[PATCH v6 2/9] mm/page_owner: add MR_NEVER to enum migrate_reason and use it for last_migrate_reason

[PATCH v6 2/9] mm/page_owner: add MR_NEVER to enum migrate_reason and use it for last_migrate_reason

[Ye Liu]

The last_migrate_reason field uses -1 as a sentinel value to mean "no
migration has happened".  Replace the four bare -1 occurrences by
adding a proper MR_NEVER member to enum migrate_reason, defining a
corresponding "never_migrated" string in the MIGRATE_REASON trace
macro, and updating the GDB page_owner script to use MR_NEVER instead
of the hardcoded -1 so that lx-dump-page-owner does not incorrectly
report unmigrated pages as migrated.

No functional change.

Signed-off-by: Ye Liu <ye.liu@linux.dev>
Reviewed-by: Zi Yan <ziy@nvidia.com>
Reviewed-by: Vlastimil Babka (SUSE) <vbabka@kernel.org>
---
 include/linux/migrate_mode.h    | 1 +
 include/trace/events/migrate.h  | 3 ++-
 mm/page_owner.c                 | 8 ++++----
 scripts/gdb/linux/page_owner.py | 4 +++-
 4 files changed, 10 insertions(+), 6 deletions(-)

diff --git a/include/linux/migrate_mode.h b/include/linux/migrate_mode.h
index 265c4328b36a..05102d4d2490 100644
--- a/include/linux/migrate_mode.h
+++ b/include/linux/migrate_mode.h
@@ -25,6 +25,7 @@ enum migrate_reason {
 	MR_LONGTERM_PIN,
 	MR_DEMOTION,
 	MR_DAMON,
+	MR_NEVER,		/* page has never been migrated */
 	MR_TYPES
 };
 
diff --git a/include/trace/events/migrate.h b/include/trace/events/migrate.h
index cd01dd7b3640..11bc0aa14c7e 100644
--- a/include/trace/events/migrate.h
+++ b/include/trace/events/migrate.h
@@ -23,7 +23,8 @@
 	EM( MR_CONTIG_RANGE,	"contig_range")			\
 	EM( MR_LONGTERM_PIN,	"longterm_pin")			\
 	EM( MR_DEMOTION,	"demotion")			\
-	EMe(MR_DAMON,		"damon")
+	EM( MR_DAMON,		"damon")			\
+	EMe(MR_NEVER,		"never_migrated")
 
 /*
  * First define the enums in the above macros to be exported to userspace
diff --git a/mm/page_owner.c b/mm/page_owner.c
index 342549891a8d..c2f43ab860eb 100644
--- a/mm/page_owner.c
+++ b/mm/page_owner.c
@@ -339,7 +339,7 @@ noinline void __set_page_owner(struct page *page, unsigned short order,
 	depot_stack_handle_t handle;
 
 	handle = save_stack(gfp_mask);
-	__update_page_owner_handle(page, handle, order, gfp_mask, -1,
+	__update_page_owner_handle(page, handle, order, gfp_mask, MR_NEVER,
 				   ts_nsec, current->pid, current->tgid,
 				   current->comm);
 	inc_stack_record_count(handle, gfp_mask, 1 << order);
@@ -596,7 +596,7 @@ print_page_owner(char __user *buf, size_t count, unsigned long pfn,
 	if (ret >= count)
 		goto err;
 
-	if (page_owner->last_migrate_reason != -1) {
+	if (page_owner->last_migrate_reason != MR_NEVER) {
 		ret += scnprintf(kbuf + ret, count - ret,
 			"Page has been migrated, last migrate reason: %s\n",
 			migrate_reason_names[page_owner->last_migrate_reason]);
@@ -667,7 +667,7 @@ void __dump_page_owner(const struct page *page)
 		stack_depot_print(handle);
 	}
 
-	if (page_owner->last_migrate_reason != -1)
+	if (page_owner->last_migrate_reason != MR_NEVER)
 		pr_alert("page has been migrated, last migrate reason: %s\n",
 			migrate_reason_names[page_owner->last_migrate_reason]);
 	page_ext_put(page_ext);
@@ -826,7 +826,7 @@ static void init_pages_in_zone(struct zone *zone)
 
