Re: [Xen-devel] [PATCH] linux_gntshr_munmap: munmap takes a length, not a page count

[Dave Scott <Dave.Scott@xxxxxxxxxx>]

On 3 Sep 2014, at 15:01, Ian Campbell <Ian.Campbell@xxxxxxxxxx> wrote:

> On Mon, 2014-09-01 at 13:16 +0100, David Scott wrote:
>> This fixes a bug where if a client shares more than 1 page, the
>> munmap call fails to clean up everything. A process which does
>> a lot of sharing and unsharing can run out of resources.
> 
> The doc comment on xc_gntshr_munmap does say count is in pages, so your
> change is correct but all of the in tree callers seem to pass a number
> of bytes not a number of pages. i.e. everything in tools/libvchan passes
> n*PAGE_SIZE.

Good point.

> So I don't think this change is complete without also updating those.

I’ll resubmit with the in-tree callers fixed.

Thanks,
Dave

> 
> Ian.
> 
>> 
>> Signed-off-by: David Scott <dave.scott@xxxxxxxxxx>
>> ---
>> tools/libxc/xc_linux_osdep.c |    2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>> 
>> diff --git a/tools/libxc/xc_linux_osdep.c b/tools/libxc/xc_linux_osdep.c
>> index 86bff3e..a19e4b6 100644
>> --- a/tools/libxc/xc_linux_osdep.c
>> +++ b/tools/libxc/xc_linux_osdep.c
>> @@ -847,7 +847,7 @@ static void *linux_gntshr_share_pages(xc_gntshr *xch, 
>> xc_osdep_handle h,
>> static int linux_gntshr_munmap(xc_gntshr *xcg, xc_osdep_handle h,
>>                                void *start_address, uint32_t count)
>> {
>> -    return munmap(start_address, count);
>> +    return munmap(start_address, count * XC_PAGE_SIZE);
>> }
>> 
>> static struct xc_osdep_ops linux_gntshr_ops = {
> 
> 


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