ipc: cleanup do_msgrcv() aroung MSG_COPY feature

MSG_COPY feature was developed for Checkpoint/Restart In User space project
and thus wrapped in CONFIG_CHECKPOINT_RESTORE macro. But code look a bit ugly.
So this patch is an attempt to cleanup do_msgrcv() a bit and make it looks
better.

Signed-off-by: Stanislav Kinsbursky <skinsbursky@parallels.com>
Cc: Serge Hallyn <serge.hallyn@canonical.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Pavel Emelyanov <xemul@parallels.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/ipc/msg.c b/ipc/msg.c
index 91873dfb2e5f9b33820a79893df40b000e21f97c..d20ffc7d3f24f41cef8e6400eef1fe14626da7b9 100644 (file)
--- a/ipc/msg.c
+++ b/ipc/msg.c
@@ -769,6 +769,45 @@ static long do_msg_fill(void __user *dest, struct msg_msg *msg, size_t bufsz)
        return msgsz;
 }
 
+#ifdef CONFIG_CHECKPOINT_RESTORE
+static inline struct msg_msg *fill_copy(unsigned long copy_nr,
+                                       unsigned long msg_nr,
+                                       struct msg_msg *msg,
+                                       struct msg_msg *copy)
+{
+       if (copy_nr == msg_nr)
+               return copy_msg(msg, copy);
+       return NULL;
+}
+
+static inline struct msg_msg *prepare_copy(void __user *buf, size_t bufsz,
+                                          int msgflg, long *msgtyp,
+                                          unsigned long *copy_number)
+{
+       struct msg_msg *copy;
+
+       *copy_number = *msgtyp;
+       *msgtyp = 0;
+       /*
+        * Create dummy message to copy real message to.
+        */
+       copy = load_msg(buf, bufsz);
+       if (!IS_ERR(copy))
+               copy->m_ts = bufsz;
+       return copy;
+}
+
+static inline void free_copy(int msgflg, struct msg_msg *copy)
+{
+       if (msgflg & MSG_COPY)
+               free_msg(copy);
+}
+#else
+#define free_copy(msgflg, copy)                                do {} while (0)
+#define prepare_copy(buf, sz, msgflg, msgtyp, copy_nr) ERR_PTR(-ENOSYS)
+#define fill_copy(copy_nr, msg_nr, msg, copy)          NULL
+#endif
+
 long do_msgrcv(int msqid, void __user *buf, size_t bufsz, long msgtyp,
               int msgflg,
               long (*msg_handler)(void __user *, struct msg_msg *, size_t))
@@ -777,38 +816,22 @@ long do_msgrcv(int msqid, void __user *buf, size_t bufsz, long msgtyp,
        struct msg_msg *msg;
        int mode;
        struct ipc_namespace *ns;
-#ifdef CONFIG_CHECKPOINT_RESTORE
-       struct msg_msg *copy = NULL;
-       unsigned long copy_number = 0;
-#endif
+       struct msg_msg *copy;
+       unsigned long __maybe_unused copy_number;
 
        if (msqid < 0 || (long) bufsz < 0)
                return -EINVAL;
        if (msgflg & MSG_COPY) {
-#ifdef CONFIG_CHECKPOINT_RESTORE
-               copy_number = msgtyp;
-               msgtyp = 0;
-
-               /*
-                * Create dummy message to copy real message to.
-                */
-               copy = load_msg(buf, bufsz);
+               copy = prepare_copy(buf, bufsz, msgflg, &msgtyp, &copy_number);
                if (IS_ERR(copy))
                        return PTR_ERR(copy);
-               copy->m_ts = bufsz;
-#else
-               return -ENOSYS;
-#endif
        }
        mode = convert_mode(&msgtyp, msgflg);
        ns = current->nsproxy->ipc_ns;
 
        msq = msg_lock_check(ns, msqid);
        if (IS_ERR(msq)) {
-#ifdef CONFIG_CHECKPOINT_RESTORE
-               if (msgflg & MSG_COPY)
-                       free_msg(copy);
-#endif
+               free_copy(msgflg, copy);
                return PTR_ERR(msq);
        }
 
@@ -835,13 +858,12 @@ long do_msgrcv(int msqid, void __user *buf, size_t bufsz, long msgtyp,
                                if (mode == SEARCH_LESSEQUAL &&
                                                walk_msg->m_type != 1) {
                                        msgtyp = walk_msg->m_type - 1;
-#ifdef CONFIG_CHECKPOINT_RESTORE
                                } else if (msgflg & MSG_COPY) {
-                                       if (copy_number == msg_counter) {
-                                               msg = copy_msg(walk_msg, copy);
+                                       msg = fill_copy(copy_number,
+                                                       msg_counter,
+                                                       walk_msg, copy);
+                                       if (msg)
                                                break;
-                                       }
-#endif
                                } else
                                        break;
                                msg_counter++;
@@ -857,10 +879,8 @@ long do_msgrcv(int msqid, void __user *buf, size_t bufsz, long msgtyp,
                                msg = ERR_PTR(-E2BIG);
                                goto out_unlock;
                        }
-#ifdef CONFIG_CHECKPOINT_RESTORE
                        if (msgflg & MSG_COPY)
                                goto out_unlock;
-#endif
                        list_del(&msg->m_list);
                        msq->q_qnum--;
                        msq->q_rtime = get_seconds();
@@ -945,10 +965,7 @@ out_unlock:
                }
        }
        if (IS_ERR(msg)) {
-#ifdef CONFIG_CHECKPOINT_RESTORE
-               if (msgflg & MSG_COPY)
-                       free_msg(copy);
-#endif
+               free_copy(msgflg, copy);
                return PTR_ERR(msg);
        }