         if (!ret)
411                 ret = blk_status_to_errno(dio->bio.bi_status);
412         if (likely(!ret))
413                 ret = dio->size;
414 
415         bio_put(&dio->bio);
416         return ret;
417 }
418 
419 static ssize_t
420 blkdev_direct_IO(struct kiocb *iocb, struct iov_iter *iter)
421 {
422         int nr_pages;
423 
424         nr_pages = iov_iter_npages(iter, BIO_MAX_PAGES + 1);
425         if (!nr_pages)
426                 return 0;
427         if (is_sync_kiocb(iocb) && nr_pages <= BIO_MAX_PAGES)
428                 return __blkdev_direct_IO_simple(iocb, iter, nr_pages);
429 
430         return __blkdev_direct_IO(iocb, iter, min(nr_pages, BIO_MAX_PAGES));
431 }
432 
433 static __init int blkdev_init(void)
434 {
435         blkdev_dio_pool = bioset_create(4, offsetof(struct blkdev_dio, bio), BIOSET_NEED_BVECS);
436         if (!blkdev_dio_pool)
437                 return -ENOMEM;
438         return 0;
439 }
440 module_init(blkdev_init);
441 
442 int __sync_blockdev(struct block_device *bdev, int wait)
443 {
444         if (!bdev)
445                 return 0;
446         if (!wait)
447                 return filemap_flush(bdev->bd_inode->i_mapping);
448         return filemap_write_and_wait(bdev->bd_inode->i_mapping);
449 }
450 
451 /*
452  * Write out and wait upon all the dirty data associated with a block
453  * device via its mapping.  Does not take the superblock lock.
454  */
455 int sync_blockdev(struct block_device *bdev)
456 {
457         return __sync_blockdev(bdev, 1);
458 }
459 EXPORT_SYMBOL(sync_blockdev);
460 
461 /*
462  * Write out and wait upon all dirty data associated with this
463  * device.   Filesystem data as well as the underlying block
464  * device.  Takes the superblock lock.
465  */
466 int fsync_bdev(struct block_device *bdev)
467 {
468         struct super_block *sb = get_super(bdev);
469         if (sb) {
470                 int res = sync_filesystem(sb);
471                 drop_super(sb);
472                 return res;
473         }
474         return sync_blockdev(bdev);
475 }
476 EXPORT_SYMBOL(fsync_bdev);
477 
478 /**
479  * freeze_bdev  --  lock a filesystem and force it into a consistent state
480  * @bdev:       blockdevice to lock
481  *
482  * If a superblock is found on this device, we take the s_umount semaphore
483  * on it to make sure nobody unmounts until the snapshot creation is done.
484  * The reference counter (bd_fsfreeze_count) guarantees that only the last
485  * unfreeze process can unfreeze the frozen filesystem actually when multiple
486  * freeze requests arrive simultaneously. It counts up in freeze_bdev() and
487  * count down in thaw_bdev(). When it becomes 0, thaw_bdev() will unfreeze
488  * actually.
489  */
490 struct super_block *freeze_bdev(struct block_device *bdev)
491 {
492         struct super_block *sb;
493         int error = 0;
494 
495         mutex_lock(&bdev->bd_fsfreeze_mutex);
496         if (++bdev->bd_fsfreeze_count > 1) {
497                 /*
498                  * We don't even need to grab a reference - the first call
499                  * to freeze_bdev grab an active reference and only the last
500                  * thaw_bdev drops it.
501                  */
502                 sb = get_super(bdev);
503                 if (sb)
504                         drop_super(sb);
505                 mutex_unlock(&bdev->bd_fsfreeze_mutex);
506                 return sb;
507         }
508 
509         sb = get_active_super(bdev);
510         if (!sb)
511                 goto out;
512         if (sb->s_op->freeze_super)
513                 error = sb->s_op->freeze_super(sb);
514         else
515                 error = freeze_super(sb);
516         if (error) {
517                 deactivate_super(sb);
518                 bdev->bd_fsfreeze_count--;
519                 mutex_unlock(&bdev->bd_fsfreeze_mutex);
520                 return ERR_PTR(error);
521         }
522         deactivate_super(sb);
523  out:
524         sync_blockdev(bdev);
525         mutex_unlock(&bdev->bd_fsfreeze_mutex);
526         return sb;      /* thaw_bdev releases s->s_umount */
527 }
528 EXPORT_SYMBOL(freeze_bdev);
529 
530 /**
531  * thaw_bdev  -- unlock filesystem
532  * @bdev:       blockdevice to unlock
533  * @sb:         associated superblock
534  *
535  * Unlocks the filesystem and marks it writeable again after freeze_bdev().
536  */
537 int thaw_bdev(struct block_device *bdev, struct super_block *sb)
538 {
539         int error = -EINVAL;
540 
541         mutex_lock(&bdev->bd_fsfreeze_mutex);
542         if (!bdev->bd_fsfreeze_count)
543                 goto out;
544 
545         error = 0;
546         if (--bdev->bd_fsfreeze_count > 0)
547                 goto out;
548 
549         if (!sb)
550                 goto out;
551 
552         if (sb->s_op->thaw_super)
553                 error = sb->s_op->thaw_super(sb);
554         else
555                 error = thaw_super(sb);
556         if (error)
557                 bdev->bd_fsfreeze_count++;
558 out:
559         mutex_unlock(&bdev->bd_fsfreeze_mutex);
560         return error;
561 }
562 EXPORT_SYMBOL(thaw_bdev);
563 
564 static int blkdev_writepage(struct page *page, struct writeback_control *wbc)
565 {
566         return block_write_full_page(page, blkdev_get_block, wbc);
567 }
568 
569 static int blkdev_readpage(struct file * file, struct page * page)
570 {
571         return block_read_full_page(page, blkdev_get_block);
572 }
573 
574 static int blkdev_readpages(struct file *file, struct address_space *mapping,
575                         struct list_head *pages, unsigned nr_pages)
576 {
577         return mpage_readpages(mapping, pages, nr_pages, blkdev_get_block);
578 }
579 
580 static int blkdev_write_begin(struct file *file, struct address_space *mapping,
581                         loff_t pos, unsigned len, unsigned flags,
582                         struct page **pagep, void **fsdata)
583 {
584         return block_write_begin(mapping, pos, len, flags, pagep,
585                                  blkdev_get_block);
586 }
587 
588 static int blkdev_write_end(struct file *file, struct address_space *mapping,
589                         loff_t pos, unsigned len, unsigned copied,
590                         struct page *page, void *fsdata)
591 {
592         int ret;
593         ret = block_write_end(file, mapping, pos, len, copied, page, fsdata);
594 
595         unlock_page(page);
596         put_page(page);
597 
598         return ret;
599 }
600 
601 /*
602  * private llseek:
603  * for a block special file file_inode(file)->i_size is zero
604  * so we compute the size by hand (just as in block_read/write above)
605  */
606 static loff_t block_llseek(struct file *file, loff_t offset, int whence)
607 {
608         struct inode *bd_inode = bdev_file_inode(file);
609         loff_t retval;
610 
611         inode_lock(bd_inode);
612         retval = fixed_size_llseek(file, offset, whence, i_size_read(bd_inode));
613         inode_unlock(bd_inode);
614         return retval;
615 }
616         
617 int blkdev_fsync(struct file *filp, loff_t start, loff_t end, int datasync)
618 {
619         struct inode *bd_inode = bdev_file_inode(filp);
620         struct block_device *bdev = I_BDEV(bd_inode);
621         int error;
622         
623         error = file_write_and_wait_range(filp, start, end);
624         if (error)
625                 return error;
626 
627         /*
628          * There is no need to serialise calls to blkdev_issue_flush with
629          * i_mutex and doing so causes performance issues with concurrent
630          * O_SYNC writers to a block device.
631          */
632         error = blkdev_issue_flush(bdev, GFP_KERNEL, NULL);
633         if (error == -EOPNOTSUPP)
634                 error = 0;
635 
636         return error;
637 }
638 EXPORT_SYMBOL(blkdev_fsync);
639 
640 /**
641  * bdev_read_page() - Start reading a page from a block device
642  * @bdev: The device to read the page from
643  * @sector: The offset on the device to read the page to (need not be aligned)
644  * @page: The page to read
645  *
646  * On entry, the page should be locked.  It will be unlocked when the page
647  * has been read.  If the block driver implements rw_page synchronously,
648  * that will be true on exit from this function, but it need not be.
