[PATCH v7 0/3] mm: clean up folio LRU and swap declarations

[PATCH v7 0/3] mm: clean up folio LRU and swap declarations

[Jianyue Wu]

This series splits folio LRU and swap cleanup into three steps:

  - move the page-cluster sysctl next to swap readahead in mm/swap_state.c
  - rename mm/swap.c to mm/folio.c after the swap-specific bits move out
  - move MM-internal reclaim declarations out of include/linux/swap.h

After this series, swap cache and swap-in readahead stay in mm/swap_state.c,
folio LRU helpers live in mm/folio.c, and MM-internal reclaim/workingset
declarations move from include/linux/swap.h to mm/internal.h (public LRU
helpers used outside mm/ remain in swap.h).

The first patch handles the swap-specific page-cluster state before the
file rename, so the rename commit only carries folio LRU code. The last
patch keeps the LRU helpers used outside mm/ in include/linux/swap.h and
moves the internal reclaim/workingset declarations to mm/internal.h.

Signed-off-by: Jianyue Wu <wujianyue000@gmail.com>
---
Changes in v7:
- Rebased onto akpm/mm-unstable (cfb8731f5396).
- Re-tested full build, swap-in readahead smoke test, and run_vmtests.sh on x86.
- Move version-history text below the "---" separator in the cover letter.
- Add Suggested-by and Acked-by Johannes Weiner on patch 1/3.
- Add Suggested-by Matthew Wilcox on patch 2/3.
- Link to v6: https://lore.kernel.org/r/20260701-ch-swap-series-plus-folio-lru-cleanup-v6-0-d4f648963382@gmail.com

Changes in v6:
- Rename mm/swap.c to mm/folio.c instead of folio_lru.c.
- Link to v5: https://lore.kernel.org/r/20260630-ch-swap-series-plus-folio-lru-cleanup-v5-0-4627aba8ed1e@gmail.com

Changes in v5:
- Rebased onto akpm/mm-unstable (81652c5a65d4).
- Fix mm/swap.h for CONFIG_SWAP=n after rebase.
- Tested swap-in readahead on x86 with swap: vm.page-cluster present
  and writable, swap in/out under anon memory pressure, page-cluster 0
  and 3 paths, no oops in dmesg; run_vmtests.sh passed.
- Link to v4: https://lore.kernel.org/r/20260603-ch-swap-series-plus-folio-lru-cleanup-v4-0-ce0219e100d9@gmail.com

Changes in v4:
- Address Baoquan He's review on v3: align patch 2 subject with
  rename-only scope; fix vm.rst sysctl documentation; refresh file
  header comments in mm/folio_lru.c and swap.h declaration comments.
- Expand patch 1 commit message on CONFIG_SWAP=n vm.page-cluster
  registration (also on CONFIG_SWAP=n kernels).
- Link to v3: https://lore.kernel.org/all/20260602-ch-swap-series-plus-folio-lru-cleanup-v3-0-5bbb567f8c99@gmail.com

---
Jianyue Wu (3):
      mm/swap: colocate page-cluster sysctl with swap readahead
      mm: rename swap.c to folio.c
      mm: move reclaim-internal declarations out of swap.h

 Documentation/admin-guide/sysctl/vm.rst |  3 --
 Documentation/core-api/mm-api.rst       |  2 +-
 MAINTAINERS                             |  3 +-
 include/linux/swap.h                    | 76 +++------------------------------
 mm/Makefile                             |  2 +-
 mm/{swap.c => folio.c}                  | 46 ++------------------
 mm/internal.h                           | 67 +++++++++++++++++++++++++++++
 mm/memfd.c                              |  1 +
 mm/swap.h                               |  9 +++-
 mm/swap_state.c                         | 37 ++++++++++++++++
 mm/vmscan.c                             |  2 +-
 11 files changed, 126 insertions(+), 122 deletions(-)
---
base-commit: cfb8731f5396cafde2d60a2e7d9d27cdb4505f45
change-id: 20260531-ch-swap-series-plus-folio-lru-cleanup-d9781c8332dc

Best regards,
-- 
Jianyue Wu <wujianyue000@gmail.com>

[PATCH v7 1/3] mm/swap: colocate page-cluster sysctl with swap readahead

[Jianyue Wu]

page_cluster and the vm.page-cluster sysctl are only used by swap-in
readahead in swap_state.c. Move them out of swap.c together with
swap_readahead_setup(), and make page_cluster static to that file.

Rename swap_setup() while moving it as well. The helper is internal to
MM and now only sets up swap readahead defaults and its sysctl hook, so
the more specific name matches its reduced scope.

swap_setup() previously lived in mm/swap.c, which is built
unconditionally, so the vm.page-cluster sysctl was registered also on
CONFIG_SWAP=n kernels. swap_readahead_setup() is now a no-op stub when
CONFIG_SWAP is disabled, so vm.page-cluster is no longer registered
there. The knob only tunes swap-in readahead and had no effect without
swap.

Suggested-by: Baoquan He <bhe@redhat.com>
Suggested-by: Barry Song <baohua@kernel.org>
Suggested-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: David Hildenbrand (Arm) <david@kernel.org>
Signed-off-by: Jianyue Wu <wujianyue000@gmail.com>
---
 include/linux/swap.h |  1 -
 mm/swap.c            | 36 ------------------------------------
 mm/swap.h            |  9 +++++++--
 mm/swap_state.c      | 37 +++++++++++++++++++++++++++++++++++++
 mm/vmscan.c          |  2 +-
 5 files changed, 45 insertions(+), 40 deletions(-)

diff --git a/include/linux/swap.h b/include/linux/swap.h
index 3f31b6a56788..45656ca9792d 100644
--- a/include/linux/swap.h
+++ b/include/linux/swap.h
@@ -340,7 +340,6 @@ extern void lru_add_drain_cpu_zone(struct zone *zone);
 extern void lru_add_drain_all(void);
 void folio_deactivate(struct folio *folio);
 void folio_mark_lazyfree(struct folio *folio);
-extern void swap_setup(void);
 