 			/* Found early allocated page */
 			__update_page_owner_handle(page, early_handle, 0, 0,
-						   -1, local_clock(), current->pid,
+						   MR_NEVER, local_clock(), current->pid,
 						   current->tgid, current->comm);
 			count++;
 ext_put_continue:
diff --git a/scripts/gdb/linux/page_owner.py b/scripts/gdb/linux/page_owner.py
index 8e713a09cfe7..eeabaeed438b 100644
--- a/scripts/gdb/linux/page_owner.py
+++ b/scripts/gdb/linux/page_owner.py
@@ -34,6 +34,7 @@ class DumpPageOwner(gdb.Command):
     max_pfn = None
     p_ops = None
     migrate_reason_names = None
+    mr_never = None
 
     def __init__(self):
         super(DumpPageOwner, self).__init__("lx-dump-page-owner", gdb.COMMAND_SUPPORT)
@@ -65,6 +66,7 @@ class DumpPageOwner(gdb.Command):
         self.max_pfn = int(gdb.parse_and_eval("max_pfn"))
         self.page_ext_size = int(gdb.parse_and_eval("page_ext_size"))
         self.migrate_reason_names = gdb.parse_and_eval('migrate_reason_names')
+        self.mr_never = int(gdb.parse_and_eval('MR_NEVER'))
 
     def page_ext_invalid(self, page_ext):
         if page_ext == gdb.Value(0):
@@ -138,7 +140,7 @@ class DumpPageOwner(gdb.Command):
         else:
             gdb.write('page last free stack trace:\n')
             stackdepot.stack_depot_print(page_owner["free_handle"])
-        if page_owner['last_migrate_reason'] != -1:
+        if page_owner['last_migrate_reason'] != self.mr_never:
             gdb.write('page has been migrated, last migrate reason: %s\n' % self.migrate_reason_names[page_owner['last_migrate_reason']])
 
     def read_page_owner(self):
-- 
2.43.0

Re: [PATCH v6 2/9] mm/page_owner: add MR_NEVER to enum migrate_reason and use it for last_migrate_reason

[David Hildenbrand (Arm)]

On 7/14/26 03:51, Ye Liu wrote:
> The last_migrate_reason field uses -1 as a sentinel value to mean "no
> migration has happened".  Replace the four bare -1 occurrences by
> adding a proper MR_NEVER member to enum migrate_reason, defining a
> corresponding "never_migrated" string in the MIGRATE_REASON trace
> macro, and updating the GDB page_owner script to use MR_NEVER instead
> of the hardcoded -1 so that lx-dump-page-owner does not incorrectly
> report unmigrated pages as migrated.
> 
> No functional change.
> 
> Signed-off-by: Ye Liu <ye.liu@linux.dev>
> Reviewed-by: Zi Yan <ziy@nvidia.com>
> Reviewed-by: Vlastimil Babka (SUSE) <vbabka@kernel.org>
> ---
>  include/linux/migrate_mode.h    | 1 +
>  include/trace/events/migrate.h  | 3 ++-
>  mm/page_owner.c                 | 8 ++++----
>  scripts/gdb/linux/page_owner.py | 4 +++-
>  4 files changed, 10 insertions(+), 6 deletions(-)
> 
> diff --git a/include/linux/migrate_mode.h b/include/linux/migrate_mode.h
> index 265c4328b36a..05102d4d2490 100644
> --- a/include/linux/migrate_mode.h
> +++ b/include/linux/migrate_mode.h
> @@ -25,6 +25,7 @@ enum migrate_reason {
>  	MR_LONGTERM_PIN,
>  	MR_DEMOTION,
>  	MR_DAMON,
> +	MR_NEVER,		/* page has never been migrated */

Shouldn't this be more like

"MR_NONE" ?

As "never" is not really a "reason" ?

