From: Yafang Shao <laoar.shao@xxxxxxxxx>
Subject: mm, memcg: fix build error around the usage of kmem_caches
When I manually set default n to MEMCG_KMEM in init/Kconfig, bellow error
occurs,
mm/slab_common.c: In function 'memcg_slab_start':
mm/slab_common.c:1530:30: error: 'struct mem_cgroup' has no member named
'kmem_caches'
return seq_list_start(&memcg->kmem_caches, *pos);
^
mm/slab_common.c: In function 'memcg_slab_next':
mm/slab_common.c:1537:32: error: 'struct mem_cgroup' has no member named
'kmem_caches'
return seq_list_next(p, &memcg->kmem_caches, pos);
^
mm/slab_common.c: In function 'memcg_slab_show':
mm/slab_common.c:1551:16: error: 'struct mem_cgroup' has no member named
'kmem_caches'
if (p == memcg->kmem_caches.next)
^
CC arch/x86/xen/smp.o
mm/slab_common.c: In function 'memcg_slab_start':
mm/slab_common.c:1531:1: warning: control reaches end of non-void function
[-Wreturn-type]
}
^
mm/slab_common.c: In function 'memcg_slab_next':
mm/slab_common.c:1538:1: warning: control reaches end of non-void function
[-Wreturn-type]
}
^
That's because kmem_caches is defined only when CONFIG_MEMCG_KMEM is set,
while memcg_slab_start() will use it no matter CONFIG_MEMCG_KMEM is defined
or not.
By the way, the reason I mannuly undefined CONFIG_MEMCG_KMEM is to verify
whether my some other code change is still stable when CONFIG_MEMCG_KMEM is
not set. Unfortunately, the existing code has been already unstable since
v4.11.
Link: http://lkml.kernel.org/r/1580970260-2045-1-git-send-email-laoar.shao@xxxxxxxxx
Fixes: bc2791f857e1 ("slab: link memcg kmem_caches on their associated memory cgroup")
Signed-off-by: Yafang Shao <laoar.shao@xxxxxxxxx>
Acked-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Tejun Heo <tj@xxxxxxxxxx>
Cc: Vladimir Davydov <vdavydov.dev@xxxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/memcontrol.c | 3 ++-
mm/slab_common.c | 2 +-
2 files changed, 3 insertions(+), 2 deletions(-)
--- a/mm/memcontrol.c~mm-memcg-fix-build-error-around-the-usage-of-kmem_caches
+++ a/mm/memcontrol.c
@@ -4792,7 +4792,8 @@ static struct cftype mem_cgroup_legacy_f
.write = mem_cgroup_reset,
.read_u64 = mem_cgroup_read_u64,
},
-#if defined(CONFIG_SLAB) || defined(CONFIG_SLUB_DEBUG)
+#if defined(CONFIG_MEMCG_KMEM) && \
+ (defined(CONFIG_SLAB) || defined(CONFIG_SLUB_DEBUG))
{
.name = "kmem.slabinfo",
.seq_start = memcg_slab_start,
--- a/mm/slab_common.c~mm-memcg-fix-build-error-around-the-usage-of-kmem_caches
+++ a/mm/slab_common.c
@@ -1521,7 +1521,7 @@ void dump_unreclaimable_slab(void)
mutex_unlock(&slab_mutex);
}
-#if defined(CONFIG_MEMCG)
+#if defined(CONFIG_MEMCG_KMEM)
void *memcg_slab_start(struct seq_file *m, loff_t *pos)
{
struct mem_cgroup *memcg = mem_cgroup_from_seq(m);
_
