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Cache user_ns in struct cred

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If !CONFIG_USERNS, have current_user_ns() defined to (&init_user_ns).

Get rid of _current_user_ns.  This requires nsown_capable() to be
defined in capability.c rather than as static inline in capability.h,
so do that.

Request_key needs init_user_ns defined at current_user_ns if
!CONFIG_USERNS, so forward-declare that in cred.h if !CONFIG_USERNS
at current_user_ns() define.

Compile-tested with and without CONFIG_USERNS.

Signed-off-by: Serge E. Hallyn <serge.hallyn@canonical.com>
[ This makes a huge performance difference for acl_permission_check(),
  up to 30%.  And that is one of the hottest kernel functions for loads
  that are pathname-lookup heavy.  ]
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Serge E. Hallyn 2011-05-13 04:27:54 +01:00 • committed by Linus Torvalds
parent 381e7863d9
commit 47a150edc2
4 changed files with 27 additions and 20 deletions
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12
kernel/capability.c
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@ -399,3 +399,15 @@ bool task_ns_capable(struct task_struct *t, int cap)
return ns_capable(task_cred_xxx(t, user)->user_ns, cap);
}
EXPORT_SYMBOL(task_ns_capable);
/**
* nsown_capable - Check superior capability to one's own user_ns
* @cap: The capability in question
*
* Return true if the current task has the given superior capability
* targeted at its own user namespace.
*/
bool nsown_capable(int cap)
{
return ns_capable(current_user_ns(), cap);
}