649  *
650  * Errors returned by this function are usually "soft", eg out of memory, or
651  * queue full; callers should try a different route to read this page rather
652  * than propagate an error back up the stack.
653  *
654  * Return: negative errno if an error occurs, 0 if submission was successful.
655  */
656 int bdev_read_page(struct block_device *bdev, sector_t sector,
657                         struct page *page)
658 {
659         const struct block_device_operations *ops = bdev->bd_disk->fops;
660         int result = -EOPNOTSUPP;
661 
662         if (!ops->rw_page || bdev_get_integrity(bdev))
663                 return result;
664 
665         result = blk_queue_enter(bdev->bd_queue, 0);
666         if (result)
667                 return result;
668         result = ops->rw_page(bdev, sector + get_start_sect(bdev), page, false);
669         blk_queue_exit(bdev->bd_queue);
670         return result;
671 }
672 EXPORT_SYMBOL_GPL(bdev_read_page);
673 
674 /**
675  * bdev_write_page() - Start writing a page to a block device
676  * @bdev: The device to write the page to
677  * @sector: The offset on the device to write the page to (need not be aligned)
678  * @page: The page to write
679  * @wbc: The writeback_control for the write
680  *
681  * On entry, the page should be locked and not currently under writeback.
682  * On exit, if the write started successfully, the page will be unlocked and
683  * under writeback.  If the write failed already (eg the driver failed to
684  * queue the page to the device), the page will still be locked.  If the
685  * caller is a ->writepage implementation, it will need to unlock the page.
686  *
687  * Errors returned by this function are usually "soft", eg out of memory, or
688  * queue full; callers should try a different route to write this page rather
689  * than propagate an error back up the stack.
690  *
691  * Return: negative errno if an error occurs, 0 if submission was successful.
692  */
693 int bdev_write_page(struct block_device *bdev, sector_t sector,
694                         struct page *page, struct writeback_control *wbc)
695 {
696         int result;
697         const struct block_device_operations *ops = bdev->bd_disk->fops;
698 
699         if (!ops->rw_page || bdev_get_integrity(bdev))
700                 return -EOPNOTSUPP;
701         result = blk_queue_enter(bdev->bd_queue, 0);
702         if (result)
703                 return result;
704 
705         set_page_writeback(page);
706         result = ops->rw_page(bdev, sector + get_start_sect(bdev), page, true);
707         if (result) {
708                 end_page_writeback(page);
709         } else {
710                 clean_page_buffers(page);
711                 unlock_page(page);
712         }
713         blk_queue_exit(bdev->bd_queue);
714         return result;
715 }
716 EXPORT_SYMBOL_GPL(bdev_write_page);
717 
718 /*
719  * pseudo-fs
720  */
721 
722 static  __cacheline_aligned_in_smp DEFINE_SPINLOCK(bdev_lock);
723 static struct kmem_cache * bdev_cachep __read_mostly;
724 
725 static struct inode *bdev_alloc_inode(struct super_block *sb)
726 {
727         struct bdev_inode *ei = kmem_cache_alloc(bdev_cachep, GFP_KERNEL);
728         if (!ei)
729                 return NULL;
730         return &ei->vfs_inode;
731 }
732 
733 static void bdev_i_callback(struct rcu_head *head)
734 {
735         struct inode *inode = container_of(head, struct inode, i_rcu);
736         struct bdev_inode *bdi = BDEV_I(inode);
737 
738         kmem_cache_free(bdev_cachep, bdi);
739 }
740 
741 static void bdev_destroy_inode(struct inode *inode)
742 {
743         call_rcu(&inode->i_rcu, bdev_i_callback);
744 }
745 
746 static void init_once(void *foo)
747 {
748         struct bdev_inode *ei = (struct bdev_inode *) foo;
749         struct block_device *bdev = &ei->bdev;
750 
751         memset(bdev, 0, sizeof(*bdev));
752         mutex_init(&bdev->bd_mutex);
753         INIT_LIST_HEAD(&bdev->bd_list);
754 #ifdef CONFIG_SYSFS
755         INIT_LIST_HEAD(&bdev->bd_holder_disks);
756 #endif
757         bdev->bd_bdi = &noop_backing_dev_info;
758         inode_init_once(&ei->vfs_inode);
759         /* Initialize mutex for freeze. */
760         mutex_init(&bdev->bd_fsfreeze_mutex);
761 }
762 
763 static void bdev_evict_inode(struct inode *inode)
764 {
765         struct block_device *bdev = &BDEV_I(inode)->bdev;
766         truncate_inode_pages_final(&inode->i_data);
767         invalidate_inode_buffers(inode); /* is it needed here? */
768         clear_inode(inode);
769         spin_lock(&bdev_lock);
770         list_del_init(&bdev->bd_list);
771         spin_unlock(&bdev_lock);
772         /* Detach inode from wb early as bdi_put() may free bdi->wb */
773         inode_detach_wb(inode);
774         if (bdev->bd_bdi != &noop_backing_dev_info) {
775                 bdi_put(bdev->bd_bdi);
776                 bdev->bd_bdi = &noop_backing_dev_info;
777         }
778 }
779 
780 static const struct super_operations bdev_sops = {
781         .statfs = simple_statfs,
782         .alloc_inode = bdev_alloc_inode,
783         .destroy_inode = bdev_destroy_inode,
784         .drop_inode = generic_delete_inode,
785         .evict_inode = bdev_evict_inode,
786 };
787 
788 static struct dentry *bd_mount(struct file_system_type *fs_type,
789         int flags, const char *dev_name, void *data)
790 {
791         struct dentry *dent;
792         dent = mount_pseudo(fs_type, "bdev:", &bdev_sops, NULL, BDEVFS_MAGIC);
793         if (!IS_ERR(dent))
794                 dent->d_sb->s_iflags |= SB_I_CGROUPWB;
795         return dent;
796 }
797 
798 static struct file_system_type bd_type = {
799         .name           = "bdev",
800         .mount          = bd_mount,
801         .kill_sb        = kill_anon_super,
802 };
803 
804 struct super_block *blockdev_superblock __read_mostly;
805 EXPORT_SYMBOL_GPL(blockdev_superblock);
806 
807 void __init bdev_cache_init(void)
808 {
809         int err;
810         static struct vfsmount *bd_mnt;
811 
812         bdev_cachep = kmem_cache_create("bdev_cache", sizeof(struct bdev_inode),
813                         0, (SLAB_HWCACHE_ALIGN|SLAB_RECLAIM_ACCOUNT|
814                                 SLAB_MEM_SPREAD|SLAB_ACCOUNT|SLAB_PANIC),
815                         init_once);
816         err = register_filesystem(&bd_type);
817         if (err)
818                 panic("Cannot register bdev pseudo-fs");
819         bd_mnt = kern_mount(&bd_type);
820         if (IS_ERR(bd_mnt))
821                 panic("Cannot create bdev pseudo-fs");
822         blockdev_superblock = bd_mnt->mnt_sb;   /* For writeback */
823 }
824 
825 /*
826  * Most likely _very_ bad one - but then it's hardly critical for small
827  * /dev and can be fixed when somebody will need really large one.
828  * Keep in mind that it will be fed through icache hash function too.
829  */
830 static inline unsigned long hash(dev_t dev)
831 {
832         return MAJOR(dev)+MINOR(dev);
833 }
834 
835 static int bdev_test(struct inode *inode, void *data)
836 {
837         return BDEV_I(inode)->bdev.bd_dev == *(dev_t *)data;
838 }
839 
840 static int bdev_set(struct inode *inode, void *data)
841 {
842         BDEV_I(inode)->bdev.bd_dev = *(dev_t *)data;
843         return 0;
844 }
845 
846 static LIST_HEAD(all_bdevs);
847 
848 /*
849  * If there is a bdev inode for this device, unhash it so that it gets evicted
850  * as soon as last inode reference is dropped.