 /* linux/mm/vmscan.c */
 extern unsigned long zone_reclaimable_pages(struct zone *zone);
diff --git a/mm/swap.c b/mm/swap.c
index 58e4eff698cc..b3ea30edbaad 100644
--- a/mm/swap.c
+++ b/mm/swap.c
@@ -43,10 +43,6 @@
 #define CREATE_TRACE_POINTS
 #include <trace/events/pagemap.h>
 
-/* How many pages do we try to swap or page in/out together? As a power of 2 */
-int page_cluster;
-static const int page_cluster_max = 31;
-
 struct cpu_fbatches {
 	/*
 	 * The following folio batches are grouped together because they are protected
@@ -1176,35 +1172,3 @@ void lru_reparent_memcg(struct mem_cgroup *memcg, struct mem_cgroup *parent, int
 		lruvec_reparent_lru(child_lruvec, parent_lruvec, lru, nid);
 }
 #endif
-
-static const struct ctl_table swap_sysctl_table[] = {
-	{
-		.procname	= "page-cluster",
-		.data		= &page_cluster,
-		.maxlen		= sizeof(int),
-		.mode		= 0644,
-		.proc_handler	= proc_dointvec_minmax,
-		.extra1		= SYSCTL_ZERO,
-		.extra2		= (void *)&page_cluster_max,
-	}
-};
-
-/*
- * Perform any setup for the swap system
- */
-void __init swap_setup(void)
-{
-	unsigned long megs = PAGES_TO_MB(totalram_pages());
-
-	/* Use a smaller cluster for small-memory machines */
-	if (megs < 16)
-		page_cluster = 2;
-	else
-		page_cluster = 3;
-	/*
-	 * Right now other parts of the system means that we
-	 * _really_ don't want to cluster much more
-	 */
-
-	register_sysctl_init("vm", swap_sysctl_table);
-}
diff --git a/mm/swap.h b/mm/swap.h
index 44ab8e1e595b..624ea8ff3d0d 100644
--- a/mm/swap.h
+++ b/mm/swap.h
@@ -8,8 +8,6 @@ struct mempolicy;
 struct swap_iocb;
 struct swap_memcg_table;
 
-extern int page_cluster;
-
 #if defined(MAX_POSSIBLE_PHYSMEM_BITS)
 #define SWAP_CACHE_PFN_BITS (MAX_POSSIBLE_PHYSMEM_BITS - PAGE_SHIFT)
 #elif defined(MAX_PHYSMEM_BITS)
@@ -79,6 +77,8 @@ enum swap_cluster_flags {
 };
 
 #ifdef CONFIG_SWAP
+void swap_readahead_setup(void);
+
 #include <linux/swapops.h> /* for swp_offset */
 #include <linux/blk_types.h> /* for bio_end_io_t */
 
@@ -336,6 +336,11 @@ static inline unsigned int folio_swap_flags(struct folio *folio)
 
 #else /* CONFIG_SWAP */
 struct swap_iocb;
+
+static inline void swap_readahead_setup(void)
+{
+}
+
 static inline struct swap_cluster_info *swap_cluster_lock(
 	struct swap_info_struct *si, pgoff_t offset, bool irq)
 {
diff --git a/mm/swap_state.c b/mm/swap_state.c
index 6fd6e3415b71..a9f5b944172b 100644
--- a/mm/swap_state.c
+++ b/mm/swap_state.c
@@ -22,10 +22,15 @@
 #include <linux/vmalloc.h>
 #include <linux/huge_mm.h>
 #include <linux/shmem_fs.h>
+#include <linux/sysctl.h>
 #include "internal.h"
 #include "swap_table.h"
 #include "swap.h"
 
+/* Swap readahead cluster size, as a power of 2 pages. */
+static int page_cluster;
+static const int page_cluster_max = 31;
+
 /*
  * swapper_space is a fiction, retained to simplify the path through
  * vmscan's shrink_folio_list.
@@ -985,6 +990,38 @@ struct folio *swapin_readahead(swp_entry_t entry, gfp_t gfp_mask,
 	return folio;
 }
 
+static const struct ctl_table swap_readahead_sysctl_table[] = {
+	{
+		.procname	= "page-cluster",
+		.data		= &page_cluster,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec_minmax,
+		.extra1		= SYSCTL_ZERO,
+		.extra2		= (void *)&page_cluster_max,
+	}
+};
+
+/**
+ * swap_readahead_setup - defaults and sysctl for swap cache readahead clustering
+ */
+void __init swap_readahead_setup(void)
+{
+	unsigned long megs = PAGES_TO_MB(totalram_pages());
+
+	/* Use a smaller cluster for small-memory machines */
+	if (megs < 16)
+		page_cluster = 2;
+	else
+		page_cluster = 3;
+	/*
+	 * Right now other parts of the system means that we
+	 * _really_ don't want to cluster much more
+	 */
+
+	register_sysctl_init("vm", swap_readahead_sysctl_table);
+}
+
 #ifdef CONFIG_SYSFS
 static ssize_t vma_ra_enabled_show(struct kobject *kobj,
 				     struct kobj_attribute *attr, char *buf)
diff --git a/mm/vmscan.c b/mm/vmscan.c
index f40cfe9d703b..ae710027d546 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -7646,7 +7646,7 @@ static int __init kswapd_init(void)
 {
 	int nid;
 
-	swap_setup();
+	swap_readahead_setup();
 	for_each_node_state(nid, N_MEMORY)
  		kswapd_run(nid);
 	register_sysctl_init("vm", vmscan_sysctl_table);

-- 
2.43.0

Re: [PATCH v7 1/3] mm/swap: colocate page-cluster sysctl with swap readahead

[Kairui Song]

