mm, mempolicy: stop adjusting current->il_next in mpol_rebind_nodemask() (45816682) · Commits · 戴 / test

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:

Vlastimil Babka <vbabka@suse.cz> Reviewed-by:

Christoph 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:

Andrew Morton <akpm@linux-foundation.org> Signed-off-by:

Linus Torvalds <torvalds@linux-foundation.org>

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;
		}

		/*

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