Subject: [PATCH v3 07/24] vmw_balloon: stop using the balloon_dev_info lock

From: "David Hildenbrand (Red Hat)" <[email-masked]>
Date: Tue, 20 Jan 2026 00:01:15 +0100

Let's not piggy-back on the existing lock and use a separate lock for the
huge page list. Now that we use a separate lock, there is no need to
disable interrupts, so use the non-irqsave variants. We only required
the irqsave variants because of the balloon device lock.

This is a preparation for changing the locking used to protect
balloon_dev_info.

While at it, talk about "page migration" instead of "page compaction".
We'll change that in core code soon as well.

Reviewed-by: Lorenzo Stoakes <[email-masked]>
Acked-by: Michael S. Tsirkin <[email-masked]>
Signed-off-by: David Hildenbrand (Red Hat) <[email-masked]>
---
 drivers/misc/vmw_balloon.c | 20 ++++++++++++--------
 1 file changed, 12 insertions(+), 8 deletions(-)

diff --git a/drivers/misc/vmw_balloon.c b/drivers/misc/vmw_balloon.c
index 52b8c0f1eead7..53e9335b6718c 100644
--- a/drivers/misc/vmw_balloon.c
+++ b/drivers/misc/vmw_balloon.c
@@ -354,10 +354,15 @@ struct vmballoon {
 	/**
 	 * @huge_pages - list of the inflated 2MB pages.
 	 *
-	 * Protected by @b_dev_info.pages_lock .
+	 * Protected by @huge_pages_lock.
 	 */
 	struct list_head huge_pages;
 
+	/**
+	 * @huge_pages_lock: lock for the list of inflated 2MB pages.
+	 */
+	spinlock_t huge_pages_lock;
+
 	/**
 	 * @vmci_doorbell.
 	 *
@@ -987,7 +992,6 @@ static void vmballoon_enqueue_page_list(struct vmballoon *b,
 					unsigned int *n_pages,
 					enum vmballoon_page_size_type page_size)
 {
-	unsigned long flags;
 	struct page *page;
 
 	if (page_size == VMW_BALLOON_4K_PAGE) {
@@ -995,9 +999,9 @@ static void vmballoon_enqueue_page_list(struct vmballoon *b,
 	} else {
 		/*
 		 * Keep the huge pages in a local list which is not available
-		 * for the balloon compaction mechanism.
+		 * for the balloon page migration.
 		 */
-		spin_lock_irqsave(&b->b_dev_info.pages_lock, flags);
+		spin_lock(&b->huge_pages_lock);
 
 		list_for_each_entry(page, pages, lru) {
 			vmballoon_mark_page_offline(page, VMW_BALLOON_2M_PAGE);
@@ -1006,7 +1010,7 @@ static void vmballoon_enqueue_page_list(struct vmballoon *b,
 		list_splice_init(pages, &b->huge_pages);
 		__count_vm_events(BALLOON_INFLATE, *n_pages *
 				  vmballoon_page_in_frames(VMW_BALLOON_2M_PAGE));
-		spin_unlock_irqrestore(&b->b_dev_info.pages_lock, flags);
+		spin_unlock(&b->huge_pages_lock);
 	}
 
 	*n_pages = 0;
@@ -1033,7 +1037,6 @@ static void vmballoon_dequeue_page_list(struct vmballoon *b,
 {
 	struct page *page, *tmp;
 	unsigned int i = 0;
-	unsigned long flags;
 
 	/* In the case of 4k pages, use the compaction infrastructure */
 	if (page_size == VMW_BALLOON_4K_PAGE) {
@@ -1043,7 +1046,7 @@ static void vmballoon_dequeue_page_list(struct vmballoon *b,
 	}
 
 	/* 2MB pages */
-	spin_lock_irqsave(&b->b_dev_info.pages_lock, flags);
+	spin_lock(&b->huge_pages_lock);
 	list_for_each_entry_safe(page, tmp, &b->huge_pages, lru) {
 		vmballoon_mark_page_online(page, VMW_BALLOON_2M_PAGE);
 
@@ -1054,7 +1057,7 @@ static void vmballoon_dequeue_page_list(struct vmballoon *b,
 
 	__count_vm_events(BALLOON_DEFLATE,
 			  i * vmballoon_page_in_frames(VMW_BALLOON_2M_PAGE));
-	spin_unlock_irqrestore(&b->b_dev_info.pages_lock, flags);
+	spin_unlock(&b->huge_pages_lock);
 	*n_pages = i;
 }
 
@@ -1828,6 +1831,7 @@ static int __init vmballoon_init(void)
 		balloon.b_dev_info.migratepage = vmballoon_migratepage;
 
 	INIT_LIST_HEAD(&balloon.huge_pages);
+	spin_lock_init(&balloon.huge_pages_lock);
 	spin_lock_init(&balloon.comm_lock);
 	init_rwsem(&balloon.conf_sem);
 	balloon.vmci_doorbell = VMCI_INVALID_HANDLE;
-- 
2.52.0