linux-kernel - [PATCH] KVM x86: remove memset, use vzalloc and don't assign the same value to a variable twice

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Date:	Sat, 30 Oct 2010 20:28:17 +0200 (CEST)
From:	Jesper Juhl <jj@...osbits.net>
To:	kvm@...r.kernel.org
cc:	Avi Kivity <avi@...hat.com>, Avi Kivity <avi@...ranet.com>,
	Marcelo Tosatti <mtosatti@...hat.com>,
	Yaniv Kamay <yaniv@...ranet.com>,
	Amit Shah <amit.shah@...ranet.com>,
	Ben-Ami Yassour <benami@...ibm.com>,
	linux-kernel@...r.kernel.org
Subject: [PATCH] KVM x86: remove memset, use vzalloc and don't assign the
 same value to a variable twice

Hi,

We can improve kvm_vm_ioctl_get_dirty_log() slightly by using vzalloc() 
rather than first allocating and then manually zero the memory with 
memset(). Also, while I was looking at this I noticed that we assign 
-ENOMEM to the 'r' variable twice even though none of the code inbetween 
the two assignments can change 'r', so I removed the second assignment.

Patch has been compile tested only.

Please consider merging and please CC me on all replies as I'm not 
subscribed to the kvm mailing list.


Signed-off-by: Jesper Juhl <jj@...osbits.net>
---
 x86.c |    4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 2288ad8..29f9c0a 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -3174,12 +3174,10 @@ int kvm_vm_ioctl_get_dirty_log(struct kvm *kvm,
 		spin_unlock(&kvm->mmu_lock);
 
 		r = -ENOMEM;
-		dirty_bitmap = vmalloc(n);
+		dirty_bitmap = vzalloc(n);
 		if (!dirty_bitmap)
 			goto out;
-		memset(dirty_bitmap, 0, n);
 
-		r = -ENOMEM;
 		slots = kzalloc(sizeof(struct kvm_memslots), GFP_KERNEL);
 		if (!slots) {
 			vfree(dirty_bitmap);


-- 
Jesper Juhl <jj@...osbits.net>             http://www.chaosbits.net/
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