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proc: Usable inode numbers for the namespace file descriptors.

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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>
This commit is contained in:
Eric W. Biederman 2011-06-15 10:21:48 -07:00
parent bf056bfa80
commit 98f842e675
18 changed files with 132 additions and 12 deletions
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7
include/linux/proc_fs.h
View file

@ -28,7 +28,11 @@ struct mm_struct;
*/
enum {
PROC_ROOT_INO = 1,
PROC_ROOT_INO = 1,
PROC_IPC_INIT_INO = 0xEFFFFFFFU,
PROC_UTS_INIT_INO = 0xEFFFFFFEU,
PROC_USER_INIT_INO = 0xEFFFFFFDU,
PROC_PID_INIT_INO = 0xEFFFFFFCU,
};
/*
@ -263,6 +267,7 @@ struct proc_ns_operations {
void *(*get)(struct task_struct *task);
void (*put)(void *ns);
int (*install)(struct nsproxy *nsproxy, void *ns);
unsigned int (*inum)(void *ns);
};
extern const struct proc_ns_operations netns_operations;
extern const struct proc_ns_operations utsns_operations;