ipc,msg: introduce msgctl_nolock

Similar to semctl, when calling msgctl, the *_INFO and *_STAT commands
can be performed without acquiring the ipc object.

Add a msgctl_nolock() function and move the logic of *_INFO and *_STAT
out of msgctl().  This change still takes the lock and it will be
properly lockless in the next patch

Signed-off-by: Davidlohr Bueso <davidlohr.bueso@hp.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Rik van Riel <riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/ipc/msg.c b/ipc/msg.c
index de422ff..f45be81 100644 (file)
--- a/ipc/msg.c
+++ b/ipc/msg.c
@@ -467,17 +467,11 @@ out_up:
        return err;
 }
 
-SYSCALL_DEFINE3(msgctl, int, msqid, int, cmd, struct msqid_ds __user *, buf)
+static int msgctl_nolock(struct ipc_namespace *ns, int msqid,
+                        int cmd, int version, void __user *buf)
 {
+       int err;
        struct msg_queue *msq;
-       int err, version;
-       struct ipc_namespace *ns;
-
-       if (msqid < 0 || cmd < 0)
-               return -EINVAL;
-
-       version = ipc_parse_version(&cmd);
-       ns = current->nsproxy->ipc_ns;
 
        switch (cmd) {
        case IPC_INFO:
@@ -488,6 +482,7 @@ SYSCALL_DEFINE3(msgctl, int, msqid, int, cmd, struct msqid_ds __user *, buf)
 
                if (!buf)
                        return -EFAULT;
+
                /*
                 * We must not return kernel stack data.
                 * due to padding, it's not enough
@@ -519,7 +514,8 @@ SYSCALL_DEFINE3(msgctl, int, msqid, int, cmd, struct msqid_ds __user *, buf)
                        return -EFAULT;
                return (max_id < 0) ? 0 : max_id;
        }
-       case MSG_STAT:  /* msqid is an index rather than a msg queue id */
+
+       case MSG_STAT:
        case IPC_STAT:
        {
                struct msqid64_ds tbuf;
@@ -563,19 +559,42 @@ SYSCALL_DEFINE3(msgctl, int, msqid, int, cmd, struct msqid_ds __user *, buf)
                        return -EFAULT;
                return success_return;
        }
-       case IPC_SET:
-       case IPC_RMID:
-               err = msgctl_down(ns, msqid, cmd, buf, version);
-               return err;
+
        default:
-               return  -EINVAL;
+               return -EINVAL;
        }
 
+       return err;
 out_unlock:
        msg_unlock(msq);
        return err;
 }
 
+SYSCALL_DEFINE3(msgctl, int, msqid, int, cmd, struct msqid_ds __user *, buf)
+{
+       int version;
+       struct ipc_namespace *ns;
+
+       if (msqid < 0 || cmd < 0)
+               return -EINVAL;
+
+       version = ipc_parse_version(&cmd);
+       ns = current->nsproxy->ipc_ns;
+
+       switch (cmd) {
+       case IPC_INFO:
+       case MSG_INFO:
+       case MSG_STAT:  /* msqid is an index rather than a msg queue id */
+       case IPC_STAT:
+               return msgctl_nolock(ns, msqid, cmd, version, buf);
+       case IPC_SET:
+       case IPC_RMID:
+               return msgctl_down(ns, msqid, cmd, buf, version);
+       default:
+               return  -EINVAL;
+       }
+}
+
 static int testmsg(struct msg_msg *msg, long type, int mode)
 {
        switch(mode)