Re: [PATCH mm-unstable v1 1/4] mm: don't hold css->refcnt during traversal
From: kernel test robot
Date: Thu Jul 25 2024 - 12:33:27 EST
Hi Kinsey,
kernel test robot noticed the following build warnings:
[auto build test WARNING on akpm-mm/mm-everything]
[also build test WARNING on linus/master v6.10 next-20240725]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]
url: https://github.com/intel-lab-lkp/linux/commits/Kinsey-Ho/mm-don-t-hold-css-refcnt-during-traversal/20240725-030750
base: https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git mm-everything
patch link: https://lore.kernel.org/r/20240724190214.1108049-2-kinseyho%40google.com
patch subject: [PATCH mm-unstable v1 1/4] mm: don't hold css->refcnt during traversal
config: x86_64-randconfig-121-20240725 (https://download.01.org/0day-ci/archive/20240726/202407260047.sIuRFLJE-lkp@xxxxxxxxx/config)
compiler: gcc-7 (Ubuntu 7.5.0-6ubuntu2) 7.5.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20240726/202407260047.sIuRFLJE-lkp@xxxxxxxxx/reproduce)
If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@xxxxxxxxx>
| Closes: https://lore.kernel.org/oe-kbuild-all/202407260047.sIuRFLJE-lkp@xxxxxxxxx/
sparse warnings: (new ones prefixed by >>)
>> mm/memcontrol.c:1063:23: sparse: sparse: incorrect type in initializer (different address spaces) @@ expected struct mem_cgroup [noderef] __rcu *__old @@ got struct mem_cgroup *[assigned] pos @@
mm/memcontrol.c:1063:23: sparse: expected struct mem_cgroup [noderef] __rcu *__old
mm/memcontrol.c:1063:23: sparse: got struct mem_cgroup *[assigned] pos
mm/memcontrol.c:1063:23: sparse: sparse: incorrect type in initializer (different address spaces) @@ expected struct mem_cgroup [noderef] __rcu *__new @@ got struct mem_cgroup *[assigned] memcg @@
mm/memcontrol.c:1063:23: sparse: expected struct mem_cgroup [noderef] __rcu *__new
mm/memcontrol.c:1063:23: sparse: got struct mem_cgroup *[assigned] memcg
>> mm/memcontrol.c:1101:17: sparse: sparse: incorrect type in initializer (different address spaces) @@ expected struct mem_cgroup [noderef] __rcu *__old @@ got struct mem_cgroup *dead_memcg @@
mm/memcontrol.c:1101:17: sparse: expected struct mem_cgroup [noderef] __rcu *__old
mm/memcontrol.c:1101:17: sparse: got struct mem_cgroup *dead_memcg
mm/memcontrol.c: note: in included file (through include/linux/cgroup-defs.h):
include/linux/list.h:83:21: sparse: sparse: self-comparison always evaluates to true
mm/memcontrol.c: note: in included file:
include/linux/memcontrol.h:747:9: sparse: sparse: context imbalance in 'folio_lruvec_lock' - wrong count at exit
include/linux/memcontrol.h:747:9: sparse: sparse: context imbalance in 'folio_lruvec_lock_irq' - wrong count at exit
include/linux/memcontrol.h:747:9: sparse: sparse: context imbalance in 'folio_lruvec_lock_irqsave' - wrong count at exit
mm/memcontrol.c: note: in included file (through include/linux/cgroup-defs.h):
include/linux/list.h:83:21: sparse: sparse: self-comparison always evaluates to true
vim +1063 mm/memcontrol.c
4b569387c0d566 Nhat Pham 2023-10-06 974
5660048ccac873 Johannes Weiner 2012-01-12 975 /**
5660048ccac873 Johannes Weiner 2012-01-12 976 * mem_cgroup_iter - iterate over memory cgroup hierarchy
5660048ccac873 Johannes Weiner 2012-01-12 977 * @root: hierarchy root
5660048ccac873 Johannes Weiner 2012-01-12 978 * @prev: previously returned memcg, NULL on first invocation
5660048ccac873 Johannes Weiner 2012-01-12 979 * @reclaim: cookie for shared reclaim walks, NULL for full walks
5660048ccac873 Johannes Weiner 2012-01-12 980 *
5660048ccac873 Johannes Weiner 2012-01-12 981 * Returns references to children of the hierarchy below @root, or
5660048ccac873 Johannes Weiner 2012-01-12 982 * @root itself, or %NULL after a full round-trip.
