Initial import

1 files changed, 1795 insertions, 0 deletions

diff --git a/fs/block_dev.c b/fs/block_dev.c
new file mode 100644
index 000000000..c7e4163ed
--- /dev/null
+++ b/fs/block_dev.c
@@ -0,0 +1,1795 @@
+/*
+ *  linux/fs/block_dev.c
+ *
+ *  Copyright (C) 1991, 1992  Linus Torvalds
+ *  Copyright (C) 2001  Andrea Arcangeli <andrea@suse.de> SuSE
+ */
+
+#include <linux/init.h>
+#include <linux/mm.h>
+#include <linux/fcntl.h>
+#include <linux/slab.h>
+#include <linux/kmod.h>
+#include <linux/major.h>
+#include <linux/device_cgroup.h>
+#include <linux/highmem.h>
+#include <linux/blkdev.h>
+#include <linux/module.h>
+#include <linux/blkpg.h>
+#include <linux/magic.h>
+#include <linux/buffer_head.h>
+#include <linux/swap.h>
+#include <linux/pagevec.h>
+#include <linux/writeback.h>
+#include <linux/mpage.h>
+#include <linux/mount.h>
+#include <linux/uio.h>
+#include <linux/namei.h>
+#include <linux/log2.h>
+#include <linux/cleancache.h>
+#include <asm/uaccess.h>
+#include "internal.h"
+
+struct bdev_inode {
+	struct block_device bdev;
+	struct inode vfs_inode;
+};
+
+static const struct address_space_operations def_blk_aops;
+
+static inline struct bdev_inode *BDEV_I(struct inode *inode)
+{
+	return container_of(inode, struct bdev_inode, vfs_inode);
+}
+
+inline struct block_device *I_BDEV(struct inode *inode)
+{
+	return &BDEV_I(inode)->bdev;
+}
+EXPORT_SYMBOL(I_BDEV);
+
+static void bdev_write_inode(struct inode *inode)
+{
+	spin_lock(&inode->i_lock);
+	while (inode->i_state & I_DIRTY) {
+		spin_unlock(&inode->i_lock);
+		WARN_ON_ONCE(write_inode_now(inode, true));
+		spin_lock(&inode->i_lock);
+	}
+	spin_unlock(&inode->i_lock);
+}
+
+/* Kill _all_ buffers and pagecache , dirty or not.. */
+void kill_bdev(struct block_device *bdev)
+{
+	struct address_space *mapping = bdev->bd_inode->i_mapping;
+
+	if (mapping->nrpages == 0 && mapping->nrshadows == 0)
+		return;
+
+	invalidate_bh_lrus();
+	truncate_inode_pages(mapping, 0);
+}	
+EXPORT_SYMBOL(kill_bdev);
+
+/* 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 == 0)
+		return;
+
+	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);
+
+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_block_size != size) {
+		sync_blockdev(bdev);
+		bdev->bd_block_size = size;
+		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);
+
+static int
+blkdev_get_block(struct inode *inode, sector_t iblock,
+		struct buffer_head *bh, int create)
+{
+	bh->b_bdev = I_BDEV(inode);
+	bh->b_blocknr = iblock;
+	set_buffer_mapped(bh);
+	return 0;
+}
+
+static ssize_t
+blkdev_direct_IO(struct kiocb *iocb, struct iov_iter *iter, loff_t offset)
+{
+	struct file *file = iocb->ki_filp;
+	struct inode *inode = file->f_mapping->host;
+
+	return __blockdev_direct_IO(iocb, inode, I_BDEV(inode), iter, offset,
+				    blkdev_get_block, NULL, NULL,
+				    DIO_SKIP_DIO_COUNT);
+}
+
+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.
+ */
+struct super_block *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) {
+		/*
+		 * We don't even need to grab a reference - the first call
+		 * to freeze_bdev grab an active reference and only the last
+		 * thaw_bdev drops it.
+		 */
+		sb = get_super(bdev);
+		drop_super(sb);
+		mutex_unlock(&bdev->bd_fsfreeze_mutex);
+		return sb;
+	}
+
+	sb = get_active_super(bdev);
+	if (!sb)
+		goto out;
+	if (sb->s_op->freeze_super)
+		error = sb->s_op->freeze_super(sb);
+	else
+		error = freeze_super(sb);
+	if (error) {
+		deactivate_super(sb);
+		bdev->bd_fsfreeze_count--;
+		mutex_unlock(&bdev->bd_fsfreeze_mutex);
+		return ERR_PTR(error);
+	}
+	deactivate_super(sb);
+ out:
+	sync_blockdev(bdev);
+	mutex_unlock(&bdev->bd_fsfreeze_mutex);
+	return sb;	/* thaw_bdev releases s->s_umount */
+}
+EXPORT_SYMBOL(freeze_bdev);
+
+/**
+ * thaw_bdev  -- unlock filesystem
+ * @bdev:	blockdevice to unlock
+ * @sb:		associated superblock
+ *
+ * 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;
+
+	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++;
+		mutex_unlock(&bdev->bd_fsfreeze_mutex);
+		return error;
+	}
+out:
+	mutex_unlock(&bdev->bd_fsfreeze_mutex);
+	return 0;
+}
+EXPORT_SYMBOL(thaw_bdev);
+
+static int blkdev_writepage(struct page *page, struct writeback_control *wbc)
+{
+	return block_write_full_page(page, blkdev_get_block, wbc);
+}
+
+static int blkdev_readpage(struct file * file, struct page * page)
+{
+	return block_read_full_page(page, blkdev_get_block);
+}
+
+static int blkdev_readpages(struct file *file, struct address_space *mapping,
+			struct list_head *pages, unsigned nr_pages)
+{
+	return mpage_readpages(mapping, pages, nr_pages, blkdev_get_block);
+}
+
+static int blkdev_write_begin(struct file *file, struct address_space *mapping,
+			loff_t pos, unsigned len, unsigned flags,
+			struct page **pagep, void **fsdata)
+{
+	return block_write_begin(mapping, pos, len, flags, pagep,
+				 blkdev_get_block);
+}
+
+static int blkdev_write_end(struct file *file, struct address_space *mapping,
+			loff_t pos, unsigned len, unsigned copied,
+			struct page *page, void *fsdata)
+{
+	int ret;
+	ret = block_write_end(file, mapping, pos, len, copied, page, fsdata);
+
+	unlock_page(page);
+	page_cache_release(page);
+
+	return ret;
+}
+
+/*
+ * private llseek:
+ * for a block special file file_inode(file)->i_size is zero
+ * so we compute the size by hand (just as in block_read/write above)
+ */
+static loff_t block_llseek(struct file *file, loff_t offset, int whence)
+{
+	struct inode *bd_inode = file->f_mapping->host;
+	loff_t retval;
+
+	mutex_lock(&bd_inode->i_mutex);
+	retval = fixed_size_llseek(file, offset, whence, i_size_read(bd_inode));
+	mutex_unlock(&bd_inode->i_mutex);
+	return retval;
+}
+	
+int blkdev_fsync(struct file *filp, loff_t start, loff_t end, int datasync)
+{
+	struct inode *bd_inode = filp->f_mapping->host;
+	struct block_device *bdev = I_BDEV(bd_inode);
+	int error;
+	
+	error = filemap_write_and_wait_range(filp->f_mapping, start, end);
+	if (error)
+		return error;
+
+	/*
+	 * There is no need to serialise calls to blkdev_issue_flush with
+	 * i_mutex and doing so causes performance issues with concurrent
+	 * O_SYNC writers to a block device.
