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	Version: linux-6.0.1 spark-3.0.0 hadoop-3.2.0-src hadoop-3.3.0-src spark-2.4.7 linux-4.15.13 hadoop-2.7.4-src Revert   Change

 // SPDX-License-Identifier: GPL-2.0-only
 /*
  *  Copyright (C) 1991, 1992  Linus Torvalds
  *  Copyright (C) 2001  Andrea Arcangeli <andrea@suse.de> SuSE
  *  Copyright (C) 2016 - 2020 Christoph Hellwig
  */
 
 #include <linux/init.h>
 #include <linux/mm.h>
 #include <linux/slab.h>
 #include <linux/kmod.h>
 #include <linux/major.h>
 #include <linux/device_cgroup.h>
 #include <linux/blkdev.h>
 #include <linux/blk-integrity.h>
 #include <linux/backing-dev.h>
 #include <linux/module.h>
 #include <linux/blkpg.h>
 #include <linux/magic.h>
 #include <linux/buffer_head.h>
 #include <linux/swap.h>
 #include <linux/writeback.h>
 #include <linux/mount.h>
 #include <linux/pseudo_fs.h>
 #include <linux/uio.h>
 #include <linux/namei.h>
 #include <linux/part_stat.h>
 #include <linux/uaccess.h>
 #include "../fs/internal.h"
 #include "blk.h"
 
 struct bdev_inode {
     struct block_device bdev;
     struct inode vfs_inode;
 };
 
 static inline struct bdev_inode *BDEV_I(struct inode *inode)
 {
     return container_of(inode, struct bdev_inode, vfs_inode);
 }
 
 struct block_device *I_BDEV(struct inode *inode)
 {
     return &BDEV_I(inode)->bdev;
 }
 EXPORT_SYMBOL(I_BDEV);
 
 static void bdev_write_inode(struct block_device *bdev)
 {
     struct inode *inode = bdev->bd_inode;
     int ret;
 
     spin_lock(&inode->i_lock);
     while (inode->i_state & I_DIRTY) {
         spin_unlock(&inode->i_lock);
         ret = write_inode_now(inode, true);
         if (ret)
             pr_warn_ratelimited(
     "VFS: Dirty inode writeback failed for block device %pg (err=%d).\n",
                 bdev, ret);
         spin_lock(&inode->i_lock);
     }
     spin_unlock(&inode->i_lock);
 }
 
 /* Kill _all_ buffers and pagecache , dirty or not.. */
 static void kill_bdev(struct block_device *bdev)
 {
     struct address_space *mapping = bdev->bd_inode->i_mapping;
 
     if (mapping_empty(mapping))
         return;
 
     invalidate_bh_lrus();
     truncate_inode_pages(mapping, 0);
 }
 
 /* Invalidate clean unused buffers and pagecache. */
 void invalidate_bdev(struct block_device *bdev)
 {
     struct address_space *mapping = bdev->bd_inode->i_mapping;
 
     if (mapping->nrpages) {
         invalidate_bh_lrus();
         lru_add_drain_all();    /* make sure all lru add caches are flushed */
         invalidate_mapping_pages(mapping, 0, -1);
     }
 }
 EXPORT_SYMBOL(invalidate_bdev);
 
 /*
  * Drop all buffers & page cache for given bdev range. This function bails
  * with error if bdev has other exclusive owner (such as filesystem).
  */
 int truncate_bdev_range(struct block_device *bdev, fmode_t mode,
             loff_t lstart, loff_t lend)
 {
     /*
      * If we don't hold exclusive handle for the device, upgrade to it
      * while we discard the buffer cache to avoid discarding buffers
      * under live filesystem.
      */
     if (!(mode & FMODE_EXCL)) {
         int err = bd_prepare_to_claim(bdev, truncate_bdev_range);
         if (err)
             goto invalidate;
     }
 
     truncate_inode_pages_range(bdev->bd_inode->i_mapping, lstart, lend);
     if (!(mode & FMODE_EXCL))
         bd_abort_claiming(bdev, truncate_bdev_range);
     return 0;
 
 invalidate:
     /*
      * Someone else has handle exclusively open. Try invalidating instead.
      * The 'end' argument is inclusive so the rounding is safe.
      */
     return invalidate_inode_pages2_range(bdev->bd_inode->i_mapping,
                          lstart >> PAGE_SHIFT,
                          lend >> PAGE_SHIFT);
 }
 
 static void set_init_blocksize(struct block_device *bdev)
 {
     unsigned int bsize = bdev_logical_block_size(bdev);
     loff_t size = i_size_read(bdev->bd_inode);
 
     while (bsize < PAGE_SIZE) {
         if (size & bsize)
             break;
         bsize <<= 1;
     }
     bdev->bd_inode->i_blkbits = blksize_bits(bsize);
 }
 
 int set_blocksize(struct block_device *bdev, int size)
 {
     /* Size must be a power of two, and between 512 and PAGE_SIZE */
     if (size > PAGE_SIZE || size < 512 || !is_power_of_2(size))
         return -EINVAL;
 
