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ipc: merge ipc_rcu and kern_ipc_perm

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ipc has two management structures that exist for every id:
 - struct kern_ipc_perm, it contains e.g. the permissions.
 - struct ipc_rcu, it contains the rcu head for rcu handling and the
   refcount.

The patch merges both structures.

As a bonus, we may save one cacheline, because both structures are
cacheline aligned.  In addition, it reduces the number of casts, instead
most codepaths can use container_of.

To simplify code, the ipc_rcu_alloc initializes the allocation to 0.

[manfred@colorfullife.com: really include the memset() into ipc_alloc_rcu()]
  Link: http://lkml.kernel.org/r/564f8612-0601-b267-514f-a9f650ec9b32@colorfullife.com
Link: http://lkml.kernel.org/r/20170525185107.12869-3-manfred@colorfullife.com
Signed-off-by: Manfred Spraul <manfred@colorfullife.com>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Kees Cook <keescook@chromium.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Manfred Spraul 2017-07-12 14:34:41 -07:00 • committed by Linus Torvalds
parent 1a23395672
commit dba4cdd39e
6 changed files with 66 additions and 61 deletions
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3
include/linux/ipc.h
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@ -20,6 +20,9 @@ struct kern_ipc_perm {
umode_t mode;
unsigned long seq;
void *security;
struct rcu_head rcu;
atomic_t refcount;
} ____cacheline_aligned_in_smp;
#endif /* _LINUX_IPC_H */