+	 */
+	error = blkdev_issue_flush(bdev, GFP_KERNEL, NULL);
+	if (error == -EOPNOTSUPP)
+		error = 0;
+
+	return error;
+}
+EXPORT_SYMBOL(blkdev_fsync);
+
+/**
+ * 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;
+	if (!ops->rw_page)
+		return -EOPNOTSUPP;
+	return ops->rw_page(bdev, sector + get_start_sect(bdev), page, READ);
+}
+EXPORT_SYMBOL_GPL(bdev_read_page);
+
+/**
+ * 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;
+	int rw = (wbc->sync_mode == WB_SYNC_ALL) ? WRITE_SYNC : WRITE;
+	const struct block_device_operations *ops = bdev->bd_disk->fops;
+	if (!ops->rw_page)
+		return -EOPNOTSUPP;
+	set_page_writeback(page);
+	result = ops->rw_page(bdev, sector + get_start_sect(bdev), page, rw);
+	if (result)
+		end_page_writeback(page);
+	else
+		unlock_page(page);
+	return result;
+}
+EXPORT_SYMBOL_GPL(bdev_write_page);
+
+/**
+ * bdev_direct_access() - Get the address for directly-accessibly memory
+ * @bdev: The device containing the memory
+ * @sector: The offset within the device
+ * @addr: Where to put the address of the memory
+ * @pfn: The Page Frame Number for the memory
+ * @size: The number of bytes requested
+ *
+ * If a block device is made up of directly addressable memory, this function
+ * will tell the caller the PFN and the address of the memory.  The address
+ * may be directly dereferenced within the kernel without the need to call
+ * ioremap(), kmap() or similar.  The PFN is suitable for inserting into
+ * page tables.
+ *
+ * Return: negative errno if an error occurs, otherwise the number of bytes
+ * accessible at this address.
+ */
+long bdev_direct_access(struct block_device *bdev, sector_t sector,
+			void **addr, unsigned long *pfn, long size)
+{
+	long avail;
+	const struct block_device_operations *ops = bdev->bd_disk->fops;
+
+	if (size < 0)
+		return size;
+	if (!ops->direct_access)
+		return -EOPNOTSUPP;
+	if ((sector + DIV_ROUND_UP(size, 512)) >
+					part_nr_sects_read(bdev->bd_part))
+		return -ERANGE;
+	sector += get_start_sect(bdev);
+	if (sector % (PAGE_SIZE / 512))
+		return -EINVAL;
+	avail = ops->direct_access(bdev, sector, addr, pfn, size);
+	if (!avail)
+		return -ERANGE;
+	return min(avail, size);
+}
+EXPORT_SYMBOL_GPL(bdev_direct_access);
+
+/*
+ * 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;
+	return &ei->vfs_inode;
+}
+
+static void bdev_i_callback(struct rcu_head *head)
+{
+	struct inode *inode = container_of(head, struct inode, i_rcu);
+	struct bdev_inode *bdi = BDEV_I(inode);
+
+	kmem_cache_free(bdev_cachep, bdi);
+}
+
+static void bdev_destroy_inode(struct inode *inode)
+{
+	call_rcu(&inode->i_rcu, bdev_i_callback);
+}
+
+static void init_once(void *foo)
+{
+	struct bdev_inode *ei = (struct bdev_inode *) foo;
+	struct block_device *bdev = &ei->bdev;
+
+	memset(bdev, 0, sizeof(*bdev));
+	mutex_init(&bdev->bd_mutex);
+	INIT_LIST_HEAD(&bdev->bd_inodes);
+	INIT_LIST_HEAD(&bdev->bd_list);
+#ifdef CONFIG_SYSFS
+	INIT_LIST_HEAD(&bdev->bd_holder_disks);
+#endif
+	inode_init_once(&ei->vfs_inode);
+	/* Initialize mutex for freeze. */
+	mutex_init(&bdev->bd_fsfreeze_mutex);
+}
+
+static inline void __bd_forget(struct inode *inode)
+{
+	list_del_init(&inode->i_devices);
+	inode->i_bdev = NULL;
+	inode->i_mapping = &inode->i_data;
+}
+
+static void bdev_evict_inode(struct inode *inode)
+{
+	struct block_device *bdev = &BDEV_I(inode)->bdev;
+	struct list_head *p;
+	truncate_inode_pages_final(&inode->i_data);
+	invalidate_inode_buffers(inode); /* is it needed here? */
+	clear_inode(inode);
+	spin_lock(&bdev_lock);
+	while ( (p = bdev->bd_inodes.next) != &bdev->bd_inodes ) {
+		__bd_forget(list_entry(p, struct inode, i_devices));
+	}
+	list_del_init(&bdev->bd_list);
+	spin_unlock(&bdev_lock);
+}
+
+static const struct super_operations bdev_sops = {
+	.statfs = simple_statfs,
+	.alloc_inode = bdev_alloc_inode,
+	.destroy_inode = bdev_destroy_inode,
+	.drop_inode = generic_delete_inode,
+	.evict_inode = bdev_evict_inode,
+};
+
+static struct dentry *bd_mount(struct file_system_type *fs_type,
+	int flags, const char *dev_name, void *data)
+{
+	return mount_pseudo(fs_type, "bdev:", &bdev_sops, NULL, BDEVFS_MAGIC);
+}
+
+static struct file_system_type bd_type = {
+	.name		= "bdev",
+	.mount		= bd_mount,
+	.kill_sb	= kill_anon_super,
+};
+
+static struct super_block *blockdev_superblock __read_mostly;
+
+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_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 */
+}
+
+/*
+ * Most likely _very_ bad one - but then it's hardly critical for small
+ * /dev and can be fixed when somebody will need really large one.
