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 @@ -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 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; } /* _ -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