5660048ccac873 Johannes Weiner 2012-01-12 983 *
5660048ccac873 Johannes Weiner 2012-01-12 984 * Caller must pass the return value in @prev on subsequent
5660048ccac873 Johannes Weiner 2012-01-12 985 * invocations for reference counting, or use mem_cgroup_iter_break()
5660048ccac873 Johannes Weiner 2012-01-12 986 * to cancel a hierarchy walk before the round-trip is complete.
5660048ccac873 Johannes Weiner 2012-01-12 987 *
05bdc520b3ad39 Miaohe Lin 2020-10-13 988 * Reclaimers can specify a node in @reclaim to divide up the memcgs
05bdc520b3ad39 Miaohe Lin 2020-10-13 989 * in the hierarchy among all concurrent reclaimers operating on the
05bdc520b3ad39 Miaohe Lin 2020-10-13 990 * same node.
5660048ccac873 Johannes Weiner 2012-01-12 991 */
694fbc0fe78518 Andrew Morton 2013-09-24 992 struct mem_cgroup *mem_cgroup_iter(struct mem_cgroup *root,
9f3a0d0933de07 Johannes Weiner 2012-01-12 993 struct mem_cgroup *prev,
694fbc0fe78518 Andrew Morton 2013-09-24 994 struct mem_cgroup_reclaim_cookie *reclaim)
7d74b06f240f1b KAMEZAWA Hiroyuki 2010-10-27 995 {
3f649ab728cda8 Kees Cook 2020-06-03 996 struct mem_cgroup_reclaim_iter *iter;
5ac8fb31ad2ebd Johannes Weiner 2014-12-10 997 struct cgroup_subsys_state *css = NULL;
9f3a0d0933de07 Johannes Weiner 2012-01-12 998 struct mem_cgroup *memcg = NULL;
5ac8fb31ad2ebd Johannes Weiner 2014-12-10 999 struct mem_cgroup *pos = NULL;
711d3d2c9bc3fb KAMEZAWA Hiroyuki 2010-10-27 1000
694fbc0fe78518 Andrew Morton 2013-09-24 1001 if (mem_cgroup_disabled())
694fbc0fe78518 Andrew Morton 2013-09-24 1002 return NULL;
5660048ccac873 Johannes Weiner 2012-01-12 1003
9f3a0d0933de07 Johannes Weiner 2012-01-12 1004 if (!root)
9f3a0d0933de07 Johannes Weiner 2012-01-12 1005 root = root_mem_cgroup;
9f3a0d0933de07 Johannes Weiner 2012-01-12 1006
542f85f9ae4acd Michal Hocko 2013-04-29 1007 rcu_read_lock();
14067bb3e24b96 KAMEZAWA Hiroyuki 2009-04-02 1008
527a5ec9a53471 Johannes Weiner 2012-01-12 1009 if (reclaim) {
ef8f2327996b5c Mel Gorman 2016-07-28 1010 struct mem_cgroup_per_node *mz;
527a5ec9a53471 Johannes Weiner 2012-01-12 1011
a3747b53b1771a Johannes Weiner 2021-04-29 1012 mz = root->nodeinfo[reclaim->pgdat->node_id];
9da83f3fc74b80 Yafang Shao 2019-11-30 1013 iter = &mz->iter;
5ac8fb31ad2ebd Johannes Weiner 2014-12-10 1014
a9320aae68a1cd Wei Yang 2022-04-28 1015 /*
a9320aae68a1cd Wei Yang 2022-04-28 1016 * On start, join the current reclaim iteration cycle.
a9320aae68a1cd Wei Yang 2022-04-28 1017 * Exit when a concurrent walker completes it.
