[PATCH v4 2/7] mm/page_owner: add MR_NEVER to enum migrate_reason and use it for last_migrate_reason
From: Ye Liu <hidden>
Date: 2026-07-01 01:23:14
Also in:
linux-mm, lkml
Subsystem:
gdb kernel debugging helper scripts, memory management, memory management - memory policy and migration, memory management - page allocator, the rest, tracing · Maintainers:
Jan Kiszka, Kieran Bingham, Andrew Morton, David Hildenbrand, Vlastimil Babka, Linus Torvalds, Steven Rostedt, Masami Hiramatsu
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 <redacted> 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