+ * Keep in mind that it will be fed through icache hash function too.
+ */
+static inline unsigned long hash(dev_t dev)
+{
+	return MAJOR(dev)+MINOR(dev);
+}
+
+static int bdev_test(struct inode *inode, void *data)
+{
+	return BDEV_I(inode)->bdev.bd_dev == *(dev_t *)data;
+}
+
+static int bdev_set(struct inode *inode, void *data)
+{
+	BDEV_I(inode)->bdev.bd_dev = *(dev_t *)data;
+	return 0;
+}
+
+static LIST_HEAD(all_bdevs);
+
+struct block_device *bdget(dev_t dev)
+{
+	struct block_device *bdev;
+	struct inode *inode;
+
+	inode = iget5_locked(blockdev_superblock, hash(dev),
+			bdev_test, bdev_set, &dev);
+
+	if (!inode)
+		return NULL;
+
+	bdev = &BDEV_I(inode)->bdev;
+
+	if (inode->i_state & I_NEW) {
+		bdev->bd_contains = NULL;
+		bdev->bd_super = NULL;
+		bdev->bd_inode = inode;
+		bdev->bd_block_size = (1 << inode->i_blkbits);
+		bdev->bd_part_count = 0;
+		bdev->bd_invalidated = 0;
+		inode->i_mode = S_IFBLK;
+		inode->i_rdev = dev;
+		inode->i_bdev = bdev;
+		inode->i_data.a_ops = &def_blk_aops;
+		mapping_set_gfp_mask(&inode->i_data, GFP_USER);
+		spin_lock(&bdev_lock);
+		list_add(&bdev->bd_list, &all_bdevs);
+		spin_unlock(&bdev_lock);
+		unlock_new_inode(inode);
+	}
+	return bdev;
+}
+
+EXPORT_SYMBOL(bdget);
+
+/**
+ * bdgrab -- Grab a reference to an already referenced block device
+ * @bdev:	Block device to grab a reference to.
+ */
+struct block_device *bdgrab(struct block_device *bdev)
+{
+	ihold(bdev->bd_inode);
+	return bdev;
+}
+EXPORT_SYMBOL(bdgrab);
+
+long nr_blockdev_pages(void)
+{
+	struct block_device *bdev;
+	long ret = 0;
+	spin_lock(&bdev_lock);
+	list_for_each_entry(bdev, &all_bdevs, bd_list) {
+		ret += bdev->bd_inode->i_mapping->nrpages;
+	}
+	spin_unlock(&bdev_lock);
+	return ret;
+}
+
+void bdput(struct block_device *bdev)
+{
+	iput(bdev->bd_inode);
+}
+
+EXPORT_SYMBOL(bdput);
+ 
+static struct block_device *bd_acquire(struct inode *inode)
+{
+	struct block_device *bdev;
+
+	spin_lock(&bdev_lock);
+	bdev = inode->i_bdev;
+	if (bdev) {
+		ihold(bdev->bd_inode);
+		spin_unlock(&bdev_lock);
+		return bdev;
+	}
+	spin_unlock(&bdev_lock);
+
+	bdev = bdget(inode->i_rdev);
+	if (bdev) {
+		spin_lock(&bdev_lock);
+		if (!inode->i_bdev) {
+			/*
+			 * We take an additional reference to bd_inode,
+			 * and it's released in clear_inode() of inode.
+			 * So, we can access it via ->i_mapping always
+			 * without igrab().
+			 */
+			ihold(bdev->bd_inode);
+			inode->i_bdev = bdev;
+			inode->i_mapping = bdev->bd_inode->i_mapping;
+			list_add(&inode->i_devices, &bdev->bd_inodes);
+		}
+		spin_unlock(&bdev_lock);
+	}
+	return bdev;
+}
+
+int sb_is_blkdev_sb(struct super_block *sb)
+{
+	return sb == blockdev_superblock;
+}
+
+/* Call when you free inode */
+
+void bd_forget(struct inode *inode)
+{
+	struct block_device *bdev = NULL;
+
+	spin_lock(&bdev_lock);
+	if (!sb_is_blkdev_sb(inode->i_sb))
+		bdev = inode->i_bdev;
+	__bd_forget(inode);
+	spin_unlock(&bdev_lock);
+
+	if (bdev)
+		iput(bdev->bd_inode);
+}
+
+/**
+ * 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 (bdev->bd_contains == 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 - prepare to claim a block device
+ * @bdev: block device of interest
+ * @whole: the whole device containing @bdev, may equal @bdev
+ * @holder: holder trying to claim @bdev
+ *
+ * Prepare to claim @bdev.  This function fails if @bdev is already
+ * claimed by another holder and waits if another claiming is in
+ * progress.  This function doesn't actually claim.  On successful
+ * return, the caller has ownership of bd_claiming and bd_holder[s].
+ *
+ * CONTEXT:
+ * spin_lock(&bdev_lock).  Might release bdev_lock, sleep and regrab
+ * it multiple times.
+ *
+ * RETURNS:
+ * 0 if @bdev can be claimed, -EBUSY otherwise.
+ */
+static int bd_prepare_to_claim(struct block_device *bdev,
+			       struct block_device *whole, void *holder)
+{
+retry:
+	/* if someone else claimed, fail */
+	if (!bd_may_claim(bdev, whole, holder))
+		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);
+		spin_lock(&bdev_lock);
+		goto retry;
+	}
+
+	/* yay, all mine */
+	return 0;
+}
+
+/**
+ * bd_start_claiming - start claiming a block device
+ * @bdev: block device of interest
+ * @holder: holder trying to claim @bdev
+ *
+ * @bdev is about to be opened exclusively.  Check @bdev can be opened
+ * exclusively and mark that an exclusive open is in progress.  Each
+ * successful call to this function must be matched with a call to
+ * either bd_finish_claiming() or bd_abort_claiming() (which do not
+ * fail).
