block: move fs/block_dev.c to block/bdev.c

Move it together with the rest of the block layer.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20210907141303.1371844-3-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 1058 insertions, 0 deletions

diff --git a/block/bdev.c b/block/bdev.c
new file mode 100644
index 000000000000..cf2780cb44a7
--- /dev/null
+++ b/block/bdev.c
@@ -0,0 +1,1058 @@
+// 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/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/cleancache.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) {
+			char name[BDEVNAME_SIZE];
+			pr_warn_ratelimited("VFS: Dirty inode writeback failed "
+					    "for block device %s (err=%d).\n",
+					    bdevname(bdev, name), 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);
+	}
+	/* 99% of the time, we don't need to flush the cleancache on the bdev.
+	 * But, for the strange corners, lets be cautious
+	 */
+	cleancache_invalidate_inode(mapping);
+}
+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(struct block_device *bdev, int wait)
+{
+	if (!bdev)
+		return 0;
+	if (!wait)
+		return filemap_flush(bdev->bd_inode->i_mapping);
+	return filemap_write_and_wait(bdev->bd_inode->i_mapping);
+}
+
+/*
+ * 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)
+{
+	return __sync_blockdev(bdev, 1);
+}
+EXPORT_SYMBOL(sync_blockdev);
+
+/*
+ * 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->bd_disk->queue, 0);
+	if (result)
+		return result;
+	result = ops->rw_page(bdev, sector + get_start_sect(bdev), page,
+			      REQ_OP_READ);
+	blk_queue_exit(bdev->bd_disk->queue);
+	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->bd_disk->queue, 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->bd_disk->queue);
+	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 = kmem_cache_alloc(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_disk = disk;
+	bdev->bd_partno = partno;
+	bdev->bd_inode = inode;
+	bdev->bd_stats = alloc_percpu(struct disk_stats);
+	if (!bdev->bd_stats) {
+		iput(inode);
+		return NULL;
+	}
+	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 = 0;
+
+	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 (!bdev->bd_openers)
+		set_init_blocksize(bdev);
+	if (test_bit(GD_NEED_PART_SCAN, &disk->state))
+		bdev_disk_changed(disk, false);
+	bdev->bd_openers++;
+	return 0;;
+}
+
+static void blkdev_put_whole(struct block_device *bdev, fmode_t mode)
+{
+	if (!--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 (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:
+	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 (--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) {
+		blk_request_module(dev);
+		inode = ilookup(blockdev_superblock, dev);
+		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);
+
+	if (!bdev)
+		return NULL;
+	if ((bdev->bd_disk->flags & GENHD_FL_HIDDEN) ||
+	    !try_module_get(bdev->bd_disk->fops->owner)) {
+		put_device(&bdev->bd_device);
+		return NULL;
+	}
+
+	return bdev;
+}
+
+void blkdev_put_no_open(struct block_device *bdev)
+{
+	module_put(bdev->bd_disk->fops->owner);
+	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 (bdev_is_partition(bdev))
+		ret = blkdev_get_part(bdev, mode);
+	else
+		ret = blkdev_get_whole(bdev, mode);
+	if (ret)
+		goto abort_claiming;
+	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->flags & GENHD_FL_BLOCK_EVENTS_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;
+
+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 (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);
+
+	blkdev_put_no_open(bdev);
+}
+EXPORT_SYMBOL(blkdev_put);
+
+/**
+ * lookup_bdev  - lookup a struct block_device by name
+ * @pathname:	special file representing the block device
+ * @dev:	return value of the block device's dev_t
+ *
+ * Get a reference to the blockdevice at @pathname in the current
+ * namespace if possible and return it.  Return ERR_PTR(error)
+ * 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 iterate_bdevs(void (*func)(struct block_device *, void *), void *arg)
+{
+	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 (bdev->bd_openers)
+			func(bdev, arg);
+		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);
+}