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author | Eric W. Biederman <ebiederm@xmission.com> | 2011-06-15 10:21:48 -0700 |
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committer | Eric W. Biederman <ebiederm@xmission.com> | 2012-11-20 04:19:49 -0800 |
commit | 98f842e675f96ffac96e6c50315790912b2812be (patch) | |
tree | ed4dee9a6e54e3443e9f3f1614c8a2fcf9b31e0a /fs/namespace.c | |
parent | bf056bfa80596a5d14b26b17276a56a0dcb080e5 (diff) | |
download | lwn-98f842e675f96ffac96e6c50315790912b2812be.tar.gz lwn-98f842e675f96ffac96e6c50315790912b2812be.zip |
proc: Usable inode numbers for the namespace file descriptors.
Assign a unique proc inode to each namespace, and use that
inode number to ensure we only allocate at most one proc
inode for every namespace in proc.
A single proc inode per namespace allows userspace to test
to see if two processes are in the same namespace.
This has been a long requested feature and only blocked because
a naive implementation would put the id in a global space and
would ultimately require having a namespace for the names of
namespaces, making migration and certain virtualization tricks
impossible.
We still don't have per superblock inode numbers for proc, which
appears necessary for application unaware checkpoint/restart and
migrations (if the application is using namespace file descriptors)
but that is now allowd by the design if it becomes important.
I have preallocated the ipc and uts initial proc inode numbers so
their structures can be statically initialized.
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Diffstat (limited to 'fs/namespace.c')
-rw-r--r-- | fs/namespace.c | 14 |
1 files changed, 14 insertions, 0 deletions
diff --git a/fs/namespace.c b/fs/namespace.c index cab78a74aca3..c1bbe86f4920 100644 --- a/fs/namespace.c +++ b/fs/namespace.c @@ -2301,6 +2301,7 @@ dput_out: static void free_mnt_ns(struct mnt_namespace *ns) { + proc_free_inum(ns->proc_inum); put_user_ns(ns->user_ns); kfree(ns); } @@ -2317,10 +2318,16 @@ static atomic64_t mnt_ns_seq = ATOMIC64_INIT(1); static struct mnt_namespace *alloc_mnt_ns(struct user_namespace *user_ns) { struct mnt_namespace *new_ns; + int ret; new_ns = kmalloc(sizeof(struct mnt_namespace), GFP_KERNEL); if (!new_ns) return ERR_PTR(-ENOMEM); + ret = proc_alloc_inum(&new_ns->proc_inum); + if (ret) { + kfree(new_ns); + return ERR_PTR(ret); + } new_ns->seq = atomic64_add_return(1, &mnt_ns_seq); atomic_set(&new_ns->count, 1); new_ns->root = NULL; @@ -2799,10 +2806,17 @@ static int mntns_install(struct nsproxy *nsproxy, void *ns) return 0; } +static unsigned int mntns_inum(void *ns) +{ + struct mnt_namespace *mnt_ns = ns; + return mnt_ns->proc_inum; +} + const struct proc_ns_operations mntns_operations = { .name = "mnt", .type = CLONE_NEWNS, .get = mntns_get, .put = mntns_put, .install = mntns_install, + .inum = mntns_inum, }; |