     /* Size cannot be smaller than the size supported by the device */
     if (size < bdev_logical_block_size(bdev))
         return -EINVAL;
 
     /* Don't change the size if it is same as current */
     if (bdev->bd_inode->i_blkbits != blksize_bits(size)) {
         sync_blockdev(bdev);
         bdev->bd_inode->i_blkbits = blksize_bits(size);
         kill_bdev(bdev);
     }
     return 0;
 }
 
 EXPORT_SYMBOL(set_blocksize);
 
 int sb_set_blocksize(struct super_block *sb, int size)
 {
     if (set_blocksize(sb->s_bdev, size))
         return 0;
     /* If we get here, we know size is power of two
      * and it's value is between 512 and PAGE_SIZE */
     sb->s_blocksize = size;
     sb->s_blocksize_bits = blksize_bits(size);
     return sb->s_blocksize;
 }
 
 EXPORT_SYMBOL(sb_set_blocksize);
 
 int sb_min_blocksize(struct super_block *sb, int size)
 {
     int minsize = bdev_logical_block_size(sb->s_bdev);
     if (size < minsize)
         size = minsize;
     return sb_set_blocksize(sb, size);
 }
 
 EXPORT_SYMBOL(sb_min_blocksize);
 
 int sync_blockdev_nowait(struct block_device *bdev)
 {
     if (!bdev)
         return 0;
     return filemap_flush(bdev->bd_inode->i_mapping);
 }
 EXPORT_SYMBOL_GPL(sync_blockdev_nowait);
 
 /*
  * Write out and wait upon all the dirty data associated with a block
  * device via its mapping.  Does not take the superblock lock.
  */
 int sync_blockdev(struct block_device *bdev)
 {
     if (!bdev)
         return 0;
     return filemap_write_and_wait(bdev->bd_inode->i_mapping);
 }
 EXPORT_SYMBOL(sync_blockdev);
 
 int sync_blockdev_range(struct block_device *bdev, loff_t lstart, loff_t lend)
 {
     return filemap_write_and_wait_range(bdev->bd_inode->i_mapping,
             lstart, lend);
 }
 EXPORT_SYMBOL(sync_blockdev_range);
 
 /*
  * Write out and wait upon all dirty data associated with this
  * device.   Filesystem data as well as the underlying block
  * device.  Takes the superblock lock.
  */
 int fsync_bdev(struct block_device *bdev)
 {
     struct super_block *sb = get_super(bdev);
     if (sb) {
         int res = sync_filesystem(sb);
         drop_super(sb);
         return res;
     }
     return sync_blockdev(bdev);
 }
 EXPORT_SYMBOL(fsync_bdev);
 
 /**
  * freeze_bdev  --  lock a filesystem and force it into a consistent state
  * @bdev:   blockdevice to lock
  *
  * If a superblock is found on this device, we take the s_umount semaphore
  * on it to make sure nobody unmounts until the snapshot creation is done.
  * The reference counter (bd_fsfreeze_count) guarantees that only the last
  * unfreeze process can unfreeze the frozen filesystem actually when multiple
  * freeze requests arrive simultaneously. It counts up in freeze_bdev() and
  * count down in thaw_bdev(). When it becomes 0, thaw_bdev() will unfreeze
  * actually.
  */
 int freeze_bdev(struct block_device *bdev)
 {
     struct super_block *sb;
     int error = 0;
 
     mutex_lock(&bdev->bd_fsfreeze_mutex);
     if (++bdev->bd_fsfreeze_count > 1)
         goto done;
 
     sb = get_active_super(bdev);
     if (!sb)
         goto sync;
     if (sb->s_op->freeze_super)
         error = sb->s_op->freeze_super(sb);
     else
         error = freeze_super(sb);
     deactivate_super(sb);
 
     if (error) {
         bdev->bd_fsfreeze_count--;
         goto done;
     }
     bdev->bd_fsfreeze_sb = sb;
 
 sync:
     sync_blockdev(bdev);
 done:
     mutex_unlock(&bdev->bd_fsfreeze_mutex);
     return error;
 }
 EXPORT_SYMBOL(freeze_bdev);
 
