[PATCH v2 12/14] fs/configfs: Add a callback to determine attribute visibility

[Tom Lendacky <thomas.lendacky@amd.com>]

In order to support dynamic decisions as to whether an attribute should be
created, add a callback that returns a bool to indicate whether the
attribute should be display. If no callback is registered, the attribute
is displayed by default.

Cc: Joel Becker <jlbec@evilplan.org>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
---
 fs/configfs/file.c       |  13 +++++
 include/linux/configfs.h | 114 +++++++++++++++++++++++++++------------
 2 files changed, 93 insertions(+), 34 deletions(-)

diff --git a/fs/configfs/file.c b/fs/configfs/file.c
index 0ad32150611e..c758bcc11235 100644
--- a/fs/configfs/file.c
+++ b/fs/configfs/file.c
@@ -451,6 +451,12 @@ int configfs_create_file(struct config_item * item, const struct configfs_attrib
 	umode_t mode = (attr->ca_mode & S_IALLUGO) | S_IFREG;
 	int error = 0;
 
+	if (attr->ca_is_visible) {
+		mode = attr->ca_is_visible(item, attr);
+		if (!mode)
+			return 0;
+	}
+
 	inode_lock_nested(d_inode(dir), I_MUTEX_NORMAL);
 	error = configfs_make_dirent(parent_sd, NULL, (void *) attr, mode,
 				     CONFIGFS_ITEM_ATTR, parent_sd->s_frag);
@@ -470,9 +476,16 @@ int configfs_create_bin_file(struct config_item *item,
 {
 	struct dentry *dir = item->ci_dentry;
 	struct configfs_dirent *parent_sd = dir->d_fsdata;
+	const struct configfs_attribute *attr = &bin_attr->cb_attr;
 	umode_t mode = (bin_attr->cb_attr.ca_mode & S_IALLUGO) | S_IFREG;
 	int error = 0;
 
+	if (attr->ca_is_visible) {
+		mode = attr->ca_is_visible(item, attr);
+		if (!mode)
+			return 0;
+	}
+
 	inode_lock_nested(dir->d_inode, I_MUTEX_NORMAL);
 	error = configfs_make_dirent(parent_sd, NULL, (void *) bin_attr, mode,
 				     CONFIGFS_ITEM_BIN_ATTR, parent_sd->s_frag);
diff --git a/include/linux/configfs.h b/include/linux/configfs.h
index 2606711adb18..18011f78ffde 100644
--- a/include/linux/configfs.h
+++ b/include/linux/configfs.h
@@ -112,39 +112,64 @@ static inline void configfs_add_default_group(struct config_group *new_group,
 	list_add_tail(&new_group->group_entry, &group->default_groups);
 }
 
+typedef umode_t (*configfs_is_visible_t)(const struct config_item *item,
+					 const struct configfs_attribute *attr);
+
 struct configfs_attribute {
 	const char		*ca_name;
 	struct module 		*ca_owner;
 	umode_t			ca_mode;
+	configfs_is_visible_t	ca_is_visible;
 	ssize_t (*show)(struct config_item *, char *);
 	ssize_t (*store)(struct config_item *, const char *, size_t);
 };
 
-#define CONFIGFS_ATTR(_pfx, _name)			\
+#define __CONFIGFS_ATTR(_pfx, _name, _vis)		\
 static struct configfs_attribute _pfx##attr_##_name = {	\
 	.ca_name	= __stringify(_name),		\
 	.ca_mode	= S_IRUGO | S_IWUSR,		\
 	.ca_owner	= THIS_MODULE,			\
+	.ca_is_visible	= _vis,				\
 	.show		= _pfx##_name##_show,		\
 	.store		= _pfx##_name##_store,		\
 }
 
-#define CONFIGFS_ATTR_RO(_pfx, _name)			\
+#define __CONFIGFS_ATTR_RO(_pfx, _name, _vis)		\
 static struct configfs_attribute _pfx##attr_##_name = {	\
 	.ca_name	= __stringify(_name),		\
 	.ca_mode	= S_IRUGO,			\
 	.ca_owner	= THIS_MODULE,			\
+	.ca_is_visible	= _vis,				\
 	.show		= _pfx##_name##_show,		\
 }
 
-#define CONFIGFS_ATTR_WO(_pfx, _name)			\
+#define __CONFIGFS_ATTR_WO(_pfx, _name, _vis)		\
 static struct configfs_attribute _pfx##attr_##_name = {	\
 	.ca_name	= __stringify(_name),		\
 	.ca_mode	= S_IWUSR,			\
 	.ca_owner	= THIS_MODULE,			\
+	.ca_is_visible	= _vis,				\
 	.store		= _pfx##_name##_store,		\
 }
 
+#define CONFIGFS_ATTR(_pfx, _name)			\
+	__CONFIGFS_ATTR(_pfx, _name, NULL)
+
+#define CONFIGFS_ATTR_RO(_pfx, _name)			\
+	__CONFIGFS_ATTR_RO(_pfx, _name, NULL)
+
+#define CONFIGFS_ATTR_WO(_pfx, _name)			\
+	__CONFIGFS_ATTR_WO(_pfx, _name, NULL)
+
+#define CONFIGFS_ATTR_VISIBLE(_pfx, _name, _vis)	\
+	__CONFIGFS_ATTR(_pfx, _name, _vis)
+
+#define CONFIGFS_ATTR_VISIBLE_RO(_pfx, _name, _vis)	\
+	__CONFIGFS_ATTR_RO(_pfx, _name, _vis)
+
+#define CONFIGFS_ATTR_VISIBLE_WO(_pfx, _name, _vis)	\
+	__CONFIGFS_ATTR_WO(_pfx, _name, _vis)
+
 struct file;
 struct vm_area_struct;
 
