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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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10
include/linux/cred.h
View file

@ -146,6 +146,7 @@ struct cred {
void *security; /* subjective LSM security */
#endif
struct user_struct *user; /* real user ID subscription */
struct user_namespace *user_ns; /* cached user->user_ns */
struct group_info *group_info; /* supplementary groups for euid/fsgid */
struct rcu_head rcu; /* RCU deletion hook */
};
@ -354,10 +355,15 @@ static inline void put_cred(const struct cred *_cred)
#define current_fsgid() (current_cred_xxx(fsgid))
#define current_cap() (current_cred_xxx(cap_effective))
#define current_user() (current_cred_xxx(user))
#define _current_user_ns() (current_cred_xxx(user)->user_ns)
#define current_security() (current_cred_xxx(security))
extern struct user_namespace *current_user_ns(void);
#ifdef CONFIG_USER_NS
#define current_user_ns() (current_cred_xxx(user_ns))
#else
extern struct user_namespace init_user_ns;
#define current_user_ns() (&init_user_ns)
#endif
#define current_uid_gid(_uid, _gid) \
do { \