On Sun, Jul 5, 2026 at 10:14 PM Jianyue Wu <wujianyue000@gmail.com> wrote:
>
> page_cluster and the vm.page-cluster sysctl are only used by swap-in
> readahead in swap_state.c. Move them out of swap.c together with
> swap_readahead_setup(), and make page_cluster static to that file.
>
> Rename swap_setup() while moving it as well. The helper is internal to
> MM and now only sets up swap readahead defaults and its sysctl hook, so
> the more specific name matches its reduced scope.
>
> swap_setup() previously lived in mm/swap.c, which is built
> unconditionally, so the vm.page-cluster sysctl was registered also on
> CONFIG_SWAP=n kernels. swap_readahead_setup() is now a no-op stub when
> CONFIG_SWAP is disabled, so vm.page-cluster is no longer registered
> there. The knob only tunes swap-in readahead and had no effect without
> swap.
>
> Suggested-by: Baoquan He <bhe@redhat.com>
> Suggested-by: Barry Song <baohua@kernel.org>
> Suggested-by: Johannes Weiner <hannes@cmpxchg.org>
> Acked-by: Johannes Weiner <hannes@cmpxchg.org>
> Acked-by: David Hildenbrand (Arm) <david@kernel.org>
> Signed-off-by: Jianyue Wu <wujianyue000@gmail.com>
> ---
>  include/linux/swap.h |  1 -
>  mm/swap.c            | 36 ------------------------------------
>  mm/swap.h            |  9 +++++++--
>  mm/swap_state.c      | 37 +++++++++++++++++++++++++++++++++++++
>  mm/vmscan.c          |  2 +-
>  5 files changed, 45 insertions(+), 40 deletions(-)
>
> diff --git a/include/linux/swap.h b/include/linux/swap.h
> index 3f31b6a56788..45656ca9792d 100644
> --- a/include/linux/swap.h
> +++ b/include/linux/swap.h
> @@ -340,7 +340,6 @@ extern void lru_add_drain_cpu_zone(struct zone *zone);
>  extern void lru_add_drain_all(void);
>  void folio_deactivate(struct folio *folio);
>  void folio_mark_lazyfree(struct folio *folio);
> -extern void swap_setup(void);
>
>  /* linux/mm/vmscan.c */
>  extern unsigned long zone_reclaimable_pages(struct zone *zone);
> diff --git a/mm/swap.c b/mm/swap.c
> index 58e4eff698cc..b3ea30edbaad 100644
> --- a/mm/swap.c
> +++ b/mm/swap.c
> @@ -43,10 +43,6 @@
>  #define CREATE_TRACE_POINTS
>  #include <trace/events/pagemap.h>
>
> -/* How many pages do we try to swap or page in/out together? As a power of 2 */
> -int page_cluster;
> -static const int page_cluster_max = 31;
> -
>  struct cpu_fbatches {
>         /*
>          * The following folio batches are grouped together because they are protected
> @@ -1176,35 +1172,3 @@ void lru_reparent_memcg(struct mem_cgroup *memcg, struct mem_cgroup *parent, int
>                 lruvec_reparent_lru(child_lruvec, parent_lruvec, lru, nid);
>  }
>  #endif
> -
> -static const struct ctl_table swap_sysctl_table[] = {
> -       {
> -               .procname       = "page-cluster",
> -               .data           = &page_cluster,
> -               .maxlen         = sizeof(int),
> -               .mode           = 0644,
> -               .proc_handler   = proc_dointvec_minmax,
> -               .extra1         = SYSCTL_ZERO,
> -               .extra2         = (void *)&page_cluster_max,
> -       }
> -};
> -
> -/*
> - * Perform any setup for the swap system
> - */
> -void __init swap_setup(void)
> -{
> -       unsigned long megs = PAGES_TO_MB(totalram_pages());
> -
> -       /* Use a smaller cluster for small-memory machines */
> -       if (megs < 16)
> -               page_cluster = 2;
> -       else
> -               page_cluster = 3;
> -       /*
> -        * Right now other parts of the system means that we
> -        * _really_ don't want to cluster much more
> -        */
> -
> -       register_sysctl_init("vm", swap_sysctl_table);
> -}
> diff --git a/mm/swap.h b/mm/swap.h
> index 44ab8e1e595b..624ea8ff3d0d 100644
> --- a/mm/swap.h
> +++ b/mm/swap.h
> @@ -8,8 +8,6 @@ struct mempolicy;
>  struct swap_iocb;
>  struct swap_memcg_table;
>
> -extern int page_cluster;
> -
>  #if defined(MAX_POSSIBLE_PHYSMEM_BITS)
>  #define SWAP_CACHE_PFN_BITS (MAX_POSSIBLE_PHYSMEM_BITS - PAGE_SHIFT)
>  #elif defined(MAX_PHYSMEM_BITS)
> @@ -79,6 +77,8 @@ enum swap_cluster_flags {
>  };
>
>  #ifdef CONFIG_SWAP
> +void swap_readahead_setup(void);
> +
>  #include <linux/swapops.h> /* for swp_offset */
>  #include <linux/blk_types.h> /* for bio_end_io_t */
>
> @@ -336,6 +336,11 @@ static inline unsigned int folio_swap_flags(struct folio *folio)
>
>  #else /* CONFIG_SWAP */
>  struct swap_iocb;
> +
> +static inline void swap_readahead_setup(void)
> +{
> +}
> +
>  static inline struct swap_cluster_info *swap_cluster_lock(
>         struct swap_info_struct *si, pgoff_t offset, bool irq)
>  {
> diff --git a/mm/swap_state.c b/mm/swap_state.c
> index 6fd6e3415b71..a9f5b944172b 100644
> --- a/mm/swap_state.c
> +++ b/mm/swap_state.c
> @@ -22,10 +22,15 @@
>  #include <linux/vmalloc.h>
>  #include <linux/huge_mm.h>
>  #include <linux/shmem_fs.h>
> +#include <linux/sysctl.h>
>  #include "internal.h"
>  #include "swap_table.h"
>  #include "swap.h"
>
> +/* Swap readahead cluster size, as a power of 2 pages. */
> +static int page_cluster;
> +static const int page_cluster_max = 31;
> +
>  /*
>   * swapper_space is a fiction, retained to simplify the path through
>   * vmscan's shrink_folio_list.
> @@ -985,6 +990,38 @@ struct folio *swapin_readahead(swp_entry_t entry, gfp_t gfp_mask,
>         return folio;
>  }
>
> +static const struct ctl_table swap_readahead_sysctl_table[] = {
> +       {
> +               .procname       = "page-cluster",
> +               .data           = &page_cluster,
> +               .maxlen         = sizeof(int),
> +               .mode           = 0644,
> +               .proc_handler   = proc_dointvec_minmax,
> +               .extra1         = SYSCTL_ZERO,
> +               .extra2         = (void *)&page_cluster_max,
> +       }
> +};
> +
> +/**
> + * swap_readahead_setup - defaults and sysctl for swap cache readahead clustering
> + */
> +void __init swap_readahead_setup(void)
> +{
> +       unsigned long megs = PAGES_TO_MB(totalram_pages());
> +
> +       /* Use a smaller cluster for small-memory machines */
> +       if (megs < 16)
> +               page_cluster = 2;
> +       else
> +               page_cluster = 3;
> +       /*
> +        * Right now other parts of the system means that we
> +        * _really_ don't want to cluster much more
> +        */
> +
> +       register_sysctl_init("vm", swap_readahead_sysctl_table);
> +}
> +