-- 
Cheers,

David

Re: [PATCH v6 2/9] mm/page_owner: add MR_NEVER to enum migrate_reason and use it for last_migrate_reason

[Vlastimil Babka (SUSE)]

On 7/14/26 15:05, David Hildenbrand (Arm) wrote:
> On 7/14/26 03:51, Ye Liu wrote:
>> The last_migrate_reason field uses -1 as a sentinel value to mean "no
>> migration has happened".  Replace the four bare -1 occurrences by
>> adding a proper MR_NEVER member to enum migrate_reason, defining a
>> corresponding "never_migrated" string in the MIGRATE_REASON trace
>> macro, and updating the GDB page_owner script to use MR_NEVER instead
>> of the hardcoded -1 so that lx-dump-page-owner does not incorrectly
>> report unmigrated pages as migrated.
>> 
>> No functional change.
>> 
>> Signed-off-by: Ye Liu <ye.liu@linux.dev>
>> Reviewed-by: Zi Yan <ziy@nvidia.com>
>> Reviewed-by: Vlastimil Babka (SUSE) <vbabka@kernel.org>
>> ---
>>  include/linux/migrate_mode.h    | 1 +
>>  include/trace/events/migrate.h  | 3 ++-
>>  mm/page_owner.c                 | 8 ++++----
>>  scripts/gdb/linux/page_owner.py | 4 +++-
>>  4 files changed, 10 insertions(+), 6 deletions(-)
>> 
>> diff --git a/include/linux/migrate_mode.h b/include/linux/migrate_mode.h
>> index 265c4328b36a..05102d4d2490 100644
>> --- a/include/linux/migrate_mode.h
>> +++ b/include/linux/migrate_mode.h
>> @@ -25,6 +25,7 @@ enum migrate_reason {
>>  	MR_LONGTERM_PIN,
>>  	MR_DEMOTION,
>>  	MR_DAMON,
>> +	MR_NEVER,		/* page has never been migrated */
> 
> Shouldn't this be more like
> 
> "MR_NONE" ?
> 
> As "never" is not really a "reason" ?

It's not used ever as a reason that would be actually passed to migration.
So I think the name is more descriptive this way.

Re: [PATCH v6 2/9] mm/page_owner: add MR_NEVER to enum migrate_reason and use it for last_migrate_reason

[David Hildenbrand (Arm)]

On 7/14/26 15:09, Vlastimil Babka (SUSE) wrote:
> On 7/14/26 15:05, David Hildenbrand (Arm) wrote:
>> On 7/14/26 03:51, Ye Liu wrote:
>>> The last_migrate_reason field uses -1 as a sentinel value to mean "no
>>> migration has happened".  Replace the four bare -1 occurrences by
>>> adding a proper MR_NEVER member to enum migrate_reason, defining a
>>> corresponding "never_migrated" string in the MIGRATE_REASON trace
>>> macro, and updating the GDB page_owner script to use MR_NEVER instead
>>> of the hardcoded -1 so that lx-dump-page-owner does not incorrectly
>>> report unmigrated pages as migrated.
>>>
>>> No functional change.
>>>
>>> Signed-off-by: Ye Liu <ye.liu@linux.dev>
>>> Reviewed-by: Zi Yan <ziy@nvidia.com>
>>> Reviewed-by: Vlastimil Babka (SUSE) <vbabka@kernel.org>
>>> ---
>>>  include/linux/migrate_mode.h    | 1 +
>>>  include/trace/events/migrate.h  | 3 ++-
>>>  mm/page_owner.c                 | 8 ++++----
>>>  scripts/gdb/linux/page_owner.py | 4 +++-
>>>  4 files changed, 10 insertions(+), 6 deletions(-)
>>>
>>> diff --git a/include/linux/migrate_mode.h b/include/linux/migrate_mode.h
>>> index 265c4328b36a..05102d4d2490 100644
>>> --- a/include/linux/migrate_mode.h
>>> +++ b/include/linux/migrate_mode.h
>>> @@ -25,6 +25,7 @@ enum migrate_reason {
>>>  	MR_LONGTERM_PIN,
>>>  	MR_DEMOTION,
>>>  	MR_DAMON,
>>> +	MR_NEVER,		/* page has never been migrated */
>>
>> Shouldn't this be more like
>>
>> "MR_NONE" ?
>>
>> As "never" is not really a "reason" ?
> 
> It's not used ever as a reason that would be actually passed to migration.

