The patch titled
Subject: mm: vmscan: fix shrinker_rwsem in free_shrinker_info()
has been added to the -mm tree. Its filename is
mm-vmscan-add-per-memcg-shrinker-nr_deferred-fix.patch
This patch should soon appear at
https://ozlabs.org/~akpm/mmots/broken-out/mm-vmscan-add-per-memcg-shrinker-nr_deferred-fix.patch
and later at
https://ozlabs.org/~akpm/mmotm/broken-out/mm-vmscan-add-per-memcg-shrinker-nr_deferred-fix.patch
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------------------------------------------------------
From: Hugh Dickins <hughd@xxxxxxxxxx>
Subject: mm: vmscan: fix shrinker_rwsem in free_shrinker_info()
Lockdep warns mm/vmscan.c: suspicious rcu_dereference_protected() usage!
when free_shrinker_info() is called from mem_cgroup_css_free(): there it
is called with no locking, whereas alloc_shrinker_info() calls it with
down_write of shrinker_rwsem - which seems appropriate. Rearrange that
so free_shrinker_info() can manage the shrinker_rwsem for itself.
Link: https://lkml.kernel.org/r/20210317140615.GB28839@xsang-OptiPlex-9020
Link: https://lkml.kernel.org/r/alpine.LSU.2.11.2103301640240.2584@eggly.anvils
Reported-by: kernel test robot <oliver.sang@xxxxxxxxx>
Signed-off-by: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Yang Shi <shy828301@xxxxxxxxx>
Cc: Roman Gushchin <guro@xxxxxx>
Cc: Kirill Tkhai <ktkhai@xxxxxxxxxxxxx>
Cc: Shakeel Butt <shakeelb@xxxxxxxxxx>
Cc: Dave Chinner <david@xxxxxxxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/vmscan.c | 10 ++++++----
1 file changed, 6 insertions(+), 4 deletions(-)
--- a/mm/vmscan.c~mm-vmscan-add-per-memcg-shrinker-nr_deferred-fix
+++ a/mm/vmscan.c
@@ -249,18 +249,20 @@ void free_shrinker_info(struct mem_cgrou
struct shrinker_info *info;
int nid;
+ down_write(&shrinker_rwsem);
for_each_node(nid) {
pn = memcg->nodeinfo[nid];
info = shrinker_info_protected(memcg, nid);
kvfree(info);
rcu_assign_pointer(pn->shrinker_info, NULL);
}
+ up_write(&shrinker_rwsem);
}
int alloc_shrinker_info(struct mem_cgroup *memcg)
{
struct shrinker_info *info;
- int nid, size, ret = 0;
+ int nid, size;
int map_size, defer_size = 0;
down_write(&shrinker_rwsem);
@@ -270,9 +272,9 @@ int alloc_shrinker_info(struct mem_cgrou
for_each_node(nid) {
info = kvzalloc_node(sizeof(*info) + size, GFP_KERNEL, nid);
if (!info) {
+ up_write(&shrinker_rwsem);
free_shrinker_info(memcg);
- ret = -ENOMEM;
- break;
+ return -ENOMEM;
}
info->nr_deferred = (atomic_long_t *)(info + 1);
info->map = (void *)info->nr_deferred + defer_size;
@@ -280,7 +282,7 @@ int alloc_shrinker_info(struct mem_cgrou
}
up_write(&shrinker_rwsem);
- return ret;
+ return 0;
}
static inline bool need_expand(int nr_max)
_
Patches currently in -mm which might be from hughd@xxxxxxxxxx are
mm-vmscan-add-per-memcg-shrinker-nr_deferred-fix.patch
mm-restore-node-stat-checking-in-proc-sys-vm-stat_refresh.patch
mm-no-more-einval-from-proc-sys-vm-stat_refresh.patch
mm-proc-sys-vm-stat_refresh-skip-checking-known-negative-stats.patch
mm-proc-sys-vm-stat_refresh-stop-checking-monotonic-numa-stats.patch
