[PATCH] bdev: add I_BDEV()

From: viro@parcelfarce.linux.theplanet.co.uk <viro@parcelfarce.linux.theplanet.co.uk>

For bdevfs inodes (ones created along with struct block_device by
fs/block_dev.c) we have inode->i_bdev equal to &BDEV_I(inode)->bdev (i.e.
it's at the constant offset from inode).  New helper added for such inodes
(I_BDEV(inode)).  A bunch of places (mostly in block_dev.c) switched to use
of that helper.  A bunch of places that used

	file->f_dentry->d_inode->i_bdev->bd_inode

switched to

	file->f_mapping->host

- those expressions are equal whenever the former is valid.

drivers/block/loop.c

@@ -683,7 +683,7 @@ static int loop_set_fd(struct loop_device *lo, struct file *lo_file,
 		lo_flags |= LO_FLAGS_READ_ONLY;
 
 	if (S_ISBLK(inode->i_mode)) {
-		lo_device = inode->i_bdev;
+		lo_device = I_BDEV(inode);
 		if (lo_device == bdev) {
 			error = -EBUSY;
 			goto out_putf;

fs/block_dev.c

@@ -25,6 +25,22 @@
 #include <linux/namei.h>
 #include <asm/uaccess.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);
+}
+
+inline struct block_device *I_BDEV(struct inode *inode)
+{
+	return &BDEV_I(inode)->bdev;
+}
+
+EXPORT_SYMBOL(I_BDEV);
 
 static sector_t max_block(struct block_device *bdev)
 {
@@ -100,10 +116,10 @@ static int
 blkdev_get_block(struct inode *inode, sector_t iblock,
 		struct buffer_head *bh, int create)
 {
-	if (iblock >= max_block(inode->i_bdev))
+	if (iblock >= max_block(I_BDEV(inode)))
 		return -EIO;
 
-	bh->b_bdev = inode->i_bdev;
+	bh->b_bdev = I_BDEV(inode);
 	bh->b_blocknr = iblock;
 	set_buffer_mapped(bh);
 	return 0;
@@ -113,10 +129,10 @@ static int
 blkdev_get_blocks(struct inode *inode, sector_t iblock,
 		unsigned long max_blocks, struct buffer_head *bh, int create)
 {
-	if ((iblock + max_blocks) > max_block(inode->i_bdev))
+	if ((iblock + max_blocks) > max_block(I_BDEV(inode)))
 		return -EIO;
 
-	bh->b_bdev = inode->i_bdev;
+	bh->b_bdev = I_BDEV(inode);
 	bh->b_blocknr = iblock;
 	bh->b_size = max_blocks << inode->i_blkbits;
 	set_buffer_mapped(bh);
@@ -130,7 +146,7 @@ blkdev_direct_IO(int rw, struct kiocb *iocb, const struct iovec *iov,
 	struct file *file = iocb->ki_filp;
 	struct inode *inode = file->f_mapping->host;
 
-	return blockdev_direct_IO(rw, iocb, inode, inode->i_bdev, iov, offset,
+	return blockdev_direct_IO(rw, iocb, inode, I_BDEV(inode), iov, offset,
 				nr_segs, blkdev_get_blocks, NULL);
 }
 
@@ -161,11 +177,10 @@ static int blkdev_commit_write(struct file *file, struct page *page, unsigned fr
  */
 static loff_t block_llseek(struct file *file, loff_t offset, int origin)
 {
-	struct inode *bd_inode;
+	struct inode *bd_inode = file->f_mapping->host;
 	loff_t size;
 	loff_t retval;
 
-	bd_inode = file->f_dentry->d_inode->i_bdev->bd_inode;
 	down(&bd_inode->i_sem);
 	size = i_size_read(bd_inode);
 
@@ -188,15 +203,13 @@ static loff_t block_llseek(struct file *file, loff_t offset, int origin)
 }
 	
 /*
- *	Filp may be NULL when we are called by an msync of a vma
- *	since the vma has no handle.
+ *	Filp is never NULL; the only case when ->fsync() is called with
+ *	NULL first argument is nfsd_sync_dir() and that's not a directory.
  */
  
 static int block_fsync(struct file *filp, struct dentry *dentry, int datasync)
 {
-	struct inode * inode = dentry->d_inode;
-
-	return sync_blockdev(inode->i_bdev);
+	return sync_blockdev(I_BDEV(filp->f_mapping->host));
 }
 
 /*
@@ -206,16 +219,6 @@ static int block_fsync(struct file *filp, struct dentry *dentry, int datasync)
 static spinlock_t bdev_lock __cacheline_aligned_in_smp = SPIN_LOCK_UNLOCKED;
 static kmem_cache_t * bdev_cachep;
 
-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);
-}
-
 static struct inode *bdev_alloc_inode(struct super_block *sb)
 {
 	struct bdev_inode *ei = kmem_cache_alloc(bdev_cachep, SLAB_KERNEL);
@@ -735,11 +738,12 @@ int blkdev_put(struct block_device *bdev, int kind)
 
 EXPORT_SYMBOL(blkdev_put);
 