Right, it's a placeholder for "there is no migrate reason because it is unset"

> So I think the name is more descriptive this way.

Not sure I agree. The usual translation of -1 -> unset is NONE or UNSET.

At least I was confused by "NEVER".

-- 
Cheers,

David

Re: [PATCH v6 2/9] mm/page_owner: add MR_NEVER to enum migrate_reason and use it for last_migrate_reason

[Vlastimil Babka (SUSE)]

On 7/14/26 15:22, David Hildenbrand (Arm) wrote:
> On 7/14/26 15:09, Vlastimil Babka (SUSE) wrote:
>> On 7/14/26 15:05, David Hildenbrand (Arm) wrote:
>>> On 7/14/26 03:51, Ye Liu wrote:
>>>> The last_migrate_reason field uses -1 as a sentinel value to mean "no
>>>> migration has happened".  Replace the four bare -1 occurrences by
>>>> adding a proper MR_NEVER member to enum migrate_reason, defining a
>>>> corresponding "never_migrated" string in the MIGRATE_REASON trace
>>>> macro, and updating the GDB page_owner script to use MR_NEVER instead
>>>> of the hardcoded -1 so that lx-dump-page-owner does not incorrectly
>>>> report unmigrated pages as migrated.
>>>>
>>>> No functional change.
>>>>
>>>> Signed-off-by: Ye Liu <ye.liu@linux.dev>
>>>> Reviewed-by: Zi Yan <ziy@nvidia.com>
>>>> Reviewed-by: Vlastimil Babka (SUSE) <vbabka@kernel.org>
>>>> ---
>>>>  include/linux/migrate_mode.h    | 1 +
>>>>  include/trace/events/migrate.h  | 3 ++-
>>>>  mm/page_owner.c                 | 8 ++++----
>>>>  scripts/gdb/linux/page_owner.py | 4 +++-
>>>>  4 files changed, 10 insertions(+), 6 deletions(-)
>>>>
>>>> diff --git a/include/linux/migrate_mode.h b/include/linux/migrate_mode.h
>>>> index 265c4328b36a..05102d4d2490 100644
>>>> --- a/include/linux/migrate_mode.h
>>>> +++ b/include/linux/migrate_mode.h
>>>> @@ -25,6 +25,7 @@ enum migrate_reason {
>>>>  	MR_LONGTERM_PIN,
>>>>  	MR_DEMOTION,
>>>>  	MR_DAMON,
>>>> +	MR_NEVER,		/* page has never been migrated */
>>>
>>> Shouldn't this be more like
>>>
>>> "MR_NONE" ?
>>>
>>> As "never" is not really a "reason" ?
>> 
>> It's not used ever as a reason that would be actually passed to migration.
> 
> Right, it's a placeholder for "there is no migrate reason because it is unset"
> 
>> So I think the name is more descriptive this way.
> 
> Not sure I agree. The usual translation of -1 -> unset is NONE or UNSET.

(note it's no longer -1 after the patch.)

> At least I was confused by "NEVER".

I won't bikeshed this, so whatever.

Just to avoid another extra respin, please also say how the following line
should change, as if we only rename MR_NEVER to MR_NONE, it will be:

+	EMe(MR_NONE,		"never_migrated")

Is that ok? Note it should never be actually printed anywhere per the
current code.

