On Tue, Feb 09, 2021 at 05:07:07PM -0800, Yang Shi wrote:

On Tue, Feb 9, 2021 at 4:22 PM Roman Gushchin [off-list ref] wrote:

quoted

On Tue, Feb 09, 2021 at 09:46:40AM -0800, Yang Shi wrote:

quoted

The shrinker_info is dereferenced in a couple of places via rcu_dereference_protected
with different calling conventions, for example, using mem_cgroup_nodeinfo helper
or dereferencing memcg->nodeinfo[nid]->shrinker_info.  And the later patch
will add more dereference places.

So extract the dereference into a helper to make the code more readable.  No
functional change.

Signed-off-by: Yang Shi <redacted>
---
 mm/vmscan.c | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 9436f9246d32..273efbf4d53c 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c

@@ -190,6 +190,13 @@ static int shrinker_nr_max;
 #define NR_MAX_TO_SHR_MAP_SIZE(nr_max) \
      (DIV_ROUND_UP(nr_max, BITS_PER_LONG) * sizeof(unsigned long))

+static struct shrinker_info *shrinker_info_protected(struct mem_cgroup *memcg,
+                                                  int nid)
+{
+     return rcu_dereference_protected(memcg->nodeinfo[nid]->shrinker_info,
+                                      lockdep_is_held(&shrinker_rwsem));
+}
+

I'd probably drop the "protected" suffix (because there is no unprotected version,
right?).

No, actually there is one "unprotected" call in set_shrinker_bit().

Ah, ok. Then it makes sense. Sorry.

quoted

Other than that LGTM.

Acked-by: Roman Gushchin <redacted>