[akpm-mm:mm-unstable 199/420] mm/memcontrol-v1.c:651:24: error: call to undeclared function 'swp_cluster_offset'; ISO C99 and later do not support implicit function declarations

[akpm-mm:mm-unstable 199/420] mm/memcontrol-v1.c:651:24: error: call to undeclared function 'swp_cluster_offset'; ISO C99 and later do not support implicit function declarations

[kernel test robot]

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git mm-unstable
head:   8a74e22643189e0ae339afc91110ddb4cab1941b
commit: 93680c2b51fa1f84fe50800b71140dbd283372b8 [199/420] mm/memcg, swap: store cgroup id in cluster table directly
config: arm-randconfig-004-20260528 (https://download.01.org/0day-ci/archive/20260528/202605281711.bSeZlErK-lkp@intel.com/config)
compiler: clang version 23.0.0git (https://github.com/llvm/llvm-project 9409c07de6378507397ecdb6f05f628f58110112)
rustc: rustc 1.88.0 (6b00bc388 2025-06-23)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260528/202605281711.bSeZlErK-lkp@intel.com/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@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202605281711.bSeZlErK-lkp@intel.com/

All errors (new ones prefixed by >>):

>> mm/memcontrol-v1.c:651:24: error: call to undeclared function 'swp_cluster_offset'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
     651 |         __swap_cgroup_set(ci, swp_cluster_offset(folio->swap), nr_entries,
         |                               ^
   mm/memcontrol-v1.c:721:31: error: call to undeclared function 'swp_cluster_offset'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
     721 |         id = __swap_cgroup_clear(ci, swp_cluster_offset(folio->swap),
         |                                      ^
   2 errors generated.


vim +/swp_cluster_offset +651 mm/memcontrol-v1.c

   606	
   607	/**
   608	 * __memcg1_swapout - transfer a memsw charge to swap
   609	 * @folio: folio whose memsw charge to transfer
   610	 * @ci: the locked swap cluster holding the swap entries
   611	 *
   612	 * Transfer the memsw charge of @folio to the swap entry stored in
   613	 * folio->swap.
   614	 *
   615	 * Context: folio must be isolated, unmapped, locked and is just about to
   616	 * be freed, and caller must disable IRQs and hold the swap cluster lock.
   617	 */
   618	void __memcg1_swapout(struct folio *folio, struct swap_cluster_info *ci)
   619	{
   620		struct mem_cgroup *memcg, *swap_memcg;
   621		struct obj_cgroup *objcg;
   622		unsigned int nr_entries;
   623	
   624		VM_WARN_ON_ONCE_FOLIO(!folio_test_swapcache(folio), folio);
   625		VM_WARN_ON_ONCE_FOLIO(!folio_test_locked(folio), folio);
   626		VM_BUG_ON_FOLIO(folio_test_lru(folio), folio);
   627		VM_BUG_ON_FOLIO(folio_ref_count(folio), folio);
   628	
   629		if (mem_cgroup_disabled())
   630			return;
   631	
   632		if (!do_memsw_account())
   633			return;
   634	
   635		objcg = folio_objcg(folio);
   636		VM_WARN_ON_ONCE_FOLIO(!objcg, folio);
   637		if (!objcg)
   638			return;
   639	
   640		rcu_read_lock();
   641		memcg = obj_cgroup_memcg(objcg);
   642		/*
   643		 * In case the memcg owning these pages has been offlined and doesn't
   644		 * have an ID allocated to it anymore, charge the closest online
   645		 * ancestor for the swap instead and transfer the memory+swap charge.
   646		 */
   647		nr_entries = folio_nr_pages(folio);
   648		swap_memcg = mem_cgroup_private_id_get_online(memcg, nr_entries);
   649		mod_memcg_state(swap_memcg, MEMCG_SWAP, nr_entries);
   650	
 > 651		__swap_cgroup_set(ci, swp_cluster_offset(folio->swap), nr_entries,
   652				  mem_cgroup_private_id(swap_memcg));
   653	
   654		folio_unqueue_deferred_split(folio);
   655		folio->memcg_data = 0;
   656	
   657		if (!obj_cgroup_is_root(objcg))
   658			page_counter_uncharge(&memcg->memory, nr_entries);
   659	
   660		if (memcg != swap_memcg) {
   661			if (!mem_cgroup_is_root(swap_memcg))
   662				page_counter_charge(&swap_memcg->memsw, nr_entries);
   663			page_counter_uncharge(&memcg->memsw, nr_entries);
   664		}
   665	
   666		/*
   667		 * The caller must hold the swap cluster lock with IRQ off. It is
   668		 * important here to have the interrupts disabled because it is the
   669		 * only synchronisation we have for updating the per-CPU variables.
   670		 */
   671		preempt_disable_nested();
   672		VM_WARN_ON_IRQS_ENABLED();
   673		memcg1_charge_statistics(memcg, -folio_nr_pages(folio));
   674		preempt_enable_nested();
   675		memcg1_check_events(memcg, folio_nid(folio));
   676	
   677		rcu_read_unlock();
   678		obj_cgroup_put(objcg);
   679	}
   680	