851  */
852 void bdev_unhash_inode(dev_t dev)
853 {
854         struct inode *inode;
855 
856         inode = ilookup5(blockdev_superblock, hash(dev), bdev_test, &dev);
857         if (inode) {
858                 remove_inode_hash(inode);
859                 iput(inode);
860         }
861 }
862 
863 struct block_device *bdget(dev_t dev)
864 {
865         struct block_device *bdev;
866         struct inode *inode;
867 
868         inode = iget5_locked(blockdev_superblock, hash(dev),
869                         bdev_test, bdev_set, &dev);
870 
871         if (!inode)
872                 return NULL;
873 
874         bdev = &BDEV_I(inode)->bdev;
875 
876         if (inode->i_state & I_NEW) {
877                 bdev->bd_contains = NULL;
878                 bdev->bd_super = NULL;
879                 bdev->bd_inode = inode;
880                 bdev->bd_block_size = i_blocksize(inode);
881                 bdev->bd_part_count = 0;
882                 bdev->bd_invalidated = 0;
883                 inode->i_mode = S_IFBLK;
884                 inode->i_rdev = dev;
885                 inode->i_bdev = bdev;
886                 inode->i_data.a_ops = &def_blk_aops;
887                 mapping_set_gfp_mask(&inode->i_data, GFP_USER);
888                 spin_lock(&bdev_lock);
889                 list_add(&bdev->bd_list, &all_bdevs);
890                 spin_unlock(&bdev_lock);
891                 unlock_new_inode(inode);
892         }
893         return bdev;
894 }
895 
896 EXPORT_SYMBOL(bdget);
897 
898 /**
899  * bdgrab -- Grab a reference to an already referenced block device
900  * @bdev:       Block device to grab a reference to.
901  */
902 struct block_device *bdgrab(struct block_device *bdev)
903 {
904         ihold(bdev->bd_inode);
905         return bdev;
906 }
907 EXPORT_SYMBOL(bdgrab);
908 
909 long nr_blockdev_pages(void)
910 {
911         struct block_device *bdev;
912         long ret = 0;
913         spin_lock(&bdev_lock);
914         list_for_each_entry(bdev, &all_bdevs, bd_list) {
915                 ret += bdev->bd_inode->i_mapping->nrpages;
916         }
917         spin_unlock(&bdev_lock);
918         return ret;
919 }
920 
921 void bdput(struct block_device *bdev)
922 {
923         iput(bdev->bd_inode);
924 }
925 
926 EXPORT_SYMBOL(bdput);
927  
928 static struct block_device *bd_acquire(struct inode *inode)
929 {
930         struct block_device *bdev;
931 
932         spin_lock(&bdev_lock);
933         bdev = inode->i_bdev;
934         if (bdev && !inode_unhashed(bdev->bd_inode)) {
935                 bdgrab(bdev);
936                 spin_unlock(&bdev_lock);
937                 return bdev;
938         }
939         spin_unlock(&bdev_lock);
940 
941         /*
942          * i_bdev references block device inode that was already shut down
943          * (corresponding device got removed).  Remove the reference and look
944          * up block device inode again just in case new device got
945          * reestablished under the same device number.
946          */
947         if (bdev)
948                 bd_forget(inode);
949 
950         bdev = bdget(inode->i_rdev);
951         if (bdev) {
952                 spin_lock(&bdev_lock);
953                 if (!inode->i_bdev) {
954                         /*
955                          * We take an additional reference to bd_inode,
956                          * and it's released in clear_inode() of inode.
957                          * So, we can access it via ->i_mapping always
958                          * without igrab().
959                          */
960                         bdgrab(bdev);
961                         inode->i_bdev = bdev;
962                         inode->i_mapping = bdev->bd_inode->i_mapping;
963                 }
964                 spin_unlock(&bdev_lock);
965         }
966         return bdev;
967 }
968 
969 /* Call when you free inode */
970 
971 void bd_forget(struct inode *inode)
972 {
973         struct block_device *bdev = NULL;
974 
975         spin_lock(&bdev_lock);
976         if (!sb_is_blkdev_sb(inode->i_sb))
977                 bdev = inode->i_bdev;
978         inode->i_bdev = NULL;
979         inode->i_mapping = &inode->i_data;
980         spin_unlock(&bdev_lock);
981 
982         if (bdev)
983                 bdput(bdev);
984 }
985 
986 /**
987  * bd_may_claim - test whether a block device can be claimed
988  * @bdev: block device of interest
989  * @whole: whole block device containing @bdev, may equal @bdev
990  * @holder: holder trying to claim @bdev
991  *
992  * Test whether @bdev can be claimed by @holder.
993  *
994  * CONTEXT:
995  * spin_lock(&bdev_lock).
996  *
997  * RETURNS:
998  * %true if @bdev can be claimed, %false otherwise.
999  */
1000 static bool bd_may_claim(struct block_device *bdev, struct block_device *whole,
1001                          void *holder)
1002 {
1003         if (bdev->bd_holder == holder)
1004                 return true;     /* already a holder */
1005         else if (bdev->bd_holder != NULL)
1006                 return false;    /* held by someone else */
1007         else if (whole == bdev)
1008                 return true;     /* is a whole device which isn't held */
1009 
1010         else if (whole->bd_holder == bd_may_claim)
1011                 return true;     /* is a partition of a device that is being partitioned */
1012         else if (whole->bd_holder != NULL)
1013                 return false;    /* is a partition of a held device */
1014         else
1015                 return true;     /* is a partition of an un-held device */
1016 }
1017 
1018 /**
1019  * bd_prepare_to_claim - prepare to claim a block device
1020  * @bdev: block device of interest
1021  * @whole: the whole device containing @bdev, may equal @bdev
1022  * @holder: holder trying to claim @bdev
1023  *
1024  * Prepare to claim @bdev.  This function fails if @bdev is already
1025  * claimed by another holder and waits if another claiming is in
1026  * progress.  This function doesn't actually claim.  On successful
1027  * return, the caller has ownership of bd_claiming and bd_holder[s].
1028  *
1029  * CONTEXT:
1030  * spin_lock(&bdev_lock).  Might release bdev_lock, sleep and regrab
1031  * it multiple times.
1032  *
1033  * RETURNS:
1034  * 0 if @bdev can be claimed, -EBUSY otherwise.
1035  */
1036 static int bd_prepare_to_claim(struct block_device *bdev,
1037                                struct block_device *whole, void *holder)
1038 {
1039 retry:
1040         /* if someone else claimed, fail */
1041         if (!bd_may_claim(bdev, whole, holder))
1042                 return -EBUSY;
1043 
1044         /* if claiming is already in progress, wait for it to finish */
1045         if (whole->bd_claiming) {
1046                 wait_queue_head_t *wq = bit_waitqueue(&whole->bd_claiming, 0);
1047                 DEFINE_WAIT(wait);
1048 
1049                 prepare_to_wait(wq, &wait, TASK_UNINTERRUPTIBLE);
1050                 spin_unlock(&bdev_lock);
1051                 schedule();
1052                 finish_wait(wq, &wait);
1053                 spin_lock(&bdev_lock);
1054                 goto retry;
1055         }
1056 
1057         /* yay, all mine */
1058         return 0;
1059 }
1060 
1061 static struct gendisk *bdev_get_gendisk(struct block_device *bdev, int *partno)
1062 {
1063         struct gendisk *disk = get_gendisk(bdev->bd_dev, partno);
1064 
1065         if (!disk)
1066                 return NULL;
1067         /*
1068          * Now that we hold gendisk reference we make sure bdev we looked up is
1069          * not stale. If it is, it means device got removed and created before
1070          * we looked up gendisk and we fail open in such case. Associating
1071          * unhashed bdev with newly created gendisk could lead to two bdevs
1072          * (and thus two independent caches) being associated with one device
1073          * which is bad.
1074          */
1075         if (inode_unhashed(bdev->bd_inode)) {
1076                 put_disk_and_module(disk);
1077                 return NULL;
1078         }
1079         return disk;
1080 }
1081 
1082 /**
1083  * bd_start_claiming - start claiming a block device
1084  * @bdev: block device of interest
1085  * @holder: holder trying to claim @bdev
1086  *
1087  * @bdev is about to be opened exclusively.  Check @bdev can be opened
1088  * exclusively and mark that an exclusive open is in progress.  Each
1089  * successful call to this function must be matched with a call to
1090  * either bd_finish_claiming() or bd_abort_claiming() (which do not
1091  * fail).
