From 03b1cde6b22f625ae832b939bc7379ec1466aec5 Mon Sep 17 00:00:00 2001 From: Aristeu Rozanski Date: Thu, 23 Aug 2012 16:53:30 -0400 Subject: cgroup: add xattr support This is one of the items in the plumber's wish list. For use cases: >> What would the use case be for this? > > Attaching meta information to services, in an easily discoverable > way. For example, in systemd we create one cgroup for each service, and > could then store data like the main pid of the specific service as an > xattr on the cgroup itself. That way we'd have almost all service state > in the cgroupfs, which would make it possible to terminate systemd and > later restart it without losing any state information. But there's more: > for example, some very peculiar services cannot be terminated on > shutdown (i.e. fakeraid DM stuff) and it would be really nice if the > services in question could just mark that on their cgroup, by setting an > xattr. On the more desktopy side of things there are other > possibilities: for example there are plans defining what an application > is along the lines of a cgroup (i.e. an app being a collection of > processes). With xattrs one could then attach an icon or human readable > program name on the cgroup. > > The key idea is that this would allow attaching runtime meta information > to cgroups and everything they model (services, apps, vms), that doesn't > need any complex userspace infrastructure, has good access control > (i.e. because the file system enforces that anyway, and there's the > "trusted." xattr namespace), notifications (inotify), and can easily be > shared among applications. > > Lennart v7: - no changes v6: - remove user xattr namespace, only allow trusted and security v5: - check for capabilities before setting/removing xattrs v4: - no changes v3: - instead of config option, use mount option to enable xattr support Original-patch-by: Li Zefan Cc: Li Zefan Cc: Tejun Heo Cc: Hugh Dickins Cc: Hillf Danton Cc: Lennart Poettering Signed-off-by: Li Zefan Signed-off-by: Aristeu Rozanski Signed-off-by: Tejun Heo --- include/linux/cgroup.h | 13 ++++++++++--- 1 file changed, 10 insertions(+), 3 deletions(-) (limited to 'include/linux/cgroup.h') diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h index c90eaa803440..145901f5ef99 100644 --- a/include/linux/cgroup.h +++ b/include/linux/cgroup.h @@ -17,6 +17,7 @@ #include #include #include +#include #ifdef CONFIG_CGROUPS @@ -216,6 +217,9 @@ struct cgroup { /* List of events which userspace want to receive */ struct list_head event_list; spinlock_t event_list_lock; + + /* directory xattrs */ + struct simple_xattrs xattrs; }; /* @@ -309,6 +313,9 @@ struct cftype { /* CFTYPE_* flags */ unsigned int flags; + /* file xattrs */ + struct simple_xattrs xattrs; + int (*open)(struct inode *inode, struct file *file); ssize_t (*read)(struct cgroup *cgrp, struct cftype *cft, struct file *file, @@ -394,7 +401,7 @@ struct cftype { */ struct cftype_set { struct list_head node; /* chained at subsys->cftsets */ - const struct cftype *cfts; + struct cftype *cfts; }; struct cgroup_scanner { @@ -406,8 +413,8 @@ struct cgroup_scanner { void *data; }; -int cgroup_add_cftypes(struct cgroup_subsys *ss, const struct cftype *cfts); -int cgroup_rm_cftypes(struct cgroup_subsys *ss, const struct cftype *cfts); +int cgroup_add_cftypes(struct cgroup_subsys *ss, struct cftype *cfts); +int cgroup_rm_cftypes(struct cgroup_subsys *ss, struct cftype *cfts); int cgroup_is_removed(const struct cgroup *cgrp); -- cgit v1.2.3