sysvipc: unteach ids->next_id for !CHECKPOINT_RESTORE

Patch series "sysvipc: ipc-key management improvements".

Here are a few improvements I spotted while eyeballing Guillaume's
rhashtable implementation for ipc keys.  The first and fourth patches
are the interesting ones, the middle two are trivial.

This patch (of 4):

The next_id object-allocation functionality was introduced in commit
03f595668017 ("ipc: add sysctl to specify desired next object id").

Given that these new entries are _only_ exported under the
CONFIG_CHECKPOINT_RESTORE option, there is no point for the common case
to even know about ->next_id.  As such rewrite ipc_buildid() such that
it can do away with the field as well as unnecessary branches when
adding a new identifier.  The end result also better differentiates both
cases, so the code ends up being cleaner; albeit the small duplications
regarding the default case.

[akpm@linux-foundation.org: coding-style fixes]
Link: http://lkml.kernel.org/r/20170831172049.14576-2-dave@stgolabs.net
Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
Cc: Manfred Spraul <manfred@colorfullife.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 2 insertions, 0 deletions

diff --git a/include/linux/ipc_namespace.h b/include/linux/ipc_namespace.h
index 474812abe773..d7cf3a850853 100644
--- a/include/linux/ipc_namespace.h
+++ b/include/linux/ipc_namespace.h
@@ -19,7 +19,9 @@ struct ipc_ids {
 	bool tables_initialized;
 	struct rw_semaphore rwsem;
 	struct idr ipcs_idr;
+#ifdef CONFIG_CHECKPOINT_RESTORE
 	int next_id;
+#endif
 	struct rhashtable key_ht;
 };