1092  *
1093  * This function is used to gain exclusive access to the block device
1094  * without actually causing other exclusive open attempts to fail. It
1095  * should be used when the open sequence itself requires exclusive
1096  * access but may subsequently fail.
1097  *
1098  * CONTEXT:
1099  * Might sleep.
1100  *
1101  * RETURNS:
1102  * Pointer to the block device containing @bdev on success, ERR_PTR()
1103  * value on failure.
1104  */
1105 static struct block_device *bd_start_claiming(struct block_device *bdev,
1106                                               void *holder)
1107 {
1108         struct gendisk *disk;
1109         struct block_device *whole;
1110         int partno, err;
1111 
1112         might_sleep();
1113 
1114         /*
1115          * @bdev might not have been initialized properly yet, look up
1116          * and grab the outer block device the hard way.
1117          */
1118         disk = bdev_get_gendisk(bdev, &partno);
1119         if (!disk)
1120                 return ERR_PTR(-ENXIO);
1121 
1122         /*
1123          * Normally, @bdev should equal what's returned from bdget_disk()
1124          * if partno is 0; however, some drivers (floppy) use multiple
1125          * bdev's for the same physical device and @bdev may be one of the
1126          * aliases.  Keep @bdev if partno is 0.  This means claimer
1127          * tracking is broken for those devices but it has always been that
1128          * way.
1129          */
1130         if (partno)
1131                 whole = bdget_disk(disk, 0);
1132         else
1133                 whole = bdgrab(bdev);
1134 
1135         put_disk_and_module(disk);
1136         if (!whole)
1137                 return ERR_PTR(-ENOMEM);
1138 
1139         /* prepare to claim, if successful, mark claiming in progress */
1140         spin_lock(&bdev_lock);
1141 
1142         err = bd_prepare_to_claim(bdev, whole, holder);
1143         if (err == 0) {
1144                 whole->bd_claiming = holder;
1145                 spin_unlock(&bdev_lock);
1146                 return whole;
1147         } else {
1148                 spin_unlock(&bdev_lock);
1149                 bdput(whole);
1150                 return ERR_PTR(err);
1151         }
1152 }
1153 
1154 #ifdef CONFIG_SYSFS
1155 struct bd_holder_disk {
1156         struct list_head        list;
1157         struct gendisk          *disk;
1158         int                     refcnt;
1159 };
1160 
1161 static struct bd_holder_disk *bd_find_holder_disk(struct block_device *bdev,
1162                                                   struct gendisk *disk)
1163 {
1164         struct bd_holder_disk *holder;
1165 
1166         list_for_each_entry(holder, &bdev->bd_holder_disks, list)
1167                 if (holder->disk == disk)
1168                         return holder;
1169         return NULL;
1170 }
1171 
1172 static int add_symlink(struct kobject *from, struct kobject *to)
1173 {
1174         return sysfs_create_link(from, to, kobject_name(to));
1175 }
1176 
1177 static void del_symlink(struct kobject *from, struct kobject *to)
1178 {
1179         sysfs_remove_link(from, kobject_name(to));
1180 }
1181 
1182 /**
1183  * bd_link_disk_holder - create symlinks between holding disk and slave bdev
1184  * @bdev: the claimed slave bdev
1185  * @disk: the holding disk
1186  *
1187  * DON'T USE THIS UNLESS YOU'RE ALREADY USING IT.
1188  *
1189  * This functions creates the following sysfs symlinks.
1190  *
1191  * - from "slaves" directory of the holder @disk to the claimed @bdev
1192  * - from "holders" directory of the @bdev to the holder @disk
1193  *
1194  * For example, if /dev/dm-0 maps to /dev/sda and disk for dm-0 is
1195  * passed to bd_link_disk_holder(), then:
1196  *
1197  *   /sys/block/dm-0/slaves/sda --> /sys/block/sda
1198  *   /sys/block/sda/holders/dm-0 --> /sys/block/dm-0
1199  *
1200  * The caller must have claimed @bdev before calling this function and
1201  * ensure that both @bdev and @disk are valid during the creation and
1202  * lifetime of these symlinks.
1203  *
1204  * CONTEXT:
1205  * Might sleep.
1206  *
1207  * RETURNS:
1208  * 0 on success, -errno on failure.
1209  */
1210 int bd_link_disk_holder(struct block_device *bdev, struct gendisk *disk)
1211 {
1212         struct bd_holder_disk *holder;
1213         int ret = 0;
1214 
1215         mutex_lock(&bdev->bd_mutex);
1216 
1217         WARN_ON_ONCE(!bdev->bd_holder);
1218 
1219         /* FIXME: remove the following once add_disk() handles errors */
1220         if (WARN_ON(!disk->slave_dir || !bdev->bd_part->holder_dir))
1221                 goto out_unlock;
1222 
1223         holder = bd_find_holder_disk(bdev, disk);
1224         if (holder) {
1225                 holder->refcnt++;
1226                 goto out_unlock;
1227         }
1228 
1229         holder = kzalloc(sizeof(*holder), GFP_KERNEL);
1230         if (!holder) {
1231                 ret = -ENOMEM;
1232                 goto out_unlock;
1233         }
1234 
1235         INIT_LIST_HEAD(&holder->list);
1236         holder->disk = disk;
1237         holder->refcnt = 1;
1238 
1239         ret = add_symlink(disk->slave_dir, &part_to_dev(bdev->bd_part)->kobj);
1240         if (ret)
1241                 goto out_free;
1242 
1243         ret = add_symlink(bdev->bd_part->holder_dir, &disk_to_dev(disk)->kobj);
1244         if (ret)
1245                 goto out_del;
1246         /*
1247          * bdev could be deleted beneath us which would implicitly destroy
1248          * the holder directory.  Hold on to it.
1249          */
1250         kobject_get(bdev->bd_part->holder_dir);
1251 
1252         list_add(&holder->list, &bdev->bd_holder_disks);
1253         goto out_unlock;
1254 
1255 out_del:
1256         del_symlink(disk->slave_dir, &part_to_dev(bdev->bd_part)->kobj);
1257 out_free:
1258         kfree(holder);
1259 out_unlock:
1260         mutex_unlock(&bdev->bd_mutex);
1261         return ret;
1262 }
1263 EXPORT_SYMBOL_GPL(bd_link_disk_holder);
1264 
1265 /**
1266  * bd_unlink_disk_holder - destroy symlinks created by bd_link_disk_holder()
1267  * @bdev: the calimed slave bdev
1268  * @disk: the holding disk
1269  *
1270  * DON'T USE THIS UNLESS YOU'RE ALREADY USING IT.
1271  *
1272  * CONTEXT:
1273  * Might sleep.
1274  */
1275 void bd_unlink_disk_holder(struct block_device *bdev, struct gendisk *disk)
1276 {
1277         struct bd_holder_disk *holder;
1278 
1279         mutex_lock(&bdev->bd_mutex);
1280 
1281         holder = bd_find_holder_disk(bdev, disk);
1282 
1283         if (!WARN_ON_ONCE(holder == NULL) && !--holder->refcnt) {
1284                 del_symlink(disk->slave_dir, &part_to_dev(bdev->bd_part)->kobj);
1285                 del_symlink(bdev->bd_part->holder_dir,
1286                             &disk_to_dev(disk)->kobj);
1287                 kobject_put(bdev->bd_part->holder_dir);
1288                 list_del_init(&holder->list);
1289                 kfree(holder);
1290         }
1291 
1292         mutex_unlock(&bdev->bd_mutex);
1293 }
1294 EXPORT_SYMBOL_GPL(bd_unlink_disk_holder);
1295 #endif
1296 
1297 /**
1298  * flush_disk - invalidates all buffer-cache entries on a disk
1299  *
1300  * @bdev:      struct block device to be flushed
1301  * @kill_dirty: flag to guide handling of dirty inodes
1302  *
1303  * Invalidates all buffer-cache entries on a disk. It should be called
1304  * when a disk has been changed -- either by a media change or online
1305  * resize.