 /**
  * thaw_bdev  -- unlock filesystem
  * @bdev:   blockdevice to unlock
  *
  * Unlocks the filesystem and marks it writeable again after freeze_bdev().
  */
 int thaw_bdev(struct block_device *bdev)
 {
     struct super_block *sb;
     int error = -EINVAL;
 
     mutex_lock(&bdev->bd_fsfreeze_mutex);
     if (!bdev->bd_fsfreeze_count)
         goto out;
 
     error = 0;
     if (--bdev->bd_fsfreeze_count > 0)
         goto out;
 
     sb = bdev->bd_fsfreeze_sb;
     if (!sb)
         goto out;
 
     if (sb->s_op->thaw_super)
         error = sb->s_op->thaw_super(sb);
     else
         error = thaw_super(sb);
     if (error)
         bdev->bd_fsfreeze_count++;
     else
         bdev->bd_fsfreeze_sb = NULL;
 out:
     mutex_unlock(&bdev->bd_fsfreeze_mutex);
     return error;
 }
 EXPORT_SYMBOL(thaw_bdev);
 
 /**
  * bdev_read_page() - Start reading a page from a block device
  * @bdev: The device to read the page from
  * @sector: The offset on the device to read the page to (need not be aligned)
  * @page: The page to read
  *
  * On entry, the page should be locked.  It will be unlocked when the page
  * has been read.  If the block driver implements rw_page synchronously,
  * that will be true on exit from this function, but it need not be.
  *
  * Errors returned by this function are usually "soft", eg out of memory, or
  * queue full; callers should try a different route to read this page rather
  * than propagate an error back up the stack.
  *
  * Return: negative errno if an error occurs, 0 if submission was successful.
  */
 int bdev_read_page(struct block_device *bdev, sector_t sector,
             struct page *page)
 {
     const struct block_device_operations *ops = bdev->bd_disk->fops;
     int result = -EOPNOTSUPP;
 
     if (!ops->rw_page || bdev_get_integrity(bdev))
         return result;
 
     result = blk_queue_enter(bdev_get_queue(bdev), 0);
     if (result)
         return result;
     result = ops->rw_page(bdev, sector + get_start_sect(bdev), page,
                   REQ_OP_READ);
     blk_queue_exit(bdev_get_queue(bdev));
     return result;
 }
 
 /**
  * bdev_write_page() - Start writing a page to a block device
  * @bdev: The device to write the page to
  * @sector: The offset on the device to write the page to (need not be aligned)
  * @page: The page to write
  * @wbc: The writeback_control for the write
  *
  * On entry, the page should be locked and not currently under writeback.
  * On exit, if the write started successfully, the page will be unlocked and
  * under writeback.  If the write failed already (eg the driver failed to
  * queue the page to the device), the page will still be locked.  If the
  * caller is a ->writepage implementation, it will need to unlock the page.
  *
  * Errors returned by this function are usually "soft", eg out of memory, or
  * queue full; callers should try a different route to write this page rather
  * than propagate an error back up the stack.
  *
  * Return: negative errno if an error occurs, 0 if submission was successful.
  */
 int bdev_write_page(struct block_device *bdev, sector_t sector,
             struct page *page, struct writeback_control *wbc)
 {
     int result;
     const struct block_device_operations *ops = bdev->bd_disk->fops;
 
     if (!ops->rw_page || bdev_get_integrity(bdev))
         return -EOPNOTSUPP;
     result = blk_queue_enter(bdev_get_queue(bdev), 0);
     if (result)
         return result;
 
     set_page_writeback(page);
     result = ops->rw_page(bdev, sector + get_start_sect(bdev), page,
                   REQ_OP_WRITE);
     if (result) {
         end_page_writeback(page);
     } else {
         clean_page_buffers(page);
         unlock_page(page);
     }
     blk_queue_exit(bdev_get_queue(bdev));
     return result;
 }
 
