FAILED: patch "[PATCH] powerpc/pseries/cmm: adjust BALLOON_MIGRATE when migrating" failed to apply to 6.1-stable tree

The patch below does not apply to the 6.1-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.1.y
git checkout FETCH_HEAD
git cherry-pick -x 0da2ba35c0d532ca0fe7af698b17d74c4d084b9a
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2026010547-partly-speller-54fa@gregkh' --subject-prefix 'PATCH 6.1.y' HEAD^..

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 0da2ba35c0d532ca0fe7af698b17d74c4d084b9a Mon Sep 17 00:00:00 2001
From: David Hildenbrand <[email protected]>
Date: Tue, 21 Oct 2025 12:06:06 +0200
Subject: [PATCH] powerpc/pseries/cmm: adjust BALLOON_MIGRATE when migrating
pages

Let's properly adjust BALLOON_MIGRATE like the other drivers.

Note that the INFLATE/DEFLATE events are triggered from the core when enqueueing/dequeueing pages.

This was found by code inspection.

index 688f5fa1c724..310dab4bc867 100644
@@ -532,6 +532,7 @@ static int cmm_migratepage(struct balloon_dev_info *b_dev_info,
 
 	spin_lock_irqsave(&b_dev_info->pages_lock, flags);
 	balloon_page_insert(b_dev_info, newpage);
+	__count_vm_event(BALLOON_MIGRATE);
 	b_dev_info->isolated_pages--;
 	spin_unlock_irqrestore(&b_dev_info->pages_lock, flags);
 

From: David Hildenbrand <[email protected]>

[ Upstream commit fb05f992b6bbb4702307d96f00703ee637b24dbf ]

Patch series "mm/migration: rework movable_ops page migration (part 1)", v2.

In the future, as we decouple "struct page" from "struct folio", pages that support "non-lru page migration" -- movable_ops page migration such as memory balloons and zsmalloc -- will no longer be folios. They will not have ->mapping, ->lru, and likely no refcount and no page lock. But they will have a type and flags 🙂

This is the first part (other parts not written yet) of decoupling movable_ops page migration from folio migration.

In this series, we get rid of the ->mapping usage, and start cleaning up the code + separating it from folio migration.

Migration core will have to be further reworked to not treat movable_ops pages like folios. This is the first step into that direction.

This patch (of 29):

The core will set PG_isolated only after mops->isolate_page() was called. In case of the balloon, that is where we will remove it from the balloon list. So we cannot have isolated pages in the balloon list.

Let's drop this unnecessary check.

Stable-dep-of: 0da2ba35c0d5 ("powerpc/pseries/cmm: adjust BALLOON_MIGRATE when migrating pages")

---
 mm/balloon_compaction.c | 6 ------
 1 file changed, 6 deletions(-)

index 22c96fed70b5..dafb7dc90cfd 100644
@@ -93,12 +93,6 @@ size_t balloon_page_list_dequeue(struct balloon_dev_info *b_dev_info,
 		if (!trylock_page(page))
 			continue;
 
-		if (IS_ENABLED(CONFIG_BALLOON_COMPACTION) &&
-		    PageIsolated(page)) {
-			/* raced with isolation */
-			unlock_page(page);
-			continue;
-		}
 		balloon_page_delete(page);
 		__count_vm_event(BALLOON_DEFLATE);
 		list_add(&page->lru, pages);

2.51.0

From: David Hildenbrand <[email protected]>

[ Upstream commit 15504b1163007bbfbd9a63460d5c14737c16e96d ]

Let's move the removal of the page from the balloon list into the single caller, to remove the dependency on the PG_isolated flag and clarify locking requirements.

Note that for now, balloon_page_delete() was used on two paths:

(1) Removing a page from the balloon for deflation through balloon_page_list_dequeue()
(2) Removing an isolated page from the balloon for migration in the per-driver migration handlers. Isolated pages were already removed from the balloon list during isolation.

So instead of relying on the flag, we can just distinguish both cases directly and handle it accordingly in the caller.

We'll shuffle the operations a bit such that they logically make more sense (e.g., remove from the list before clearing flags).

In balloon migration functions we can now move the balloon_page_finalize() out of the balloon lock and perform the finalization just before dropping the balloon reference.