1306  */
1307 static void flush_disk(struct block_device *bdev, bool kill_dirty)
1308 {
1309         if (__invalidate_device(bdev, kill_dirty)) {
1310                 printk(KERN_WARNING "VFS: busy inodes on changed media or "
1311                        "resized disk %s\n",
1312                        bdev->bd_disk ? bdev->bd_disk->disk_name : "");
1313         }
1314 
1315         if (!bdev->bd_disk)
1316                 return;
1317         if (disk_part_scan_enabled(bdev->bd_disk))
1318                 bdev->bd_invalidated = 1;
1319 }
1320 
1321 /**
1322  * check_disk_size_change - checks for disk size change and adjusts bdev size.
1323  * @disk: struct gendisk to check
1324  * @bdev: struct bdev to adjust.
1325  *
1326  * This routine checks to see if the bdev size does not match the disk size
1327  * and adjusts it if it differs. When shrinking the bdev size, its all caches
1328  * are freed.
1329  */
1330 void check_disk_size_change(struct gendisk *disk, struct block_device *bdev)
1331 {
1332         loff_t disk_size, bdev_size;
1333 
1334         disk_size = (loff_t)get_capacity(disk) << 9;
1335         bdev_size = i_size_read(bdev->bd_inode);
1336         if (disk_size != bdev_size) {
1337                 printk(KERN_INFO
1338                        "%s: detected capacity change from %lld to %lld\n",
1339                        disk->disk_name, bdev_size, disk_size);
1340                 i_size_write(bdev->bd_inode, disk_size);
1341                 if (bdev_size > disk_size)
1342                         flush_disk(bdev, false);
1343         }
1344 }
1345 EXPORT_SYMBOL(check_disk_size_change);
1346 
1347 /**
1348  * revalidate_disk - wrapper for lower-level driver's revalidate_disk call-back
1349  * @disk: struct gendisk to be revalidated
1350  *
1351  * This routine is a wrapper for lower-level driver's revalidate_disk
1352  * call-backs.  It is used to do common pre and post operations needed
1353  * for all revalidate_disk operations.
1354  */
1355 int revalidate_disk(struct gendisk *disk)
1356 {
1357         struct block_device *bdev;
1358         int ret = 0;
1359 
1360         if (disk->fops->revalidate_disk)
1361                 ret = disk->fops->revalidate_disk(disk);
1362         bdev = bdget_disk(disk, 0);
1363         if (!bdev)
1364                 return ret;
1365 
1366         mutex_lock(&bdev->bd_mutex);
1367         check_disk_size_change(disk, bdev);
1368         bdev->bd_invalidated = 0;
1369         mutex_unlock(&bdev->bd_mutex);
1370         bdput(bdev);
1371         return ret;
1372 }
1373 EXPORT_SYMBOL(revalidate_disk);
1374 
1375 /*
1376  * This routine checks whether a removable media has been changed,
1377  * and invalidates all buffer-cache-entries in that case. This
1378  * is a relatively slow routine, so we have to try to minimize using
1379  * it. Thus it is called only upon a 'mount' or 'open'. This
1380  * is the best way of combining speed and utility, I think.
1381  * People changing diskettes in the middle of an operation deserve
1382  * to lose :-)
1383  */
1384 int check_disk_change(struct block_device *bdev)
1385 {
1386         struct gendisk *disk = bdev->bd_disk;
1387         const struct block_device_operations *bdops = disk->fops;
1388         unsigned int events;
1389 
1390         events = disk_clear_events(disk, DISK_EVENT_MEDIA_CHANGE |
1391                                    DISK_EVENT_EJECT_REQUEST);
1392         if (!(events & DISK_EVENT_MEDIA_CHANGE))
1393                 return 0;
1394 
1395         flush_disk(bdev, true);
1396         if (bdops->revalidate_disk)
1397                 bdops->revalidate_disk(bdev->bd_disk);
1398         return 1;
1399 }
1400 
1401 EXPORT_SYMBOL(check_disk_change);
1402 
1403 void bd_set_size(struct block_device *bdev, loff_t size)
1404 {
1405         unsigned bsize = bdev_logical_block_size(bdev);
1406 
1407         inode_lock(bdev->bd_inode);
1408         i_size_write(bdev->bd_inode, size);
1409         inode_unlock(bdev->bd_inode);
1410         while (bsize < PAGE_SIZE) {
1411                 if (size & bsize)
1412                         break;
1413                 bsize <<= 1;
1414         }
1415         bdev->bd_block_size = bsize;
1416         bdev->bd_inode->i_blkbits = blksize_bits(bsize);
1417 }
1418 EXPORT_SYMBOL(bd_set_size);
1419 
1420 static void __blkdev_put(struct block_device *bdev, fmode_t mode, int for_part);
1421 
1422 /*
1423  * bd_mutex locking:
1424  *
1425  *  mutex_lock(part->bd_mutex)
1426  *    mutex_lock_nested(whole->bd_mutex, 1)
1427  */
1428 
1429 static int __blkdev_get(struct block_device *bdev, fmode_t mode, int for_part)
1430 {
1431         struct gendisk *disk;
1432         int ret;
1433         int partno;
1434         int perm = 0;
1435         bool first_open = false;
1436 
1437         if (mode & FMODE_READ)
1438                 perm |= MAY_READ;
1439         if (mode & FMODE_WRITE)
1440                 perm |= MAY_WRITE;
1441         /*
1442          * hooks: /n/, see "layering violations".
1443          */
1444         if (!for_part) {
1445                 ret = devcgroup_inode_permission(bdev->bd_inode, perm);
1446                 if (ret != 0) {
1447                         bdput(bdev);
1448                         return ret;
1449                 }
1450         }
1451 
1452  restart:
1453 
1454         ret = -ENXIO;
1455         disk = bdev_get_gendisk(bdev, &partno);
1456         if (!disk)
1457                 goto out;
1458 
1459         disk_block_events(disk);
1460         mutex_lock_nested(&bdev->bd_mutex, for_part);
1461         if (!bdev->bd_openers) {
1462                 first_open = true;
1463                 bdev->bd_disk = disk;
1464                 bdev->bd_queue = disk->queue;
1465                 bdev->bd_contains = bdev;
1466                 bdev->bd_partno = partno;
1467 
1468                 if (!partno) {
1469                         ret = -ENXIO;
1470                         bdev->bd_part = disk_get_part(disk, partno);
1471                         if (!bdev->bd_part)
1472                                 goto out_clear;
1473 
1474                         ret = 0;
1475                         if (disk->fops->open) {
1476                                 ret = disk->fops->open(bdev, mode);
1477                                 if (ret == -ERESTARTSYS) {
1478                                         /* Lost a race with 'disk' being
1479                                          * deleted, try again.
1480                                          * See md.c
1481                                          */
1482                                         disk_put_part(bdev->bd_part);
1483                                         bdev->bd_part = NULL;
1484                                         bdev->bd_disk = NULL;
1485                                         bdev->bd_queue = NULL;
1486                                         mutex_unlock(&bdev->bd_mutex);
1487                                         disk_unblock_events(disk);
1488                                         put_disk_and_module(disk);
1489                                         goto restart;
1490                                 }
1491                         }
1492 
1493                         if (!ret)
1494                                 bd_set_size(bdev,(loff_t)get_capacity(disk)<<9);
1495 
1496                         /*
1497                          * If the device is invalidated, rescan partition
1498                          * if open succeeded or failed with -ENOMEDIUM.
1499                          * The latter is necessary to prevent ghost
1500                          * partitions on a removed medium.
