[PATCH 0/2] mmzone.h: fix kernel-doc and simplify is_highmem_idx

[PATCH 0/2] mmzone.h: fix kernel-doc and simplify is_highmem_idx

[Mike Rapoport]

From: Mike Rapoport <rppt@linux.ibm.com>

Hi,

There are several kernel-doc comments in include/linux/mmzone.h, but
they have some formatting issues and they are not linked to the rest of
the documentation.

The first patch here fixes the formatting and adds the kernel-doc
comments to the core-api/mm-api.rst.

The second patch simplifies a bit detection if a zone is a highmem zone.
It does not generally depends on the first one, but they have a textual
conflict.

Mike Rapoport (2):
  mm/mmzone.h: fix existing kernel-doc comments and link them to core-api
  mm/mmzone.h: simplify is_highmem_idx()

 Documentation/core-api/mm-api.rst |  2 ++
 include/linux/mmzone.h            | 56 ++++++++++++++-----------------
 2 files changed, 27 insertions(+), 31 deletions(-)

-- 
2.29.2

[PATCH 1/2] mm/mmzone.h: fix existing kernel-doc comments and link them to core-api

[Mike Rapoport]

From: Mike Rapoport <rppt@linux.ibm.com>

There are a couple of kernel-doc comments in include/linux/mmzone.h but
they have minor formatting issues that would cause kernel-doc warnings.

Fix the formatting of those comments, add missing Return: descriptions and
link include/linux/mmzone.h to Documentation/core-api/mm-api.rst

Signed-off-by: Mike Rapoport <rppt@linux.ibm.com>
---
 Documentation/core-api/mm-api.rst |  2 ++
 include/linux/mmzone.h            | 43 +++++++++++++++++--------------
 2 files changed, 26 insertions(+), 19 deletions(-)

diff --git a/Documentation/core-api/mm-api.rst b/Documentation/core-api/mm-api.rst
index 201b5423303b..3079af5a2404 100644
--- a/Documentation/core-api/mm-api.rst
+++ b/Documentation/core-api/mm-api.rst
@@ -92,3 +92,5 @@ More Memory Management Functions
    :export:
 
 .. kernel-doc:: mm/page_alloc.c
+
+.. kernel-doc:: include/linux/mmzone.h
diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index 47946cec7584..3b2205741048 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -993,7 +993,8 @@ static inline int is_highmem_idx(enum zone_type idx)
  * is_highmem - helper function to quickly check if a struct zone is a
  *              highmem zone or not.  This is an attempt to keep references
  *              to ZONE_{DMA/NORMAL/HIGHMEM/etc} in general code to a minimum.
- * @zone - pointer to struct zone variable
+ * @zone: pointer to struct zone variable
+ * Return: 1 for a highmem zone, 0 otherwise
  */
 static inline int is_highmem(struct zone *zone)
 {
@@ -1044,7 +1045,7 @@ extern struct zone *next_zone(struct zone *zone);
 
 /**
  * for_each_online_pgdat - helper macro to iterate over all online nodes
- * @pgdat - pointer to a pg_data_t variable
+ * @pgdat: pointer to a pg_data_t variable
  */
 #define for_each_online_pgdat(pgdat)			\
 	for (pgdat = first_online_pgdat();		\
@@ -1052,7 +1053,7 @@ extern struct zone *next_zone(struct zone *zone);
 	     pgdat = next_online_pgdat(pgdat))
 /**
  * for_each_zone - helper macro to iterate over all memory zones
- * @zone - pointer to struct zone variable
+ * @zone: pointer to struct zone variable
  *
  * The user only needs to declare the zone variable, for_each_zone
  * fills it in.
@@ -1091,15 +1092,18 @@ struct zoneref *__next_zones_zonelist(struct zoneref *z,
 
