squashfs: use bdev_nr_bytes instead of open coding it

Use the proper helper to read the block device size.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Kees Cook <keescook@chromium.org>
Acked-by: Phillip Lougher <phillip@squashfs.org.uk>
Link: https://lore.kernel.org/r/20211018101130.1838532-24-hch@lst.deSigned-off-by: Jens Axboe <axboe@kernel.dk>

fs/squashfs/super.c

@@ -16,6 +16,7 @@
 
 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
 
+#include <linux/blkdev.h>
 #include <linux/fs.h>
 #include <linux/fs_context.h>
 #include <linux/fs_parser.h>
@@ -179,8 +180,8 @@ static int squashfs_fill_super(struct super_block *sb, struct fs_context *fc)
 	/* Check the filesystem does not extend beyond the end of the
 	   block device */
 	msblk->bytes_used = le64_to_cpu(sblk->bytes_used);
-	if (msblk->bytes_used < 0 || msblk->bytes_used >
-			i_size_read(sb->s_bdev->bd_inode))
+	if (msblk->bytes_used < 0 ||
+	    msblk->bytes_used > bdev_nr_bytes(sb->s_bdev))
 		goto failed_mount;
 
 	/* Check block size for sanity */