1501                          */
1502                         if (bdev->bd_invalidated) {
1503                                 if (!ret)
1504                                         rescan_partitions(disk, bdev);
1505                                 else if (ret == -ENOMEDIUM)
1506                                         invalidate_partitions(disk, bdev);
1507                         }
1508 
1509                         if (ret)
1510                                 goto out_clear;
1511                 } else {
1512                         struct block_device *whole;
1513                         whole = bdget_disk(disk, 0);
1514                         ret = -ENOMEM;
1515                         if (!whole)
1516                                 goto out_clear;
1517                         BUG_ON(for_part);
1518                         ret = __blkdev_get(whole, mode, 1);
1519                         if (ret)
1520                                 goto out_clear;
1521                         bdev->bd_contains = whole;
1522                         bdev->bd_part = disk_get_part(disk, partno);
1523                         if (!(disk->flags & GENHD_FL_UP) ||
1524                             !bdev->bd_part || !bdev->bd_part->nr_sects) {
1525                                 ret = -ENXIO;
1526                                 goto out_clear;
1527                         }
1528                         bd_set_size(bdev, (loff_t)bdev->bd_part->nr_sects << 9);
1529                 }
1530 
1531                 if (bdev->bd_bdi == &noop_backing_dev_info)
1532                         bdev->bd_bdi = bdi_get(disk->queue->backing_dev_info);
1533         } else {
1534                 if (bdev->bd_contains == bdev) {
1535                         ret = 0;
1536                         if (bdev->bd_disk->fops->open)
1537                                 ret = bdev->bd_disk->fops->open(bdev, mode);
1538                         /* the same as first opener case, read comment there */
1539                         if (bdev->bd_invalidated) {
1540                                 if (!ret)
1541                                         rescan_partitions(bdev->bd_disk, bdev);
1542                                 else if (ret == -ENOMEDIUM)
1543                                         invalidate_partitions(bdev->bd_disk, bdev);
1544                         }
1545                         if (ret)
1546                                 goto out_unlock_bdev;
1547                 }
1548         }
1549         bdev->bd_openers++;
1550         if (for_part)
1551                 bdev->bd_part_count++;
1552         mutex_unlock(&bdev->bd_mutex);
1553         disk_unblock_events(disk);
1554         /* only one opener holds refs to the module and disk */
1555         if (!first_open)
1556                 put_disk_and_module(disk);
1557         return 0;
1558 
1559  out_clear:
1560         disk_put_part(bdev->bd_part);
1561         bdev->bd_disk = NULL;
1562         bdev->bd_part = NULL;
1563         bdev->bd_queue = NULL;
1564         if (bdev != bdev->bd_contains)
1565                 __blkdev_put(bdev->bd_contains, mode, 1);
1566         bdev->bd_contains = NULL;
1567  out_unlock_bdev:
1568         mutex_unlock(&bdev->bd_mutex);
1569         disk_unblock_events(disk);
1570         put_disk_and_module(disk);
1571  out:
1572         bdput(bdev);
1573 
1574         return ret;
1575 }
1576 
1577 /**
1578  * blkdev_get - open a block device
1579  * @bdev: block_device to open
1580  * @mode: FMODE_* mask
1581  * @holder: exclusive holder identifier
1582  *
1583  * Open @bdev with @mode.  If @mode includes %FMODE_EXCL, @bdev is
1584  * open with exclusive access.  Specifying %FMODE_EXCL with %NULL
1585  * @holder is invalid.  Exclusive opens may nest for the same @holder.
1586  *
1587  * On success, the reference count of @bdev is unchanged.  On failure,
1588  * @bdev is put.
1589  *
1590  * CONTEXT:
1591  * Might sleep.
1592  *
1593  * RETURNS:
1594  * 0 on success, -errno on failure.
1595  */
1596 int blkdev_get(struct block_device *bdev, fmode_t mode, void *holder)
1597 {
1598         struct block_device *whole = NULL;
1599         int res;
1600 
1601         WARN_ON_ONCE((mode & FMODE_EXCL) && !holder);
1602 
1603         if ((mode & FMODE_EXCL) && holder) {
1604                 whole = bd_start_claiming(bdev, holder);
1605                 if (IS_ERR(whole)) {
1606                         bdput(bdev);
1607                         return PTR_ERR(whole);
1608                 }
1609         }
1610 
1611         res = __blkdev_get(bdev, mode, 0);
1612 
1613         if (whole) {
1614                 struct gendisk *disk = whole->bd_disk;
1615 
1616                 /* finish claiming */
1617                 mutex_lock(&bdev->bd_mutex);
1618                 spin_lock(&bdev_lock);
1619 
1620                 if (!res) {
1621                         BUG_ON(!bd_may_claim(bdev, whole, holder));
1622                         /*
1623                          * Note that for a whole device bd_holders
1624                          * will be incremented twice, and bd_holder
1625                          * will be set to bd_may_claim before being
1626                          * set to holder
1627                          */
1628                         whole->bd_holders++;
1629                         whole->bd_holder = bd_may_claim;
1630                         bdev->bd_holders++;
1631                         bdev->bd_holder = holder;
1632                 }
1633 
1634                 /* tell others that we're done */
1635                 BUG_ON(whole->bd_claiming != holder);
1636                 whole->bd_claiming = NULL;
1637                 wake_up_bit(&whole->bd_claiming, 0);
1638 
1639                 spin_unlock(&bdev_lock);
1640 
1641                 /*
1642                  * Block event polling for write claims if requested.  Any
1643                  * write holder makes the write_holder state stick until
1644                  * all are released.  This is good enough and tracking
1645                  * individual writeable reference is too fragile given the
1646                  * way @mode is used in blkdev_get/put().
1647                  */
1648                 if (!res && (mode & FMODE_WRITE) && !bdev->bd_write_holder &&
1649                     (disk->flags & GENHD_FL_BLOCK_EVENTS_ON_EXCL_WRITE)) {
1650                         bdev->bd_write_holder = true;
1651                         disk_block_events(disk);
1652                 }
1653 
1654                 mutex_unlock(&bdev->bd_mutex);
1655                 bdput(whole);
1656         }
1657 
1658         return res;
1659 }
1660 EXPORT_SYMBOL(blkdev_get);
1661 
1662 /**
1663  * blkdev_get_by_path - open a block device by name
1664  * @path: path to the block device to open
1665  * @mode: FMODE_* mask
1666  * @holder: exclusive holder identifier
1667  *
1668  * Open the blockdevice described by the device file at @path.  @mode
1669  * and @holder are identical to blkdev_get().
1670  *
1671  * On success, the returned block_device has reference count of one.
1672  *
1673  * CONTEXT:
1674  * Might sleep.
1675  *
1676  * RETURNS:
1677  * Pointer to block_device on success, ERR_PTR(-errno) on failure.
1678  */
1679 struct block_device *blkdev_get_by_path(const char *path, fmode_t mode,
1680                                         void *holder)
1681 {
1682         struct block_device *bdev;
1683         int err;
1684 
1685         bdev = lookup_bdev(path);
1686         if (IS_ERR(bdev))
1687                 return bdev;
1688 
1689         err = blkdev_get(bdev, mode, holder);
1690         if (err)
1691                 return ERR_PTR(err);
1692 
1693         if ((mode & FMODE_WRITE) && bdev_read_only(bdev)) {
1694                 blkdev_put(bdev, mode);
1695                 return ERR_PTR(-EACCES);
1696         }
1697 
1698         return bdev;
1699 }
1700 EXPORT_SYMBOL(blkdev_get_by_path);
1701 
1702 /**
1703  * blkdev_get_by_dev - open a block device by device number
1704  * @dev: device number of block device to open
1705  * @mode: FMODE_* mask
1706  * @holder: exclusive holder identifier
1707  *
1708  * Open the blockdevice described by device number @dev.  @mode and
1709  * @holder are identical to blkdev_get().
1710  *
1711  * Use it ONLY if you really do not have anything better - i.e. when
1712  * you are behind a truly sucky interface and all you are given is a
1713  * device number.  _Never_ to be used for internal purposes.  If you
1714  * ever need it - reconsider your API.
1715  *
1716  * On success, the returned block_device has reference count of one.
1717  *
1718  * CONTEXT:
1719  * Might sleep.
1720  *
1721  * RETURNS:
1722  * Pointer to block_device on success, ERR_PTR(-errno) on failure.
1723  */
1724 struct block_device *blkdev_get_by_dev(dev_t dev, fmode_t mode, void *holder)
1725 {
1726         struct block_device *bdev;
1727         int err;
1728 
1729         bdev = bdget(dev);
1730         if (!bdev)
1731                 return ERR_PTR(-ENOMEM);
1732 
1733         err = blkdev_get(bdev, mode, holder);
1734         if (err)
1735                 return ERR_PTR(err);
1736 
1737         return bdev;
1738 }
1739 EXPORT_SYMBOL(blkdev_get_by_dev);
1740 
1741 static int blkdev_open(struct inode * inode, struct file * filp)
1742 {
1743         struct block_device *bdev;
1744 
1745         /*
1746          * Preserve backwards compatibility and allow large file access
1747          * even if userspace doesn't ask for it explicitly. Some mkfs
1748          * binary needs it. We might want to drop this workaround
1749          * during an unstable branch.