 /*
  * pseudo-fs
  */
 
 static  __cacheline_aligned_in_smp DEFINE_SPINLOCK(bdev_lock);
 static struct kmem_cache * bdev_cachep __read_mostly;
 
 static struct inode *bdev_alloc_inode(struct super_block *sb)
 {
     struct bdev_inode *ei = alloc_inode_sb(sb, bdev_cachep, GFP_KERNEL);
 
     if (!ei)
         return NULL;
     memset(&ei->bdev, 0, sizeof(ei->bdev));
     return &ei->vfs_inode;
 }
 
 static void bdev_free_inode(struct inode *inode)
 {
     struct block_device *bdev = I_BDEV(inode);
 
     free_percpu(bdev->bd_stats);
     kfree(bdev->bd_meta_info);
 
     if (!bdev_is_partition(bdev)) {
         if (bdev->bd_disk && bdev->bd_disk->bdi)
             bdi_put(bdev->bd_disk->bdi);
         kfree(bdev->bd_disk);
     }
 
     if (MAJOR(bdev->bd_dev) == BLOCK_EXT_MAJOR)
         blk_free_ext_minor(MINOR(bdev->bd_dev));
 
     kmem_cache_free(bdev_cachep, BDEV_I(inode));
 }
 
 static void init_once(void *data)
 {
     struct bdev_inode *ei = data;
 
     inode_init_once(&ei->vfs_inode);
 }
 
 static void bdev_evict_inode(struct inode *inode)
 {
     truncate_inode_pages_final(&inode->i_data);
     invalidate_inode_buffers(inode); /* is it needed here? */
     clear_inode(inode);
 }
 
 static const struct super_operations bdev_sops = {
     .statfs = simple_statfs,
     .alloc_inode = bdev_alloc_inode,
     .free_inode = bdev_free_inode,
     .drop_inode = generic_delete_inode,
     .evict_inode = bdev_evict_inode,
 };
 
 static int bd_init_fs_context(struct fs_context *fc)
 {
     struct pseudo_fs_context *ctx = init_pseudo(fc, BDEVFS_MAGIC);
     if (!ctx)
         return -ENOMEM;
     fc->s_iflags |= SB_I_CGROUPWB;
     ctx->ops = &bdev_sops;
     return 0;
 }
 
 static struct file_system_type bd_type = {
     .name       = "bdev",
     .init_fs_context = bd_init_fs_context,
     .kill_sb    = kill_anon_super,
 };
 
 struct super_block *blockdev_superblock __read_mostly;
 EXPORT_SYMBOL_GPL(blockdev_superblock);
 
 void __init bdev_cache_init(void)
 {
     int err;
     static struct vfsmount *bd_mnt;
 
     bdev_cachep = kmem_cache_create("bdev_cache", sizeof(struct bdev_inode),
             0, (SLAB_HWCACHE_ALIGN|SLAB_RECLAIM_ACCOUNT|
                 SLAB_MEM_SPREAD|SLAB_ACCOUNT|SLAB_PANIC),
             init_once);
     err = register_filesystem(&bd_type);
     if (err)
         panic("Cannot register bdev pseudo-fs");
     bd_mnt = kern_mount(&bd_type);
     if (IS_ERR(bd_mnt))
         panic("Cannot create bdev pseudo-fs");
     blockdev_superblock = bd_mnt->mnt_sb;   /* For writeback */
 }
 
 struct block_device *bdev_alloc(struct gendisk *disk, u8 partno)
 {
     struct block_device *bdev;
     struct inode *inode;
 
     inode = new_inode(blockdev_superblock);
     if (!inode)
         return NULL;
     inode->i_mode = S_IFBLK;
     inode->i_rdev = 0;
     inode->i_data.a_ops = &def_blk_aops;
     mapping_set_gfp_mask(&inode->i_data, GFP_USER);
 
     bdev = I_BDEV(inode);
     mutex_init(&bdev->bd_fsfreeze_mutex);
     spin_lock_init(&bdev->bd_size_lock);
     bdev->bd_partno = partno;
     bdev->bd_inode = inode;
     bdev->bd_queue = disk->queue;
     bdev->bd_stats = alloc_percpu(struct disk_stats);
     if (!bdev->bd_stats) {
         iput(inode);
         return NULL;
     }
     bdev->bd_disk = disk;
     return bdev;
 }
 
 void bdev_add(struct block_device *bdev, dev_t dev)
 {
     bdev->bd_dev = dev;
     bdev->bd_inode->i_rdev = dev;
     bdev->bd_inode->i_ino = dev;
     insert_inode_hash(bdev->bd_inode);
 }
 
 long nr_blockdev_pages(void)
 {
     struct inode *inode;
     long ret = 0;
 
     spin_lock(&blockdev_superblock->s_inode_list_lock);
     list_for_each_entry(inode, &blockdev_superblock->s_inodes, i_sb_list)
         ret += inode->i_mapping->nrpages;
     spin_unlock(&blockdev_superblock->s_inode_list_lock);
 