Re: [PATCH v6 2/9] mm/page_owner: add MR_NEVER to enum migrate_reason and use it for last_migrate_reason

[David Hildenbrand (Arm)]

On 7/14/26 15:49, Vlastimil Babka (SUSE) wrote:
> On 7/14/26 15:22, David Hildenbrand (Arm) wrote:
>> On 7/14/26 15:09, Vlastimil Babka (SUSE) wrote:
>>>
>>> It's not used ever as a reason that would be actually passed to migration.
>>
>> Right, it's a placeholder for "there is no migrate reason because it is unset"
>>
>>> So I think the name is more descriptive this way.
>>
>> Not sure I agree. The usual translation of -1 -> unset is NONE or UNSET.
> 
> (note it's no longer -1 after the patch.)
> 
>> At least I was confused by "NEVER".
> 
> I won't bikeshed this, so whatever.

Just to be clear: if everybody here agrees that MR_NEVER is the right thing to
use, fine with me.

I just stumbled over it and it caught my attention.

> 
> Just to avoid another extra respin, please also say how the following line
> should change, as if we only rename MR_NEVER to MR_NONE, it will be:
> 
> +	EMe(MR_NONE,		"never_migrated")

I would probably just have use "not set".

And if "last_migrate_reason == MR_NONE" that would imply "never".

Ye Liu, feel free to keep it as is if you agree that using NEVER is better here.


-- 
Cheers,

David

[PATCH v6 3/9] mm: use enum migrate_reason instead of int for migration reason parameters

[Ye Liu]

Replace all 'int reason' function parameters that carry migrate_reason
values with the proper 'enum migrate_reason' type.  This makes the
intent explicit and leverages compiler type checking.  The affected
subsystems are:

  - page_owner: __folio_set_owner_migrate_reason(),
                folio_set_owner_migrate_reason()
  - migrate: migrate_pages(), migrate_pages_sync(),
             migrate_pages_batch(), migrate_folios_move(),
             migrate_hugetlbs(), unmap_and_move_huge_page()
  - hugetlb: move_hugetlb_state(), htlb_allow_alloc_fallback()
  - trace: mm_migrate_pages and mm_migrate_pages_start events

The 'short last_migrate_reason' struct field and internal helper
parameter in page_owner are intentionally left as 'short' since they
store per-page metadata where size matters.

No functional change.

Signed-off-by: Ye Liu <ye.liu@linux.dev>
Reviewed-by: Zi Yan <ziy@nvidia.com>
Reviewed-by: Vlastimil Babka (SUSE) <vbabka@kernel.org>
Reviewed-by: Lorenzo Stoakes <ljs@kernel.org>
---
Changes in v6:
- Drop unnecessary 'extern' from __folio_set_owner_migrate_reason()
  declaration in page_owner.h.
- Adjust the indentation.
- Link: https://lore.kernel.org/all/20260701061101.344679-4-ye.liu@linux.dev/
 include/linux/hugetlb.h        |  9 +++++----
 include/linux/migrate.h        |  8 +++++---
 include/linux/page_owner.h     |  7 ++++---
 include/trace/events/migrate.h |  8 ++++----
 mm/hugetlb.c                   |  3 ++-
 mm/migrate.c                   | 12 ++++++------
 mm/page_owner.c                |  2 +-
 7 files changed, 27 insertions(+), 22 deletions(-)

diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
index 2abaf99321e9..d6967fc94a49 100644
--- a/include/linux/hugetlb.h
+++ b/include/linux/hugetlb.h
@@ -154,7 +154,8 @@ long hugetlb_unreserve_pages(struct inode *inode, long start, long end,
 bool folio_isolate_hugetlb(struct folio *folio, struct list_head *list);
 int get_hwpoison_hugetlb_folio(struct folio *folio, bool *hugetlb, bool unpoison);
 void folio_putback_hugetlb(struct folio *folio);
-void move_hugetlb_state(struct folio *old_folio, struct folio *new_folio, int reason);
+void move_hugetlb_state(struct folio *old_folio, struct folio *new_folio,
+		enum migrate_reason reason);
 void hugetlb_fix_reserve_counts(struct inode *inode);
 extern struct mutex *hugetlb_fault_mutex_table;
 u32 hugetlb_fault_mutex_hash(struct address_space *mapping, pgoff_t idx);
@@ -424,7 +425,7 @@ static inline void folio_putback_hugetlb(struct folio *folio)
 }
 
 static inline void move_hugetlb_state(struct folio *old_folio,
-					struct folio *new_folio, int reason)
+		struct folio *new_folio, enum migrate_reason reason)
 {
 }
 