Thanks, I also think they belong here.

>  #ifdef CONFIG_SYSFS
>  static ssize_t vma_ra_enabled_show(struct kobject *kobj,
>                                      struct kobj_attribute *attr, char *buf)
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index f40cfe9d703b..ae710027d546 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -7646,7 +7646,7 @@ static int __init kswapd_init(void)
>  {
>         int nid;
>
> -       swap_setup();
> +       swap_readahead_setup();

There is already a subsys_initcall(swap_init); in swap_state.c so
perhaps calling this in that init function is even cleaner. And that
init hook runs earlier than kswapd init so totally fine I think.

Reviewed-by: Kairui Song <kasong@tencent.com>

Re: [PATCH v7 1/3] mm/swap: colocate page-cluster sysctl with swap readahead

[Jianyue Wu]

On Tue, Jul 7, 2026 at 1:24 AM Kairui Song <ryncsn@gmail.com> wrote:
>
> On Sun, Jul 5, 2026 at 10:14 PM Jianyue Wu <wujianyue000@gmail.com> wrote:
> >
> > page_cluster and the vm.page-cluster sysctl are only used by swap-in
> > readahead in swap_state.c. Move them out of swap.c together with
> > swap_readahead_setup(), and make page_cluster static to that file.
> >
> > Rename swap_setup() while moving it as well. The helper is internal to
> > MM and now only sets up swap readahead defaults and its sysctl hook, so
> > the more specific name matches its reduced scope.
> >
> > swap_setup() previously lived in mm/swap.c, which is built
> > unconditionally, so the vm.page-cluster sysctl was registered also on
> > CONFIG_SWAP=n kernels. swap_readahead_setup() is now a no-op stub when
> > CONFIG_SWAP is disabled, so vm.page-cluster is no longer registered
> > there. The knob only tunes swap-in readahead and had no effect without
> > swap.
> >
> > Suggested-by: Baoquan He <bhe@redhat.com>
> > Suggested-by: Barry Song <baohua@kernel.org>
> > Suggested-by: Johannes Weiner <hannes@cmpxchg.org>
> > Acked-by: Johannes Weiner <hannes@cmpxchg.org>
> > Acked-by: David Hildenbrand (Arm) <david@kernel.org>
> > Signed-off-by: Jianyue Wu <wujianyue000@gmail.com>
> > ---
> >  include/linux/swap.h |  1 -
> >  mm/swap.c            | 36 ------------------------------------
> >  mm/swap.h            |  9 +++++++--
> >  mm/swap_state.c      | 37 +++++++++++++++++++++++++++++++++++++
> >  mm/vmscan.c          |  2 +-
> >  5 files changed, 45 insertions(+), 40 deletions(-)
> >
> > diff --git a/include/linux/swap.h b/include/linux/swap.h
> > index 3f31b6a56788..45656ca9792d 100644
> > --- a/include/linux/swap.h
> > +++ b/include/linux/swap.h
> > @@ -340,7 +340,6 @@ extern void lru_add_drain_cpu_zone(struct zone *zone);
> >  extern void lru_add_drain_all(void);
> >  void folio_deactivate(struct folio *folio);
> >  void folio_mark_lazyfree(struct folio *folio);
> > -extern void swap_setup(void);
> >
> >  /* linux/mm/vmscan.c */
> >  extern unsigned long zone_reclaimable_pages(struct zone *zone);
> > diff --git a/mm/swap.c b/mm/swap.c
> > index 58e4eff698cc..b3ea30edbaad 100644
> > --- a/mm/swap.c
> > +++ b/mm/swap.c
> > @@ -43,10 +43,6 @@
> >  #define CREATE_TRACE_POINTS
> >  #include <trace/events/pagemap.h>
> >
> > -/* How many pages do we try to swap or page in/out together? As a power of 2 */
> > -int page_cluster;
> > -static const int page_cluster_max = 31;
> > -
> >  struct cpu_fbatches {
> >         /*
> >          * The following folio batches are grouped together because they are protected
> > @@ -1176,35 +1172,3 @@ void lru_reparent_memcg(struct mem_cgroup *memcg, struct mem_cgroup *parent, int
> >                 lruvec_reparent_lru(child_lruvec, parent_lruvec, lru, nid);
> >  }
> >  #endif
> > -
> > -static const struct ctl_table swap_sysctl_table[] = {
> > -       {
> > -               .procname       = "page-cluster",
> > -               .data           = &page_cluster,
> > -               .maxlen         = sizeof(int),
> > -               .mode           = 0644,
> > -               .proc_handler   = proc_dointvec_minmax,
> > -               .extra1         = SYSCTL_ZERO,
> > -               .extra2         = (void *)&page_cluster_max,
> > -       }
> > -};
> > -
> > -/*
> > - * Perform any setup for the swap system
> > - */
> > -void __init swap_setup(void)
> > -{
> > -       unsigned long megs = PAGES_TO_MB(totalram_pages());
> > -
> > -       /* Use a smaller cluster for small-memory machines */
> > -       if (megs < 16)
> > -               page_cluster = 2;
> > -       else
> > -               page_cluster = 3;
> > -       /*
> > -        * Right now other parts of the system means that we
> > -        * _really_ don't want to cluster much more
> > -        */
> > -
> > -       register_sysctl_init("vm", swap_sysctl_table);
> > -}
> > diff --git a/mm/swap.h b/mm/swap.h
> > index 44ab8e1e595b..624ea8ff3d0d 100644
> > --- a/mm/swap.h
> > +++ b/mm/swap.h
> > @@ -8,8 +8,6 @@ struct mempolicy;
> >  struct swap_iocb;
> >  struct swap_memcg_table;
> >
> > -extern int page_cluster;
> > -
> >  #if defined(MAX_POSSIBLE_PHYSMEM_BITS)
