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SubjectRe: [PATCH] vhost: correctly set bits of dirty pages
On Mon, Nov 29, 2010 at 10:18:40AM +0200, Michael S. Tsirkin wrote:
> 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@redhat.com>
>
>
> 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?
>
> 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@redhat.com>
> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

And then this on top:


vhost: better variable name in logging

We really store a page offset in write_address,
so rename it write_page to avoid confusion.

Signed-off-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

---

diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index d0a3552..1a3d3ed 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -884,15 +884,15 @@ static int set_bit_to_user(int nr, void __user *addr)
static int log_write(void __user *log_base,
u64 write_address, u64 write_length)
{
+ u64 write_page = write_address / VHOST_PAGE_SIZE
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;
- u64 log = base + write_address / 8;
- int bit = write_address % 8;
+ u64 log = base + write_page / 8;
+ int bit = write_page % 8;
if ((u64)(unsigned long)log != log)
return -EFAULT;
r = set_bit_to_user(bit, (void __user *)(unsigned long)log);
@@ -901,7 +901,7 @@ static int log_write(void __user *log_base,
if (write_length <= VHOST_PAGE_SIZE)
break;
write_length -= VHOST_PAGE_SIZE;
- write_address += 1;
+ write_page += 1;
}
return r;
}

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