Re: [akpm-mm:mm-unstable 179/192] mm/zswap.c:825:17: error: dereferencing pointer to incomplete type 'struct mem_cgroup'

[Andrew Morton <akpm@linux-foundation.org>]

On Wed, 29 Nov 2023 13:43:13 -0800 Andrew Morton <akpm@linux-foundation.org> wrote:

> On Wed, 29 Nov 2023 23:42:11 +0800 kernel test robot <lkp@intel.com> wrote:
> 
> > >> mm/zswap.c:825:17: error: dereferencing pointer to incomplete type 'struct mem_cgroup'
> >       css_get(&memcg->css);
> >                     ^~
> 
> OK, thanks, patchset needs work for CONFIG_MEMCG=n.  I'll drop this version.

Well that's annoying - the "mm: memcg: subtree stats flushing and
thresholds" series had lots of dependencies on this series.

So I'll restore this series with this hack:


 include/linux/memcontrol.h |    5 +++++
 mm/zswap.c                 |    3 +++
 2 files changed, 8 insertions(+)

--- a/include/linux/memcontrol.h~zswap-make-shrinking-memcg-aware-fix
+++ a/include/linux/memcontrol.h
@@ -1165,6 +1165,11 @@ unsigned long mem_cgroup_soft_limit_recl
 
 #define MEM_CGROUP_ID_SHIFT	0
 
+static inline struct mem_cgroup *obj_cgroup_memcg(struct obj_cgroup *objcg)
+{
+	return NULL;
+}
+
 static inline struct mem_cgroup *folio_memcg(struct folio *folio)
 {
 	return NULL;
--- a/mm/zswap.c~zswap-make-shrinking-memcg-aware-fix
+++ a/mm/zswap.c
@@ -32,6 +32,7 @@
 #include <linux/mm_types.h>
 #include <linux/page-flags.h>
 #include <linux/swapops.h>
+#include <linux/memcontrol.h>
 #include <linux/writeback.h>
 #include <linux/pagemap.h>
 #include <linux/workqueue.h>
@@ -822,7 +823,9 @@ static void shrink_worker(struct work_st
 		 * Acquire an extra reference to the iterated memcg in case the
 		 * original reference is dropped by the zswap offlining callback.
 		 */
+#ifdef CONFIG_MEMCG
 		css_get(&memcg->css);
+#endif
 		spin_unlock(&zswap_pools_lock);
 
 		ret = shrink_memcg(memcg);
_