1750          */
1751         filp->f_flags |= O_LARGEFILE;
1752 
1753         filp->f_mode |= FMODE_NOWAIT;
1754 
1755         if (filp->f_flags & O_NDELAY)
1756                 filp->f_mode |= FMODE_NDELAY;
1757         if (filp->f_flags & O_EXCL)
1758                 filp->f_mode |= FMODE_EXCL;
1759         if ((filp->f_flags & O_ACCMODE) == 3)
1760                 filp->f_mode |= FMODE_WRITE_IOCTL;
1761 
1762         bdev = bd_acquire(inode);
1763         if (bdev == NULL)
1764                 return -ENOMEM;
1765 
1766         filp->f_mapping = bdev->bd_inode->i_mapping;
1767         filp->f_wb_err = filemap_sample_wb_err(filp->f_mapping);
1768 
1769         return blkdev_get(bdev, filp->f_mode, filp);
1770 }
1771 
1772 static void __blkdev_put(struct block_device *bdev, fmode_t mode, int for_part)
1773 {
1774         struct gendisk *disk = bdev->bd_disk;
1775         struct block_device *victim = NULL;
1776 
1777         mutex_lock_nested(&bdev->bd_mutex, for_part);
1778         if (for_part)
1779                 bdev->bd_part_count--;
1780 
1781         if (!--bdev->bd_openers) {
1782                 WARN_ON_ONCE(bdev->bd_holders);
1783                 sync_blockdev(bdev);
1784                 kill_bdev(bdev);
1785 
1786                 bdev_write_inode(bdev);
1787         }
1788         if (bdev->bd_contains == bdev) {
1789                 if (disk->fops->release)
1790                         disk->fops->release(disk, mode);
1791         }
1792         if (!bdev->bd_openers) {
1793                 disk_put_part(bdev->bd_part);
1794                 bdev->bd_part = NULL;
1795                 bdev->bd_disk = NULL;
1796                 if (bdev != bdev->bd_contains)
1797                         victim = bdev->bd_contains;
1798                 bdev->bd_contains = NULL;
1799 
1800                 put_disk_and_module(disk);
1801         }
1802         mutex_unlock(&bdev->bd_mutex);
1803         bdput(bdev);
1804         if (victim)
1805                 __blkdev_put(victim, mode, 1);
1806 }
1807 
1808 void blkdev_put(struct block_device *bdev, fmode_t mode)
1809 {
1810         mutex_lock(&bdev->bd_mutex);
1811 
1812         if (mode & FMODE_EXCL) {
1813                 bool bdev_free;
1814 
1815                 /*
1816                  * Release a claim on the device.  The holder fields
1817                  * are protected with bdev_lock.  bd_mutex is to
1818                  * synchronize disk_holder unlinking.
1819                  */
1820                 spin_lock(&bdev_lock);
1821 
1822                 WARN_ON_ONCE(--bdev->bd_holders < 0);
1823                 WARN_ON_ONCE(--bdev->bd_contains->bd_holders < 0);
1824 
1825                 /* bd_contains might point to self, check in a separate step */
1826                 if ((bdev_free = !bdev->bd_holders))
1827                         bdev->bd_holder = NULL;
1828                 if (!bdev->bd_contains->bd_holders)
1829                         bdev->bd_contains->bd_holder = NULL;
1830 
1831                 spin_unlock(&bdev_lock);
1832 
1833                 /*
1834                  * If this was the last claim, remove holder link and
1835                  * unblock evpoll if it was a write holder.
1836                  */
1837                 if (bdev_free && bdev->bd_write_holder) {
1838                         disk_unblock_events(bdev->bd_disk);
1839                         bdev->bd_write_holder = false;
1840                 }
1841         }
1842 
1843         /*
1844          * Trigger event checking and tell drivers to flush MEDIA_CHANGE
1845          * event.  This is to ensure detection of media removal commanded
1846          * from userland - e.g. eject(1).
1847          */
1848         disk_flush_events(bdev->bd_disk, DISK_EVENT_MEDIA_CHANGE);
1849 
1850         mutex_unlock(&bdev->bd_mutex);
1851 
1852         __blkdev_put(bdev, mode, 0);
1853 }
1854 EXPORT_SYMBOL(blkdev_put);
1855 
1856 static int blkdev_close(struct inode * inode, struct file * filp)
1857 {
1858         struct block_device *bdev = I_BDEV(bdev_file_inode(filp));
1859         blkdev_put(bdev, filp->f_mode);
1860         return 0;
1861 }
1862 
1863 static long block_ioctl(struct file *file, unsigned cmd, unsigned long arg)
1864 {
1865         struct block_device *bdev = I_BDEV(bdev_file_inode(file));
1866         fmode_t mode = file->f_mode;
1867 
1868         /*
1869          * O_NDELAY can be altered using fcntl(.., F_SETFL, ..), so we have
1870          * to updated it before every ioctl.
1871          */
1872         if (file->f_flags & O_NDELAY)
1873                 mode |= FMODE_NDELAY;
1874         else
1875                 mode &= ~FMODE_NDELAY;
1876 
1877         return blkdev_ioctl(bdev, mode, cmd, arg);
1878 }
1879 
1880 /*
1881  * Write data to the block device.  Only intended for the block device itself
1882  * and the raw driver which basically is a fake block device.
1883  *
1884  * Does not take i_mutex for the write and thus is not for general purpose
1885  * use.
1886  */
1887 ssize_t blkdev_write_iter(struct kiocb *iocb, struct iov_iter *from)
1888 {
1889         struct file *file = iocb->ki_filp;
1890         struct inode *bd_inode = bdev_file_inode(file);
1891         loff_t size = i_size_read(bd_inode);
1892         struct blk_plug plug;
1893         ssize_t ret;
1894 
1895         if (bdev_read_only(I_BDEV(bd_inode)))
1896                 return -EPERM;
1897 
1898         if (!iov_iter_count(from))
1899                 return 0;
1900 
1901         if (iocb->ki_pos >= size)
1902                 return -ENOSPC;
1903 
1904         if ((iocb->ki_flags & (IOCB_NOWAIT | IOCB_DIRECT)) == IOCB_NOWAIT)
1905                 return -EOPNOTSUPP;
1906 
1907         iov_iter_truncate(from, size - iocb->ki_pos);
1908 
1909         blk_start_plug(&plug);
1910         ret = __generic_file_write_iter(iocb, from);
1911         if (ret > 0)
1912                 ret = generic_write_sync(iocb, ret);
1913         blk_finish_plug(&plug);
1914         return ret;
1915 }
1916 EXPORT_SYMBOL_GPL(blkdev_write_iter);
1917 
1918 ssize_t blkdev_read_iter(struct kiocb *iocb, struct iov_iter *to)
1919 {
1920         struct file *file = iocb->ki_filp;
1921         struct inode *bd_inode = bdev_file_inode(file);
1922         loff_t size = i_size_read(bd_inode);
1923         loff_t pos = iocb->ki_pos;
1924 
1925         if (pos >= size)
1926                 return 0;
1927 
1928         size -= pos;
1929         iov_iter_truncate(to, size);
1930         return generic_file_read_iter(iocb, to);
1931 }
1932 EXPORT_SYMBOL_GPL(blkdev_read_iter);
1933 
1934 /*
1935  * Try to release a page associated with block device when the system
1936  * is under memory pressure.