a9320aae68a1cd Wei Yang 2022-04-28 1018 */
a9320aae68a1cd Wei Yang 2022-04-28 1019 if (!prev)
a9320aae68a1cd Wei Yang 2022-04-28 1020 reclaim->generation = iter->generation;
a9320aae68a1cd Wei Yang 2022-04-28 1021 else if (reclaim->generation != iter->generation)
542f85f9ae4acd Michal Hocko 2013-04-29 1022 goto out_unlock;
5ac8fb31ad2ebd Johannes Weiner 2014-12-10 1023
fe6faac115aa89 Kinsey Ho 2024-07-24 1024 pos = rcu_dereference(iter->position);
89d8330ccf2ad4 Wei Yang 2022-04-28 1025 } else if (prev) {
89d8330ccf2ad4 Wei Yang 2022-04-28 1026 pos = prev;
5ac8fb31ad2ebd Johannes Weiner 2014-12-10 1027 }
5ac8fb31ad2ebd Johannes Weiner 2014-12-10 1028
5ac8fb31ad2ebd Johannes Weiner 2014-12-10 1029 if (pos)
5ac8fb31ad2ebd Johannes Weiner 2014-12-10 1030 css = &pos->css;
5ac8fb31ad2ebd Johannes Weiner 2014-12-10 1031
5ac8fb31ad2ebd Johannes Weiner 2014-12-10 1032 for (;;) {
5ac8fb31ad2ebd Johannes Weiner 2014-12-10 1033 css = css_next_descendant_pre(css, &root->css);
5ac8fb31ad2ebd Johannes Weiner 2014-12-10 1034 if (!css) {
5ac8fb31ad2ebd Johannes Weiner 2014-12-10 1035 /*
5ac8fb31ad2ebd Johannes Weiner 2014-12-10 1036 * Reclaimers share the hierarchy walk, and a
5ac8fb31ad2ebd Johannes Weiner 2014-12-10 1037 * new one might jump in right at the end of
5ac8fb31ad2ebd Johannes Weiner 2014-12-10 1038 * the hierarchy - make sure they see at least
5ac8fb31ad2ebd Johannes Weiner 2014-12-10 1039 * one group and restart from the beginning.
5ac8fb31ad2ebd Johannes Weiner 2014-12-10 1040 */
5ac8fb31ad2ebd Johannes Weiner 2014-12-10 1041 if (!prev)
5ac8fb31ad2ebd Johannes Weiner 2014-12-10 1042 continue;
5ac8fb31ad2ebd Johannes Weiner 2014-12-10 1043 break;
542f85f9ae4acd Michal Hocko 2013-04-29 1044 }
5f578161971863 Michal Hocko 2013-04-29 1045
5ac8fb31ad2ebd Johannes Weiner 2014-12-10 1046 /*
5ac8fb31ad2ebd Johannes Weiner 2014-12-10 1047 * Verify the css and acquire a reference. The root
5ac8fb31ad2ebd Johannes Weiner 2014-12-10 1048 * is provided by the caller, so we know it's alive
5ac8fb31ad2ebd Johannes Weiner 2014-12-10 1049 * and kicking, and don't take an extra reference.
5ac8fb31ad2ebd Johannes Weiner 2014-12-10 1050 */
41555dadbff8d2 Wei Yang 2022-04-28 1051 if (css == &root->css || css_tryget(css)) {
5ac8fb31ad2ebd Johannes Weiner 2014-12-10 1052 memcg = mem_cgroup_from_css(css);
5ac8fb31ad2ebd Johannes Weiner 2014-12-10 1053 break;
41555dadbff8d2 Wei Yang 2022-04-28 1054 }
5ac8fb31ad2ebd Johannes Weiner 2014-12-10 1055 }
9f3a0d0933de07 Johannes Weiner 2012-01-12 1056
527a5ec9a53471 Johannes Weiner 2012-01-12 1057 if (reclaim) {
5ac8fb31ad2ebd Johannes Weiner 2014-12-10 1058 /*
6df38689e0e9a0 Vladimir Davydov 2015-12-29 1059 * The position could have already been updated by a competing
6df38689e0e9a0 Vladimir Davydov 2015-12-29 1060 * thread, so check that the value hasn't changed since we read
6df38689e0e9a0 Vladimir Davydov 2015-12-29 1061 * it to avoid reclaiming from the same cgroup twice.
