On 2019/10/18 2:01, Ira Weiny wrote:
> On Thu, Oct 17, 2019 at 11:19:46AM +0800, zhong jiang wrote:
>> With the help of unsigned_lesser_than_zero.cocci. Unsigned 'nr_pages"'
>> compare with zero. And __get_user_pages_locked will return an long value.
>>
>> The patch use a new local variable to store the return value of
>> __get_user_pages_locked(). Then use it to compare with zero.
>>
>> Suggested-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
>> Signed-off-by: zhong jiang <zhongjiang@xxxxxxxxxx>
>> ---
>> mm/gup.c | 8 +++++---
>> 1 file changed, 5 insertions(+), 3 deletions(-)
>>
>> diff --git a/mm/gup.c b/mm/gup.c
>> index 8f236a3..1fe0ceb 100644
>> --- a/mm/gup.c
>> +++ b/mm/gup.c
>> @@ -1443,6 +1443,7 @@ static long check_and_migrate_cma_pages(struct task_struct *tsk,
>> bool drain_allow = true;
>> bool migrate_allow = true;
>> LIST_HEAD(cma_page_list);
>> + long ret;
>>
>> check_again:
>> for (i = 0; i < nr_pages;) {
>> @@ -1504,17 +1505,18 @@ static long check_and_migrate_cma_pages(struct task_struct *tsk,
>> * again migrating any new CMA pages which we failed to isolate
>> * earlier.
>> */
>> - nr_pages = __get_user_pages_locked(tsk, mm, start, nr_pages,
>> + ret = __get_user_pages_locked(tsk, mm, start, nr_pages,
>> pages, vmas, NULL,
>> gup_flags);
>>
>> - if ((nr_pages > 0) && migrate_allow) {
>> + nr_pages = ret;
> I think if ret is negative we want to return the error here.
I think the code works. Because we alway return the ret. we will return the error value if the ret is negative .
>> + if ((ret > 0) && migrate_allow) {
>> drain_allow = true;
>> goto check_again;
>> }
>> }
>>
>> - return nr_pages;
>> + return ret;
> If the cma_page_list is empty doesn't this return uninitialized data?
You're right. I miss that. Thanks for pointing out.
Sincerely,
zhong jiang
> Ira
>
>> }
>> #else
>> static long check_and_migrate_cma_pages(struct task_struct *tsk,
>> --
>> 1.7.12.4
>>
>>
> .
>