> >  #define SWAP_CACHE_PFN_BITS (MAX_POSSIBLE_PHYSMEM_BITS - PAGE_SHIFT)
> >  #elif defined(MAX_PHYSMEM_BITS)
> > @@ -79,6 +77,8 @@ enum swap_cluster_flags {
> >  };
> >
> >  #ifdef CONFIG_SWAP
> > +void swap_readahead_setup(void);
> > +
> >  #include <linux/swapops.h> /* for swp_offset */
> >  #include <linux/blk_types.h> /* for bio_end_io_t */
> >
> > @@ -336,6 +336,11 @@ static inline unsigned int folio_swap_flags(struct folio *folio)
> >
> >  #else /* CONFIG_SWAP */
> >  struct swap_iocb;
> > +
> > +static inline void swap_readahead_setup(void)
> > +{
> > +}
> > +
> >  static inline struct swap_cluster_info *swap_cluster_lock(
> >         struct swap_info_struct *si, pgoff_t offset, bool irq)
> >  {
> > diff --git a/mm/swap_state.c b/mm/swap_state.c
> > index 6fd6e3415b71..a9f5b944172b 100644
> > --- a/mm/swap_state.c
> > +++ b/mm/swap_state.c
> > @@ -22,10 +22,15 @@
> >  #include <linux/vmalloc.h>
> >  #include <linux/huge_mm.h>
> >  #include <linux/shmem_fs.h>
> > +#include <linux/sysctl.h>
> >  #include "internal.h"
> >  #include "swap_table.h"
> >  #include "swap.h"
> >
> > +/* Swap readahead cluster size, as a power of 2 pages. */
> > +static int page_cluster;
> > +static const int page_cluster_max = 31;
> > +
> >  /*
> >   * swapper_space is a fiction, retained to simplify the path through
> >   * vmscan's shrink_folio_list.
> > @@ -985,6 +990,38 @@ struct folio *swapin_readahead(swp_entry_t entry, gfp_t gfp_mask,
> >         return folio;
> >  }
> >
> > +static const struct ctl_table swap_readahead_sysctl_table[] = {
> > +       {
> > +               .procname       = "page-cluster",
> > +               .data           = &page_cluster,
> > +               .maxlen         = sizeof(int),
> > +               .mode           = 0644,
> > +               .proc_handler   = proc_dointvec_minmax,
> > +               .extra1         = SYSCTL_ZERO,
> > +               .extra2         = (void *)&page_cluster_max,
> > +       }
> > +};
> > +
> > +/**
> > + * swap_readahead_setup - defaults and sysctl for swap cache readahead clustering
> > + */
> > +void __init swap_readahead_setup(void)
> > +{
> > +       unsigned long megs = PAGES_TO_MB(totalram_pages());
> > +
> > +       /* Use a smaller cluster for small-memory machines */
> > +       if (megs < 16)
> > +               page_cluster = 2;
> > +       else
> > +               page_cluster = 3;
> > +       /*
> > +        * Right now other parts of the system means that we
> > +        * _really_ don't want to cluster much more
> > +        */
> > +
> > +       register_sysctl_init("vm", swap_readahead_sysctl_table);
> > +}
> > +
>
> Thanks, I also think they belong here.
>
> >  #ifdef CONFIG_SYSFS
> >  static ssize_t vma_ra_enabled_show(struct kobject *kobj,
> >                                      struct kobj_attribute *attr, char *buf)
> > diff --git a/mm/vmscan.c b/mm/vmscan.c
> > index f40cfe9d703b..ae710027d546 100644
> > --- a/mm/vmscan.c
> > +++ b/mm/vmscan.c
> > @@ -7646,7 +7646,7 @@ static int __init kswapd_init(void)
> >  {
> >         int nid;
> >
> > -       swap_setup();
> > +       swap_readahead_setup();
>
> There is already a subsys_initcall(swap_init); in swap_state.c so
> perhaps calling this in that init function is even cleaner. And that
> init hook runs earlier than kswapd init so totally fine I think.
>
> Reviewed-by: Kairui Song <kasong@tencent.com>

Hi Kairui,

Thanks for the review. That sounds cleaner to me as well: the readahead
default and sysctl setup should stay with swap_state.c initialization.

I'll move swap_readahead_setup() into swap_init() and send an updated
version after testing.

Best regards,
Jianyue

[PATCH v7 2/3] mm: rename swap.c to folio.c

[Jianyue Wu]

Rename mm/swap.c to mm/folio.c so the filename better matches
the code's main responsibility.

This keeps the implementation split from swap-specific code without
changing the published LRU helper interfaces.

Update MAINTAINERS and the remaining mm/swap.c documentation references
after the rename.

Suggested-by: Baoquan He <bhe@redhat.com>
Suggested-by: David Hildenbrand <david@kernel.org>
Suggested-by: Matthew Wilcox <willy@infradead.org>
Reviewed-by: Lorenzo Stoakes <ljs@kernel.org>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: David Hildenbrand (Arm) <david@kernel.org>
Signed-off-by: Jianyue Wu <wujianyue000@gmail.com>
---
 Documentation/admin-guide/sysctl/vm.rst |  3 ---
 Documentation/core-api/mm-api.rst       |  2 +-
 MAINTAINERS                             |  3 +--
 mm/Makefile                             |  2 +-
 mm/{swap.c => folio.c}                  | 10 +++-------
 5 files changed, 6 insertions(+), 14 deletions(-)

diff --git a/Documentation/admin-guide/sysctl/vm.rst b/Documentation/admin-guide/sysctl/vm.rst
index 22cc54cac3b2..5b318d17aa4b 100644
--- a/Documentation/admin-guide/sysctl/vm.rst
+++ b/Documentation/admin-guide/sysctl/vm.rst
@@ -19,9 +19,6 @@ The files in this directory can be used to tune the operation
 of the virtual memory (VM) subsystem of the Linux kernel and
 the writeout of dirty data to disk.
 