 /**
  * next_zones_zonelist - Returns the next zone at or below highest_zoneidx within the allowed nodemask using a cursor within a zonelist as a starting point
- * @z - The cursor used as a starting point for the search
- * @highest_zoneidx - The zone index of the highest zone to return
- * @nodes - An optional nodemask to filter the zonelist with
+ * @z: The cursor used as a starting point for the search
+ * @highest_zoneidx: The zone index of the highest zone to return
+ * @nodes: An optional nodemask to filter the zonelist with
  *
  * This function returns the next zone at or below a given zone index that is
  * within the allowed nodemask using a cursor as the starting point for the
  * search. The zoneref returned is a cursor that represents the current zone
  * being examined. It should be advanced by one before calling
  * next_zones_zonelist again.
+ *
+ * Return: the next zone at or below highest_zoneidx within the allowed
+ * nodemask using a cursor within a zonelist as a starting point
  */
 static __always_inline struct zoneref *next_zones_zonelist(struct zoneref *z,
 					enum zone_type highest_zoneidx,
@@ -1112,10 +1116,9 @@ static __always_inline struct zoneref *next_zones_zonelist(struct zoneref *z,
 
 /**
  * first_zones_zonelist - Returns the first zone at or below highest_zoneidx within the allowed nodemask in a zonelist
- * @zonelist - The zonelist to search for a suitable zone
- * @highest_zoneidx - The zone index of the highest zone to return
- * @nodes - An optional nodemask to filter the zonelist with
- * @return - Zoneref pointer for the first suitable zone found (see below)
+ * @zonelist: The zonelist to search for a suitable zone
+ * @highest_zoneidx: The zone index of the highest zone to return
+ * @nodes: An optional nodemask to filter the zonelist with
  *
  * This function returns the first zone at or below a given zone index that is
  * within the allowed nodemask. The zoneref returned is a cursor that can be
@@ -1125,6 +1128,8 @@ static __always_inline struct zoneref *next_zones_zonelist(struct zoneref *z,
  * When no eligible zone is found, zoneref->zone is NULL (zoneref itself is
  * never NULL). This may happen either genuinely, or due to concurrent nodemask
  * update due to cpuset modification.
+ *
+ * Return: Zoneref pointer for the first suitable zone found
  */
 static inline struct zoneref *first_zones_zonelist(struct zonelist *zonelist,
 					enum zone_type highest_zoneidx,
@@ -1136,11 +1141,11 @@ static inline struct zoneref *first_zones_zonelist(struct zonelist *zonelist,
 
 /**
  * for_each_zone_zonelist_nodemask - helper macro to iterate over valid zones in a zonelist at or below a given zone index and within a nodemask
- * @zone - The current zone in the iterator
- * @z - The current pointer within zonelist->_zonerefs being iterated
- * @zlist - The zonelist being iterated
- * @highidx - The zone index of the highest zone to return
- * @nodemask - Nodemask allowed by the allocator
+ * @zone: The current zone in the iterator
+ * @z: The current pointer within zonelist->_zonerefs being iterated
+ * @zlist: The zonelist being iterated
+ * @highidx: The zone index of the highest zone to return
+ * @nodemask: Nodemask allowed by the allocator
  *
  * This iterator iterates though all zones at or below a given zone index and
  * within a given nodemask
@@ -1160,10 +1165,10 @@ static inline struct zoneref *first_zones_zonelist(struct zonelist *zonelist,
 
 /**
  * for_each_zone_zonelist - helper macro to iterate over valid zones in a zonelist at or below a given zone index
- * @zone - The current zone in the iterator
- * @z - The current pointer within zonelist->zones being iterated
- * @zlist - The zonelist being iterated
- * @highidx - The zone index of the highest zone to return
+ * @zone: The current zone in the iterator
+ * @z: The current pointer within zonelist->zones being iterated
+ * @zlist: The zonelist being iterated
+ * @highidx: The zone index of the highest zone to return
  *
  * This iterator iterates though all zones at or below a given zone index.
  */
-- 
2.29.2

Re: [PATCH 1/2] mm/mmzone.h: fix existing kernel-doc comments and link them to core-api