@@ -956,7 +957,7 @@ static inline gfp_t htlb_modify_alloc_mask(struct hstate *h, gfp_t gfp_mask)
 	return modified_mask;
 }
 
-static inline bool htlb_allow_alloc_fallback(int reason)
+static inline bool htlb_allow_alloc_fallback(enum migrate_reason reason)
 {
 	bool allowed_fallback = false;
 
@@ -1238,7 +1239,7 @@ static inline gfp_t htlb_modify_alloc_mask(struct hstate *h, gfp_t gfp_mask)
 	return 0;
 }
 
-static inline bool htlb_allow_alloc_fallback(int reason)
+static inline bool htlb_allow_alloc_fallback(enum migrate_reason reason)
 {
 	return false;
 }
diff --git a/include/linux/migrate.h b/include/linux/migrate.h
index d5af2b7f577b..78424b3824c2 100644
--- a/include/linux/migrate.h
+++ b/include/linux/migrate.h
@@ -57,8 +57,9 @@ void putback_movable_pages(struct list_head *l);
 int migrate_folio(struct address_space *mapping, struct folio *dst,
 		struct folio *src, enum migrate_mode mode);
 int migrate_pages(struct list_head *l, new_folio_t new, free_folio_t free,
-		  unsigned long private, enum migrate_mode mode, int reason,
-		  unsigned int *ret_succeeded);
+		unsigned long private, enum migrate_mode mode,
+		enum migrate_reason reason,
+		unsigned int *ret_succeeded);
 struct folio *alloc_migration_target(struct folio *src, unsigned long private);
 bool isolate_movable_ops_page(struct page *page, isolate_mode_t mode);
 bool isolate_folio_to_list(struct folio *folio, struct list_head *list);
@@ -77,7 +78,8 @@ int set_movable_ops(const struct movable_operations *ops, enum pagetype type);
 static inline void putback_movable_pages(struct list_head *l) {}
 static inline int migrate_pages(struct list_head *l, new_folio_t new,
 		free_folio_t free, unsigned long private,
-		enum migrate_mode mode, int reason, unsigned int *ret_succeeded)
+		enum migrate_mode mode, enum migrate_reason reason,
+		unsigned int *ret_succeeded)
 	{ return -ENOSYS; }
 static inline struct folio *alloc_migration_target(struct folio *src,
 		unsigned long private)
diff --git a/include/linux/page_owner.h b/include/linux/page_owner.h
index 3328357f6dba..8188ddc5c412 100644
--- a/include/linux/page_owner.h
+++ b/include/linux/page_owner.h
@@ -3,6 +3,7 @@
 #define __LINUX_PAGE_OWNER_H
 
