The patch titled
Subject: mm, mempolicy: stop adjusting current->il_next in mpol_rebind_nodemask()
has been added to the -mm tree. Its filename is
mm-mempolicy-stop-adjusting-current-il_next-in-mpol_rebind_nodemask.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-mempolicy-stop-adjusting-current-il_next-in-mpol_rebind_nodemask.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-mempolicy-stop-adjusting-current-il_next-in-mpol_rebind_nodemask.patch
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------------------------------------------------------
From: Vlastimil Babka <vbabka@xxxxxxx>
Subject: 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@xxxxxxx
Signed-off-by: Vlastimil Babka <vbabka@xxxxxxx>
Reviewed-by: Christoph Lameter <cl@xxxxxxxxx>
Cc: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx>
Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Cc: Anshuman Khandual <khandual@xxxxxxxxxxxxxxxxxx>
Cc: David Rientjes <rientjes@xxxxxxxxxx>
Cc: Dimitri Sivanich <sivanich@xxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Li Zefan <lizefan@xxxxxxxxxx>
Cc: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/sched.h | 2 +-
mm/mempolicy.c | 22 +++++++---------------
2 files changed, 8 insertions(+), 16 deletions(-)
diff -puN include/linux/sched.h~mm-mempolicy-stop-adjusting-current-il_next-in-mpol_rebind_nodemask include/linux/sched.h
--- a/include/linux/sched.h~mm-mempolicy-stop-adjusting-current-il_next-in-mpol_rebind_nodemask
+++ a/include/linux/sched.h
@@ -886,7 +886,7 @@ 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
diff -puN mm/mempolicy.c~mm-mempolicy-stop-adjusting-current-il_next-in-mpol_rebind_nodemask mm/mempolicy.c
--- a/mm/mempolicy.c~mm-mempolicy-stop-adjusting-current-il_next-in-mpol_rebind_nodemask
+++ a/mm/mempolicy.c
@@ -349,12 +349,6 @@ static void mpol_rebind_nodemask(struct
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 sh
}
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
*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(
/* 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;
}
/*
_
Patches currently in -mm which might be from vbabka@xxxxxxx are
mm-page_alloc-fix-more-premature-oom-due-to-race-with-cpuset-update.patch
mm-mempolicy-stop-adjusting-current-il_next-in-mpol_rebind_nodemask.patch
mm-page_alloc-pass-preferred-nid-instead-of-zonelist-to-allocator.patch
mm-mempolicy-simplify-rebinding-mempolicies-when-updating-cpusets.patch
mm-cpuset-always-use-seqlock-when-changing-tasks-nodemask.patch
mm-mempolicy-dont-check-cpuset-seqlock-where-it-doesnt-matter.patch
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