block: hoist block size validation code to a separate function

Hoist the block size validation code to bdev_validate_blocksize so that
we can call it from filesystems that don't care about the bdev pagecache
manipulations of set_blocksize.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Luis Chamberlain <mcgrof@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/174543795720.4139148.840349813093799165.stgit@frogsfrogsfrogs
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Author: Darrick J. Wong

block/bdev.c

@@ -152,18 +152,39 @@ static void set_init_blocksize(struct block_device *bdev)
 				    get_order(bsize));
 }
 
-int set_blocksize(struct file *file, int size)
+/**
+ * bdev_validate_blocksize - check that this block size is acceptable
+ * @bdev:	blockdevice to check
+ * @block_size:	block size to check
+ *
+ * For block device users that do not use buffer heads or the block device
+ * page cache, make sure that this block size can be used with the device.
+ *
+ * Return: On success zero is returned, negative error code on failure.
+ */
+int bdev_validate_blocksize(struct block_device *bdev, int block_size)
 {
-	struct inode *inode = file->f_mapping->host;
-	struct block_device *bdev = I_BDEV(inode);
-
-	if (blk_validate_block_size(size))
+	if (blk_validate_block_size(block_size))
 		return -EINVAL;
 
 	/* Size cannot be smaller than the size supported by the device */
-	if (size < bdev_logical_block_size(bdev))
+	if (block_size < bdev_logical_block_size(bdev))
 		return -EINVAL;
 
+	return 0;
+}
+EXPORT_SYMBOL_GPL(bdev_validate_blocksize);
+
+int set_blocksize(struct file *file, int size)
+{
+	struct inode *inode = file->f_mapping->host;
+	struct block_device *bdev = I_BDEV(inode);
+	int ret;
+
+	ret = bdev_validate_blocksize(bdev, size);
+	if (ret)
+		return ret;
+
 	if (!file->private_data)
 		return -EINVAL;
 

include/linux/blkdev.h

@@ -1614,6 +1614,7 @@ static inline void bio_end_io_acct(struct bio *bio, unsigned long start_time)
 	return bio_end_io_acct_remapped(bio, start_time, bio->bi_bdev);
 }
 
+int bdev_validate_blocksize(struct block_device *bdev, int block_size);
 int set_blocksize(struct file *file, int size);
 
 int lookup_bdev(const char *pathname, dev_t *dev);