kernfs: make kernfs_open_file->mmapped a bitfield

More kernfs_open_file->mutex synchronized flags are planned to be
added.  Convert ->mmapped to a bitfield in preparation.

While at it, make kernfs_fop_mmap() use "true" instead of "1" on
->mmapped.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Acked-by: Acked-by: Zefan Li <lizefan@huawei.com>

fs/kernfs/file.c

@@ -516,7 +516,7 @@ static int kernfs_fop_mmap(struct file *file, struct vm_area_struct *vma)
 		goto out_put;
 
 	rc = 0;
-	of->mmapped = 1;
+	of->mmapped = true;
 	of->vm_ops = vma->vm_ops;
 	vma->vm_ops = &kernfs_vm_ops;
 out_put:

include/linux/kernfs.h

@@ -185,7 +185,7 @@ struct kernfs_open_file {
 	char			*prealloc_buf;
 
 	size_t			atomic_write_len;
-	bool			mmapped;
+	bool			mmapped:1;
 	const struct vm_operations_struct *vm_ops;
 };