stagaing/lustre: Improve statahead debug messages

The statahead debug messages include the pid of the current
process in their body.  This is both redudant (because all
lustre log messages contain the pid), and sometimes downright
misleading.  For instance the messages would say something like
"stopping statahead thread 3446".  One would probably think
that 3446 is the pid of the process that is being stopped,
but in fact it was the pid of the caller issuing the stop signal.

We remove all superfluous pids from the messages.

Next we have the ll_statahead_thread() and the ll_agl_thread() record
their respective pids in their respective ptlrpc_thread structures.
This allows to print the pid of the thread that we are trying to
stop (which is actually useful info) from other threads, such as those
calling ll_stop_statahead().
Signed-off-by: Christopher J. Morrone <morrone2@llnl.gov>
Reviewed-on: http://review.whamcloud.com/9360
Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-4624Reviewed-by: Fan Yong <fan.yong@intel.com>
Reviewed-by: Lai Siyao <lai.siyao@intel.com>
Signed-off-by: Oleg Drokin <oleg.drokin@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/lustre/lustre/llite/statahead.c

@@ -958,8 +958,9 @@ static int ll_agl_thread(void *arg)
 	struct ptlrpc_thread     *thread = &sai->sai_agl_thread;
 	struct l_wait_info	lwi    = { 0 };
 
-	CDEBUG(D_READA, "agl thread started: [pid %d] [parent %.*s]\n",
-	       current_pid(), parent->d_name.len, parent->d_name.name);
+	thread->t_pid = current_pid();
+	CDEBUG(D_READA, "agl thread started: sai %p, parent %.*s\n",
+	       sai, parent->d_name.len, parent->d_name.name);
 
 	atomic_inc(&sbi->ll_agl_total);
 	spin_lock(&plli->lli_agl_lock);
@@ -1008,8 +1009,8 @@ static int ll_agl_thread(void *arg)
 	spin_unlock(&plli->lli_agl_lock);
 	wake_up(&thread->t_ctl_waitq);
 	ll_sai_put(sai);
-	CDEBUG(D_READA, "agl thread stopped: [pid %d] [parent %.*s]\n",
-	       current_pid(), parent->d_name.len, parent->d_name.name);
+	CDEBUG(D_READA, "agl thread stopped: sai %p, parent %.*s\n",
+	       sai, parent->d_name.len, parent->d_name.name);
 	return 0;
 }
 
@@ -1020,8 +1021,8 @@ static void ll_start_agl(struct dentry *parent, struct ll_statahead_info *sai)
 	struct ll_inode_info  *plli;
 	struct task_struct *task;
 
-	CDEBUG(D_READA, "start agl thread: [pid %d] [parent %.*s]\n",
-	       current_pid(), parent->d_name.len, parent->d_name.name);
+	CDEBUG(D_READA, "start agl thread: sai %p, parent %.*s\n",
+	       sai, parent->d_name.len, parent->d_name.name);
 
 	plli = ll_i2info(parent->d_inode);
 	task = kthread_run(ll_agl_thread, parent,
@@ -1054,8 +1055,9 @@ static int ll_statahead_thread(void *arg)
 	struct ll_dir_chain       chain;
 	struct l_wait_info	lwi    = { 0 };
 
-	CDEBUG(D_READA, "statahead thread started: [pid %d] [parent %.*s]\n",
-	       current_pid(), parent->d_name.len, parent->d_name.name);
+	thread->t_pid = current_pid();
+	CDEBUG(D_READA, "statahead thread starting: sai %p, parent %.*s\n",
+	       sai, parent->d_name.len, parent->d_name.name);
 
 	if (sbi->ll_flags & LL_SBI_AGL_ENABLED)
 		ll_start_agl(parent, sai);
@@ -1247,8 +1249,8 @@ static int ll_statahead_thread(void *arg)
 		spin_unlock(&plli->lli_agl_lock);
 		wake_up(&agl_thread->t_ctl_waitq);
 
-		CDEBUG(D_READA, "stop agl thread: [pid %d]\n",
-		       current_pid());
+		CDEBUG(D_READA, "stop agl thread: sai %p pid %u\n",
+		       sai, (unsigned int)agl_thread->t_pid);
 		l_wait_event(agl_thread->t_ctl_waitq,
 			     thread_is_stopped(agl_thread),
 			     &lwi);
@@ -1274,8 +1276,8 @@ static int ll_statahead_thread(void *arg)
 	wake_up(&thread->t_ctl_waitq);
 	ll_sai_put(sai);
 	dput(parent);
-	CDEBUG(D_READA, "statahead thread stopped: [pid %d] [parent %.*s]\n",
-	       current_pid(), parent->d_name.len, parent->d_name.name);
+	CDEBUG(D_READA, "statahead thread stopped: sai %p, parent %.*s\n",
+	       sai, parent->d_name.len, parent->d_name.name);
 	return rc;
 }
 
@@ -1306,8 +1308,8 @@ void ll_stop_statahead(struct inode *dir, void *key)
 			spin_unlock(&lli->lli_sa_lock);
 			wake_up(&thread->t_ctl_waitq);
 
-			CDEBUG(D_READA, "stop statahead thread: [pid %d]\n",
-			       current_pid());
+			CDEBUG(D_READA, "stop statahead thread: sai %p pid %u\n",
+			       lli->lli_sai, (unsigned int)thread->t_pid);
 			l_wait_event(thread->t_ctl_waitq,
 				     thread_is_stopped(thread),
 				     &lwi);
@@ -1481,10 +1483,10 @@ ll_sai_unplug(struct ll_statahead_info *sai, struct ll_sa_entry *entry)
 			CDEBUG(D_READA, "Statahead for dir "DFID" hit "
 			       "ratio too low: hit/miss "LPU64"/"LPU64
 			       ", sent/replied "LPU64"/"LPU64", stopping "
-			       "statahead thread: pid %d\n",
+			       "statahead thread\n",
 			       PFID(&lli->lli_fid), sai->sai_hit,
 			       sai->sai_miss, sai->sai_sent,
-			       sai->sai_replied, current_pid());
+			       sai->sai_replied);
 			spin_lock(&lli->lli_sa_lock);
 			if (!thread_is_stopped(thread))
 				thread_set_flags(thread, SVC_STOPPING);
@@ -1663,8 +1665,8 @@ int do_statahead_enter(struct inode *dir, struct dentry **dentryp,
 		GOTO(out, rc = -EAGAIN);
 	}
 
-	CDEBUG(D_READA, "start statahead thread: [pid %d] [parent %.*s]\n",
-	       current_pid(), parent->d_name.len, parent->d_name.name);
+	CDEBUG(D_READA, "start statahead thread: sai %p, parent %.*s\n",
+	       sai, parent->d_name.len, parent->d_name.name);
 
 	/* The sai buffer already has one reference taken at allocation time,
 	 * but as soon as we expose the sai by attaching it to the lli that