[RFC PATCH] efivarfs: Introduce efivarfs refresh remount

[Weizhao Ouyang <o451686892@gmail.com>]

Currently, when setting efi variables through the runtime service,
efivarfs cannot sync variable updates properly. Introduce efivarfs
refresh remount to support efivarfs information updates from other
sources.

Signed-off-by: Weizhao Ouyang <o451686892@gmail.com>
---
 Documentation/filesystems/efivarfs.rst |  6 ++++
 fs/efivarfs/super.c                    | 40 +++++++++++++++++++++++++-
 2 files changed, 45 insertions(+), 1 deletion(-)

diff --git a/Documentation/filesystems/efivarfs.rst b/Documentation/filesystems/efivarfs.rst
index f646c3f0980f..58461e02ad01 100644
--- a/Documentation/filesystems/efivarfs.rst
+++ b/Documentation/filesystems/efivarfs.rst
@@ -18,6 +18,12 @@ efivarfs is typically mounted like this::
 
 	mount -t efivarfs none /sys/firmware/efi/efivars
 
+To support efivar updates from other sources (efi_test ioctl, runtime
+driver, etc.), set ``efivarfs.refresh=1``. After that, remount will
+update the efivar information in efivarfs, like this::
+
+	mount -t efivarfs none /sys/firmware/efi/efivars -o remount
+
 Due to the presence of numerous firmware bugs where removing non-standard
 UEFI variables causes the system firmware to fail to POST, efivarfs
 files that are not well-known standardized variables are created
diff --git a/fs/efivarfs/super.c b/fs/efivarfs/super.c
index beba15673be8..7ae22ca120e3 100644
--- a/fs/efivarfs/super.c
+++ b/fs/efivarfs/super.c
@@ -277,6 +277,44 @@ static const struct fs_parameter_spec efivarfs_parameters[] = {
 	{},
 };
 
+static bool efivarfs_refresh_default __read_mostly;
+module_param_named(refresh, efivarfs_refresh_default, bool, 0444);
+
+static void efivarfs_clean_dentry(struct dentry *dentry)
+{
+	struct dentry *child;
+
+	if (!dentry)
+		return;
+
+	if (d_is_dir(dentry)) {
+		spin_lock(&dentry->d_lock);
+		hlist_for_each_entry(child, &dentry->d_children, d_sib) {
+			if (child)
+				efivarfs_clean_dentry(child);
+		}
+		spin_unlock(&dentry->d_lock);
+	} else {
+		d_invalidate(dentry);
+	}
+}
+
+static int efivarfs_refresh(struct fs_context *fc)
+{
+	struct efivarfs_fs_info *sbi = fc->s_fs_info;
+
+	if (!efivarfs_refresh_default)
+		return 0;
+
+	if (!fc->root)
+		return -EINVAL;
+
+	efivarfs_clean_dentry(fc->root);
+	efivar_init(efivarfs_callback, fc->root->d_sb, &sbi->efivarfs_list);
+
+	return 0;
+}
+
 static int efivarfs_parse_param(struct fs_context *fc, struct fs_parameter *param)
 {
 	struct efivarfs_fs_info *sbi = fc->s_fs_info;
@@ -351,7 +389,7 @@ static int efivarfs_reconfigure(struct fs_context *fc)
 		return -EINVAL;
 	}
 
-	return 0;
+	return efivarfs_refresh(fc);
 }
 
 static const struct fs_context_operations efivarfs_context_ops = {
-- 
2.45.2