     return ret;
 }
 
 /**
  * bd_may_claim - test whether a block device can be claimed
  * @bdev: block device of interest
  * @whole: whole block device containing @bdev, may equal @bdev
  * @holder: holder trying to claim @bdev
  *
  * Test whether @bdev can be claimed by @holder.
  *
  * CONTEXT:
  * spin_lock(&bdev_lock).
  *
  * RETURNS:
  * %true if @bdev can be claimed, %false otherwise.
  */
 static bool bd_may_claim(struct block_device *bdev, struct block_device *whole,
              void *holder)
 {
     if (bdev->bd_holder == holder)
         return true;     /* already a holder */
     else if (bdev->bd_holder != NULL)
         return false;    /* held by someone else */
     else if (whole == bdev)
         return true;     /* is a whole device which isn't held */
 
     else if (whole->bd_holder == bd_may_claim)
         return true;     /* is a partition of a device that is being partitioned */
     else if (whole->bd_holder != NULL)
         return false;    /* is a partition of a held device */
     else
         return true;     /* is a partition of an un-held device */
 }
 
 /**
  * bd_prepare_to_claim - claim a block device
  * @bdev: block device of interest
  * @holder: holder trying to claim @bdev
  *
  * Claim @bdev.  This function fails if @bdev is already claimed by another
  * holder and waits if another claiming is in progress. return, the caller
  * has ownership of bd_claiming and bd_holder[s].
  *
  * RETURNS:
  * 0 if @bdev can be claimed, -EBUSY otherwise.
  */
 int bd_prepare_to_claim(struct block_device *bdev, void *holder)
 {
     struct block_device *whole = bdev_whole(bdev);
 
     if (WARN_ON_ONCE(!holder))
         return -EINVAL;
 retry:
     spin_lock(&bdev_lock);
     /* if someone else claimed, fail */
     if (!bd_may_claim(bdev, whole, holder)) {
         spin_unlock(&bdev_lock);
         return -EBUSY;
     }
 
     /* if claiming is already in progress, wait for it to finish */
     if (whole->bd_claiming) {
         wait_queue_head_t *wq = bit_waitqueue(&whole->bd_claiming, 0);
         DEFINE_WAIT(wait);
 
         prepare_to_wait(wq, &wait, TASK_UNINTERRUPTIBLE);
         spin_unlock(&bdev_lock);
         schedule();
         finish_wait(wq, &wait);
         goto retry;
     }
 
     /* yay, all mine */
     whole->bd_claiming = holder;
     spin_unlock(&bdev_lock);
     return 0;
 }
 EXPORT_SYMBOL_GPL(bd_prepare_to_claim); /* only for the loop driver */
 
 static void bd_clear_claiming(struct block_device *whole, void *holder)
 {
     lockdep_assert_held(&bdev_lock);
     /* tell others that we're done */
     BUG_ON(whole->bd_claiming != holder);
     whole->bd_claiming = NULL;
     wake_up_bit(&whole->bd_claiming, 0);
 }
 
 /**
  * bd_finish_claiming - finish claiming of a block device
  * @bdev: block device of interest
  * @holder: holder that has claimed @bdev
  *
  * Finish exclusive open of a block device. Mark the device as exlusively
  * open by the holder and wake up all waiters for exclusive open to finish.
  */
 static void bd_finish_claiming(struct block_device *bdev, void *holder)
 {
     struct block_device *whole = bdev_whole(bdev);
 
     spin_lock(&bdev_lock);
     BUG_ON(!bd_may_claim(bdev, whole, holder));
     /*
      * Note that for a whole device bd_holders will be incremented twice,
      * and bd_holder will be set to bd_may_claim before being set to holder
      */
     whole->bd_holders++;
     whole->bd_holder = bd_may_claim;
     bdev->bd_holders++;
     bdev->bd_holder = holder;
     bd_clear_claiming(whole, holder);
     spin_unlock(&bdev_lock);
 }
 
 /**
  * bd_abort_claiming - abort claiming of a block device
  * @bdev: block device of interest
  * @holder: holder that has claimed @bdev
  *
  * Abort claiming of a block device when the exclusive open failed. This can be
  * also used when exclusive open is not actually desired and we just needed
  * to block other exclusive openers for a while.
  */
 void bd_abort_claiming(struct block_device *bdev, void *holder)
 {
     spin_lock(&bdev_lock);
     bd_clear_claiming(bdev_whole(bdev), holder);
     spin_unlock(&bdev_lock);
 }
 EXPORT_SYMBOL(bd_abort_claiming);
 