Document that the page lock is currently required when modifying the movability aspects of a page; hopefully we can soon decouple this from the page lock.

Stable-dep-of: 0da2ba35c0d5 ("powerpc/pseries/cmm: adjust BALLOON_MIGRATE when migrating pages")

---
 arch/powerpc/platforms/pseries/cmm.c |  2 +-
 drivers/misc/vmw_balloon.c           |  3 +-
 drivers/virtio/virtio_balloon.c      |  4 +--
 include/linux/balloon_compaction.h   | 43 +++++++++++-----------------
 mm/balloon_compaction.c              |  3 +-
 5 files changed, 21 insertions(+), 34 deletions(-)

index 5f4037c1d7fe..5e0a718d1be7 100644
@@ -532,7 +532,6 @@ static int cmm_migratepage(struct balloon_dev_info *b_dev_info,
 
 	spin_lock_irqsave(&b_dev_info->pages_lock, flags);
 	balloon_page_insert(b_dev_info, newpage);
-	balloon_page_delete(page);
 	b_dev_info->isolated_pages--;
 	spin_unlock_irqrestore(&b_dev_info->pages_lock, flags);
 

@@ -542,6 +541,7 @@ static int cmm_migratepage(struct balloon_dev_info *b_dev_info,
 	 */
 	plpar_page_set_active(page);
 
+	balloon_page_finalize(page);
 	/* balloon page list reference */
 	put_page(page);
 

index 9ce9b9e0e9b6..ad41e9af8102 100644
@@ -1789,8 +1789,7 @@ static int vmballoon_migratepage(struct balloon_dev_info *b_dev_info,
 	 * @pages_lock . We keep holding @comm_lock since we will need it in a
 	 * second.
 	 */
-	balloon_page_delete(page);
-
+	balloon_page_finalize(page);
 	put_page(page);
 
 	/* Inflate */

index aa90bd0199d7..41fa694d8257 100644
@@ -789,15 +789,13 @@ static int virtballoon_migratepage(struct balloon_dev_info *vb_dev_info,
 	tell_host(vb, vb->inflate_vq);
 
 	/* balloon's page migration 2nd step -- deflate "page" */
-	spin_lock_irqsave(&vb_dev_info->pages_lock, flags);
-	balloon_page_delete(page);
-	spin_unlock_irqrestore(&vb_dev_info->pages_lock, flags);
 	vb->num_pfns = VIRTIO_BALLOON_PAGES_PER_PAGE;
 	set_page_pfns(vb, vb->pfns, page);
 	tell_host(vb, vb->deflate_vq);
 
 	mutex_unlock(&vb->balloon_lock);
 
+	balloon_page_finalize(page);
 	put_page(page); /* balloon reference */
 
 	return MIGRATEPAGE_SUCCESS;

index dafb7dc90cfd..2a7dabab4533 100644
@@ -93,7 +93,8 @@ size_t balloon_page_list_dequeue(struct balloon_dev_info *b_dev_info,
 		if (!trylock_page(page))
 			continue;
 
-		balloon_page_delete(page);
+		list_del(&page->lru);
+		balloon_page_finalize(page);
 		__count_vm_event(BALLOON_DEFLATE);
 		list_add(&page->lru, pages);
 		unlock_page(page);

2.51.0

From: David Hildenbrand <[email protected]>

[ Upstream commit 0da2ba35c0d532ca0fe7af698b17d74c4d084b9a ]

Let's properly adjust BALLOON_MIGRATE like the other drivers.

Note that the INFLATE/DEFLATE events are triggered from the core when enqueueing/dequeueing pages.

This was found by code inspection.

---
 arch/powerpc/platforms/pseries/cmm.c | 1 +
 1 file changed, 1 insertion(+)

index 5e0a718d1be7..8c1f9721756e 100644
@@ -532,6 +532,7 @@ static int cmm_migratepage(struct balloon_dev_info *b_dev_info,
 
 	spin_lock_irqsave(&b_dev_info->pages_lock, flags);
 	balloon_page_insert(b_dev_info, newpage);
+	__count_vm_event(BALLOON_MIGRATE);
 	b_dev_info->isolated_pages--;
 	spin_unlock_irqrestore(&b_dev_info->pages_lock, flags);
 

2.51.0