Date:	Sun, 10 Feb 2008 14:29:24 +0900
From:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
To:	Lee Schermerhorn <Lee.Schermerhorn@...com>
Cc:	kosaki.motohiro@...fujitsu.com, linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Christoph Lameter <clameter@....com>,
	Paul Jackson <pj@....com>,
	David Rientjes <rientjes@...gle.com>,
	Mel Gorman <mel@....ul.ie>, linux-mm <linux-mm@...ck.org>,
	torvalds@...ux-foundation.org, Eric Whitney <eric.whitney@...com>,
	Greg KH <greg@...ah.com>
Subject: Re: [PATCH 2.6.24-mm1]  Mempolicy:  silently restrict nodemask to allowed nodes V3

CC'd Greg KH <greg@...ah.com>

I tested this patch on fujitsu memoryless node.
(2.6.24 + silently-restrict-nodemask-to-allowed-nodes-V3 insted 2.6.24-mm1)
it seems works good.

Tested-by: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>


Greg, I hope this patch merge to 2.6.24.x stable tree because
this patch is regression fixed patch.
Please tell me what do i doing for it.


[intentional full quote]

> Was "Re: [2.6.24 regression][BUGFIX] numactl --interleave=all doesn't
> works on memoryless node."
> 
> [Aside:  I noticed there were two slightly different distributions for
> this topic.  I've unified the distribution lists w/o dropping anyone, I
> think.  Apologies if you'd rather have been dropped...]
> 
> Here's V3 of the patch, accomodating Kosaki Motohiro's suggestion for
> folding contextualize_policy() into mpol_check_policy() [because my
> "was_empty" argument "was ugly" ;-)].  It does seem to clean up the
> code.
> 
> I'm still deferring David Rientjes' suggestion to fold
> mpol_check_policy() into mpol_new().  We need to sort out whether
> mempolicies specified for tmpfs and hugetlbfs mounts always need the
> same "contextualization" as user/application installed policies.  I
> don't want to hold up this bug fix for that discussion.  This is
> something Paul J will need to address with his cpuset/mempolicy rework,
> so we can sort it out in that context.
> 
> Again, tested with "numactl --interleave=all" and memtoy on ia64 using
> mem= command line argument to simulate memoryless node.
> 
> 
> Lee
> 
> ============================
> [PATCH] 2.6.24-mm1 - mempolicy:  silently restrict nodemask to allowed nodes
> 
> V2 -> V3:
> + As suggested by Kosaki Motohito, fold the "contextualization"
>   of policy nodemask into mpol_check_policy().  Looks a little
>   cleaner. 
> 
> V1 -> V2:
> + Communicate whether or not incoming node mask was empty to
>   mpol_check_policy() for better error checking.
> + As suggested by David Rientjes, remove the now unused
>    cpuset_nodes_subset_current_mems_allowed() from cpuset.h
> 
> Kosaki Motohito noted that "numactl --interleave=all ..." failed in the
> presence of memoryless nodes.  This patch attempts to fix that problem.
> 
> Some background:  
> 
> numactl --interleave=all calls set_mempolicy(2) with a fully
> populated [out to MAXNUMNODES] nodemask.  set_mempolicy()
> [in do_set_mempolicy()] calls contextualize_policy() which
> requires that the nodemask be a subset of the current task's
> mems_allowed; else EINVAL will be returned.  A task's
> mems_allowed will always be a subset of node_states[N_HIGH_MEMORY]--
> i.e., nodes with memory.  So, a fully populated nodemask will
> be declared invalid if it includes memoryless nodes.
> 
>   NOTE:  the same thing will occur when running in a cpuset
>          with restricted mem_allowed--for the same reason:
>          node mask contains dis-allowed nodes.
> 
> mbind(2), on the other hand, just masks off any nodes in the 
> nodemask that are not included in the caller's mems_allowed.
> 
> In each case [mbind() and set_mempolicy()], mpol_check_policy()
> will complain [again, resulting in EINVAL] if the nodemask contains 
> any memoryless nodes.  This is somewhat redundant as mpol_new() 
> will remove memoryless nodes for interleave policy, as will 
> bind_zonelist()--called by mpol_new() for BIND policy.
> 
> Proposed fix:
> 
> 1) modify contextualize_policy logic to:
>    a) remember whether the incoming node mask is empty.
>    b) if not, restrict the nodemask to allowed nodes, as is
>       currently done in-line for mbind().  This guarantees
>       that the resulting mask includes only nodes with memory.
> 
>       NOTE:  this is a [benign, IMO] change in behavior for
>              set_mempolicy().  Dis-allowed nodes will be
>              silently ignored, rather than returning an error.
> 
>    c) fold this code into mpol_check_policy(), replace 2 calls to
>       contextualize_policy() to call mpol_check_policy() directly
>       and remove contextualize_policy().
> 
> 2) In existing mpol_check_policy() logic, after "contextualization":
>    a) MPOL_DEFAULT:  require that in coming mask "was_empty"
>    b) MPOL_{BIND|INTERLEAVE}:  require that contextualized nodemask
>       contains at least one node.
>    c) add a case for MPOL_PREFERRED:  if in coming was not empty
>       and resulting mask IS empty, user specified invalid nodes.
>       Return EINVAL.
>    c) remove the now redundant check for memoryless nodes
> 
> 3) remove the now redundant masking of policy nodes for interleave
>    policy from mpol_new().
> 
> 4) Now that mpol_check_policy() contextualizes the nodemask, remove
>    the in-line nodes_and() from sys_mbind().  I believe that this
>    restores mbind() to the behavior before the memoryless-nodes
>    patch series.  E.g., we'll no longer treat an invalid nodemask
>    with MPOL_PREFERRED as local allocation.
> 
> Signed-off-by:  Lee Schermerhorn <lee.schermerhorn@...com>
> 
>  include/linux/cpuset.h |    3 --
>  mm/mempolicy.c         |   61 ++++++++++++++++++++++++++++---------------------
>  2 files changed, 36 insertions(+), 28 deletions(-)
> 
> Index: Linux/mm/mempolicy.c
> ===================================================================
> --- Linux.orig/mm/mempolicy.c	2008-02-08 11:11:34.000000000 -0500
> +++ Linux/mm/mempolicy.c	2008-02-08 13:40:40.000000000 -0500
> @@ -116,22 +116,51 @@ static void mpol_rebind_policy(struct me
>  /* Do sanity checking on a policy */
>  static int mpol_check_policy(int mode, nodemask_t *nodes)
>  {
> -	int empty = nodes_empty(*nodes);
> +	int was_empty, is_empty;
> +
> +	if (!nodes)
> +		return 0;
> +
> +	/*
> +	 * "Contextualize" the in-coming nodemast for cpusets:
> +	 * Remember whether in-coming nodemask was empty,  If not,
> +	 * restrict the nodes to the allowed nodes in the cpuset.
> +	 * This is guaranteed to be a subset of nodes with memory.
> +	 */
> +	cpuset_update_task_memory_state();
> +	is_empty = was_empty = nodes_empty(*nodes);
> +	if (!was_empty) {
> +		nodes_and(*nodes, *nodes, cpuset_current_mems_allowed);
> +		is_empty = nodes_empty(*nodes);	/* after "contextualization" */
> +	}
>  
>  	switch (mode) {
>  	case MPOL_DEFAULT:
> -		if (!empty)
> +		/*
> +		 * require caller to specify an empty nodemask