-int blkdev_close(struct inode * inode, struct file * filp)
+static int blkdev_close(struct inode * inode, struct file * filp)
 {
-	if (inode->i_bdev->bd_holder == filp)
-		bd_release(inode->i_bdev);
-	return blkdev_put(inode->i_bdev, BDEV_FILE);
+	struct block_device *bdev = I_BDEV(filp->f_mapping->host);
+	if (bdev->bd_holder == filp)
+		bd_release(bdev);
+	return blkdev_put(bdev, BDEV_FILE);
 }
 
 static ssize_t blkdev_file_write(struct file *file, const char __user *buf,
@@ -758,6 +762,11 @@ static ssize_t blkdev_file_aio_write(struct kiocb *iocb, const char __user *buf,
 	return generic_file_aio_write_nolock(iocb, &local_iov, 1, &iocb->ki_pos);
 }
 
+static int block_ioctl(struct inode *inode, struct file *file, unsigned cmd,
+			unsigned long arg)
+{
+	return blkdev_ioctl(file->f_mapping->host, file, cmd, arg);
+}
 
 struct address_space_operations def_blk_aops = {
 	.readpage	= blkdev_readpage,
@@ -779,7 +788,7 @@ struct file_operations def_blk_fops = {
   	.aio_write	= blkdev_file_aio_write, 
 	.mmap		= generic_file_mmap,
 	.fsync		= block_fsync,
-	.ioctl		= blkdev_ioctl,
+	.ioctl		= block_ioctl,
 	.readv		= generic_file_readv,
 	.writev		= generic_file_writev,
 	.sendfile	= generic_file_sendfile,

fs/reiserfs/journal.c

@@ -1937,18 +1937,13 @@ static int journal_init_dev( struct super_block *super,
 
 	journal -> j_dev_file = filp_open( jdev_name, 0, 0 );
 	if( !IS_ERR( journal -> j_dev_file ) ) {
-		struct inode *jdev_inode;
-
-		jdev_inode = journal -> j_dev_file -> f_dentry -> d_inode;
-		journal -> j_dev_bd = jdev_inode -> i_bdev;
+		struct inode *jdev_inode = journal->j_dev_file->f_mapping->host;
 		if( !S_ISBLK( jdev_inode -> i_mode ) ) {
 			printk( "journal_init_dev: '%s' is not a block device\n", jdev_name );
 			result = -ENOTBLK;
-		} else if( jdev_inode -> i_bdev == NULL ) {
-			printk( "journal_init_dev: bdev uninitialized for '%s'\n", jdev_name );
-			result = -ENOMEM;
 		} else  {
 			/* ok */
+			journal->j_dev_bd = I_BDEV(jdev_inode);
 			set_blocksize(journal->j_dev_bd, super->s_blocksize);
 		}
 	} else {

include/linux/fs.h

@@ -480,6 +480,8 @@ static inline unsigned imajor(struct inode *inode)
 	return MAJOR(inode->i_rdev);
 }
 
+extern struct block_device *I_BDEV(struct inode *inode);
+
 struct fown_struct {
 	rwlock_t lock;          /* protects pid, uid, euid fields */
 	int pid;		/* pid or -pgrp where SIGIO should be sent */
@@ -1128,7 +1130,6 @@ extern struct block_device *bdget(dev_t);
 extern void bd_forget(struct inode *inode);
 extern void bdput(struct block_device *);
 extern int blkdev_open(struct inode *, struct file *);
-extern int blkdev_close(struct inode *, struct file *);
 extern struct block_device *open_by_devnum(dev_t, unsigned, int);
 extern struct file_operations def_blk_fops;
 extern struct address_space_operations def_blk_aops;

mm/filemap.c

@@ -1690,7 +1690,7 @@ inline int generic_write_checks(struct file *file, loff_t *pos, size_t *count, i
 			*count = inode->i_sb->s_maxbytes - *pos;
 	} else {
 		loff_t isize;
-		if (bdev_read_only(inode->i_bdev))
+		if (bdev_read_only(I_BDEV(inode)))
 			return -EPERM;
 		isize = i_size_read(inode);
 		if (*pos >= isize) {

mm/swapfile.c

@@ -1100,8 +1100,7 @@ asmlinkage long sys_swapoff(const char __user * specialfile)
 	swap_list_unlock();
 	vfree(swap_map);
 	if (S_ISBLK(mapping->host->i_mode)) {
-		struct block_device *bdev;
-		bdev = mapping->host->i_bdev;
+		struct block_device *bdev = I_BDEV(mapping->host);
 		set_blocksize(bdev, p->old_block_size);
 		bd_release(bdev);
 	} else {
@@ -1294,14 +1293,14 @@ asmlinkage long sys_swapon(const char __user * specialfile, int swap_flags)
 
 	error = -EINVAL;
 	if (S_ISBLK(inode->i_mode)) {
-		bdev = inode->i_bdev;
+		bdev = I_BDEV(inode);
 		error = bd_claim(bdev, sys_swapon);
 		if (error < 0) {
 			bdev = NULL;
 			goto bad_swap;
 		}
 		p->old_block_size = block_size(bdev);
-		error = set_blocksize(inode->i_bdev, PAGE_SIZE);
+		error = set_blocksize(bdev, PAGE_SIZE);
 		if (error < 0)
 			goto bad_swap;
 		p->bdev = bdev;