ipc: add more comments to message copying related code

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>

1 files changed, 8 insertions, 0 deletions

diff --git a/ipc/msg.c b/ipc/msg.c
index 8493e1d7e353..950572f9d796 100644
--- 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);