From 1a7b8969e664d6af328f00fe6eb7aabd61a71d13 Mon Sep 17 00:00:00 2001 From: Kirill Tkhai Date: Mon, 3 Aug 2020 13:16:42 +0300 Subject: [PATCH] mnt: Use generic ns_common::count Switch over mount namespaces to use the newly introduced common lifetime counter. Currently every namespace type has its own lifetime counter which is stored in the specific namespace struct. The lifetime counters are used identically for all namespaces types. Namespaces may of course have additional unrelated counters and these are not altered. This introduces a common lifetime counter into struct ns_common. The ns_common struct encompasses information that all namespaces share. That should include the lifetime counter since its common for all of them. It also allows us to unify the type of the counters across all namespaces. Most of them use refcount_t but one uses atomic_t and at least one uses kref. Especially the last one doesn't make much sense since it's just a wrapper around refcount_t since 2016 and actually complicates cleanup operations by having to use container_of() to cast the correct namespace struct out of struct ns_common. Having the lifetime counter for the namespaces in one place reduces maintenance cost. Not just because after switching all namespaces over we will have removed more code than we added but also because the logic is more easily understandable and we indicate to the user that the basic lifetime requirements for all namespaces are currently identical. Signed-off-by: Kirill Tkhai Reviewed-by: Kees Cook Acked-by: Christian Brauner Link: https://lore.kernel.org/r/159644980287.604812.761686947449081169.stgit@localhost.localdomain Signed-off-by: Christian Brauner --- fs/mount.h | 3 +-- fs/namespace.c | 4 ++-- 2 files changed, 3 insertions(+), 4 deletions(-) diff --git a/fs/mount.h b/fs/mount.h index c7abb7b394d8..ce6c376e0bc2 100644 --- a/fs/mount.h +++ b/fs/mount.h @@ -6,7 +6,6 @@ #include struct mnt_namespace { - atomic_t count; struct ns_common ns; struct mount * root; /* @@ -120,7 +119,7 @@ static inline void detach_mounts(struct dentry *dentry) static inline void get_mnt_ns(struct mnt_namespace *ns) { - atomic_inc(&ns->count); + refcount_inc(&ns->ns.count); } extern seqlock_t mount_lock; diff --git a/fs/namespace.c b/fs/namespace.c index bae0e95b3713..f887247165b3 100644 --- a/fs/namespace.c +++ b/fs/namespace.c @@ -3261,7 +3261,7 @@ static struct mnt_namespace *alloc_mnt_ns(struct user_namespace *user_ns, bool a new_ns->ns.ops = &mntns_operations; if (!anon) new_ns->seq = atomic64_add_return(1, &mnt_ns_seq); - atomic_set(&new_ns->count, 1); + refcount_set(&new_ns->ns.count, 1); INIT_LIST_HEAD(&new_ns->list); init_waitqueue_head(&new_ns->poll); spin_lock_init(&new_ns->ns_lock); @@ -3835,7 +3835,7 @@ void __init mnt_init(void) void put_mnt_ns(struct mnt_namespace *ns) { - if (!atomic_dec_and_test(&ns->count)) + if (!refcount_dec_and_test(&ns->ns.count)) return; drop_collected_mounts(&ns->root->mnt); free_mnt_ns(ns);