--
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki

Re: [akpm-mm:mm-unstable 199/420] mm/memcontrol-v1.c:651:24: error: call to undeclared function 'swp_cluster_offset'; ISO C99 and later do not support implicit function declarations

[Andrew Morton]

On Thu, 28 May 2026 17:58:34 +0800 kernel test robot <lkp@intel.com> wrote:

> tree:   https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git mm-unstable
> head:   8a74e22643189e0ae339afc91110ddb4cab1941b
> commit: 93680c2b51fa1f84fe50800b71140dbd283372b8 [199/420] mm/memcg, swap: store cgroup id in cluster table directly
> config: arm-randconfig-004-20260528 (https://download.01.org/0day-ci/archive/20260528/202605281711.bSeZlErK-lkp@intel.com/config)
> compiler: clang version 23.0.0git (https://github.com/llvm/llvm-project 9409c07de6378507397ecdb6f05f628f58110112)
> rustc: rustc 1.88.0 (6b00bc388 2025-06-23)
> reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260528/202605281711.bSeZlErK-lkp@intel.com/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@intel.com>
> | Closes: https://lore.kernel.org/oe-kbuild-all/202605281711.bSeZlErK-lkp@intel.com/
> 
> All errors (new ones prefixed by >>):
> 
> >> mm/memcontrol-v1.c:651:24: error: call to undeclared function 'swp_cluster_offset'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
>      651 |         __swap_cgroup_set(ci, swp_cluster_offset(folio->swap), nr_entries,
>          |                               ^
>    mm/memcontrol-v1.c:721:31: error: call to undeclared function 'swp_cluster_offset'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
>      721 |         id = __swap_cgroup_clear(ci, swp_cluster_offset(folio->swap),
>          |                                      ^
>    2 errors generated.

OK, CONFIG_SWAP=n.

We could hack in a stub for swp_cluster_offset(), but why are we
compiling __memcg1_swapout() at all when CONFIG_SWAP=n?  Ditto
memcg1_swapin().

How does the below look?

Really this should be done as a preparatory thing, but we'll survive.



From: Andrew Morton <akpm@linux-foundation.org>
Subject: memcgv1: don't compile swap functions when CONFIG_SWAP=n
Date: Thu May 28 02:35:22 PM PDT 2026

Stub these out to save some dead code and to fix a build error with the
upcoming "mm/memcg, swap: store cgroup id in cluster table directly".

Link: https://lore.kernel.org/202605281711.bSeZlErK-lkp@intel.com
Cc: David Hildenbrand <david@kernel.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Kairui Song <kasong@tencent.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Shakeel Butt <shakeel.butt@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 include/linux/memcontrol.h |   15 ++++++++++-----
 mm/memcontrol-v1.c         |    2 ++
 2 files changed, 12 insertions(+), 5 deletions(-)

--- a/include/linux/memcontrol.h~mm-memcg-swap-store-cgroup-id-in-cluster-table-directly-fix
+++ a/include/linux/memcontrol.h
@@ -1900,9 +1900,6 @@ static inline void mem_cgroup_exit_user_
 	current->in_user_fault = 0;
 }
 