5ac8fb31ad2ebd Johannes Weiner 2014-12-10 1062 */
6df38689e0e9a0 Vladimir Davydov 2015-12-29 @1063 (void)cmpxchg(&iter->position, pos, memcg);
6df38689e0e9a0 Vladimir Davydov 2015-12-29 1064
19f39402864ea3 Michal Hocko 2013-04-29 1065 if (!memcg)
527a5ec9a53471 Johannes Weiner 2012-01-12 1066 iter->generation++;
527a5ec9a53471 Johannes Weiner 2012-01-12 1067 }
14067bb3e24b96 KAMEZAWA Hiroyuki 2009-04-02 1068
542f85f9ae4acd Michal Hocko 2013-04-29 1069 out_unlock:
542f85f9ae4acd Michal Hocko 2013-04-29 1070 rcu_read_unlock();
c40046f3ad5e87 Michal Hocko 2013-04-29 1071 if (prev && prev != root)
c40046f3ad5e87 Michal Hocko 2013-04-29 1072 css_put(&prev->css);
c40046f3ad5e87 Michal Hocko 2013-04-29 1073
9f3a0d0933de07 Johannes Weiner 2012-01-12 1074 return memcg;
9f3a0d0933de07 Johannes Weiner 2012-01-12 1075 }
14067bb3e24b96 KAMEZAWA Hiroyuki 2009-04-02 1076
5660048ccac873 Johannes Weiner 2012-01-12 1077 /**
5660048ccac873 Johannes Weiner 2012-01-12 1078 * mem_cgroup_iter_break - abort a hierarchy walk prematurely
5660048ccac873 Johannes Weiner 2012-01-12 1079 * @root: hierarchy root
5660048ccac873 Johannes Weiner 2012-01-12 1080 * @prev: last visited hierarchy member as returned by mem_cgroup_iter()
5660048ccac873 Johannes Weiner 2012-01-12 1081 */
5660048ccac873 Johannes Weiner 2012-01-12 1082 void mem_cgroup_iter_break(struct mem_cgroup *root,
9f3a0d0933de07 Johannes Weiner 2012-01-12 1083 struct mem_cgroup *prev)
9f3a0d0933de07 Johannes Weiner 2012-01-12 1084 {
711d3d2c9bc3fb KAMEZAWA Hiroyuki 2010-10-27 1085 if (!root)
711d3d2c9bc3fb KAMEZAWA Hiroyuki 2010-10-27 1086 root = root_mem_cgroup;
9f3a0d0933de07 Johannes Weiner 2012-01-12 1087 if (prev && prev != root)
9f3a0d0933de07 Johannes Weiner 2012-01-12 1088 css_put(&prev->css);
14067bb3e24b96 KAMEZAWA Hiroyuki 2009-04-02 1089 }
9f3a0d0933de07 Johannes Weiner 2012-01-12 1090
54a83d6bcbf8f4 Miles Chen 2019-08-13 1091 static void __invalidate_reclaim_iterators(struct mem_cgroup *from,
54a83d6bcbf8f4 Miles Chen 2019-08-13 1092 struct mem_cgroup *dead_memcg)
6df38689e0e9a0 Vladimir Davydov 2015-12-29 1093 {
6df38689e0e9a0 Vladimir Davydov 2015-12-29 1094 struct mem_cgroup_reclaim_iter *iter;
ef8f2327996b5c Mel Gorman 2016-07-28 1095 struct mem_cgroup_per_node *mz;
ef8f2327996b5c Mel Gorman 2016-07-28 1096 int nid;
6df38689e0e9a0 Vladimir Davydov 2015-12-29 1097
6df38689e0e9a0 Vladimir Davydov 2015-12-29 1098 for_each_node(nid) {
a3747b53b1771a Johannes Weiner 2021-04-29 1099 mz = from->nodeinfo[nid];
9da83f3fc74b80 Yafang Shao 2019-11-30 1100 iter = &mz->iter;
9da83f3fc74b80 Yafang Shao 2019-11-30 @1101 cmpxchg(&iter->position, dead_memcg, NULL);
6df38689e0e9a0 Vladimir Davydov 2015-12-29 1102 }
6df38689e0e9a0 Vladimir Davydov 2015-12-29 1103 }
54a83d6bcbf8f4 Miles Chen 2019-08-13 1104
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