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From: Tom Lendacky <thomas.lendacky@amd.com>
To: <linux-kernel@vger.kernel.org>, <x86@kernel.org>,
	<linux-coco@lists.linux.dev>, <svsm-devel@coconut-svsm.dev>
CC: Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@redhat.com>,
	Borislav Petkov <bp@alien8.de>, Dave Hansen <dave.hansen@linux.intel.com>,
	"H. Peter Anvin" <hpa@zytor.com>, Andy Lutomirski <luto@kernel.org>, "Peter
 Zijlstra" <peterz@infradead.org>, Dan Williams <dan.j.williams@intel.com>,
	Michael Roth <michael.roth@amd.com>, Ashish Kalra <ashish.kalra@amd.com>,
	Joel Becker <jlbec@evilplan.org>, Christoph Hellwig <hch@lst.de>
Subject: [PATCH v3 12/14] fs/configfs: Add a callback to determine attribute visibility
Date: Mon, 25 Mar 2024 17:26:31 -0500
Message-ID: <e881a70fda1da98882241fc46fd57c3063fde55f.1711405593.git.thomas.lendacky@amd.com>
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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       |   7 +++
 include/linux/configfs.h | 111 +++++++++++++++++++++++++++------------
 2 files changed, 84 insertions(+), 34 deletions(-)

diff --git a/fs/configfs/file.c b/fs/configfs/file.c
index 0ad32150611e..a976c183756c 100644
--- a/fs/configfs/file.c
+++ b/fs/configfs/file.c
@@ -451,6 +451,9 @@ 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->is_visible && !attr->is_visible(item, attr))
+		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 +473,13 @@ 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->is_visible && !attr->is_visible(item, attr))
+		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..c836d7bc7c9e 100644
--- a/include/linux/configfs.h
+++ b/include/linux/configfs.h
@@ -116,35 +116,57 @@ struct configfs_attribute {
 	const char		*ca_name;
 	struct module 		*ca_owner;
 	umode_t			ca_mode;
+	bool (*is_visible)(const struct config_item *, const struct configfs_attribute *);
 	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,			\
+	.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,			\
+	.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,			\
+	.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 +178,64 @@ 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,				\
+		.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,				\
+		.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,				\
+		.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