[Matthew Wilcox]

On Fri, Apr 23, 2021 at 11:38:10PM +0300, Mike Rapoport wrote:
> +++ b/Documentation/core-api/mm-api.rst
> @@ -92,3 +92,5 @@ More Memory Management Functions
>     :export:
>  
>  .. kernel-doc:: mm/page_alloc.c
> +
> +.. kernel-doc:: include/linux/mmzone.h

You didn't do this against linux-next ... I added a few other files this
cycle:

.. kernel-doc:: mm/page_alloc.c
.. kernel-doc:: mm/mempolicy.c
.. kernel-doc:: include/linux/mm_types.h
   :internal:
.. kernel-doc:: include/linux/mm.h
   :internal:

The content looks good.

Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>

Re: [PATCH 1/2] mm/mmzone.h: fix existing kernel-doc comments and link them to core-api

[Anshuman Khandual]

On 4/24/21 2:08 AM, Mike Rapoport wrote:
> From: Mike Rapoport <rppt@linux.ibm.com>
> 
> There are a couple of kernel-doc comments in include/linux/mmzone.h but
> they have minor formatting issues that would cause kernel-doc warnings.
> 
> Fix the formatting of those comments, add missing Return: descriptions and
> link include/linux/mmzone.h to Documentation/core-api/mm-api.rst
> 
> Signed-off-by: Mike Rapoport <rppt@linux.ibm.com>
> ---
>  Documentation/core-api/mm-api.rst |  2 ++
>  include/linux/mmzone.h            | 43 +++++++++++++++++--------------
>  2 files changed, 26 insertions(+), 19 deletions(-)

Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com>

[PATCH 2/2] mm/mmzone.h: simplify is_highmem_idx()

[Mike Rapoport]

From: Mike Rapoport <rppt@linux.ibm.com>

There is a lot of historical ifdefery in is_highmem_idx() and its helper
zone_movable_is_highmem() that was required because of two different paths
for nodes and zones initialization that were selected at compile time.

Until commit 3f08a302f533 ("mm: remove CONFIG_HAVE_MEMBLOCK_NODE_MAP
option") the movable_zone variable was only available for configurations
that had CONFIG_HAVE_MEMBLOCK_NODE_MAP enabled so the test in
zone_movable_is_highmem() used that variable only for such configurations.
For other configurations the test checked if the index of ZONE_MOVABLE was
greater by 1 than the index of ZONE_HIGMEM and then movable zone was
considered a highmem zone. Needless to say, ZONE_MOVABLE - 1 equals
ZONE_HIGMEM by definition when CONFIG_HIGHMEM=y.

Commit 3f08a302f533 ("mm: remove CONFIG_HAVE_MEMBLOCK_NODE_MAP option")
made movable_zone variable always available. Since this variable is set to
ZONE_HIGHMEM if CONFIG_HIGHMEM is enabled and highmem zone is populated, it
is enough to check whether

	zone_idx == ZONE_MOVABLE && movable_zone == ZONE_HIGMEM

to test if zone index points to a highmem zone.

Remove zone_movable_is_highmem() that is not used anywhere except
is_highmem_idx() and use the test above in is_highmem_idx() instead.

Signed-off-by: Mike Rapoport <rppt@linux.ibm.com>
---
 include/linux/mmzone.h | 13 +------------
 1 file changed, 1 insertion(+), 12 deletions(-)

diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index 3b2205741048..6a1ac643b65e 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -968,22 +968,11 @@ static inline void zone_set_nid(struct zone *zone, int nid) {}
 
 extern int movable_zone;
 
