block: use bdev_nr_bytes instead of open coding it in blkdev_fallocate

Use the proper helper to read the block device size.

Signed-off-by: Christoph Hellwig <[email protected]>
Reviewed-by: Kees Cook <[email protected]>
Reviewed-by: Jan Kara <[email protected]>
Reviewed-by: Chaitanya Kulkarni <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Jens Axboe <[email protected]>

Author: Christoph Hellwig

block/fops.c

@@ -535,7 +535,7 @@ static long blkdev_fallocate(struct file *file, int mode, loff_t start,
 		return -EOPNOTSUPP;
 
 	/* Don't go off the end of the device. */
-	isize = i_size_read(bdev->bd_inode);
+	isize = bdev_nr_bytes(bdev);
 	if (start >= isize)
 		return -EINVAL;
 	if (end >= isize) {