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>

1 files changed, 34 insertions, 15 deletions

diff --git a/ipc/msg.c b/ipc/msg.c
index de422ff71c87..f45be81f6de9 100644
--- 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)