-#ifdef CONFIG_HIGHMEM
-static inline int zone_movable_is_highmem(void)
-{
-#ifdef CONFIG_NEED_MULTIPLE_NODES
-	return movable_zone == ZONE_HIGHMEM;
-#else
-	return (ZONE_MOVABLE - 1) == ZONE_HIGHMEM;
-#endif
-}
-#endif
-
 static inline int is_highmem_idx(enum zone_type idx)
 {
 #ifdef CONFIG_HIGHMEM
 	return (idx == ZONE_HIGHMEM ||
-		(idx == ZONE_MOVABLE && zone_movable_is_highmem()));
+		(idx == ZONE_MOVABLE && movable_zone == ZONE_HIGHMEM));
 #else
 	return 0;
 #endif
-- 
2.29.2

Re: [PATCH 2/2] mm/mmzone.h: simplify is_highmem_idx()

[Anshuman Khandual]

On 4/24/21 2:08 AM, Mike Rapoport wrote:
> From: Mike Rapoport <rppt@linux.ibm.com>
> 
> There is a lot of historical ifdefery in is_highmem_idx() and its helper
> zone_movable_is_highmem() that was required because of two different paths
> for nodes and zones initialization that were selected at compile time.
> 
> Until commit 3f08a302f533 ("mm: remove CONFIG_HAVE_MEMBLOCK_NODE_MAP
> option") the movable_zone variable was only available for configurations
> that had CONFIG_HAVE_MEMBLOCK_NODE_MAP enabled so the test in
> zone_movable_is_highmem() used that variable only for such configurations.
> For other configurations the test checked if the index of ZONE_MOVABLE was
> greater by 1 than the index of ZONE_HIGMEM and then movable zone was
> considered a highmem zone. Needless to say, ZONE_MOVABLE - 1 equals
> ZONE_HIGMEM by definition when CONFIG_HIGHMEM=y.

Right with CONFIG_HIGHMEM is enabled, ZONE_MOVABLE = ZONE_HIGHMEM + 1 holds
always true from the very definition in enum zone_type { }.

> 
> Commit 3f08a302f533 ("mm: remove CONFIG_HAVE_MEMBLOCK_NODE_MAP option")
> made movable_zone variable always available. Since this variable is set to
> ZONE_HIGHMEM if CONFIG_HIGHMEM is enabled and highmem zone is populated, it
> is enough to check whether
> 
> 	zone_idx == ZONE_MOVABLE && movable_zone == ZONE_HIGMEM

Right. A small nit. s/HIGMEM/HIGHMEM

> 
> to test if zone index points to a highmem zone.

If the CONFIG_HIGHMEM is enabled but ZONE_HIGHMEM is not populated, then
movable_node would point to a zone below ZONE_HIGHMEM and is_highmem_idx()
would also return false.

> 
> Remove zone_movable_is_highmem() that is not used anywhere except
> is_highmem_idx() and use the test above in is_highmem_idx() instead.
> 
> Signed-off-by: Mike Rapoport <rppt@linux.ibm.com>
> ---
>  include/linux/mmzone.h | 13 +------------
>  1 file changed, 1 insertion(+), 12 deletions(-)
> 
> diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
> index 3b2205741048..6a1ac643b65e 100644
> --- a/include/linux/mmzone.h
> +++ b/include/linux/mmzone.h
> @@ -968,22 +968,11 @@ static inline void zone_set_nid(struct zone *zone, int nid) {}
>  
>  extern int movable_zone;
>  
> -#ifdef CONFIG_HIGHMEM
> -static inline int zone_movable_is_highmem(void)
> -{
> -#ifdef CONFIG_NEED_MULTIPLE_NODES
> -	return movable_zone == ZONE_HIGHMEM;
> -#else
> -	return (ZONE_MOVABLE - 1) == ZONE_HIGHMEM;
> -#endif
> -}
> -#endif
> -
>  static inline int is_highmem_idx(enum zone_type idx)
>  {
>  #ifdef CONFIG_HIGHMEM
>  	return (idx == ZONE_HIGHMEM ||
> -		(idx == ZONE_MOVABLE && zone_movable_is_highmem()));
> +		(idx == ZONE_MOVABLE && movable_zone == ZONE_HIGHMEM));
>  #else
>  	return 0;
>  #endif
> 

LGTM.

Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com>