 #include <linux/jump_label.h>
+#include <linux/migrate_mode.h>
 
 #ifdef CONFIG_PAGE_OWNER
 extern struct static_key_false page_owner_inited;
@@ -14,7 +15,7 @@ extern void __set_page_owner(struct page *page,
 extern void __split_page_owner(struct page *page, int old_order,
 			int new_order);
 extern void __folio_copy_owner(struct folio *newfolio, struct folio *old);
-extern void __folio_set_owner_migrate_reason(struct folio *folio, int reason);
+void __folio_set_owner_migrate_reason(struct folio *folio, enum migrate_reason reason);
 extern void __dump_page_owner(const struct page *page);
 extern void pagetypeinfo_showmixedcount_print(struct seq_file *m,
 					pg_data_t *pgdat, struct zone *zone);
@@ -43,7 +44,7 @@ static inline void folio_copy_owner(struct folio *newfolio, struct folio *old)
 	if (static_branch_unlikely(&page_owner_inited))
 		__folio_copy_owner(newfolio, old);
 }
-static inline void folio_set_owner_migrate_reason(struct folio *folio, int reason)
+static inline void folio_set_owner_migrate_reason(struct folio *folio, enum migrate_reason reason)
 {
 	if (static_branch_unlikely(&page_owner_inited))
 		__folio_set_owner_migrate_reason(folio, reason);
@@ -68,7 +69,7 @@ static inline void split_page_owner(struct page *page, int old_order,
 static inline void folio_copy_owner(struct folio *newfolio, struct folio *folio)
 {
 }
-static inline void folio_set_owner_migrate_reason(struct folio *folio, int reason)
+static inline void folio_set_owner_migrate_reason(struct folio *folio, enum migrate_reason reason)
 {
 }
 static inline void dump_page_owner(const struct page *page)
diff --git a/include/trace/events/migrate.h b/include/trace/events/migrate.h
index 11bc0aa14c7e..15ee2ef201b5 100644
--- a/include/trace/events/migrate.h
+++ b/include/trace/events/migrate.h
@@ -52,7 +52,7 @@ TRACE_EVENT(mm_migrate_pages,
 	TP_PROTO(unsigned long succeeded, unsigned long failed,
 		 unsigned long thp_succeeded, unsigned long thp_failed,
 		 unsigned long thp_split, unsigned long large_folio_split,
-		 enum migrate_mode mode, int reason),
+		 enum migrate_mode mode, enum migrate_reason reason),
 
 	TP_ARGS(succeeded, failed, thp_succeeded, thp_failed,
 		thp_split, large_folio_split, mode, reason),
@@ -65,7 +65,7 @@ TRACE_EVENT(mm_migrate_pages,
 		__field(	unsigned long,		thp_split)
 		__field(	unsigned long,		large_folio_split)
 		__field(	enum migrate_mode,	mode)
-		__field(	int,			reason)
+		__field(	enum migrate_reason,	reason)
 	),
 
 	TP_fast_assign(
@@ -92,13 +92,13 @@ TRACE_EVENT(mm_migrate_pages,
 
 TRACE_EVENT(mm_migrate_pages_start,
 
-	TP_PROTO(enum migrate_mode mode, int reason),
+	TP_PROTO(enum migrate_mode mode, enum migrate_reason reason),
 
 	TP_ARGS(mode, reason),
 
 	TP_STRUCT__entry(
 		__field(enum migrate_mode, mode)
-		__field(int, reason)
+		__field(enum migrate_reason, reason)
 	),
 
 	TP_fast_assign(
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 571212b80835..17732d1fdc5e 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -7182,7 +7182,8 @@ void folio_putback_hugetlb(struct folio *folio)
 	folio_put(folio);
 }
 
-void move_hugetlb_state(struct folio *old_folio, struct folio *new_folio, int reason)
+void move_hugetlb_state(struct folio *old_folio, struct folio *new_folio,
+			enum migrate_reason reason)
 {
 	struct hstate *h = folio_hstate(old_folio);
 
diff --git a/mm/migrate.c b/mm/migrate.c
index d9b23909d716..49e10feeb094 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -1469,7 +1469,7 @@ static int migrate_folio_move(free_folio_t put_new_folio, unsigned long private,
 static int unmap_and_move_huge_page(new_folio_t get_new_folio,
 		free_folio_t put_new_folio, unsigned long private,
 		struct folio *src, int force, enum migrate_mode mode,
-		int reason, struct list_head *ret)
+		enum migrate_reason reason, struct list_head *ret)
 {
 	struct folio *dst;
 	int rc = -EAGAIN;
@@ -1626,7 +1626,7 @@ struct migrate_pages_stats {
  */
 static int migrate_hugetlbs(struct list_head *from, new_folio_t get_new_folio,
 			    free_folio_t put_new_folio, unsigned long private,
-			    enum migrate_mode mode, int reason,
+			    enum migrate_mode mode, enum migrate_reason reason,
 			    struct migrate_pages_stats *stats,
 			    struct list_head *ret_folios)
 {
@@ -1716,7 +1716,7 @@ static int migrate_hugetlbs(struct list_head *from, new_folio_t get_new_folio,
 static void migrate_folios_move(struct list_head *src_folios,
 		struct list_head *dst_folios,
 		free_folio_t put_new_folio, unsigned long private,
-		enum migrate_mode mode, int reason,
+		enum migrate_mode mode, enum migrate_reason reason,
 		struct list_head *ret_folios,
 		struct migrate_pages_stats *stats,
 		int *retry, int *thp_retry, int *nr_failed,
@@ -1799,7 +1799,7 @@ static void migrate_folios_undo(struct list_head *src_folios,
  */
 static int migrate_pages_batch(struct list_head *from,
 		new_folio_t get_new_folio, free_folio_t put_new_folio,
-		unsigned long private, enum migrate_mode mode, int reason,
+		unsigned long private, enum migrate_mode mode, enum migrate_reason reason,
 		struct list_head *ret_folios, struct list_head *split_folios,
 		struct migrate_pages_stats *stats, int nr_pass)
 {
@@ -2011,7 +2011,7 @@ static int migrate_pages_batch(struct list_head *from,
 