1937  */
1938 static int blkdev_releasepage(struct page *page, gfp_t wait)
1939 {
1940         struct super_block *super = BDEV_I(page->mapping->host)->bdev.bd_super;
1941 
1942         if (super && super->s_op->bdev_try_to_free_page)
1943                 return super->s_op->bdev_try_to_free_page(super, page, wait);
1944 
1945         return try_to_free_buffers(page);
1946 }
1947 
1948 static int blkdev_writepages(struct address_space *mapping,
1949                              struct writeback_control *wbc)
1950 {
1951         return generic_writepages(mapping, wbc);
1952 }
1953 
1954 static const struct address_space_operations def_blk_aops = {
1955         .readpage       = blkdev_readpage,
1956         .readpages      = blkdev_readpages,
1957         .writepage      = blkdev_writepage,
1958         .write_begin    = blkdev_write_begin,
1959         .write_end      = blkdev_write_end,
1960         .writepages     = blkdev_writepages,
1961         .releasepage    = blkdev_releasepage,
1962         .direct_IO      = blkdev_direct_IO,
1963         .is_dirty_writeback = buffer_check_dirty_writeback,
1964 };
1965 
1966 #define BLKDEV_FALLOC_FL_SUPPORTED                                      \
1967                 (FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE |           \
1968                  FALLOC_FL_ZERO_RANGE | FALLOC_FL_NO_HIDE_STALE)
1969 
1970 static long blkdev_fallocate(struct file *file, int mode, loff_t start,
1971                              loff_t len)
1972 {
1973         struct block_device *bdev = I_BDEV(bdev_file_inode(file));
1974         struct address_space *mapping;
1975         loff_t end = start + len - 1;
1976         loff_t isize;
1977         int error;
1978 
1979         /* Fail if we don't recognize the flags. */
1980         if (mode & ~BLKDEV_FALLOC_FL_SUPPORTED)
1981                 return -EOPNOTSUPP;
1982 
1983         /* Don't go off the end of the device. */
1984         isize = i_size_read(bdev->bd_inode);
1985         if (start >= isize)
1986                 return -EINVAL;
1987         if (end >= isize) {
1988                 if (mode & FALLOC_FL_KEEP_SIZE) {
1989                         len = isize - start;
1990                         end = start + len - 1;
1991                 } else
1992                         return -EINVAL;
1993         }
1994 
1995         /*
1996          * Don't allow IO that isn't aligned to logical block size.
1997          */
1998         if ((start | len) & (bdev_logical_block_size(bdev) - 1))
1999                 return -EINVAL;
2000 
2001         /* Invalidate the page cache, including dirty pages. */
2002         mapping = bdev->bd_inode->i_mapping;
2003         truncate_inode_pages_range(mapping, start, end);
2004 
2005         switch (mode) {
2006         case FALLOC_FL_ZERO_RANGE:
2007         case FALLOC_FL_ZERO_RANGE | FALLOC_FL_KEEP_SIZE:
2008                 error = blkdev_issue_zeroout(bdev, start >> 9, len >> 9,
2009                                             GFP_KERNEL, BLKDEV_ZERO_NOUNMAP);
2010                 break;
2011         case FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE:
2012                 error = blkdev_issue_zeroout(bdev, start >> 9, len >> 9,
2013                                              GFP_KERNEL, BLKDEV_ZERO_NOFALLBACK);
2014                 break;
2015         case FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE | FALLOC_FL_NO_HIDE_STALE:
2016                 error = blkdev_issue_discard(bdev, start >> 9, len >> 9,
2017                                              GFP_KERNEL, 0);
2018                 break;
2019         default:
2020                 return -EOPNOTSUPP;
2021         }
2022         if (error)
2023                 return error;
2024 
2025         /*
2026          * Invalidate again; if someone wandered in and dirtied a page,
2027          * the caller will be given -EBUSY.  The third argument is
2028          * inclusive, so the rounding here is safe.
2029          */
2030         return invalidate_inode_pages2_range(mapping,
2031                                              start >> PAGE_SHIFT,
2032                                              end >> PAGE_SHIFT);
2033 }
2034 
2035 const struct file_operations def_blk_fops = {
2036         .open           = blkdev_open,
2037         .release        = blkdev_close,
2038         .llseek         = block_llseek,
2039         .read_iter      = blkdev_read_iter,
2040         .write_iter     = blkdev_write_iter,
2041         .mmap           = generic_file_mmap,
2042         .fsync          = blkdev_fsync,
2043         .unlocked_ioctl = block_ioctl,
2044 #ifdef CONFIG_COMPAT
2045         .compat_ioctl   = compat_blkdev_ioctl,
2046 #endif
2047         .splice_read    = generic_file_splice_read,
2048         .splice_write   = iter_file_splice_write,
2049         .fallocate      = blkdev_fallocate,
2050 };
2051 
2052 int ioctl_by_bdev(struct block_device *bdev, unsigned cmd, unsigned long arg)
2053 {
2054         int res;
2055         mm_segment_t old_fs = get_fs();
2056         set_fs(KERNEL_DS);
2057         res = blkdev_ioctl(bdev, 0, cmd, arg);
2058         set_fs(old_fs);
2059         return res;
2060 }
2061 
2062 EXPORT_SYMBOL(ioctl_by_bdev);
2063 
2064 /**
2065  * lookup_bdev  - lookup a struct block_device by name
2066  * @pathname:   special file representing the block device
2067  *
2068  * Get a reference to the blockdevice at @pathname in the current
2069  * namespace if possible and return it.  Return ERR_PTR(error)
2070  * otherwise.
2071  */
2072 struct block_device *lookup_bdev(const char *pathname)
2073 {
2074         struct block_device *bdev;
2075         struct inode *inode;
2076         struct path path;
2077         int error;
2078 
2079         if (!pathname || !*pathname)
2080                 return ERR_PTR(-EINVAL);
2081 
2082         error = kern_path(pathname, LOOKUP_FOLLOW, &path);
2083         if (error)
2084                 return ERR_PTR(error);
2085 
2086         inode = d_backing_inode(path.dentry);
2087         error = -ENOTBLK;
2088         if (!S_ISBLK(inode->i_mode))
2089                 goto fail;
2090         error = -EACCES;
2091         if (!may_open_dev(&path))
2092                 goto fail;
2093         error = -ENOMEM;
2094         bdev = bd_acquire(inode);
2095         if (!bdev)
2096                 goto fail;
2097 out:
2098         path_put(&path);
2099         return bdev;
2100 fail:
2101         bdev = ERR_PTR(error);
2102         goto out;
2103 }
2104 EXPORT_SYMBOL(lookup_bdev);
2105 
2106 int __invalidate_device(struct block_device *bdev, bool kill_dirty)
2107 {
2108         struct super_block *sb = get_super(bdev);
2109         int res = 0;
2110 
2111         if (sb) {
2112                 /*
2113                  * no need to lock the super, get_super holds the
2114                  * read mutex so the filesystem cannot go away
2115                  * under us (->put_super runs with the write lock
2116                  * hold).
2117                  */
2118                 shrink_dcache_sb(sb);
2119                 res = invalidate_inodes(sb, kill_dirty);
2120                 drop_super(sb);
2121         }
2122         invalidate_bdev(bdev);
2123         return res;
2124 }
2125 EXPORT_SYMBOL(__invalidate_device);
2126 
2127 void iterate_bdevs(void (*func)(struct block_device *, void *), void *arg)
2128 {
2129         struct inode *inode, *old_inode = NULL;
2130 
2131         spin_lock(&blockdev_superblock->s_inode_list_lock);
2132         list_for_each_entry(inode, &blockdev_superblock->s_inodes, i_sb_list) {
2133                 struct address_space *mapping = inode->i_mapping;
2134                 struct block_device *bdev;
2135 
2136                 spin_lock(&inode->i_lock);
2137                 if (inode->i_state & (I_FREEING|I_WILL_FREE|I_NEW) ||
2138                     mapping->nrpages == 0) {
2139                         spin_unlock(&inode->i_lock);
2140                         continue;
2141                 }
2142                 __iget(inode);
2143                 spin_unlock(&inode->i_lock);
2144                 spin_unlock(&blockdev_superblock->s_inode_list_lock);
2145                 /*
2146                  * We hold a reference to 'inode' so it couldn't have been
2147                  * removed from s_inodes list while we dropped the
2148                  * s_inode_list_lock  We cannot iput the inode now as we can
2149                  * be holding the last reference and we cannot iput it under
2150                  * s_inode_list_lock. So we keep the reference and iput it
2151                  * later.
2152                  */
2153                 iput(old_inode);
2154                 old_inode = inode;
2155                 bdev = I_BDEV(inode);
2156 
2157                 mutex_lock(&bdev->bd_mutex);
2158                 if (bdev->bd_openers)
2159                         func(bdev, arg);
2160                 mutex_unlock(&bdev->bd_mutex);
2161 
2162                 spin_lock(&blockdev_superblock->s_inode_list_lock);
2163         }
2164         spin_unlock(&blockdev_superblock->s_inode_list_lock);
2165         iput(old_inode);
2166 }
2167 

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