[PATCH] efi/efivars: Create efivars mount point in the registration of efivars abstraction

["Lee, Chun-Yi" <joeyli.kernel@gmail.com>]

This patch moved the logic of creating efivars mount point to the
registration of efivars abstraction. It's useful for userland to
determine the availability of efivars filesystem by checking the
existence of mount point.

The 'efivars' platform device be created on generic EFI runtime services
platform, so it can be used to determine the availability of efivarfs.
But this approach is not available for google gsmi efivars abstraction.

This patch be tested on Here on qemu-OVMF and qemu-uboot.

Cc: Ard Biesheuvel <ardb@kernel.org>
Cc: Matthias Brugger <mbrugger@suse.com>
Cc: Fabian Vogt <fvogt@suse.com>
Cc: Ilias Apalodimas <ilias.apalodimas@linaro.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Arthur Heymans <arthur@aheymans.xyz>
Cc: Patrick Rudolph <patrick.rudolph@9elements.com>
Signed-off-by: "Lee, Chun-Yi" <jlee@suse.com>
---
 drivers/firmware/efi/efi.c  |  7 -------
 drivers/firmware/efi/vars.c | 17 +++++++++++++++++
 2 files changed, 17 insertions(+), 7 deletions(-)

diff --git a/drivers/firmware/efi/efi.c b/drivers/firmware/efi/efi.c
index 3aa07c3b5136..23c11a2a3f4d 100644
--- a/drivers/firmware/efi/efi.c
+++ b/drivers/firmware/efi/efi.c
@@ -405,13 +405,6 @@ static int __init efisubsys_init(void)
 	if (error)
 		goto err_remove_group;
 
-	/* and the standard mountpoint for efivarfs */
-	error = sysfs_create_mount_point(efi_kobj, "efivars");
-	if (error) {
-		pr_err("efivars: Subsystem registration failed.\n");
-		goto err_remove_group;
-	}
-
 	if (efi_enabled(EFI_DBG) && efi_enabled(EFI_PRESERVE_BS_REGIONS))
 		efi_debugfs_init();
 
diff --git a/drivers/firmware/efi/vars.c b/drivers/firmware/efi/vars.c
index 973eef234b36..6fa7f288d635 100644
--- a/drivers/firmware/efi/vars.c
+++ b/drivers/firmware/efi/vars.c
@@ -1179,6 +1179,8 @@ int efivars_register(struct efivars *efivars,
 		     const struct efivar_operations *ops,
 		     struct kobject *kobject)
 {
+	int error;
+
 	if (down_interruptible(&efivars_lock))
 		return -EINTR;
 
@@ -1191,6 +1193,19 @@ int efivars_register(struct efivars *efivars,
 
 	up(&efivars_lock);
 
+	/* and the standard mountpoint for efivarfs */
+	if (efi_kobj) {
+		error = sysfs_create_mount_point(efi_kobj, "efivars");
+		if (error) {
+			if (down_interruptible(&efivars_lock))
+				return -EINTR;
+			__efivars = NULL;
+			up(&efivars_lock);
+			pr_err("efivars: Subsystem registration failed.\n");
+			return error;
+		}
+	}
+
 	return 0;
 }
 EXPORT_SYMBOL_GPL(efivars_register);
@@ -1222,6 +1237,8 @@ int efivars_unregister(struct efivars *efivars)
 
 	pr_info("Unregistered efivars operations\n");
 	__efivars = NULL;
+	if (efi_kobj)
+		sysfs_remove_mount_point(efi_kobj, "efivars");
 
 	rv = 0;
 out:
-- 
2.16.4