ipc: add more comments to message copying related code
Stanislav Kinsbursky [Fri, 4 Jan 2013 23:35:03 +0000 (15:35 -0800)]
Signed-off-by: Stanislav Kinsbursky <skinsbursky@parallels.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: James Morris <jmorris@namei.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

ipc/msg.c

index 8493e1d..950572f 100644 (file)
--- a/ipc/msg.c
+++ b/ipc/msg.c
@@ -770,6 +770,10 @@ static long do_msg_fill(void __user *dest, struct msg_msg *msg, size_t bufsz)
 }
 
 #ifdef CONFIG_CHECKPOINT_RESTORE
+/*
+ * This function creates new kernel message structure, large enough to store
+ * bufsz message bytes.
+ */
 static inline struct msg_msg *prepare_copy(void __user *buf, size_t bufsz,
                                           int msgflg, long *msgtyp,
                                           unsigned long *copy_number)
@@ -881,6 +885,10 @@ long do_msgrcv(int msqid, void __user *buf, size_t bufsz, long msgtyp,
                                msg = ERR_PTR(-E2BIG);
                                goto out_unlock;
                        }
+                       /*
+                        * If we are copying, then do not unlink message and do
+                        * not update queue parameters.
+                        */
                        if (msgflg & MSG_COPY)
                                goto out_unlock;
                        list_del(&msg->m_list);