-void __memcg1_swapout(struct folio *folio, struct swap_cluster_info *ci);
-void memcg1_swapin(struct folio *folio);
-
 #else /* CONFIG_MEMCG_V1 */
 static inline
 unsigned long memcg1_soft_limit_reclaim(pg_data_t *pgdat, int order,
@@ -1930,6 +1927,15 @@ static inline void mem_cgroup_exit_user_
 {
 }
 
+#endif /* CONFIG_MEMCG_V1 */
+
+#if defined(CONFIG_MEMCG_V1) && defined(CONFIG_SWAP)
+
+void __memcg1_swapout(struct folio *folio, struct swap_cluster_info *ci);
+void memcg1_swapin(struct folio *folio);
+
+#else
+
 static inline void __memcg1_swapout(struct folio *folio,
 		struct swap_cluster_info *ci)
 {
@@ -1938,7 +1944,6 @@ static inline void __memcg1_swapout(stru
 static inline void memcg1_swapin(struct folio *folio)
 {
 }
-
-#endif /* CONFIG_MEMCG_V1 */
+#endif
 
 #endif /* _LINUX_MEMCONTROL_H */
--- a/mm/memcontrol-v1.c~mm-memcg-swap-store-cgroup-id-in-cluster-table-directly-fix
+++ a/mm/memcontrol-v1.c
@@ -604,6 +604,7 @@ void memcg1_commit_charge(struct folio *
 	local_irq_restore(flags);
 }
 
+#ifdef CONFIG_SWAP
 /**
  * __memcg1_swapout - transfer a memsw charge to swap
  * @folio: folio whose memsw charge to transfer
@@ -723,6 +724,7 @@ void memcg1_swapin(struct folio *folio)
 	swap_cluster_unlock(ci);
 	mem_cgroup_uncharge_swap(id, nr_pages);
 }
+#endif
 
 void memcg1_uncharge_batch(struct mem_cgroup *memcg, unsigned long pgpgout,
 			   unsigned long nr_memory, int nid)
_

Re: [akpm-mm:mm-unstable 199/420] mm/memcontrol-v1.c:651:24: error: call to undeclared function 'swp_cluster_offset'; ISO C99 and later do not support implicit function declarations

[Kairui Song]

On Thu, May 28, 2026 at 02:45:02PM +0800, Andrew Morton wrote:
> On Thu, 28 May 2026 17:58:34 +0800 kernel test robot <lkp@intel.com> wrote:
> 
> > tree:   https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git mm-unstable
> > head:   8a74e22643189e0ae339afc91110ddb4cab1941b
> > commit: 93680c2b51fa1f84fe50800b71140dbd283372b8 [199/420] mm/memcg, swap: store cgroup id in cluster table directly
> > config: arm-randconfig-004-20260528 (https://download.01.org/0day-ci/archive/20260528/202605281711.bSeZlErK-lkp@intel.com/config)
> > compiler: clang version 23.0.0git (https://github.com/llvm/llvm-project 9409c07de6378507397ecdb6f05f628f58110112)
> > rustc: rustc 1.88.0 (6b00bc388 2025-06-23)
> > reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260528/202605281711.bSeZlErK-lkp@intel.com/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@intel.com>
> > | Closes: https://lore.kernel.org/oe-kbuild-all/202605281711.bSeZlErK-lkp@intel.com/
> > 
> > All errors (new ones prefixed by >>):
> > 
> > >> mm/memcontrol-v1.c:651:24: error: call to undeclared function 'swp_cluster_offset'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
> >      651 |         __swap_cgroup_set(ci, swp_cluster_offset(folio->swap), nr_entries,
> >          |                               ^
> >    mm/memcontrol-v1.c:721:31: error: call to undeclared function 'swp_cluster_offset'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
> >      721 |         id = __swap_cgroup_clear(ci, swp_cluster_offset(folio->swap),
> >          |                                      ^
> >    2 errors generated.
> 
> OK, CONFIG_SWAP=n.

