linux-kernel - [PATCH 4/4] KVM: Remove unused dirty_bitmap_head and nr_dirty

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Message-Id: <20120223203632.cc79abe2.yoshikawa.takuya@oss.ntt.co.jp>
Date:	Thu, 23 Feb 2012 20:36:32 +0900
From:	Takuya Yoshikawa <yoshikawa.takuya@....ntt.co.jp>
To:	avi@...hat.com, mtosatti@...hat.com
Cc:	kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
	peterz@...radead.org, paulmck@...ux.vnet.ibm.com
Subject: [PATCH 4/4] KVM: Remove unused dirty_bitmap_head and nr_dirty_pages

Now that we do neither double buffering nor heuristic selection of the
write protection method these are not needed anymore.

Note: some drivers have their own implementation of set_bit_le() and
making it generic needs a bit of work; so we use test_and_set_bit_le()
and will later replace it with generic set_bit_le().

Signed-off-by: Takuya Yoshikawa <yoshikawa.takuya@....ntt.co.jp>
---
 include/linux/kvm_host.h |    2 --
 virt/kvm/kvm_main.c      |   14 +++++---------
 2 files changed, 5 insertions(+), 11 deletions(-)

diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 355e445..73c7d76 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -177,8 +177,6 @@ struct kvm_memory_slot {
 	unsigned long flags;
 	unsigned long *rmap;
 	unsigned long *dirty_bitmap;
-	unsigned long *dirty_bitmap_head;
-	unsigned long nr_dirty_pages;
 	struct kvm_arch_memory_slot arch;
 	unsigned long userspace_addr;
 	int user_alloc;
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index e4431ad..27a1083 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -522,12 +522,11 @@ static void kvm_destroy_dirty_bitmap(struct kvm_memory_slot *memslot)
 		return;
 
 	if (2 * kvm_dirty_bitmap_bytes(memslot) > PAGE_SIZE)
-		vfree(memslot->dirty_bitmap_head);
+		vfree(memslot->dirty_bitmap);
 	else
-		kfree(memslot->dirty_bitmap_head);
+		kfree(memslot->dirty_bitmap);
 
 	memslot->dirty_bitmap = NULL;
-	memslot->dirty_bitmap_head = NULL;
 }
 
 /*
@@ -611,8 +610,7 @@ static int kvm_vm_release(struct inode *inode, struct file *filp)
 
 /*
  * Allocation size is twice as large as the actual dirty bitmap size.
- * This makes it possible to do double buffering: see x86's
- * kvm_vm_ioctl_get_dirty_log().
+ * See x86's kvm_vm_ioctl_get_dirty_log() why this is needed.
  */
 static int kvm_create_dirty_bitmap(struct kvm_memory_slot *memslot)
 {
@@ -627,8 +625,6 @@ static int kvm_create_dirty_bitmap(struct kvm_memory_slot *memslot)
 	if (!memslot->dirty_bitmap)
 		return -ENOMEM;
 
-	memslot->dirty_bitmap_head = memslot->dirty_bitmap;
-	memslot->nr_dirty_pages = 0;
 #endif /* !CONFIG_S390 */
 	return 0;
 }
@@ -1476,8 +1472,8 @@ void mark_page_dirty_in_slot(struct kvm *kvm, struct kvm_memory_slot *memslot,
 	if (memslot && memslot->dirty_bitmap) {
 		unsigned long rel_gfn = gfn - memslot->base_gfn;
 
-		if (!test_and_set_bit_le(rel_gfn, memslot->dirty_bitmap))
-			memslot->nr_dirty_pages++;
+		/* TODO: introduce set_bit_le() and use it */
+		test_and_set_bit_le(rel_gfn, memslot->dirty_bitmap);
 	}
 }
 
-- 
1.7.5.4

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