linux-kernel - Re: [BUG] set_mempolicy(MPOL_INTERLEAV) cause kernel panic

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Message-ID: <alpine.DEB.2.00.0907161257190.31844@chino.kir.corp.google.com>
Date:	Thu, 16 Jul 2009 13:05:31 -0700 (PDT)
From:	David Rientjes <rientjes@...gle.com>
To:	Lee Schermerhorn <Lee.Schermerhorn@...com>
cc:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Miao Xie <miaox@...fujitsu.com>, Ingo Molnar <mingo@...e.hu>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Christoph Lameter <cl@...ux-foundation.org>,
	Paul Menage <menage@...gle.com>,
	Nick Piggin <nickpiggin@...oo.com.au>,
	Yasunori Goto <y-goto@...fujitsu.com>,
	Pekka Enberg <penberg@...helsinki.fi>,
	linux-mm <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [BUG] set_mempolicy(MPOL_INTERLEAV) cause kernel panic

On Wed, 15 Jul 2009, Lee Schermerhorn wrote:

> Interestingly, on ia64, the top cpuset mems_allowed gets set to all
> possible nodes, while on x86_64, it gets set to on-line nodes [or nodes
> with memory].  Maybe this is a to support hot-plug?
> 

numactl --interleave=all simply passes a nodemask with all bits set, so if 
cpuset_current_mems_allowed includes offline nodes from node_possible_map, 
then mpol_set_nodemask() doesn't mask them off.

Seems like we could handle this strictly in mempolicies without worrying 
about top_cpuset like in the following?
---
diff --git a/mm/mempolicy.c b/mm/mempolicy.c
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -194,6 +194,7 @@ static int mpol_new_bind(struct mempolicy *pol, const nodemask_t *nodes)
 static int mpol_set_nodemask(struct mempolicy *pol, const nodemask_t *nodes)
 {
 	nodemask_t cpuset_context_nmask;
+	nodemask_t mems_allowed;
 	int ret;
 
 	/* if mode is MPOL_DEFAULT, pol is NULL. This is right. */
@@ -201,20 +202,21 @@ static int mpol_set_nodemask(struct mempolicy *pol, const nodemask_t *nodes)
 		return 0;
 
 	VM_BUG_ON(!nodes);
+	nodes_and(mems_allowed, cpuset_current_mems_allowed,
+				node_states[N_HIGH_MEMORY]);
 	if (pol->mode == MPOL_PREFERRED && nodes_empty(*nodes))
 		nodes = NULL;	/* explicit local allocation */
 	else {
 		if (pol->flags & MPOL_F_RELATIVE_NODES)
 			mpol_relative_nodemask(&cpuset_context_nmask, nodes,
-					       &cpuset_current_mems_allowed);
+					       &mems_allowed);
 		else
 			nodes_and(cpuset_context_nmask, *nodes,
-				  cpuset_current_mems_allowed);
+				  mems_allowed);
 		if (mpol_store_user_nodemask(pol))
 			pol->w.user_nodemask = *nodes;
 		else
-			pol->w.cpuset_mems_allowed =
-						cpuset_current_mems_allowed;
+			pol->w.cpuset_mems_allowed = mems_allowed;
 	}
 
 	ret = mpol_ops[pol->mode].create(pol,
--
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