@@ -156,43 +181,64 @@ struct configfs_bin_attribute {
 	ssize_t (*write)(struct config_item *, const void *, size_t);
 };
 
-#define CONFIGFS_BIN_ATTR(_pfx, _name, _priv, _maxsz)		\
-static struct configfs_bin_attribute _pfx##attr_##_name = {	\
-	.cb_attr = {						\
-		.ca_name	= __stringify(_name),		\
-		.ca_mode	= S_IRUGO | S_IWUSR,		\
-		.ca_owner	= THIS_MODULE,			\
-	},							\
-	.cb_private	= _priv,				\
-	.cb_max_size	= _maxsz,				\
-	.read		= _pfx##_name##_read,			\
-	.write		= _pfx##_name##_write,			\
+#define __CONFIGFS_BIN_ATTR(_pfx, _name, _priv, _maxsz, _vis)		\
+static struct configfs_bin_attribute _pfx##attr_##_name = {		\
+	.cb_attr = {							\
+		.ca_name	= __stringify(_name),			\
+		.ca_mode	= S_IRUGO | S_IWUSR,			\
+		.ca_owner	= THIS_MODULE,				\
+		.ca_is_visible	= _vis,					\
+	},								\
+	.cb_private	= _priv,					\
+	.cb_max_size	= _maxsz,					\
+	.read		= _pfx##_name##_read,				\
+	.write		= _pfx##_name##_write,				\
 }
 
-#define CONFIGFS_BIN_ATTR_RO(_pfx, _name, _priv, _maxsz)	\
-static struct configfs_bin_attribute _pfx##attr_##_name = {	\
-	.cb_attr = {						\
-		.ca_name	= __stringify(_name),		\
-		.ca_mode	= S_IRUGO,			\
-		.ca_owner	= THIS_MODULE,			\
-	},							\
-	.cb_private	= _priv,				\
-	.cb_max_size	= _maxsz,				\
-	.read		= _pfx##_name##_read,			\
+#define __CONFIGFS_BIN_ATTR_RO(_pfx, _name, _priv, _maxsz, _vis)	\
+static struct configfs_bin_attribute _pfx##attr_##_name = {		\
+	.cb_attr = {							\
+		.ca_name	= __stringify(_name),			\
+		.ca_mode	= S_IRUGO,				\
+		.ca_owner	= THIS_MODULE,				\
+		.ca_is_visible	= _vis,					\
+	},								\
+	.cb_private	= _priv,					\
+	.cb_max_size	= _maxsz,					\
+	.read		= _pfx##_name##_read,				\
 }
 
-#define CONFIGFS_BIN_ATTR_WO(_pfx, _name, _priv, _maxsz)	\
-static struct configfs_bin_attribute _pfx##attr_##_name = {	\
-	.cb_attr = {						\
-		.ca_name	= __stringify(_name),		\
-		.ca_mode	= S_IWUSR,			\
-		.ca_owner	= THIS_MODULE,			\
-	},							\
-	.cb_private	= _priv,				\
-	.cb_max_size	= _maxsz,				\
-	.write		= _pfx##_name##_write,			\
+#define __CONFIGFS_BIN_ATTR_WO(_pfx, _name, _priv, _maxsz, _vis)	\
+static struct configfs_bin_attribute _pfx##attr_##_name = {		\
+	.cb_attr = {							\
+		.ca_name	= __stringify(_name),			\
+		.ca_mode	= S_IWUSR,				\
+		.ca_owner	= THIS_MODULE,				\
+		.ca_is_visible	= _vis,					\
+	},								\
+	.cb_private	= _priv,					\
+	.cb_max_size	= _maxsz,					\
+	.write		= _pfx##_name##_write,				\
 }
 
+#define CONFIGFS_BIN_ATTR(_pfx, _name, _priv, _maxsz)			\
+	__CONFIGFS_BIN_ATTR(_pfx, _name, _priv, _maxsz, NULL)
+
+#define CONFIGFS_BIN_ATTR_RO(_pfx, _name, _priv, _maxsz)		\
+	__CONFIGFS_BIN_ATTR_RO(_pfx, _name, _priv, _maxsz, NULL)
+
+#define CONFIGFS_BIN_ATTR_WO(_pfx, _name, _priv, _maxsz)		\
+	__CONFIGFS_BIN_ATTR_WO(_pfx, _name, _priv, _maxsz, NULL)
+
+#define CONFIGFS_BIN_ATTR_VISIBLE(_pfx, _name, _priv, _maxs, _vis)	\
+	__CONFIGFS_BIN_ATTR(_pfx, _name, _priv, _maxsz, _vis)
+
+#define CONFIGFS_BIN_ATTR_VISIBLE_RO(_pfx, _name, _priv, _maxsz, _vis)	\
+	__CONFIGFS_BIN_ATTR_RO(_pfx, _name, _priv, _maxsz, _vis)
+
+#define CONFIGFS_BIN_ATTR_VISIBLE_WO(_pfx, _name, _priv, _maxsz, _vis)	\
+	__CONFIGFS_BIN_ATTR_WO(_pfx, _name, _priv, _maxsz, _vis)
+
 /*
  * If allow_link() exists, the item can symlink(2) out to other
  * items.  If the item is a group, it may support mkdir(2).
-- 
2.43.2