blockdev: remove bd_block_size_semaphore again

This reverts the block-device direct access code to the previous
unlocked code, now that fs/buffer.c no longer needs external locking.

With this, fs/block_dev.c is back to the original version, apart from a
whitespace cleanup that I didn't want to revert.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/char/raw.c

@@ -285,7 +285,7 @@ static long raw_ctl_compat_ioctl(struct file *file, unsigned int cmd,
 
 static const struct file_operations raw_fops = {
 	.read		= do_sync_read,
-	.aio_read	= blkdev_aio_read,
+	.aio_read	= generic_file_aio_read,
 	.write		= do_sync_write,
 	.aio_write	= blkdev_aio_write,
 	.fsync		= blkdev_fsync,

fs/block_dev.c

@@ -116,8 +116,6 @@ EXPORT_SYMBOL(invalidate_bdev);
 
 int set_blocksize(struct block_device *bdev, int size)
 {
-	struct address_space *mapping;
-
 	/* 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;
@@ -126,19 +124,6 @@ int set_blocksize(struct block_device *bdev, int size)
 	if (size < bdev_logical_block_size(bdev))
 		return -EINVAL;
 
-	/* Prevent starting I/O or mapping the device */
-	percpu_down_write(&bdev->bd_block_size_semaphore);
-
-	/* Check that the block device is not memory mapped */
-	mapping = bdev->bd_inode->i_mapping;
-	mutex_lock(&mapping->i_mmap_mutex);
-	if (mapping_mapped(mapping)) {
-		mutex_unlock(&mapping->i_mmap_mutex);
-		percpu_up_write(&bdev->bd_block_size_semaphore);
-		return -EBUSY;
-	}
-	mutex_unlock(&mapping->i_mmap_mutex);
-
 	/* Don't change the size if it is same as current */
 	if (bdev->bd_block_size != size) {
 		sync_blockdev(bdev);
@@ -146,9 +131,6 @@ int set_blocksize(struct block_device *bdev, int size)
 		bdev->bd_inode->i_blkbits = blksize_bits(size);
 		kill_bdev(bdev);
 	}
-
-	percpu_up_write(&bdev->bd_block_size_semaphore);
-
 	return 0;
 }
 
@@ -459,12 +441,6 @@ 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;
-
-	if (unlikely(percpu_init_rwsem(&ei->bdev.bd_block_size_semaphore))) {
-		kmem_cache_free(bdev_cachep, ei);
-		return NULL;
-	}
-
 	return &ei->vfs_inode;
 }
 
@@ -473,8 +449,6 @@ 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);
 
-	percpu_free_rwsem(&bdi->bdev.bd_block_size_semaphore);
-
 	kmem_cache_free(bdev_cachep, bdi);
 }
 
@@ -1593,22 +1567,6 @@ static long block_ioctl(struct file *file, unsigned cmd, unsigned long arg)
 	return blkdev_ioctl(bdev, mode, cmd, arg);
 }
 
-ssize_t blkdev_aio_read(struct kiocb *iocb, const struct iovec *iov,
-			unsigned long nr_segs, loff_t pos)
-{
-	ssize_t ret;
-	struct block_device *bdev = I_BDEV(iocb->ki_filp->f_mapping->host);
-
-	percpu_down_read(&bdev->bd_block_size_semaphore);
-
-	ret = generic_file_aio_read(iocb, iov, nr_segs, pos);
-
-	percpu_up_read(&bdev->bd_block_size_semaphore);
-
-	return ret;
-}
-EXPORT_SYMBOL_GPL(blkdev_aio_read);
-
 /*
  * Write data to the block device.  Only intended for the block device itself
  * and the raw driver which basically is a fake block device.
@@ -1620,16 +1578,12 @@ ssize_t blkdev_aio_write(struct kiocb *iocb, const struct iovec *iov,
 			 unsigned long nr_segs, loff_t pos)
 {
 	struct file *file = iocb->ki_filp;
-	struct block_device *bdev = I_BDEV(file->f_mapping->host);
 	struct blk_plug plug;
 	ssize_t ret;
 
