The sample registers three subsystems and none implements ->allow_link(), so the symlink(2) half of the configfs ABI has no small in-tree user to test against.
Add 04-symlink-children, whose children take a link to any config_item and export the number of links they hold. Signed-off-by: Breno Leitao <[email protected]> --- samples/configfs/configfs_sample.c | 121 +++++++++++++++++++++++++++++++++++++ 1 file changed, 121 insertions(+) diff --git a/samples/configfs/configfs_sample.c b/samples/configfs/configfs_sample.c index c1b108ec4ea02..08403e787aef6 100644 --- a/samples/configfs/configfs_sample.c +++ b/samples/configfs/configfs_sample.c @@ -313,6 +313,126 @@ static struct configfs_subsystem group_children_subsys = { /* ----------------------------------------------------------------- */ +/* + * 04-symlink-children + * + * This example has children that are valid sources for symlink(2). A + * child accepts a link to any other config_item and reports how many + * links it currently holds, so ->allow_link() and ->drop_link() are + * observable from userspace. + */ + +struct symlink_child { + struct config_item item; + int nlinks; +}; + +static inline struct symlink_child *to_symlink_child(struct config_item *item) +{ + return container_of(item, struct symlink_child, item); +} + +static ssize_t symlink_child_nlinks_show(struct config_item *item, char *page) +{ + return sprintf(page, "%d\n", to_symlink_child(item)->nlinks); +} + +CONFIGFS_ATTR_RO(symlink_child_, nlinks); + +static struct configfs_attribute *symlink_child_attrs[] = { + &symlink_child_attr_nlinks, + NULL, +}; + +/* + * The VFS holds the source item's directory locked across symlink(2) and + * unlink(2), so ->nlinks needs no lock of its own. + */ +static int symlink_child_allow_link(struct config_item *src, + struct config_item *target) +{ + to_symlink_child(src)->nlinks++; + + return 0; +} + +static void symlink_child_drop_link(struct config_item *src, + struct config_item *target) +{ + to_symlink_child(src)->nlinks--; +} + +static void symlink_child_release(struct config_item *item) +{ + kfree(to_symlink_child(item)); +} + +static const struct configfs_item_operations symlink_child_item_ops = { + .release = symlink_child_release, + .allow_link = symlink_child_allow_link, + .drop_link = symlink_child_drop_link, +}; + +static const struct config_item_type symlink_child_type = { + .ct_item_ops = &symlink_child_item_ops, + .ct_attrs = symlink_child_attrs, + .ct_owner = THIS_MODULE, +}; + +static struct config_item *symlink_children_make_item( + struct config_group *group, const char *name) +{ + struct symlink_child *symlink_child; + + symlink_child = kzalloc_obj(*symlink_child, GFP_KERNEL); + if (!symlink_child) + return ERR_PTR(-ENOMEM); + + config_item_init_type_name(&symlink_child->item, name, + &symlink_child_type); + + return &symlink_child->item; +} + +static ssize_t symlink_children_description_show(struct config_item *item, + char *page) +{ + return sprintf(page, +"[04-symlink-children]\n" +"\n" +"This subsystem allows the creation of child config_items that\n" +"symlink(2) can point at other config_items from. Each child\n" +"reports the number of links it holds.\n"); +} + +CONFIGFS_ATTR_RO(symlink_children_, description); + +static struct configfs_attribute *symlink_children_attrs[] = { + &symlink_children_attr_description, + NULL, +}; + +static const struct configfs_group_operations symlink_children_group_ops = { + .make_item = symlink_children_make_item, +}; + +static const struct config_item_type symlink_children_type = { + .ct_group_ops = &symlink_children_group_ops, + .ct_attrs = symlink_children_attrs, + .ct_owner = THIS_MODULE, +}; + +static struct configfs_subsystem symlink_children_subsys = { + .su_group = { + .cg_item = { + .ci_namebuf = "04-symlink-children", + .ci_type = &symlink_children_type, + }, + }, +}; + +/* ----------------------------------------------------------------- */ + /* * We're now done with our subsystem definitions. * For convenience in this module, here's a list of them all. It @@ -324,6 +444,7 @@ static struct configfs_subsystem *example_subsys[] = { &childless_subsys.subsys, &simple_children_subsys, &group_children_subsys, + &symlink_children_subsys, NULL, }; -- 2.53.0-Meta