+ *
+ * This function is used to gain exclusive access to the block device
+ * without actually causing other exclusive open attempts to fail. It
+ * should be used when the open sequence itself requires exclusive
+ * access but may subsequently fail.
+ *
+ * CONTEXT:
+ * Might sleep.
+ *
+ * RETURNS:
+ * Pointer to the block device containing @bdev on success, ERR_PTR()
+ * value on failure.
+ */
+static struct block_device *bd_start_claiming(struct block_device *bdev,
+					      void *holder)
+{
+	struct gendisk *disk;
+	struct block_device *whole;
+	int partno, err;
+
+	might_sleep();
+
+	/*
+	 * @bdev might not have been initialized properly yet, look up
+	 * and grab the outer block device the hard way.
+	 */
+	disk = get_gendisk(bdev->bd_dev, &partno);
+	if (!disk)
+		return ERR_PTR(-ENXIO);
+
+	/*
+	 * Normally, @bdev should equal what's returned from bdget_disk()
+	 * if partno is 0; however, some drivers (floppy) use multiple
+	 * bdev's for the same physical device and @bdev may be one of the
+	 * aliases.  Keep @bdev if partno is 0.  This means claimer
+	 * tracking is broken for those devices but it has always been that
+	 * way.
+	 */
+	if (partno)
+		whole = bdget_disk(disk, 0);
+	else
+		whole = bdgrab(bdev);
+
+	module_put(disk->fops->owner);
+	put_disk(disk);
+	if (!whole)
+		return ERR_PTR(-ENOMEM);
+
+	/* prepare to claim, if successful, mark claiming in progress */
+	spin_lock(&bdev_lock);
+
+	err = bd_prepare_to_claim(bdev, whole, holder);
+	if (err == 0) {
+		whole->bd_claiming = holder;
+		spin_unlock(&bdev_lock);
+		return whole;
+	} else {
+		spin_unlock(&bdev_lock);
+		bdput(whole);
+		return ERR_PTR(err);
+	}
+}
+
+#ifdef CONFIG_SYSFS
+struct bd_holder_disk {
+	struct list_head	list;
+	struct gendisk		*disk;
+	int			refcnt;
+};
+
+static struct bd_holder_disk *bd_find_holder_disk(struct block_device *bdev,
+						  struct gendisk *disk)
+{
+	struct bd_holder_disk *holder;
+
+	list_for_each_entry(holder, &bdev->bd_holder_disks, list)
+		if (holder->disk == disk)
+			return holder;
+	return NULL;
+}
+
+static int add_symlink(struct kobject *from, struct kobject *to)
+{
+	return sysfs_create_link(from, to, kobject_name(to));
+}
+
+static void del_symlink(struct kobject *from, struct kobject *to)
+{
+	sysfs_remove_link(from, kobject_name(to));
+}
+
+/**
+ * bd_link_disk_holder - create symlinks between holding disk and slave bdev
+ * @bdev: the claimed slave bdev
+ * @disk: the holding disk
+ *
+ * DON'T USE THIS UNLESS YOU'RE ALREADY USING IT.
+ *
+ * This functions creates the following sysfs symlinks.
+ *
+ * - from "slaves" directory of the holder @disk to the claimed @bdev
+ * - from "holders" directory of the @bdev to the holder @disk
+ *
+ * For example, if /dev/dm-0 maps to /dev/sda and disk for dm-0 is
+ * passed to bd_link_disk_holder(), then:
+ *
+ *   /sys/block/dm-0/slaves/sda --> /sys/block/sda
+ *   /sys/block/sda/holders/dm-0 --> /sys/block/dm-0
+ *
+ * The caller must have claimed @bdev before calling this function and
+ * ensure that both @bdev and @disk are valid during the creation and
+ * lifetime of these symlinks.
+ *
+ * CONTEXT:
+ * Might sleep.
+ *
+ * RETURNS:
+ * 0 on success, -errno on failure.
+ */
+int bd_link_disk_holder(struct block_device *bdev, struct gendisk *disk)
+{
+	struct bd_holder_disk *holder;
+	int ret = 0;
+
+	mutex_lock(&bdev->bd_mutex);
+
+	WARN_ON_ONCE(!bdev->bd_holder);
+
+	/* FIXME: remove the following once add_disk() handles errors */
+	if (WARN_ON(!disk->slave_dir || !bdev->bd_part->holder_dir))
+		goto out_unlock;
+
+	holder = bd_find_holder_disk(bdev, disk);
+	if (holder) {
+		holder->refcnt++;
+		goto out_unlock;
+	}
+
+	holder = kzalloc(sizeof(*holder), GFP_KERNEL);
+	if (!holder) {
+		ret = -ENOMEM;
+		goto out_unlock;
+	}
+
+	INIT_LIST_HEAD(&holder->list);
+	holder->disk = disk;
+	holder->refcnt = 1;
+
+	ret = add_symlink(disk->slave_dir, &part_to_dev(bdev->bd_part)->kobj);
+	if (ret)
+		goto out_free;
+
+	ret = add_symlink(bdev->bd_part->holder_dir, &disk_to_dev(disk)->kobj);
+	if (ret)
+		goto out_del;
+	/*
+	 * bdev could be deleted beneath us which would implicitly destroy
+	 * the holder directory.  Hold on to it.
+	 */
+	kobject_get(bdev->bd_part->holder_dir);
+
+	list_add(&holder->list, &bdev->bd_holder_disks);
+	goto out_unlock;
+
+out_del:
+	del_symlink(disk->slave_dir, &part_to_dev(bdev->bd_part)->kobj);
+out_free:
+	kfree(holder);
+out_unlock:
+	mutex_unlock(&bdev->bd_mutex);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(bd_link_disk_holder);
+
+/**
+ * bd_unlink_disk_holder - destroy symlinks created by bd_link_disk_holder()
+ * @bdev: the calimed slave bdev
+ * @disk: the holding disk
+ *
+ * DON'T USE THIS UNLESS YOU'RE ALREADY USING IT.
