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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/shm.c
View file

@ -174,9 +174,10 @@ static inline void shm_lock_by_ptr(struct shmid_kernel *ipcp)
static void shm_rcu_free(struct rcu_head *head)
{
struct ipc_rcu *p = container_of(head, struct ipc_rcu, rcu);
struct shmid_kernel *shp = ipc_rcu_to_struct(p);
struct kern_ipc_perm *ptr = container_of(head, struct kern_ipc_perm,
rcu);
struct shmid_kernel *shp = container_of(ptr, struct shmid_kernel,
shm_perm);
security_shm_free(shp);
ipc_rcu_free(head);
}
@ -241,7 +242,7 @@ static void shm_destroy(struct ipc_namespace *ns, struct shmid_kernel *shp)
user_shm_unlock(i_size_read(file_inode(shm_file)),
shp->mlock_user);
fput(shm_file);
ipc_rcu_putref(shp, shm_rcu_free);
ipc_rcu_putref(&shp->shm_perm, shm_rcu_free);
}
/*
@ -542,7 +543,10 @@ static int newseg(struct ipc_namespace *ns, struct ipc_params *params)
ns->shm_tot + numpages > ns->shm_ctlall)
return -ENOSPC;
shp = ipc_rcu_alloc(sizeof(*shp));
BUILD_BUG_ON(offsetof(struct shmid_kernel, shm_perm) != 0);
shp = container_of(ipc_rcu_alloc(sizeof(*shp)), struct shmid_kernel,
shm_perm);
if (!shp)
return -ENOMEM;
@ -553,7 +557,7 @@ static int newseg(struct ipc_namespace *ns, struct ipc_params *params)
shp->shm_perm.security = NULL;
error = security_shm_alloc(shp);
if (error) {
ipc_rcu_putref(shp, ipc_rcu_free);
ipc_rcu_putref(&shp->shm_perm, ipc_rcu_free);
return error;
}
@ -624,7 +628,7 @@ no_id:
user_shm_unlock(size, shp->mlock_user);
fput(file);
no_file:
ipc_rcu_putref(shp, shm_rcu_free);
ipc_rcu_putref(&shp->shm_perm, shm_rcu_free);
return error;
}