Re: [PATCH v2 1/3] xen/privcmd: Corrected error handling path

["Jürgen Groß" <jgross@suse.com>]

On 07.07.20 13:40, Souptick Joarder wrote:
> On Tue, Jul 7, 2020 at 3:05 PM Jürgen Groß <jgross@suse.com> wrote:
>>
>> On 06.07.20 20:16, Souptick Joarder wrote:
>>> Previously, if lock_pages() end up partially mapping pages, it used
>>> to return -ERRNO due to which unlock_pages() have to go through
>>> each pages[i] till *nr_pages* to validate them. This can be avoided
>>> by passing correct number of partially mapped pages & -ERRNO separately,
>>> while returning from lock_pages() due to error.
>>>
>>> With this fix unlock_pages() doesn't need to validate pages[i] till
>>> *nr_pages* for error scenario and few condition checks can be ignored.
>>>
>>> Signed-off-by: Souptick Joarder <jrdr.linux@gmail.com>
>>> Cc: John Hubbard <jhubbard@nvidia.com>
>>> Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
>>> Cc: Paul Durrant <xadimgnik@gmail.com>
>>> ---
>>>    drivers/xen/privcmd.c | 31 +++++++++++++++----------------
>>>    1 file changed, 15 insertions(+), 16 deletions(-)
>>>
>>> diff --git a/drivers/xen/privcmd.c b/drivers/xen/privcmd.c
>>> index a250d11..33677ea 100644
>>> --- a/drivers/xen/privcmd.c
>>> +++ b/drivers/xen/privcmd.c
>>> @@ -580,13 +580,13 @@ static long privcmd_ioctl_mmap_batch(
>>>
>>>    static int lock_pages(
>>>        struct privcmd_dm_op_buf kbufs[], unsigned int num,
>>> -     struct page *pages[], unsigned int nr_pages)
>>> +     struct page *pages[], unsigned int nr_pages, unsigned int *pinned)
>>>    {
>>>        unsigned int i;
>>> +     int page_count = 0;
>>
>> Initial value shouldn't be needed, and ...
>>
>>>
>>>        for (i = 0; i < num; i++) {
>>>                unsigned int requested;
>>> -             int pinned;
>>
>> ... you could move the declaration here.
>>
>> With that done you can add my
>>
>> Reviewed-by: Juergen Gross <jgross@suse.com>
> 
> Ok. But does it going make any difference other than limiting scope ?

Dropping the initializer surely does, and in the end page_count just
replaces the former pinned variable, so why would we want to widen the
scope with this patch?


Juergen