-Default values and initialization routines for most of these
-files can be found in mm/swap.c.
-
 Currently, these files are in /proc/sys/vm:
 
 - admin_reserve_kbytes
diff --git a/Documentation/core-api/mm-api.rst b/Documentation/core-api/mm-api.rst
index 4df7d5edbee5..c1d03a5a2a19 100644
--- a/Documentation/core-api/mm-api.rst
+++ b/Documentation/core-api/mm-api.rst
@@ -118,7 +118,7 @@ More Memory Management Functions
 .. #kernel-doc:: mm/hmm.c (build warnings)
 .. kernel-doc:: mm/memremap.c
 .. kernel-doc:: mm/hugetlb.c
-.. kernel-doc:: mm/swap.c
+.. kernel-doc:: mm/folio.c
 .. kernel-doc:: mm/memcontrol.c
 .. #kernel-doc:: mm/memory-tiers.c (build warnings)
 .. kernel-doc:: mm/shmem.c
diff --git a/MAINTAINERS b/MAINTAINERS
index 29c302e9c17b..e853622a9b96 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -17086,7 +17086,7 @@ F:	Documentation/admin-guide/mm/multigen_lru.rst
 F:	Documentation/mm/multigen_lru.rst
 F:	include/linux/mm_inline.h
 F:	include/linux/mmzone.h
-F:	mm/swap.c
+F:	mm/folio.c
 F:	mm/vmscan.c
 F:	mm/workingset.c
 
@@ -17237,7 +17237,6 @@ F:	include/linux/swap.h
 F:	include/linux/swapfile.h
 F:	include/linux/swapops.h
 F:	mm/page_io.c
-F:	mm/swap.c
 F:	mm/swap.h
 F:	mm/swap_table.h
 F:	mm/swap_state.c
diff --git a/mm/Makefile b/mm/Makefile
index 4fc713867b9b..8e7e964b99a4 100644
--- a/mm/Makefile
+++ b/mm/Makefile
@@ -50,7 +50,7 @@ endif
 
 obj-y			:= filemap.o mempool.o oom_kill.o fadvise.o \
 			   maccess.o page-writeback.o folio-compat.o \
-			   readahead.o swap.o truncate.o vmscan.o shrinker.o \
+			   readahead.o folio.o truncate.o vmscan.o shrinker.o \
 			   shmem.o util.o mmzone.o vmstat.o backing-dev.o \
 			   mm_init.o percpu.o slab_common.o \
 			   compaction.o show_mem.o \
diff --git a/mm/swap.c b/mm/folio.c
similarity index 99%
rename from mm/swap.c
rename to mm/folio.c
index b3ea30edbaad..4acad3e94cbd 100644
--- a/mm/swap.c
+++ b/mm/folio.c
@@ -1,17 +1,13 @@
 // SPDX-License-Identifier: GPL-2.0-only
 /*
- *  linux/mm/swap.c
+ *  linux/mm/folio.c
  *
  *  Copyright (C) 1991, 1992, 1993, 1994  Linus Torvalds
  */
 
 /*
- * This file contains the default values for the operation of the
- * Linux VM subsystem. Fine-tuning documentation can be found in
- * Documentation/admin-guide/sysctl/vm.rst.
- * Started 18.12.91
- * Swap aging added 23.2.95, Stephen Tweedie.
- * Buffermem limits added 12.3.98, Rik van Riel.
+ * Folio LRU helpers: add/remove folios from LRU lists, batching,
+ * activation/deactivation, and page cache release paths.
  */
 
 #include <linux/mm.h>

-- 
2.43.0

Re: [PATCH v7 2/3] mm: rename swap.c to folio.c

[David Hildenbrand (Arm)]

On 7/5/26 16:12, Jianyue Wu wrote:
> Rename mm/swap.c to mm/folio.c so the filename better matches
> the code's main responsibility.
> 
> This keeps the implementation split from swap-specific code without
> changing the published LRU helper interfaces.
> 
> Update MAINTAINERS and the remaining mm/swap.c documentation references
> after the rename.
> 
> Suggested-by: Baoquan He <bhe@redhat.com>
> Suggested-by: David Hildenbrand <david@kernel.org>
> Suggested-by: Matthew Wilcox <willy@infradead.org>
> Reviewed-by: Lorenzo Stoakes <ljs@kernel.org>
> Acked-by: Johannes Weiner <hannes@cmpxchg.org>
> Acked-by: David Hildenbrand (Arm) <david@kernel.org>
> Signed-off-by: Jianyue Wu <wujianyue000@gmail.com>
> ---

Acked-by: David Hildenbrand (Arm) <david@kernel.org>

-- 
Cheers,

David

[PATCH v7 3/3] mm: move reclaim-internal declarations out of swap.h

[Jianyue Wu]

Keep include/linux/swap.h focused on swap-facing interfaces by moving
MM-internal reclaim and workingset declarations into mm/internal.h.

Leave the small set of LRU helper declarations that are used outside mm/
in swap.h so this cleanup does not need a new public header under
include/linux/.

