ext4 exports per-filesystem information via sysfs. The lifetime rules have historically been painful for this but the solution has been to pair the kobject with a completion and call complete in the kobject's release function. Since this is a pattern I've used in btrfs as well, it makes sense to turn the pairing into a convenience structure with a standard API. Signed-off-by: Jeff Mahoney <jeffm@xxxxxxxx> --- include/linux/kobj_completion.h | 18 +++++++++++++++ lib/kobject.c | 47 ++++++++++++++++++++++++++++++++++++++++ 2 files changed, 65 insertions(+) --- /dev/null 1970-01-01 00:00:00.000000000 +0000 +++ b/include/linux/kobj_completion.h 2013-09-10 12:58:03.530554144 -0400 @@ -0,0 +1,18 @@ +#ifndef _KOBJ_COMPLETION_H_ +#define _KOBJ_COMPLETION_H_ + +#include <linux/kobject.h> +#include <linux/completion.h> + +struct kobj_completion { + struct kobject kc_kobj; + struct completion kc_unregister; +}; + +#define kobj_to_kobj_completion(kobj) \ + container_of(kobj, struct kobj_completion, kc_kobj) + +void kobj_completion_init(struct kobj_completion *kc, struct kobj_type *ktype); +void kobj_completion_release(struct kobject *kobj); +void kobj_completion_del_and_wait(struct kobj_completion *kc); +#endif /* _KOBJ_COMPLETION_H_ */ --- a/lib/kobject.c 2013-09-10 12:57:54.198666613 -0400 +++ b/lib/kobject.c 2013-09-10 13:16:31.750607946 -0400 @@ -13,6 +13,7 @@ */ #include <linux/kobject.h> +#include <linux/kobj_completion.h> #include <linux/string.h> #include <linux/export.h> #include <linux/stat.h> @@ -711,6 +712,52 @@ const struct sysfs_ops kobj_sysfs_ops = }; /** + * kobj_completion_init - initialize a kobj_completion object. + * @kc: kobj_completion + * @ktype: type of kobject to initialize + * + * kobj_completion structures can be embedded within structures with different + * lifetime rules. During the release of the enclosing object, we can + * wait on the release of the kobject so that we don't free it while it's + * still busy. + */ +void kobj_completion_init(struct kobj_completion *kc, struct kobj_type *ktype) +{ + init_completion(&kc->kc_unregister); + kobject_init(&kc->kc_kobj, ktype); +} +EXPORT_SYMBOL_GPL(kobj_completion_init); + +/** + * kobj_completion_release - release a kobj_completion object + * @kobj: kobject embedded in kobj_completion + * + * Used with kobject_release to notify waiters that the kobject has been + * released. + */ +void kobj_completion_release(struct kobject *kobj) +{ + struct kobj_completion *kc = kobj_to_kobj_completion(kobj); + complete(&kc->kc_unregister); +} +EXPORT_SYMBOL_GPL(kobj_completion_release); + +/** + * kobj_completion_del_and_wait - release the kobject and wait for it + * @kc: kobj_completion object to release + * + * Delete the kobject from sysfs and drop the reference count. Then wait + * until any outstanding references are also dropped. + */ +void kobj_completion_del_and_wait(struct kobj_completion *kc) +{ + kobject_del(&kc->kc_kobj); + kobject_put(&kc->kc_kobj); + wait_for_completion(&kc->kc_unregister); +} +EXPORT_SYMBOL_GPL(kobj_completion_del_and_wait); + +/** * kset_register - initialize and add a kset. * @k: kset. */ -- Jeff Mahoney SUSE Labs -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html