+ *
+ * CONTEXT:
+ * Might sleep.
+ */
+void bd_unlink_disk_holder(struct block_device *bdev, struct gendisk *disk)
+{
+	struct bd_holder_disk *holder;
+
+	mutex_lock(&bdev->bd_mutex);
+
+	holder = bd_find_holder_disk(bdev, disk);
+
+	if (!WARN_ON_ONCE(holder == NULL) && !--holder->refcnt) {
+		del_symlink(disk->slave_dir, &part_to_dev(bdev->bd_part)->kobj);
+		del_symlink(bdev->bd_part->holder_dir,
+			    &disk_to_dev(disk)->kobj);
+		kobject_put(bdev->bd_part->holder_dir);
+		list_del_init(&holder->list);
+		kfree(holder);
+	}
+
+	mutex_unlock(&bdev->bd_mutex);
+}
+EXPORT_SYMBOL_GPL(bd_unlink_disk_holder);
+#endif
+
+/**
+ * flush_disk - invalidates all buffer-cache entries on a disk
+ *
+ * @bdev:      struct block device to be flushed
+ * @kill_dirty: flag to guide handling of dirty inodes
+ *
+ * Invalidates all buffer-cache entries on a disk. It should be called
+ * when a disk has been changed -- either by a media change or online
+ * resize.
+ */
+static void flush_disk(struct block_device *bdev, bool kill_dirty)
+{
+	if (__invalidate_device(bdev, kill_dirty)) {
+		char name[BDEVNAME_SIZE] = "";
+
+		if (bdev->bd_disk)
+			disk_name(bdev->bd_disk, 0, name);
+		printk(KERN_WARNING "VFS: busy inodes on changed media or "
+		       "resized disk %s\n", name);
+	}
+
+	if (!bdev->bd_disk)
+		return;
+	if (disk_part_scan_enabled(bdev->bd_disk))
+		bdev->bd_invalidated = 1;
+}
+
+/**
+ * check_disk_size_change - checks for disk size change and adjusts bdev size.
+ * @disk: struct gendisk to check
+ * @bdev: struct bdev to adjust.
+ *
+ * This routine checks to see if the bdev size does not match the disk size
+ * and adjusts it if it differs.
+ */
+void check_disk_size_change(struct gendisk *disk, struct block_device *bdev)
+{
+	loff_t disk_size, bdev_size;
+
+	disk_size = (loff_t)get_capacity(disk) << 9;
+	bdev_size = i_size_read(bdev->bd_inode);
+	if (disk_size != bdev_size) {
+		char name[BDEVNAME_SIZE];
+
+		disk_name(disk, 0, name);
+		printk(KERN_INFO
+		       "%s: detected capacity change from %lld to %lld\n",
+		       name, bdev_size, disk_size);
+		i_size_write(bdev->bd_inode, disk_size);
+		flush_disk(bdev, false);
+	}
+}
+EXPORT_SYMBOL(check_disk_size_change);
+
+/**
+ * revalidate_disk - wrapper for lower-level driver's revalidate_disk call-back
+ * @disk: struct gendisk to be revalidated
+ *
+ * This routine is a wrapper for lower-level driver's revalidate_disk
+ * call-backs.  It is used to do common pre and post operations needed
+ * for all revalidate_disk operations.
+ */
+int revalidate_disk(struct gendisk *disk)
+{
+	struct block_device *bdev;
+	int ret = 0;
+
+	if (disk->fops->revalidate_disk)
+		ret = disk->fops->revalidate_disk(disk);
+
+	bdev = bdget_disk(disk, 0);
+	if (!bdev)
+		return ret;
+
+	mutex_lock(&bdev->bd_mutex);
+	check_disk_size_change(disk, bdev);
+	bdev->bd_invalidated = 0;
+	mutex_unlock(&bdev->bd_mutex);
+	bdput(bdev);
+	return ret;
+}
+EXPORT_SYMBOL(revalidate_disk);
+
+/*
+ * This routine checks whether a removable media has been changed,
+ * and invalidates all buffer-cache-entries in that case. This
+ * is a relatively slow routine, so we have to try to minimize using
+ * it. Thus it is called only upon a 'mount' or 'open'. This
+ * is the best way of combining speed and utility, I think.
+ * People changing diskettes in the middle of an operation deserve
+ * to lose :-)
+ */
+int check_disk_change(struct block_device *bdev)
+{
+	struct gendisk *disk = bdev->bd_disk;
+	const struct block_device_operations *bdops = disk->fops;
+	unsigned int events;
+
+	events = disk_clear_events(disk, DISK_EVENT_MEDIA_CHANGE |
+				   DISK_EVENT_EJECT_REQUEST);
+	if (!(events & DISK_EVENT_MEDIA_CHANGE))
+		return 0;
+
+	flush_disk(bdev, true);
+	if (bdops->revalidate_disk)
+		bdops->revalidate_disk(bdev->bd_disk);
+	return 1;
+}
+
+EXPORT_SYMBOL(check_disk_change);
+
+void bd_set_size(struct block_device *bdev, loff_t size)
+{
+	unsigned bsize = bdev_logical_block_size(bdev);
+
+	mutex_lock(&bdev->bd_inode->i_mutex);
+	i_size_write(bdev->bd_inode, size);
+	mutex_unlock(&bdev->bd_inode->i_mutex);
+	while (bsize < PAGE_CACHE_SIZE) {
+		if (size & bsize)
+			break;
+		bsize <<= 1;
+	}
+	bdev->bd_block_size = bsize;
+	bdev->bd_inode->i_blkbits = blksize_bits(bsize);
+}
+EXPORT_SYMBOL(bd_set_size);
+
+static void __blkdev_put(struct block_device *bdev, fmode_t mode, int for_part);
+
+/*
+ * bd_mutex locking:
+ *
+ *  mutex_lock(part->bd_mutex)
+ *    mutex_lock_nested(whole->bd_mutex, 1)
+ */
+
+static int __blkdev_get(struct block_device *bdev, fmode_t mode, int for_part)
+{
+	struct gendisk *disk;
+	struct module *owner;
+	int ret;
+	int partno;
+	int perm = 0;
+
+	if (mode & FMODE_READ)
+		perm |= MAY_READ;
+	if (mode & FMODE_WRITE)
+		perm |= MAY_WRITE;
+	/*
+	 * hooks: /n/, see "layering violations".