Suggested-by: Barry Song <baohua@kernel.org>
Suggested-by: Baoquan He <bhe@redhat.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Jianyue Wu <wujianyue000@gmail.com>
---
 include/linux/swap.h | 75 +++++-----------------------------------------------
 mm/internal.h        | 67 ++++++++++++++++++++++++++++++++++++++++++++++
 mm/memfd.c           |  1 +
 3 files changed, 75 insertions(+), 68 deletions(-)

diff --git a/include/linux/swap.h b/include/linux/swap.h
index 45656ca9792d..696ed01709c2 100644
--- a/include/linux/swap.h
+++ b/include/linux/swap.h
@@ -287,39 +287,19 @@ static inline swp_entry_t page_swap_entry(struct page *page)
 	return entry;
 }
 
-/* linux/mm/workingset.c */
-bool workingset_test_recent(void *shadow, bool file, bool *workingset,
-				bool flush);
-void workingset_age_nonresident(struct lruvec *lruvec, unsigned long nr_pages);
-void *workingset_eviction(struct folio *folio, struct mem_cgroup *target_memcg);
-void workingset_refault(struct folio *folio, void *shadow);
-void workingset_activation(struct folio *folio);
-
 /* linux/mm/page_alloc.c */
 extern unsigned long totalreserve_pages;
 
 /* Definition of global_zone_page_state not available yet */
 #define nr_free_pages() global_zone_page_state(NR_FREE_PAGES)
 
+/* linux/mm/folio.c */
+void folio_add_lru(struct folio *folio);
+void folio_mark_accessed(struct folio *folio);
+void lru_add_drain_all(void);
 
-/* linux/mm/swap.c */
-void lru_note_cost_unlock_irq(struct lruvec *lruvec, bool file,
-		unsigned int nr_io, unsigned int nr_rotated);
-void lru_note_cost_refault(struct folio *);
-void folio_add_lru(struct folio *);
-void folio_add_lru_vma(struct folio *, struct vm_area_struct *);
-void mark_page_accessed(struct page *);
-void folio_mark_accessed(struct folio *);
-
-static inline bool folio_may_be_lru_cached(struct folio *folio)
-{
-	/*
-	 * Holding PMD-sized folios in per-CPU LRU cache unbalances accounting.
-	 * Holding small numbers of low-order mTHP folios in per-CPU LRU cache
-	 * will be sensible, but nobody has implemented and tested that yet.
-	 */
-	return !folio_test_large(folio);
-}
+/* linux/mm/folio-compat.c */
+void mark_page_accessed(struct page *page);
 
 extern atomic_t lru_disable_count;
 
@@ -328,42 +308,6 @@ static inline bool lru_cache_disabled(void)
 	return atomic_read(&lru_disable_count);
 }
 
-static inline void lru_cache_enable(void)
-{
-	atomic_dec(&lru_disable_count);
-}
-
-extern void lru_cache_disable(void);
-extern void lru_add_drain(void);
-extern void lru_add_drain_cpu(int cpu);
-extern void lru_add_drain_cpu_zone(struct zone *zone);
-extern void lru_add_drain_all(void);
-void folio_deactivate(struct folio *folio);
-void folio_mark_lazyfree(struct folio *folio);
-
-/* linux/mm/vmscan.c */
-extern unsigned long zone_reclaimable_pages(struct zone *zone);
-extern unsigned long try_to_free_pages(struct zonelist *zonelist, int order,
-					gfp_t gfp_mask, const nodemask_t *mask);
-unsigned long lruvec_lru_size(struct lruvec *lruvec, enum lru_list lru, int zone_idx);
-
-#define MEMCG_RECLAIM_MAY_SWAP (1 << 1)
-#define MEMCG_RECLAIM_PROACTIVE (1 << 2)
-#define MIN_SWAPPINESS 0
-#define MAX_SWAPPINESS 200
-
-/* Just reclaim from anon folios in proactive memory reclaim */
-#define SWAPPINESS_ANON_ONLY (MAX_SWAPPINESS + 1)
-
-extern unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *memcg,
-						  unsigned long nr_pages,
-						  gfp_t gfp_mask,
-						  unsigned int reclaim_options,
-						  int *swappiness);
-extern unsigned long mem_cgroup_shrink_node(struct mem_cgroup *mem,
-						gfp_t gfp_mask, bool noswap,
-						pg_data_t *pgdat,
-						unsigned long *nr_scanned);
 extern unsigned long shrink_all_memory(unsigned long nr_pages);
 extern int vm_swappiness;
 long remove_mapping(struct address_space *mapping, struct folio *folio);
@@ -384,11 +328,6 @@ static inline void reclaim_unregister_node(struct node *node)
 }
 #endif /* CONFIG_SYSFS && CONFIG_NUMA */
 
-#ifdef CONFIG_NUMA
-extern int sysctl_min_unmapped_ratio;
-extern int sysctl_min_slab_ratio;
-#endif
-
 void check_move_unevictable_folios(struct folio_batch *fbatch);
 
 extern void __meminit kswapd_run(int nid);
@@ -544,7 +483,7 @@ static inline int mem_cgroup_swappiness(struct mem_cgroup *memcg)
 
 void lru_reparent_memcg(struct mem_cgroup *memcg, struct mem_cgroup *parent, int nid);
 #else
-static inline int mem_cgroup_swappiness(struct mem_cgroup *mem)
+static inline int mem_cgroup_swappiness(struct mem_cgroup *memcg)
 {
 	return READ_ONCE(vm_swappiness);
 }
diff --git a/mm/internal.h b/mm/internal.h
index fa4fb69444ec..771bd3581fc7 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -31,6 +31,73 @@ struct huge_bootmem_page {
 	unsigned long flags;
 };
 