 static int migrate_pages_sync(struct list_head *from, new_folio_t get_new_folio,
 		free_folio_t put_new_folio, unsigned long private,
-		enum migrate_mode mode, int reason,
+		enum migrate_mode mode, enum migrate_reason reason,
 		struct list_head *ret_folios, struct list_head *split_folios,
 		struct migrate_pages_stats *stats)
 {
@@ -2088,7 +2088,7 @@ static int migrate_pages_sync(struct list_head *from, new_folio_t get_new_folio,
  */
 int migrate_pages(struct list_head *from, new_folio_t get_new_folio,
 		free_folio_t put_new_folio, unsigned long private,
-		enum migrate_mode mode, int reason, unsigned int *ret_succeeded)
+		enum migrate_mode mode, enum migrate_reason reason, unsigned int *ret_succeeded)
 {
 	int rc, rc_gather;
 	int nr_pages;
diff --git a/mm/page_owner.c b/mm/page_owner.c
index c2f43ab860eb..4e352941a6e2 100644
--- a/mm/page_owner.c
+++ b/mm/page_owner.c
@@ -345,7 +345,7 @@ noinline void __set_page_owner(struct page *page, unsigned short order,
 	inc_stack_record_count(handle, gfp_mask, 1 << order);
 }
 
-void __folio_set_owner_migrate_reason(struct folio *folio, int reason)
+void __folio_set_owner_migrate_reason(struct folio *folio, enum migrate_reason reason)
 {
 	struct page_ext *page_ext = page_ext_get(&folio->page);
 	struct page_owner *page_owner;
-- 
2.43.0

Re: [PATCH v6 3/9] mm: use enum migrate_reason instead of int for migration reason parameters

[David Hildenbrand (Arm)]

On 7/14/26 03:51, Ye Liu wrote:
> Replace all 'int reason' function parameters that carry migrate_reason
> values with the proper 'enum migrate_reason' type.  This makes the
> intent explicit and leverages compiler type checking.  The affected
> subsystems are:
> 
>   - page_owner: __folio_set_owner_migrate_reason(),
>                 folio_set_owner_migrate_reason()
>   - migrate: migrate_pages(), migrate_pages_sync(),
>              migrate_pages_batch(), migrate_folios_move(),
>              migrate_hugetlbs(), unmap_and_move_huge_page()
>   - hugetlb: move_hugetlb_state(), htlb_allow_alloc_fallback()
>   - trace: mm_migrate_pages and mm_migrate_pages_start events
> 
> The 'short last_migrate_reason' struct field and internal helper
> parameter in page_owner are intentionally left as 'short' since they
> store per-page metadata where size matters.
> 
> No functional change.
> 
> Signed-off-by: Ye Liu <ye.liu@linux.dev>
> Reviewed-by: Zi Yan <ziy@nvidia.com>
> Reviewed-by: Vlastimil Babka (SUSE) <vbabka@kernel.org>
> Reviewed-by: Lorenzo Stoakes <ljs@kernel.org>
> ---

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

-- 
Cheers,

David