 static void blkdev_flush_mapping(struct block_device *bdev)
 {
     WARN_ON_ONCE(bdev->bd_holders);
     sync_blockdev(bdev);
     kill_bdev(bdev);
     bdev_write_inode(bdev);
 }
 
 static int blkdev_get_whole(struct block_device *bdev, fmode_t mode)
 {
     struct gendisk *disk = bdev->bd_disk;
     int ret;
 
     if (disk->fops->open) {
         ret = disk->fops->open(bdev, mode);
         if (ret) {
             /* avoid ghost partitions on a removed medium */
             if (ret == -ENOMEDIUM &&
                  test_bit(GD_NEED_PART_SCAN, &disk->state))
                 bdev_disk_changed(disk, true);
             return ret;
         }
     }
 
     if (!atomic_read(&bdev->bd_openers))
         set_init_blocksize(bdev);
     if (test_bit(GD_NEED_PART_SCAN, &disk->state))
         bdev_disk_changed(disk, false);
     atomic_inc(&bdev->bd_openers);
     return 0;
 }
 
 static void blkdev_put_whole(struct block_device *bdev, fmode_t mode)
 {
     if (atomic_dec_and_test(&bdev->bd_openers))
         blkdev_flush_mapping(bdev);
     if (bdev->bd_disk->fops->release)
         bdev->bd_disk->fops->release(bdev->bd_disk, mode);
 }
 
 static int blkdev_get_part(struct block_device *part, fmode_t mode)
 {
     struct gendisk *disk = part->bd_disk;
     int ret;
 
     if (atomic_read(&part->bd_openers))
         goto done;
 
     ret = blkdev_get_whole(bdev_whole(part), mode);
     if (ret)
         return ret;
 
     ret = -ENXIO;
     if (!bdev_nr_sectors(part))
         goto out_blkdev_put;
 
     disk->open_partitions++;
     set_init_blocksize(part);
 done:
     atomic_inc(&part->bd_openers);
     return 0;
 
 out_blkdev_put:
     blkdev_put_whole(bdev_whole(part), mode);
     return ret;
 }
 
 static void blkdev_put_part(struct block_device *part, fmode_t mode)
 {
     struct block_device *whole = bdev_whole(part);
 
     if (!atomic_dec_and_test(&part->bd_openers))
         return;
     blkdev_flush_mapping(part);
     whole->bd_disk->open_partitions--;
     blkdev_put_whole(whole, mode);
 }
 
 struct block_device *blkdev_get_no_open(dev_t dev)
 {
     struct block_device *bdev;
     struct inode *inode;
 
     inode = ilookup(blockdev_superblock, dev);
     if (!inode && IS_ENABLED(CONFIG_BLOCK_LEGACY_AUTOLOAD)) {
         blk_request_module(dev);
         inode = ilookup(blockdev_superblock, dev);
         if (inode)
             pr_warn_ratelimited(
 "block device autoloading is deprecated and will be removed.\n");
     }
     if (!inode)
         return NULL;
 
     /* switch from the inode reference to a device mode one: */
     bdev = &BDEV_I(inode)->bdev;
     if (!kobject_get_unless_zero(&bdev->bd_device.kobj))
         bdev = NULL;
     iput(inode);
     return bdev;
 }
 
 void blkdev_put_no_open(struct block_device *bdev)
 {
     put_device(&bdev->bd_device);
 }
 
 /**
  * blkdev_get_by_dev - open a block device by device number
  * @dev: device number of block device to open
  * @mode: FMODE_* mask
  * @holder: exclusive holder identifier
  *
  * Open the block device described by device number @dev. If @mode includes
  * %FMODE_EXCL, the block device is opened with exclusive access.  Specifying
  * %FMODE_EXCL with a %NULL @holder is invalid.  Exclusive opens may nest for
  * the same @holder.
  *
  * Use this interface ONLY if you really do not have anything better - i.e. when
  * you are behind a truly sucky interface and all you are given is a device
  * number.  Everything else should use blkdev_get_by_path().
  *
  * CONTEXT:
  * Might sleep.
  *
  * RETURNS:
  * Reference to the block_device on success, ERR_PTR(-errno) on failure.
  */
 struct block_device *blkdev_get_by_dev(dev_t dev, fmode_t mode, void *holder)
 {
     bool unblock_events = true;
     struct block_device *bdev;
     struct gendisk *disk;
     int ret;
 
     ret = devcgroup_check_permission(DEVCG_DEV_BLOCK,
             MAJOR(dev), MINOR(dev),
             ((mode & FMODE_READ) ? DEVCG_ACC_READ : 0) |
             ((mode & FMODE_WRITE) ? DEVCG_ACC_WRITE : 0));
     if (ret)
         return ERR_PTR(ret);
 