 	BUG_ON(iocb->ki_pos != pos);
 
 	blk_start_plug(&plug);
-
-	percpu_down_read(&bdev->bd_block_size_semaphore);
-
 	ret = __generic_file_aio_write(iocb, iov, nr_segs, &iocb->ki_pos);
 	if (ret > 0 || ret == -EIOCBQUEUED) {
 		ssize_t err;
@@ -1638,62 +1592,11 @@ ssize_t blkdev_aio_write(struct kiocb *iocb, const struct iovec *iov,
 		if (err < 0 && ret > 0)
 			ret = err;
 	}
-
-	percpu_up_read(&bdev->bd_block_size_semaphore);
-
 	blk_finish_plug(&plug);
-
 	return ret;
 }
 EXPORT_SYMBOL_GPL(blkdev_aio_write);
 
-static int blkdev_mmap(struct file *file, struct vm_area_struct *vma)
-{
-	int ret;
-	struct block_device *bdev = I_BDEV(file->f_mapping->host);
-
-	percpu_down_read(&bdev->bd_block_size_semaphore);
-
-	ret = generic_file_mmap(file, vma);
-
-	percpu_up_read(&bdev->bd_block_size_semaphore);
-
-	return ret;
-}
-
-static ssize_t blkdev_splice_read(struct file *file, loff_t *ppos,
-				  struct pipe_inode_info *pipe, size_t len,
-				  unsigned int flags)
-{
-	ssize_t ret;
-	struct block_device *bdev = I_BDEV(file->f_mapping->host);
-
-	percpu_down_read(&bdev->bd_block_size_semaphore);
-
-	ret = generic_file_splice_read(file, ppos, pipe, len, flags);
-
-	percpu_up_read(&bdev->bd_block_size_semaphore);
-
-	return ret;
-}
-
-static ssize_t blkdev_splice_write(struct pipe_inode_info *pipe,
-				   struct file *file, loff_t *ppos, size_t len,
-				   unsigned int flags)
-{
-	ssize_t ret;
-	struct block_device *bdev = I_BDEV(file->f_mapping->host);
-
-	percpu_down_read(&bdev->bd_block_size_semaphore);
-
-	ret = generic_file_splice_write(pipe, file, ppos, len, flags);
-
-	percpu_up_read(&bdev->bd_block_size_semaphore);
-
-	return ret;
-}
-
-
 /*
  * Try to release a page associated with block device when the system
  * is under memory pressure.
@@ -1724,16 +1627,16 @@ const struct file_operations def_blk_fops = {
 	.llseek		= block_llseek,
 	.read		= do_sync_read,
 	.write		= do_sync_write,
-  	.aio_read	= blkdev_aio_read,
+	.aio_read	= generic_file_aio_read,
 	.aio_write	= blkdev_aio_write,
-	.mmap		= blkdev_mmap,
+	.mmap		= generic_file_mmap,
 	.fsync		= blkdev_fsync,
 	.unlocked_ioctl	= block_ioctl,
 #ifdef CONFIG_COMPAT
 	.compat_ioctl	= compat_blkdev_ioctl,
 #endif
-	.splice_read	= blkdev_splice_read,
-	.splice_write	= blkdev_splice_write,
+	.splice_read	= generic_file_splice_read,
+	.splice_write	= generic_file_splice_write,
 };
 
 int ioctl_by_bdev(struct block_device *bdev, unsigned cmd, unsigned long arg)

include/linux/fs.h

@@ -462,8 +462,6 @@ struct block_device {
 	int			bd_fsfreeze_count;
 	/* Mutex for freeze */
 	struct mutex		bd_fsfreeze_mutex;
-	/* A semaphore that prevents I/O while block size is being changed */
-	struct percpu_rw_semaphore	bd_block_size_semaphore;
 };
 
 /*
@@ -2379,8 +2377,6 @@ extern int generic_segment_checks(const struct iovec *iov,
 		unsigned long *nr_segs, size_t *count, int access_flags);
 
 /* fs/block_dev.c */
-extern ssize_t blkdev_aio_read(struct kiocb *iocb, const struct iovec *iov,
-			       unsigned long nr_segs, loff_t pos);
 extern ssize_t blkdev_aio_write(struct kiocb *iocb, const struct iovec *iov,
 				unsigned long nr_segs, loff_t pos);
 extern int blkdev_fsync(struct file *filp, loff_t start, loff_t end,