I though we have already fixed this, and this is trigger by the bot
just because its not a squashed commit, so building while iterating
the commit will still fail? Or maybe I have some misunderstanding
here..

https://lore.kernel.org/linux-mm/20260519152620.b7b5fd2d68d635ec8d34ad2c@linux-foundation.org/

> 
> We could hack in a stub for swp_cluster_offset(), but why are we
> compiling __memcg1_swapout() at all when CONFIG_SWAP=n?  Ditto
> memcg1_swapin().
> 
> How does the below look?
> 
> Really this should be done as a preparatory thing, but we'll survive.
> 
> From: Andrew Morton <akpm@linux-foundation.org>
> Subject: memcgv1: don't compile swap functions when CONFIG_SWAP=n
> Date: Thu May 28 02:35:22 PM PDT 2026
> 
> Stub these out to save some dead code and to fix a build error with the
> upcoming "mm/memcg, swap: store cgroup id in cluster table directly".
> 
> Link: https://lore.kernel.org/202605281711.bSeZlErK-lkp@intel.com
> Cc: David Hildenbrand <david@kernel.org>
> Cc: Johannes Weiner <hannes@cmpxchg.org>
> Cc: Kairui Song <kasong@tencent.com>
> Cc: Michal Hocko <mhocko@kernel.org>
> Cc: Muchun Song <muchun.song@linux.dev>
> Cc: Roman Gushchin <roman.gushchin@linux.dev>
> Cc: Shakeel Butt <shakeel.butt@linux.dev>
> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
> ---
> 
>  include/linux/memcontrol.h |   15 ++++++++++-----
>  mm/memcontrol-v1.c         |    2 ++
>  2 files changed, 12 insertions(+), 5 deletions(-)
> 
> --- a/include/linux/memcontrol.h~mm-memcg-swap-store-cgroup-id-in-cluster-table-directly-fix
> +++ a/include/linux/memcontrol.h
> @@ -1900,9 +1900,6 @@ static inline void mem_cgroup_exit_user_
>  	current->in_user_fault = 0;
>  }
>  
> -void __memcg1_swapout(struct folio *folio, struct swap_cluster_info *ci);
> -void memcg1_swapin(struct folio *folio);
> -
>  #else /* CONFIG_MEMCG_V1 */
>  static inline
>  unsigned long memcg1_soft_limit_reclaim(pg_data_t *pgdat, int order,
> @@ -1930,6 +1927,15 @@ static inline void mem_cgroup_exit_user_
>  {
>  }
>  
> +#endif /* CONFIG_MEMCG_V1 */
> +
> +#if defined(CONFIG_MEMCG_V1) && defined(CONFIG_SWAP)
> +
> +void __memcg1_swapout(struct folio *folio, struct swap_cluster_info *ci);
> +void memcg1_swapin(struct folio *folio);
> +
> +#else
> +
>  static inline void __memcg1_swapout(struct folio *folio,
>  		struct swap_cluster_info *ci)
>  {
> @@ -1938,7 +1944,6 @@ static inline void __memcg1_swapout(stru
>  static inline void memcg1_swapin(struct folio *folio)
>  {
>  }
> -
> -#endif /* CONFIG_MEMCG_V1 */
> +#endif
>  
>  #endif /* _LINUX_MEMCONTROL_H */
> --- a/mm/memcontrol-v1.c~mm-memcg-swap-store-cgroup-id-in-cluster-table-directly-fix
> +++ a/mm/memcontrol-v1.c
> @@ -604,6 +604,7 @@ void memcg1_commit_charge(struct folio *
>  	local_irq_restore(flags);
>  }
>  
> +#ifdef CONFIG_SWAP
>  /**
>   * __memcg1_swapout - transfer a memsw charge to swap
>   * @folio: folio whose memsw charge to transfer
> @@ -723,6 +724,7 @@ void memcg1_swapin(struct folio *folio)
>  	swap_cluster_unlock(ci);
>  	mem_cgroup_uncharge_swap(id, nr_pages);
>  }
> +#endif
>  
>  void memcg1_uncharge_batch(struct mem_cgroup *memcg, unsigned long pgpgout,
>  			   unsigned long nr_memory, int nid)
> _
> 

Thanks again, looks good to me, the simple is simple and it looks the
same thing I posted previously:
https://lore.kernel.org/linux-mm/ag0mdxBWcrZ8hxPP@KASONG-MC4/