+/* mm/workingset.c */
+bool workingset_test_recent(void *shadow, bool file, bool *workingset,
+			    bool flush);
+void workingset_age_nonresident(struct lruvec *lruvec, unsigned long nr_pages);
+void *workingset_eviction(struct folio *folio,
+			  struct mem_cgroup *target_memcg);
+void workingset_refault(struct folio *folio, void *shadow);
+void workingset_activation(struct folio *folio);
+
+/* mm/folio.c */
+void lru_note_cost_unlock_irq(struct lruvec *lruvec, bool file,
+		unsigned int nr_io, unsigned int nr_rotated);
+void lru_note_cost_refault(struct folio *folio);
+void folio_add_lru_vma(struct folio *folio, struct vm_area_struct *vma);
+
+static inline bool folio_may_be_lru_cached(struct folio *folio)
+{
+	/*
+	 * Holding PMD-sized folios in per-CPU LRU cache unbalances accounting.
+	 * Holding small numbers of low-order mTHP folios in per-CPU LRU cache
+	 * will be sensible, but nobody has implemented and tested that yet.
+	 */
+	return !folio_test_large(folio);
+}
+
+static inline void lru_cache_enable(void)
+{
+	atomic_dec(&lru_disable_count);
+}
+
+void lru_cache_disable(void);
+void lru_add_drain(void);
+void lru_add_drain_cpu(int cpu);
+void lru_add_drain_cpu_zone(struct zone *zone);
+void folio_deactivate(struct folio *folio);
+void folio_mark_lazyfree(struct folio *folio);
+
+/* mm/vmscan.c */
+unsigned long zone_reclaimable_pages(struct zone *zone);
+unsigned long try_to_free_pages(struct zonelist *zonelist, int order,
+				gfp_t gfp_mask, const nodemask_t *mask);
+unsigned long lruvec_lru_size(struct lruvec *lruvec, enum lru_list lru,
+			      int zone_idx);
+
+#define MEMCG_RECLAIM_MAY_SWAP (1 << 1)
+#define MEMCG_RECLAIM_PROACTIVE (1 << 2)
+#define MIN_SWAPPINESS 0
+#define MAX_SWAPPINESS 200
+
+/* Just reclaim from anon folios in proactive memory reclaim */
+#define SWAPPINESS_ANON_ONLY (MAX_SWAPPINESS + 1)
+
+unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *memcg,
+					   unsigned long nr_pages,
+					   gfp_t gfp_mask,
+					   unsigned int reclaim_options,
+					   int *swappiness);
+unsigned long mem_cgroup_shrink_node(struct mem_cgroup *memcg,
+				     gfp_t gfp_mask, bool noswap,
+				     pg_data_t *pgdat,
+				     unsigned long *nr_scanned);
+
+#ifdef CONFIG_NUMA
+extern int sysctl_min_unmapped_ratio;
+extern int sysctl_min_slab_ratio;
+#endif
+
 /*
  * Maintains state across a page table move. The operation assumes both source
  * and destination VMAs already exist and are specified by the user.
diff --git a/mm/memfd.c b/mm/memfd.c
index abe13b291ddc..6c72fe6caef7 100644
--- a/mm/memfd.c
+++ b/mm/memfd.c
@@ -19,6 +19,7 @@
 #include <linux/memfd.h>
 #include <linux/pid_namespace.h>
 #include <uapi/linux/memfd.h>
+#include "internal.h"
 #include "swap.h"
 
 /*

-- 
2.43.0

Re: [PATCH v7 3/3] mm: move reclaim-internal declarations out of swap.h

[David Hildenbrand (Arm)]

On 7/5/26 16:12, Jianyue Wu wrote:
> Keep include/linux/swap.h focused on swap-facing interfaces by moving
> MM-internal reclaim and workingset declarations into mm/internal.h.
> 
> Leave the small set of LRU helper declarations that are used outside mm/
> in swap.h so this cleanup does not need a new public header under
> include/linux/.
> 
> Suggested-by: Barry Song <baohua@kernel.org>
> Suggested-by: Baoquan He <bhe@redhat.com>
> Acked-by: Johannes Weiner <hannes@cmpxchg.org>
> Signed-off-by: Jianyue Wu <wujianyue000@gmail.com>
> ---
>  include/linux/swap.h | 75 +++++-----------------------------------------------
>  mm/internal.h        | 67 ++++++++++++++++++++++++++++++++++++++++++++++

We likely want to split that up soon, but let's do that separately.

Acked-by: David Hildenbrand (Arm) <david@kernel.org>

-- 
Cheers,

David

Re: [PATCH v7 3/3] mm: move reclaim-internal declarations out of swap.h

[Jianyue Wu]

On Mon, Jul 6, 2026 at 4:51 PM David Hildenbrand (Arm) <david@kernel.org> wrote:
>
> On 7/5/26 16:12, Jianyue Wu wrote:
> > Keep include/linux/swap.h focused on swap-facing interfaces by moving
> > MM-internal reclaim and workingset declarations into mm/internal.h.
> >
> > Leave the small set of LRU helper declarations that are used outside mm/
> > in swap.h so this cleanup does not need a new public header under
> > include/linux/.
> >
> > Suggested-by: Barry Song <baohua@kernel.org>
> > Suggested-by: Baoquan He <bhe@redhat.com>
> > Acked-by: Johannes Weiner <hannes@cmpxchg.org>
> > Signed-off-by: Jianyue Wu <wujianyue000@gmail.com>
> > ---
> >  include/linux/swap.h | 75 +++++-----------------------------------------------
> >  mm/internal.h        | 67 ++++++++++++++++++++++++++++++++++++++++++++++
>
> We likely want to split that up soon, but let's do that separately.
>
> Acked-by: David Hildenbrand (Arm) <david@kernel.org>
>
> --
> Cheers,
>
> David

Thanks David. Agreed, that can be handled separately.

Re: [PATCH v7 0/3] mm: clean up folio LRU and swap declarations

[Andrew Morton]

On Sun, 05 Jul 2026 22:12:30 +0800 Jianyue Wu <wujianyue000@gmail.com> wrote:

> This series splits folio LRU and swap cleanup into three steps:
> 
>   - move the page-cluster sysctl next to swap readahead in mm/swap_state.c
>   - rename mm/swap.c to mm/folio.c after the swap-specific bits move out
>   - move MM-internal reclaim declarations out of include/linux/swap.h
> 
> After this series, swap cache and swap-in readahead stay in mm/swap_state.c,
> folio LRU helpers live in mm/folio.c, and MM-internal reclaim/workingset
> declarations move from include/linux/swap.h to mm/internal.h (public LRU
> helpers used outside mm/ remain in swap.h).

Thanks, I've added this to mm.git's mm-new branch - in a few days I'll
move it into mm-unstable for linux-next inclusion.  After -rc4 (approx)
I'll move it into mm.git's non-rebasing mm-stable branch for
upstreaming during the 7.3-rc1 merge window.