+	 */
+	if (!for_part) {
+		ret = devcgroup_inode_permission(bdev->bd_inode, perm);
+		if (ret != 0) {
+			bdput(bdev);
+			return ret;
+		}
+	}
+
+ restart:
+
+	ret = -ENXIO;
+	disk = get_gendisk(bdev->bd_dev, &partno);
+	if (!disk)
+		goto out;
+	owner = disk->fops->owner;
+
+	disk_block_events(disk);
+	mutex_lock_nested(&bdev->bd_mutex, for_part);
+	if (!bdev->bd_openers) {
+		bdev->bd_disk = disk;
+		bdev->bd_queue = disk->queue;
+		bdev->bd_contains = bdev;
+		if (!partno) {
+			ret = -ENXIO;
+			bdev->bd_part = disk_get_part(disk, partno);
+			if (!bdev->bd_part)
+				goto out_clear;
+
+			ret = 0;
+			if (disk->fops->open) {
+				ret = disk->fops->open(bdev, mode);
+				if (ret == -ERESTARTSYS) {
+					/* Lost a race with 'disk' being
+					 * deleted, try again.
+					 * See md.c
+					 */
+					disk_put_part(bdev->bd_part);
+					bdev->bd_part = NULL;
+					bdev->bd_disk = NULL;
+					bdev->bd_queue = NULL;
+					mutex_unlock(&bdev->bd_mutex);
+					disk_unblock_events(disk);
+					put_disk(disk);
+					module_put(owner);
+					goto restart;
+				}
+			}
+
+			if (!ret)
+				bd_set_size(bdev,(loff_t)get_capacity(disk)<<9);
+
+			/*
+			 * If the device is invalidated, rescan partition
+			 * if open succeeded or failed with -ENOMEDIUM.
+			 * The latter is necessary to prevent ghost
+			 * partitions on a removed medium.
+			 */
+			if (bdev->bd_invalidated) {
+				if (!ret)
+					rescan_partitions(disk, bdev);
+				else if (ret == -ENOMEDIUM)
+					invalidate_partitions(disk, bdev);
+			}
+			if (ret)
+				goto out_clear;
+		} else {
+			struct block_device *whole;
+			whole = bdget_disk(disk, 0);
+			ret = -ENOMEM;
+			if (!whole)
+				goto out_clear;
+			BUG_ON(for_part);
+			ret = __blkdev_get(whole, mode, 1);
+			if (ret)
+				goto out_clear;
+			bdev->bd_contains = whole;
+			bdev->bd_part = disk_get_part(disk, partno);
+			if (!(disk->flags & GENHD_FL_UP) ||
+			    !bdev->bd_part || !bdev->bd_part->nr_sects) {
+				ret = -ENXIO;
+				goto out_clear;
+			}
+			bd_set_size(bdev, (loff_t)bdev->bd_part->nr_sects << 9);
+		}
+	} else {
+		if (bdev->bd_contains == bdev) {
+			ret = 0;
+			if (bdev->bd_disk->fops->open)
+				ret = bdev->bd_disk->fops->open(bdev, mode);
+			/* the same as first opener case, read comment there */
+			if (bdev->bd_invalidated) {
+				if (!ret)
+					rescan_partitions(bdev->bd_disk, bdev);
+				else if (ret == -ENOMEDIUM)
+					invalidate_partitions(bdev->bd_disk, bdev);
+			}
+			if (ret)
+				goto out_unlock_bdev;
+		}
+		/* only one opener holds refs to the module and disk */
+		put_disk(disk);
+		module_put(owner);
+	}
+	bdev->bd_openers++;
+	if (for_part)
+		bdev->bd_part_count++;
+	mutex_unlock(&bdev->bd_mutex);
+	disk_unblock_events(disk);
+	return 0;
+
+ out_clear:
+	disk_put_part(bdev->bd_part);
+	bdev->bd_disk = NULL;
+	bdev->bd_part = NULL;
+	bdev->bd_queue = NULL;
+	if (bdev != bdev->bd_contains)
+		__blkdev_put(bdev->bd_contains, mode, 1);
+	bdev->bd_contains = NULL;
+ out_unlock_bdev:
+	mutex_unlock(&bdev->bd_mutex);
+	disk_unblock_events(disk);
+	put_disk(disk);
+	module_put(owner);
+ out:
+	bdput(bdev);
+
+	return ret;
+}
+
+/**
+ * blkdev_get - open a block device
+ * @bdev: block_device to open
+ * @mode: FMODE_* mask
+ * @holder: exclusive holder identifier
+ *
+ * Open @bdev with @mode.  If @mode includes %FMODE_EXCL, @bdev is
+ * open with exclusive access.  Specifying %FMODE_EXCL with %NULL
+ * @holder is invalid.  Exclusive opens may nest for the same @holder.
+ *
+ * On success, the reference count of @bdev is unchanged.  On failure,
+ * @bdev is put.
+ *
+ * CONTEXT:
+ * Might sleep.
+ *
+ * RETURNS:
+ * 0 on success, -errno on failure.
+ */
+int blkdev_get(struct block_device *bdev, fmode_t mode, void *holder)
+{
+	struct block_device *whole = NULL;
+	int res;
+
+	WARN_ON_ONCE((mode & FMODE_EXCL) && !holder);
+
+	if ((mode & FMODE_EXCL) && holder) {
+		whole = bd_start_claiming(bdev, holder);
+		if (IS_ERR(whole)) {
+			bdput(bdev);
+			return PTR_ERR(whole);
+		}
+	}
+
+	res = __blkdev_get(bdev, mode, 0);
+
+	if (whole) {
+		struct gendisk *disk = whole->bd_disk;
+
+		/* finish claiming */
+		mutex_lock(&bdev->bd_mutex);
+		spin_lock(&bdev_lock);
+
+		if (!res) {
+			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;
+		}
+
+		/* tell others that we're done */
+		BUG_ON(whole->bd_claiming != holder);
+		whole->bd_claiming = NULL;
+		wake_up_bit(&whole->bd_claiming, 0);
+
+		spin_unlock(&bdev_lock);
+
+		/*
+		 * 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 (!res && (mode & FMODE_WRITE) && !bdev->bd_write_holder &&
+		    (disk->flags & GENHD_FL_BLOCK_EVENTS_ON_EXCL_WRITE)) {
+			bdev->bd_write_holder = true;
+			disk_block_events(disk);
+		}
+
+		mutex_unlock(&bdev->bd_mutex);
+		bdput(whole);
+	}
+
+	return res;
+}
+EXPORT_SYMBOL(blkdev_get);
+
+/**
+ * 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 blockdevice described by the device file at @path.  @mode
+ * and @holder are identical to blkdev_get().
