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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.

[[email protected]: really include the memset() into ipc_alloc_rcu()]
  Link: http://lkml.kernel.org/r/[email protected]
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Manfred Spraul <[email protected]>
Cc: Davidlohr Bueso <[email protected]>
Cc: Kees Cook <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
This commit is contained in:
Manfred Spraul 2017-07-12 14:34:41 -07:00 • committed by Linus Torvalds
commit dba4cdd39e
6 changed files with 66 additions and 61 deletions
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18
ipc/util.h
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@ -47,13 +47,6 @@ static inline void msg_exit_ns(struct ipc_namespace *ns) { }
static inline void shm_exit_ns(struct ipc_namespace *ns) { }
#endif
struct ipc_rcu {
struct rcu_head rcu;
atomic_t refcount;
} ____cacheline_aligned_in_smp;
#define ipc_rcu_to_struct(p) ((void *)(p+1))
/*
* Structure that holds the parameters needed by the ipc operations
* (see after)
@ -125,11 +118,14 @@ void ipc_free(void *ptr);
* Objects are reference counted, they start with reference count 1.
* getref increases the refcount, the putref call that reduces the recount
* to 0 schedules the rcu destruction. Caller must guarantee locking.
*
* struct kern_ipc_perm must be the first member in the allocated structure.
*/
void *ipc_rcu_alloc(int size);
int ipc_rcu_getref(void *ptr);
void ipc_rcu_putref(void *ptr, void (*func)(struct rcu_head *head));
void ipc_rcu_free(struct rcu_head *head);
struct kern_ipc_perm *ipc_rcu_alloc(int size);
int ipc_rcu_getref(struct kern_ipc_perm *ptr);
void ipc_rcu_putref(struct kern_ipc_perm *ptr,
void (*func)(struct rcu_head *head));
void ipc_rcu_free(struct rcu_head *h);
struct kern_ipc_perm *ipc_lock(struct ipc_ids *, int);
struct kern_ipc_perm *ipc_obtain_object_idr(struct ipc_ids *ids, int id);