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Commit 45816682 authored by Vlastimil Babka's avatar Vlastimil Babka Committed by Linus Torvalds
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mm, mempolicy: stop adjusting current->il_next in mpol_rebind_nodemask() 

The task->il_next variable stores the next allocation node id for task's
MPOL_INTERLEAVE policy.  mpol_rebind_nodemask() updates interleave and
bind mempolicies due to changing cpuset mems.  Currently it also tries
to make sure that current->il_next is valid within the updated nodemask.
This is bogus, because 1) we are updating potentially any task's
mempolicy, not just current, and 2) we might be updating a per-vma
mempolicy, not task one.

The interleave_nodes() function that uses il_next can cope fine with the
value not being within the currently allowed nodes, so this hasn't
manifested as an actual issue.

We can remove the need for updating il_next completely by changing it to
il_prev and store the node id of the previous interleave allocation
instead of the next id.  Then interleave_nodes() can calculate the next
id using the current nodemask and also store it as il_prev, except when
querying the next node via do_get_mempolicy().

Link: http://lkml.kernel.org/r/20170517081140.30654-3-vbabka@suse.cz


Signed-off-by: default avatarVlastimil Babka <vbabka@suse.cz>
Reviewed-by: default avatarChristoph Lameter <cl@linux.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Anshuman Khandual <khandual@linux.vnet.ibm.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Dimitri Sivanich <sivanich@sgi.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Li Zefan <lizefan@huawei.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Michal Hocko <mhocko@suse.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 902b6281

include/linux/sched.h

+1 −1
Original line number Diff line number Diff line
@@ -904,7 +904,7 @@ struct task_struct { 
#ifdef CONFIG_NUMA

	/* Protected by alloc_lock: */

	struct mempolicy		*mempolicy;

	short				il_next;

	short				il_prev;

	short				pref_node_fork;

#endif

#ifdef CONFIG_NUMA_BALANCING

mm/mempolicy.c

+7 −15
Original line number Diff line number Diff line
@@ -349,12 +349,6 @@ static void mpol_rebind_nodemask(struct mempolicy *pol, const nodemask_t *nodes, 
		pol->v.nodes = tmp;

	else

		BUG();



	if (!node_isset(current->il_next, tmp)) {

		current->il_next = next_node_in(current->il_next, tmp);

		if (current->il_next >= MAX_NUMNODES)

			current->il_next = numa_node_id();

	}

}



static void mpol_rebind_preferred(struct mempolicy *pol,
@@ -812,9 +806,8 @@ static long do_set_mempolicy(unsigned short mode, unsigned short flags, 
	}

	old = current->mempolicy;

	current->mempolicy = new;

	if (new && new->mode == MPOL_INTERLEAVE &&

	    nodes_weight(new->v.nodes))

		current->il_next = first_node(new->v.nodes);

	if (new && new->mode == MPOL_INTERLEAVE)

		current->il_prev = MAX_NUMNODES-1;

	task_unlock(current);

	mpol_put(old);

	ret = 0;
@@ -916,7 +909,7 @@ static long do_get_mempolicy(int *policy, nodemask_t *nmask, 
			*policy = err;

		} else if (pol == current->mempolicy &&

				pol->mode == MPOL_INTERLEAVE) {

			*policy = current->il_next;

			*policy = next_node_in(current->il_prev, pol->v.nodes);

		} else {

			err = -EINVAL;

			goto out;
@@ -1697,14 +1690,13 @@ static struct zonelist *policy_zonelist(gfp_t gfp, struct mempolicy *policy, 
/* Do dynamic interleaving for a process */

static unsigned interleave_nodes(struct mempolicy *policy)

{

	unsigned nid, next;

	unsigned next;

	struct task_struct *me = current;



	nid = me->il_next;

	next = next_node_in(nid, policy->v.nodes);

	next = next_node_in(me->il_prev, policy->v.nodes);

	if (next < MAX_NUMNODES)

		me->il_next = next;

	return nid;

		me->il_prev = next;

	return next;

}



/*