On 7/14/26 15:22, David Hildenbrand (Arm) wrote:

On 7/14/26 15:09, Vlastimil Babka (SUSE) wrote:

quoted

On 7/14/26 15:05, David Hildenbrand (Arm) wrote:

quoted

On 7/14/26 03:51, Ye Liu wrote:

quoted

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 */

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"

quoted

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.