     bdev = blkdev_get_no_open(dev);
     if (!bdev)
         return ERR_PTR(-ENXIO);
     disk = bdev->bd_disk;
 
     if (mode & FMODE_EXCL) {
         ret = bd_prepare_to_claim(bdev, holder);
         if (ret)
             goto put_blkdev;
     }
 
     disk_block_events(disk);
 
     mutex_lock(&disk->open_mutex);
     ret = -ENXIO;
     if (!disk_live(disk))
         goto abort_claiming;
     if (!try_module_get(disk->fops->owner))
         goto abort_claiming;
     if (bdev_is_partition(bdev))
         ret = blkdev_get_part(bdev, mode);
     else
         ret = blkdev_get_whole(bdev, mode);
     if (ret)
         goto put_module;
     if (mode & FMODE_EXCL) {
         bd_finish_claiming(bdev, holder);
 
         /*
          * Block event polling for write claims if requested.  Any write
          * holder makes the write_holder state stick until all are
          * released.  This is good enough and tracking individual
          * writeable reference is too fragile given the way @mode is
          * used in blkdev_get/put().
          */
         if ((mode & FMODE_WRITE) && !bdev->bd_write_holder &&
             (disk->event_flags & DISK_EVENT_FLAG_BLOCK_ON_EXCL_WRITE)) {
             bdev->bd_write_holder = true;
             unblock_events = false;
         }
     }
     mutex_unlock(&disk->open_mutex);
 
     if (unblock_events)
         disk_unblock_events(disk);
     return bdev;
 put_module:
     module_put(disk->fops->owner);
 abort_claiming:
     if (mode & FMODE_EXCL)
         bd_abort_claiming(bdev, holder);
     mutex_unlock(&disk->open_mutex);
     disk_unblock_events(disk);
 put_blkdev:
     blkdev_put_no_open(bdev);
     return ERR_PTR(ret);
 }
 EXPORT_SYMBOL(blkdev_get_by_dev);
 
 /**
  * blkdev_get_by_path - open a block device by name
  * @path: path to the block device to open
  * @mode: FMODE_* mask
  * @holder: exclusive holder identifier
  *
  * Open the block device described by the device file at @path.  If @mode
  * includes %FMODE_EXCL, the block device is opened with exclusive access.
  * Specifying %FMODE_EXCL with a %NULL @holder is invalid.  Exclusive opens may
  * nest for the same @holder.
  *
  * CONTEXT:
  * Might sleep.
  *
  * RETURNS:
  * Reference to the block_device on success, ERR_PTR(-errno) on failure.
  */
 struct block_device *blkdev_get_by_path(const char *path, fmode_t mode,
                     void *holder)
 {
     struct block_device *bdev;
     dev_t dev;
     int error;
 
     error = lookup_bdev(path, &dev);
     if (error)
         return ERR_PTR(error);
 
     bdev = blkdev_get_by_dev(dev, mode, holder);
     if (!IS_ERR(bdev) && (mode & FMODE_WRITE) && bdev_read_only(bdev)) {
         blkdev_put(bdev, mode);
         return ERR_PTR(-EACCES);
     }
 
     return bdev;
 }
 EXPORT_SYMBOL(blkdev_get_by_path);
 
 void blkdev_put(struct block_device *bdev, fmode_t mode)
 {
     struct gendisk *disk = bdev->bd_disk;
 
     /*
      * Sync early if it looks like we're the last one.  If someone else
      * opens the block device between now and the decrement of bd_openers
      * then we did a sync that we didn't need to, but that's not the end
      * of the world and we want to avoid long (could be several minute)
      * syncs while holding the mutex.
      */
     if (atomic_read(&bdev->bd_openers) == 1)
         sync_blockdev(bdev);
 
     mutex_lock(&disk->open_mutex);
     if (mode & FMODE_EXCL) {
         struct block_device *whole = bdev_whole(bdev);
         bool bdev_free;
 
         /*
          * Release a claim on the device.  The holder fields
          * are protected with bdev_lock.  open_mutex is to
          * synchronize disk_holder unlinking.
          */
         spin_lock(&bdev_lock);
 
         WARN_ON_ONCE(--bdev->bd_holders < 0);
         WARN_ON_ONCE(--whole->bd_holders < 0);
 
         if ((bdev_free = !bdev->bd_holders))
             bdev->bd_holder = NULL;
         if (!whole->bd_holders)
             whole->bd_holder = NULL;
 
         spin_unlock(&bdev_lock);
 