+ *
+ * On success, the returned block_device has reference count of one.
+ *
+ * CONTEXT:
+ * Might sleep.
+ *
+ * RETURNS:
+ * Pointer to 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;
+	int err;
+
+	bdev = lookup_bdev(path);
+	if (IS_ERR(bdev))
+		return bdev;
+
+	err = blkdev_get(bdev, mode, holder);
+	if (err)
+		return ERR_PTR(err);
+
+	if ((mode & FMODE_WRITE) && bdev_read_only(bdev)) {
+		blkdev_put(bdev, mode);
+		return ERR_PTR(-EACCES);
+	}
+
+	return bdev;
+}
+EXPORT_SYMBOL(blkdev_get_by_path);
+
+/**
+ * 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 blockdevice described by device number @dev.  @mode and
+ * @holder are identical to blkdev_get().
+ *
+ * Use it 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.  _Never_ to be used for internal purposes.  If you
+ * ever need it - reconsider your API.
+ *
+ * On success, the returned block_device has reference count of one.
+ *
+ * CONTEXT:
+ * Might sleep.
+ *
+ * RETURNS:
+ * Pointer to block_device on success, ERR_PTR(-errno) on failure.
+ */
+struct block_device *blkdev_get_by_dev(dev_t dev, fmode_t mode, void *holder)
+{
+	struct block_device *bdev;
+	int err;
+
+	bdev = bdget(dev);
+	if (!bdev)
+		return ERR_PTR(-ENOMEM);
+
+	err = blkdev_get(bdev, mode, holder);
+	if (err)
+		return ERR_PTR(err);
+
+	return bdev;
+}
+EXPORT_SYMBOL(blkdev_get_by_dev);
+
+static int blkdev_open(struct inode * inode, struct file * filp)
+{
+	struct block_device *bdev;
+
+	/*
+	 * Preserve backwards compatibility and allow large file access
+	 * even if userspace doesn't ask for it explicitly. Some mkfs
+	 * binary needs it. We might want to drop this workaround
+	 * during an unstable branch.
+	 */
+	filp->f_flags |= O_LARGEFILE;
+
+	if (filp->f_flags & O_NDELAY)
+		filp->f_mode |= FMODE_NDELAY;
+	if (filp->f_flags & O_EXCL)
+		filp->f_mode |= FMODE_EXCL;
+	if ((filp->f_flags & O_ACCMODE) == 3)
+		filp->f_mode |= FMODE_WRITE_IOCTL;
+
+	bdev = bd_acquire(inode);
+	if (bdev == NULL)
+		return -ENOMEM;
+
+	filp->f_mapping = bdev->bd_inode->i_mapping;
+
+	return blkdev_get(bdev, filp->f_mode, filp);
+}
+
+static void __blkdev_put(struct block_device *bdev, fmode_t mode, int for_part)
+{
+	struct gendisk *disk = bdev->bd_disk;
+	struct block_device *victim = NULL;
+
+	mutex_lock_nested(&bdev->bd_mutex, for_part);
+	if (for_part)
+		bdev->bd_part_count--;
+
+	if (!--bdev->bd_openers) {
+		WARN_ON_ONCE(bdev->bd_holders);
+		sync_blockdev(bdev);
+		kill_bdev(bdev);
+		/*
+		 * ->release can cause the queue to disappear, so flush all
+		 * dirty data before.
+		 */
+		bdev_write_inode(bdev->bd_inode);
+	}
+	if (bdev->bd_contains == bdev) {
+		if (disk->fops->release)
+			disk->fops->release(disk, mode);
+	}
+	if (!bdev->bd_openers) {
+		struct module *owner = disk->fops->owner;
+
+		disk_put_part(bdev->bd_part);
+		bdev->bd_part = NULL;
+		bdev->bd_disk = NULL;
+		if (bdev != bdev->bd_contains)
+			victim = bdev->bd_contains;
+		bdev->bd_contains = NULL;
+
+		put_disk(disk);
+		module_put(owner);
+	}
+	mutex_unlock(&bdev->bd_mutex);
+	bdput(bdev);
+	if (victim)
+		__blkdev_put(victim, mode, 1);
+}
+
+void blkdev_put(struct block_device *bdev, fmode_t mode)
+{
+	mutex_lock(&bdev->bd_mutex);
+
+	if (mode & FMODE_EXCL) {
+		bool bdev_free;
+
+		/*
+		 * Release a claim on the device.  The holder fields
+		 * are protected with bdev_lock.  bd_mutex is to
+		 * synchronize disk_holder unlinking.
+		 */
+		spin_lock(&bdev_lock);
+
+		WARN_ON_ONCE(--bdev->bd_holders < 0);
+		WARN_ON_ONCE(--bdev->bd_contains->bd_holders < 0);
+
+		/* bd_contains might point to self, check in a separate step */
+		if ((bdev_free = !bdev->bd_holders))
+			bdev->bd_holder = NULL;
+		if (!bdev->bd_contains->bd_holders)
+			bdev->bd_contains->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(bdev->bd_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(bdev->bd_disk, DISK_EVENT_MEDIA_CHANGE);
+
+	mutex_unlock(&bdev->bd_mutex);
+
+	__blkdev_put(bdev, mode, 0);
+}
+EXPORT_SYMBOL(blkdev_put);
+
+static int blkdev_close(struct inode * inode, struct file * filp)
+{
+	struct block_device *bdev = I_BDEV(filp->f_mapping->host);
+	blkdev_put(bdev, filp->f_mode);
+	return 0;
+}
+
+static long block_ioctl(struct file *file, unsigned cmd, unsigned long arg)
+{
+	struct block_device *bdev = I_BDEV(file->f_mapping->host);
+	fmode_t mode = file->f_mode;
+
+	/*
+	 * O_NDELAY can be altered using fcntl(.., F_SETFL, ..), so we have
+	 * to updated it before every ioctl.