> +		 * before "contextualization"
> +		 */
> +		if (!was_empty)
>  			return -EINVAL;
>  		break;
>  	case MPOL_BIND:
>  	case MPOL_INTERLEAVE:
> -		/* Preferred will only use the first bit, but allow
> -		   more for now. */
> -		if (empty)
> +		/*
> +		 * require at least 1 valid node after "contextualization"
> +		 */
> +		if (is_empty)
> +			return -EINVAL;
> +		break;
> +	case MPOL_PREFERRED:
> +		/*
> +		 * Did caller specify invalid nodes?
> +		 * Don't silently accept this as "local allocation".
> +		 */
> +		if (!was_empty && is_empty)
>  			return -EINVAL;
>  		break;
>  	}
> - 	return nodes_subset(*nodes, node_states[N_HIGH_MEMORY]) ? 0 : -EINVAL;
> + 	return 0;
>  }
>  
>  /* Generate a custom zonelist for the BIND policy. */
> @@ -188,8 +217,6 @@ static struct mempolicy *mpol_new(int mo
>  	switch (mode) {
>  	case MPOL_INTERLEAVE:
>  		policy->v.nodes = *nodes;
> -		nodes_and(policy->v.nodes, policy->v.nodes,
> -					node_states[N_HIGH_MEMORY]);
>  		if (nodes_weight(policy->v.nodes) == 0) {
>  			kmem_cache_free(policy_cache, policy);
>  			return ERR_PTR(-EINVAL);
> @@ -421,18 +448,6 @@ static int mbind_range(struct vm_area_st
>  	return err;
>  }
>  
> -static int contextualize_policy(int mode, nodemask_t *nodes)
> -{
> -	if (!nodes)
> -		return 0;
> -
> -	cpuset_update_task_memory_state();
> -	if (!cpuset_nodes_subset_current_mems_allowed(*nodes))
> -		return -EINVAL;
> -	return mpol_check_policy(mode, nodes);
> -}
> -
> -
>  /*
>   * Update task->flags PF_MEMPOLICY bit: set iff non-default
>   * mempolicy.  Allows more rapid checking of this (combined perhaps
> @@ -468,7 +483,7 @@ static long do_set_mempolicy(int mode, n
>  {
>  	struct mempolicy *new;
>  
> -	if (contextualize_policy(mode, nodes))
> +	if (mpol_check_policy(mode, nodes))
>  		return -EINVAL;
>  	new = mpol_new(mode, nodes);
>  	if (IS_ERR(new))
> @@ -915,10 +930,6 @@ asmlinkage long sys_mbind(unsigned long 
>  	err = get_nodes(&nodes, nmask, maxnode);
>  	if (err)
>  		return err;
> -#ifdef CONFIG_CPUSETS
> -	/* Restrict the nodes to the allowed nodes in the cpuset */
> -	nodes_and(nodes, nodes, current->mems_allowed);
> -#endif
>  	return do_mbind(start, len, mode, &nodes, flags);
>  }
>  
> Index: Linux/include/linux/cpuset.h
> ===================================================================
> --- Linux.orig/include/linux/cpuset.h	2008-02-08 11:11:34.000000000 -0500
> +++ Linux/include/linux/cpuset.h	2008-02-08 11:12:43.000000000 -0500
> @@ -26,8 +26,6 @@ extern nodemask_t cpuset_mems_allowed(st
>  #define cpuset_current_mems_allowed (current->mems_allowed)
>  void cpuset_init_current_mems_allowed(void);
>  void cpuset_update_task_memory_state(void);
> -#define cpuset_nodes_subset_current_mems_allowed(nodes) \
> -		nodes_subset((nodes), current->mems_allowed)
>  int cpuset_zonelist_valid_mems_allowed(struct zonelist *zl);
>  
>  extern int __cpuset_zone_allowed_softwall(struct zone *z, gfp_t gfp_mask);
> @@ -103,7 +101,6 @@ static inline nodemask_t cpuset_mems_all
>  #define cpuset_current_mems_allowed (node_states[N_HIGH_MEMORY])
>  static inline void cpuset_init_current_mems_allowed(void) {}
>  static inline void cpuset_update_task_memory_state(void) {}
> -#define cpuset_nodes_subset_current_mems_allowed(nodes) (1)
>  
>  static inline int cpuset_zonelist_valid_mems_allowed(struct zonelist *zl)
>  {
> 
> 
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