         /*
          * If this was the last claim, remove holder link and
          * unblock evpoll if it was a write holder.
          */
         if (bdev_free && bdev->bd_write_holder) {
             disk_unblock_events(disk);
             bdev->bd_write_holder = false;
         }
     }
 
     /*
      * Trigger event checking and tell drivers to flush MEDIA_CHANGE
      * event.  This is to ensure detection of media removal commanded
      * from userland - e.g. eject(1).
      */
     disk_flush_events(disk, DISK_EVENT_MEDIA_CHANGE);
 
     if (bdev_is_partition(bdev))
         blkdev_put_part(bdev, mode);
     else
         blkdev_put_whole(bdev, mode);
     mutex_unlock(&disk->open_mutex);
 
     module_put(disk->fops->owner);
     blkdev_put_no_open(bdev);
 }
 EXPORT_SYMBOL(blkdev_put);
 
 /**
  * lookup_bdev() - Look up a struct block_device by name.
  * @pathname: Name of the block device in the filesystem.
  * @dev: Pointer to the block device's dev_t, if found.
  *
  * Lookup the block device's dev_t at @pathname in the current
  * namespace if possible and return it in @dev.
  *
  * Context: May sleep.
  * Return: 0 if succeeded, negative errno otherwise.
  */
 int lookup_bdev(const char *pathname, dev_t *dev)
 {
     struct inode *inode;
     struct path path;
     int error;
 
     if (!pathname || !*pathname)
         return -EINVAL;
 
     error = kern_path(pathname, LOOKUP_FOLLOW, &path);
     if (error)
         return error;
 
     inode = d_backing_inode(path.dentry);
     error = -ENOTBLK;
     if (!S_ISBLK(inode->i_mode))
         goto out_path_put;
     error = -EACCES;
     if (!may_open_dev(&path))
         goto out_path_put;
 
     *dev = inode->i_rdev;
     error = 0;
 out_path_put:
     path_put(&path);
     return error;
 }
 EXPORT_SYMBOL(lookup_bdev);
 
 int __invalidate_device(struct block_device *bdev, bool kill_dirty)
 {
     struct super_block *sb = get_super(bdev);
     int res = 0;
 
     if (sb) {
         /*
          * no need to lock the super, get_super holds the
          * read mutex so the filesystem cannot go away
          * under us (->put_super runs with the write lock
          * hold).
          */
         shrink_dcache_sb(sb);
         res = invalidate_inodes(sb, kill_dirty);
         drop_super(sb);
     }
     invalidate_bdev(bdev);
     return res;
 }
 EXPORT_SYMBOL(__invalidate_device);
 
 void sync_bdevs(bool wait)
 {
     struct inode *inode, *old_inode = NULL;
 
     spin_lock(&blockdev_superblock->s_inode_list_lock);
     list_for_each_entry(inode, &blockdev_superblock->s_inodes, i_sb_list) {
         struct address_space *mapping = inode->i_mapping;
         struct block_device *bdev;
 
         spin_lock(&inode->i_lock);
         if (inode->i_state & (I_FREEING|I_WILL_FREE|I_NEW) ||
             mapping->nrpages == 0) {
             spin_unlock(&inode->i_lock);
             continue;
         }
         __iget(inode);
         spin_unlock(&inode->i_lock);
         spin_unlock(&blockdev_superblock->s_inode_list_lock);
         /*
          * We hold a reference to 'inode' so it couldn't have been
          * removed from s_inodes list while we dropped the
          * s_inode_list_lock  We cannot iput the inode now as we can
          * be holding the last reference and we cannot iput it under
          * s_inode_list_lock. So we keep the reference and iput it
          * later.
          */
         iput(old_inode);
         old_inode = inode;
         bdev = I_BDEV(inode);
 
         mutex_lock(&bdev->bd_disk->open_mutex);
         if (!atomic_read(&bdev->bd_openers)) {
             ; /* skip */
         } else if (wait) {
             /*
              * We keep the error status of individual mapping so
              * that applications can catch the writeback error using
              * fsync(2). See filemap_fdatawait_keep_errors() for
              * details.
              */
             filemap_fdatawait_keep_errors(inode->i_mapping);
         } else {
             filemap_fdatawrite(inode->i_mapping);
         }
         mutex_unlock(&bdev->bd_disk->open_mutex);
 
         spin_lock(&blockdev_superblock->s_inode_list_lock);
     }
     spin_unlock(&blockdev_superblock->s_inode_list_lock);
     iput(old_inode);
 }

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