+	 */
+	if (file->f_flags & O_NDELAY)
+		mode |= FMODE_NDELAY;
+	else
+		mode &= ~FMODE_NDELAY;
+
+	return blkdev_ioctl(bdev, mode, cmd, arg);
+}
+
+/*
+ * Write data to the block device.  Only intended for the block device itself
+ * and the raw driver which basically is a fake block device.
+ *
+ * Does not take i_mutex for the write and thus is not for general purpose
+ * use.
+ */
+ssize_t blkdev_write_iter(struct kiocb *iocb, struct iov_iter *from)
+{
+	struct file *file = iocb->ki_filp;
+	struct inode *bd_inode = file->f_mapping->host;
+	loff_t size = i_size_read(bd_inode);
+	struct blk_plug plug;
+	ssize_t ret;
+
+	if (bdev_read_only(I_BDEV(bd_inode)))
+		return -EPERM;
+
+	if (!iov_iter_count(from))
+		return 0;
+
+	if (iocb->ki_pos >= size)
+		return -ENOSPC;
+
+	iov_iter_truncate(from, size - iocb->ki_pos);
+
+	blk_start_plug(&plug);
+	ret = __generic_file_write_iter(iocb, from);
+	if (ret > 0) {
+		ssize_t err;
+		err = generic_write_sync(file, iocb->ki_pos - ret, ret);
+		if (err < 0)
+			ret = err;
+	}
+	blk_finish_plug(&plug);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(blkdev_write_iter);
+
+ssize_t blkdev_read_iter(struct kiocb *iocb, struct iov_iter *to)
+{
+	struct file *file = iocb->ki_filp;
+	struct inode *bd_inode = file->f_mapping->host;
+	loff_t size = i_size_read(bd_inode);
+	loff_t pos = iocb->ki_pos;
+
+	if (pos >= size)
+		return 0;
+
+	size -= pos;
+	iov_iter_truncate(to, size);
+	return generic_file_read_iter(iocb, to);
+}
+EXPORT_SYMBOL_GPL(blkdev_read_iter);
+
+/*
+ * Try to release a page associated with block device when the system
+ * is under memory pressure.
+ */
+static int blkdev_releasepage(struct page *page, gfp_t wait)
+{
+	struct super_block *super = BDEV_I(page->mapping->host)->bdev.bd_super;
+
+	if (super && super->s_op->bdev_try_to_free_page)
+		return super->s_op->bdev_try_to_free_page(super, page, wait);
+
+	return try_to_free_buffers(page);
+}
+
+static const struct address_space_operations def_blk_aops = {
+	.readpage	= blkdev_readpage,
+	.readpages	= blkdev_readpages,
+	.writepage	= blkdev_writepage,
+	.write_begin	= blkdev_write_begin,
+	.write_end	= blkdev_write_end,
+	.writepages	= generic_writepages,
+	.releasepage	= blkdev_releasepage,
+	.direct_IO	= blkdev_direct_IO,
+	.is_dirty_writeback = buffer_check_dirty_writeback,
+};
+
+const struct file_operations def_blk_fops = {
+	.open		= blkdev_open,
+	.release	= blkdev_close,
+	.llseek		= block_llseek,
+	.read_iter	= blkdev_read_iter,
+	.write_iter	= blkdev_write_iter,
+	.mmap		= generic_file_mmap,
+	.fsync		= blkdev_fsync,
+	.unlocked_ioctl	= block_ioctl,
+#ifdef CONFIG_COMPAT
+	.compat_ioctl	= compat_blkdev_ioctl,
+#endif
+	.splice_read	= generic_file_splice_read,
+	.splice_write	= iter_file_splice_write,
+};
+
+int ioctl_by_bdev(struct block_device *bdev, unsigned cmd, unsigned long arg)
+{
+	int res;
+	mm_segment_t old_fs = get_fs();
+	set_fs(KERNEL_DS);
+	res = blkdev_ioctl(bdev, 0, cmd, arg);
+	set_fs(old_fs);
+	return res;
+}
+
+EXPORT_SYMBOL(ioctl_by_bdev);
+
+/**
+ * lookup_bdev  - lookup a struct block_device by name
+ * @pathname:	special file representing the block device
+ *
+ * Get a reference to the blockdevice at @pathname in the current
+ * namespace if possible and return it.  Return ERR_PTR(error)
+ * otherwise.
+ */
+struct block_device *lookup_bdev(const char *pathname)
+{
+	struct block_device *bdev;
+	struct inode *inode;
+	struct path path;
+	int error;
+
+	if (!pathname || !*pathname)
+		return ERR_PTR(-EINVAL);
+
+	error = kern_path(pathname, LOOKUP_FOLLOW, &path);
+	if (error)
+		return ERR_PTR(error);
+
+	inode = d_backing_inode(path.dentry);
+	error = -ENOTBLK;
+	if (!S_ISBLK(inode->i_mode))
+		goto fail;
+	error = -EACCES;
+	if (path.mnt->mnt_flags & MNT_NODEV)
+		goto fail;
+	error = -ENOMEM;
+	bdev = bd_acquire(inode);
+	if (!bdev)
+		goto fail;
+out:
+	path_put(&path);
+	return bdev;
+fail:
+	bdev = ERR_PTR(error);
+	goto out;
+}
+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(&inode_sb_list_lock);
+	list_for_each_entry(inode, &blockdev_superblock->s_inodes, i_sb_list) {
+		struct address_space *mapping = inode->i_mapping;
+
+		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(&inode_sb_list_lock);
+		/*
+		 * We hold a reference to 'inode' so it couldn't have been
+		 * removed from s_inodes list while we dropped the
+		 * inode_sb_list_lock.  We cannot iput the inode now as we can
+		 * be holding the last reference and we cannot iput it under
+		 * inode_sb_list_lock. So we keep the reference and iput it
+		 * later.
+		 */
+		iput(old_inode);
+		old_inode = inode;
+
+		func(I_BDEV(inode), arg);
+
+		spin_lock(&inode_sb_list_lock);
+	}
+	spin_unlock(&inode_sb_list_lock);
+	iput(old_inode);
+}