linux-kernel - Re: [PATCH] vhost: correctly set bits of dirty pages

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Message-ID: <19699.44942.204823.848838@gargle.gargle.HOWL>
Date:	Mon, 29 Nov 2010 21:50:06 +0800
From:	Jason Wang <jasowang@...hat.com>
To:	"Michael S. Tsirkin" <mst@...hat.com>
Cc:	Jason Wang <jasowang@...hat.com>, virtualization@...ts.osdl.org,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	kvm@...r.kernel.org
Subject: Re: [PATCH] vhost: correctly set bits of dirty pages

Michael S. Tsirkin writes:
 > On Mon, Nov 29, 2010 at 01:48:20PM +0800, Jason Wang wrote:
 > > When counting pages we should increase it by 1 instead of VHOST_PAGE_SIZE,
 > > and also make log_write() can correctly process the request across
 > > pages with write_address not start at page boundary.
 > > 
 > > Signed-off-by: Jason Wang <jasowang@...hat.com>
 > 
 > dd
 > Thanks, good catch!
 > But let's to it in small steps: first, a small patch to fix the bug:
 > I think this is equivalent, right?
 > 

Yes.

 > Subject: vhost: correctly set bits of dirty pages
 > 
 > When counting pages we should increase address by 1 instead of
 > VHOST_PAGE_SIZE, and also make log_write() can correctly process the
 > request across pages with write_address not starting at page boundary.
 > 
 > Reported-by: Jason Wang <jasowang@...hat.com>
 > Signed-off-by: Michael S. Tsirkin <mst@...hat.com>
 > 

I'm fine with this, thanks!

 > ---
 > 
 > diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
 > index 568eb70..d0a3552 100644
 > --- a/drivers/vhost/vhost.c
 > +++ b/drivers/vhost/vhost.c
 > @@ -887,6 +887,7 @@ static int log_write(void __user *log_base,
 >  	int r;
 >  	if (!write_length)
 >  		return 0;
 > +	write_length += write_address % VHOST_PAGE_SIZE;
 >  	write_address /= VHOST_PAGE_SIZE;
 >  	for (;;) {
 >  		u64 base = (u64)(unsigned long)log_base;
 > @@ -900,7 +901,7 @@ static int log_write(void __user *log_base,
 >  		if (write_length <= VHOST_PAGE_SIZE)
 >  			break;
 >  		write_length -= VHOST_PAGE_SIZE;
 > -		write_address += VHOST_PAGE_SIZE;
 > +		write_address += 1;
 >  	}
 >  	return r;
 >  }
 > --
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