[SCSI] sysfs: make group is_valid return a mode_t

We have a problem in scsi_transport_spi in that we need to customise
not only the visibility of the attributes, but also their mode.  Fix
this by making the is_visible() callback return a mode, with 0
indicating is not visible.

Also add a sysfs_update_group() API to allow us to change either the
visibility or mode of the files at any time on the fly.
Acked-by: Kay Sievers <kay.sievers@vrfy.org>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>

fs/sysfs/file.c

@@ -477,11 +477,10 @@ const struct file_operations sysfs_file_operations = {
 	.poll		= sysfs_poll,
 };
 
-
-int sysfs_add_file(struct sysfs_dirent *dir_sd, const struct attribute *attr,
-		   int type)
+int sysfs_add_file_mode(struct sysfs_dirent *dir_sd,
+			const struct attribute *attr, int type, mode_t amode)
 {
-	umode_t mode = (attr->mode & S_IALLUGO) | S_IFREG;
+	umode_t mode = (amode & S_IALLUGO) | S_IFREG;
 	struct sysfs_addrm_cxt acxt;
 	struct sysfs_dirent *sd;
 	int rc;
@@ -502,6 +501,13 @@ int sysfs_add_file(struct sysfs_dirent *dir_sd, const struct attribute *attr,
 }
 
 
+int sysfs_add_file(struct sysfs_dirent *dir_sd, const struct attribute *attr,
+		   int type)
+{
+	return sysfs_add_file_mode(dir_sd, attr, type, attr->mode);
+}
+
+
 /**
  *	sysfs_create_file - create an attribute file for an object.
  *	@kobj:	object we're creating for. 

fs/sysfs/group.c

@@ -23,35 +23,50 @@ static void remove_files(struct sysfs_dirent *dir_sd, struct kobject *kobj,
 	int i;
 
 	for (i = 0, attr = grp->attrs; *attr; i++, attr++)
-		if (!grp->is_visible ||
-		    grp->is_visible(kobj, *attr, i))
 		sysfs_hash_and_remove(dir_sd, (*attr)->name);
 }
 
 static int create_files(struct sysfs_dirent *dir_sd, struct kobject *kobj,
-			const struct attribute_group *grp)
+			const struct attribute_group *grp, int update)
 {
 	struct attribute *const* attr;
 	int error = 0, i;
 
-	for (i = 0, attr = grp->attrs; *attr && !error; i++, attr++)
-		if (!grp->is_visible ||
-		    grp->is_visible(kobj, *attr, i))
-			error |=
-				sysfs_add_file(dir_sd, *attr, SYSFS_KOBJ_ATTR);
+	for (i = 0, attr = grp->attrs; *attr && !error; i++, attr++) {
+		mode_t mode = 0;
+
+		/* in update mode, we're changing the permissions or
+		 * visibility.  Do this by first removing then
+		 * re-adding (if required) the file */
+		if (update)
+			sysfs_hash_and_remove(dir_sd, (*attr)->name);
+		if (grp->is_visible) {
+			mode = grp->is_visible(kobj, *attr, i);
+			if (!mode)
+				continue;
+		}
+		error = sysfs_add_file_mode(dir_sd, *attr, SYSFS_KOBJ_ATTR,
+					    (*attr)->mode | mode);
+		if (unlikely(error))
+			break;
+	}
 	if (error)
 		remove_files(dir_sd, kobj, grp);
 	return error;
 }
 
 
-int sysfs_create_group(struct kobject * kobj, 
-		       const struct attribute_group * grp)
+static int internal_create_group(struct kobject *kobj, int update,
+				 const struct attribute_group *grp)
 {
 	struct sysfs_dirent *sd;
 	int error;
 
-	BUG_ON(!kobj || !kobj->sd);
+	BUG_ON(!kobj || (!update && !kobj->sd));
+
+	/* Updates may happen before the object has been instantiated */
+	if (unlikely(update && !kobj->sd))
+		return -EINVAL;
 
 	if (grp->name) {
 		error = sysfs_create_subdir(kobj, grp->name, &sd);
@@ -60,7 +75,7 @@ int sysfs_create_group(struct kobject * kobj,
 	} else
 		sd = kobj->sd;
 	sysfs_get(sd);
-	error = create_files(sd, kobj, grp);
+	error = create_files(sd, kobj, grp, update);
 	if (error) {
 		if (grp->name)
 			sysfs_remove_subdir(sd);
@@ -69,6 +84,47 @@ int sysfs_create_group(struct kobject * kobj,
 	return error;
 }
 
+/**
+ * sysfs_create_group - given a directory kobject, create an attribute group
+ * @kobj:	The kobject to create the group on
+ * @grp:	The attribute group to create
+ *
+ * This function creates a group for the first time.  It will explicitly
+ * warn and error if any of the attribute files being created already exist.
+ *
+ * Returns 0 on success or error.
+ */
+int sysfs_create_group(struct kobject *kobj,
+		       const struct attribute_group *grp)
+{
+	return internal_create_group(kobj, 0, grp);
+}
+
+/**
+ * sysfs_update_group - given a directory kobject, create an attribute group
+ * @kobj:	The kobject to create the group on
+ * @grp:	The attribute group to create
+ *
+ * This function updates an attribute group.  Unlike
+ * sysfs_create_group(), it will explicitly not warn or error if any
+ * of the attribute files being created already exist.  Furthermore,
+ * if the visibility of the files has changed through the is_visible()
+ * callback, it will update the permissions and add or remove the
+ * relevant files.
+ *
+ * The primary use for this function is to call it after making a change
+ * that affects group visibility.
+ *
+ * Returns 0 on success or error.
+ */
+int sysfs_update_group(struct kobject *kobj,
+		       const struct attribute_group *grp)
+{
+	return internal_create_group(kobj, 1, grp);
+}
+
+
+
 void sysfs_remove_group(struct kobject * kobj, 
 			const struct attribute_group * grp)
 {
@@ -95,4 +151,5 @@ void sysfs_remove_group(struct kobject * kobj,
 
 
 EXPORT_SYMBOL_GPL(sysfs_create_group);
+EXPORT_SYMBOL_GPL(sysfs_update_group);
 EXPORT_SYMBOL_GPL(sysfs_remove_group);

fs/sysfs/sysfs.h

@@ -154,6 +154,8 @@ extern const struct file_operations sysfs_file_operations;
 int sysfs_add_file(struct sysfs_dirent *dir_sd,
 		   const struct attribute *attr, int type);
 
+int sysfs_add_file_mode(struct sysfs_dirent *dir_sd,
+			const struct attribute *attr, int type, mode_t amode);
 /*
  * bin.c
  */

include/linux/sysfs.h

@@ -32,7 +32,7 @@ struct attribute {
 
 struct attribute_group {
 	const char		*name;
-	int			(*is_visible)(struct kobject *,
+	mode_t			(*is_visible)(struct kobject *,
 					      struct attribute *, int);
 	struct attribute	**attrs;
 };
@@ -105,6 +105,8 @@ void sysfs_remove_link(struct kobject *kobj, const char *name);
 
 int __must_check sysfs_create_group(struct kobject *kobj,
 				    const struct attribute_group *grp);
+int sysfs_update_group(struct kobject *kobj,
+		       const struct attribute_group *grp);
 void sysfs_remove_group(struct kobject *kobj,
 			const struct attribute_group *grp);
 int sysfs_add_file_to_group(struct kobject *kobj,