fs/configfs: Add a callback to determine attribute visibility

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 displayed. If no callback is registered, the attribute
is displayed by default.

Co-developed-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/e555c8740a263fab9f83b2cbb44da1af49a2813c.1717600736.git.thomas.lendacky@amd.com

diff --git a/fs/configfs/dir.c b/fs/configfs/dir.c
index 18677cd4e62f543187966501bb52364b5f6b3a55..43d6bde1adcc04e59c9add3297d6ab326c246b83 100644 (file)
--- a/fs/configfs/dir.c
+++ b/fs/configfs/dir.c
@@ -580,6 +580,7 @@ static void detach_attrs(struct config_item * item)
 static int populate_attrs(struct config_item *item)
 {
        const struct config_item_type *t = item->ci_type;
+       struct configfs_group_operations *ops;
        struct configfs_attribute *attr;
        struct configfs_bin_attribute *bin_attr;
        int error = 0;
@@ -587,14 +588,23 @@ static int populate_attrs(struct config_item *item)
 
        if (!t)
                return -EINVAL;
+
+       ops = t->ct_group_ops;
+
        if (t->ct_attrs) {
                for (i = 0; (attr = t->ct_attrs[i]) != NULL; i++) {
+                       if (ops && ops->is_visible && !ops->is_visible(item, attr, i))
+                               continue;
+
                        if ((error = configfs_create_file(item, attr)))
                                break;
                }
        }
        if (t->ct_bin_attrs) {
                for (i = 0; (bin_attr = t->ct_bin_attrs[i]) != NULL; i++) {
+                       if (ops && ops->is_bin_visible && !ops->is_bin_visible(item, bin_attr, i))
+                               continue;
+
                        error = configfs_create_bin_file(item, bin_attr);
                        if (error)
                                break;

diff --git a/include/linux/configfs.h b/include/linux/configfs.h
index 2606711adb18c76abca1d18bc7cd2caed28186f4..c771e9d0d0b92eee3826d5df1782e0cd5935fea2 100644 (file)
--- a/include/linux/configfs.h
+++ b/include/linux/configfs.h
@@ -216,6 +216,9 @@ struct configfs_group_operations {
        struct config_group *(*make_group)(struct config_group *group, const char *name);
        void (*disconnect_notify)(struct config_group *group, struct config_item *item);
        void (*drop_item)(struct config_group *group, struct config_item *item);
+       bool (*is_visible)(struct config_item *item, struct configfs_attribute *attr, int n);
+       bool (*is_bin_visible)(struct config_item *item, struct configfs_bin_attribute *attr,
+                              int n);
 };
 
 struct configfs_subsystem {