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Subject[PATCH 1/4] sysvipc: unteach ids->next_id for !CHECKPOINT_RESTORE
Date
The next_id object-allocation functionality was introduced in
03f595668017f (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.

Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
---
include/linux/ipc_namespace.h | 2 ++
ipc/util.c | 60 ++++++++++++++++++++++++++++++++-----------
ipc/util.h | 5 ----
3 files changed, 47 insertions(+), 20 deletions(-)

diff --git a/include/linux/ipc_namespace.h b/include/linux/ipc_namespace.h
index 83f0bf7a587d..058051566ced 100644
--- a/include/linux/ipc_namespace.h
+++ b/include/linux/ipc_namespace.h
@@ -18,7 +18,9 @@ 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;
};

diff --git a/ipc/util.c b/ipc/util.c
index 78755873cc5b..fb69152705e6 100644
--- a/ipc/util.c
+++ b/ipc/util.c
@@ -115,13 +115,15 @@ int ipc_init_ids(struct ipc_ids *ids)
int err;
ids->in_use = 0;
ids->seq = 0;
- ids->next_id = -1;
init_rwsem(&ids->rwsem);
err = rhashtable_init(&ids->key_ht, &ipc_kht_params);
if (err)
return err;
idr_init(&ids->ipcs_idr);
ids->tables_initialized = true;
+#ifdef CONFIG_CHECKPOINT_RESTORE
+ ids->next_id = -1;
+#endif
return 0;
}

@@ -215,6 +217,46 @@ int ipc_get_maxid(struct ipc_ids *ids)
return max_id;
}

+#ifdef CONFIG_CHECKPOINT_RESTORE
+/*
+ * Specify desired id for next allocated IPC object.
+ */
+#define ipc_idr_alloc(ids, new) \
+ idr_alloc(&(ids)->ipcs_idr, (new), \
+ (ids)->next_id < 0 ? 0: ipcid_to_idx((ids)->next_id), \
+ 0, GFP_NOWAIT);
+
+static inline int ipc_buildid(int id, struct ipc_ids *ids,
+ struct kern_ipc_perm *new)
+{
+ if (ids->next_id < 0) { /* default, behave as !CHECKPOINT_RESTORE */
+ new->seq = ids->seq++;
+ if (ids->seq > IPCID_SEQ_MAX)
+ ids->seq = 0;
+ } else {
+ new->seq = ipcid_to_seqx(ids->next_id);
+ ids->next_id = -1;
+ }
+
+ return SEQ_MULTIPLIER * new->seq + id;
+}
+
+#else
+#define ipc_idr_alloc(ids, new) \
+ idr_alloc(&(ids)->ipcs_idr, (new), 0, 0, GFP_NOWAIT);
+
+static inline int ipc_buildid(int id, struct ipc_ids *ids,
+ struct kern_ipc_perm *new)
+{
+ new->seq = ids->seq++;
+ if (ids->seq > IPCID_SEQ_MAX)
+ ids->seq = 0;
+
+ return SEQ_MULTIPLIER * new->seq + id;
+}
+
+#endif /* CONFIG_CHECKPOINT_RESTORE */
+
/**
* ipc_addid - add an ipc identifier
* @ids: ipc identifier set
@@ -233,7 +275,6 @@ int ipc_addid(struct ipc_ids *ids, struct kern_ipc_perm *new, int size)
kuid_t euid;
kgid_t egid;
int id, err;
- int next_id = ids->next_id;

if (size > IPCMNI)
size = IPCMNI;
@@ -253,9 +294,7 @@ int ipc_addid(struct ipc_ids *ids, struct kern_ipc_perm *new, int size)
new->cuid = new->uid = euid;
new->gid = new->cgid = egid;

- id = idr_alloc(&ids->ipcs_idr, new,
- (next_id < 0) ? 0 : ipcid_to_idx(next_id), 0,
- GFP_NOWAIT);
+ id = ipc_idr_alloc(ids, new);
idr_preload_end();

if (id >= 0 && new->key != IPC_PRIVATE) {
@@ -273,17 +312,8 @@ int ipc_addid(struct ipc_ids *ids, struct kern_ipc_perm *new, int size)
}

ids->in_use++;
+ new->id = ipc_buildid(id, ids, new);

- if (next_id < 0) {
- new->seq = ids->seq++;
- if (ids->seq > IPCID_SEQ_MAX)
- ids->seq = 0;
- } else {
- new->seq = ipcid_to_seqx(next_id);
- ids->next_id = -1;
- }
-
- new->id = ipc_buildid(id, new->seq);
return id;
}

diff --git a/ipc/util.h b/ipc/util.h
index 80c9f51c3f07..17c8d2f14990 100644
--- a/ipc/util.h
+++ b/ipc/util.h
@@ -145,11 +145,6 @@ extern struct msg_msg *load_msg(const void __user *src, size_t len);
extern struct msg_msg *copy_msg(struct msg_msg *src, struct msg_msg *dst);
extern int store_msg(void __user *dest, struct msg_msg *msg, size_t len);

-static inline int ipc_buildid(int id, int seq)
-{
- return SEQ_MULTIPLIER * seq + id;
-}
-
static inline int ipc_checkid(struct kern_ipc_perm *ipcp, int uid)
{
return uid / SEQ_MULTIPLIER != ipcp->seq;
--
2.12.0
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