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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>
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1 parent 51eeaca commit 3fcfe78658695b424314ddb76abc8d58b4fc98e6 Stanislav Kinsbursky committed with Jan 4, 2013
Showing with 8 additions and 0 deletions.
  1. +8 −0 ipc/msg.c
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@@ -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);

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