Messages in this thread | | | Subject | Re: [PATCH v1 2/6] mm/hwpoison: remove race consideration | From | Ding Hui <> | Date | Wed, 16 Jun 2021 08:40:58 +0800 |
| |
On 2021/6/16 8:11, HORIGUCHI NAOYA(堀口 直也) wrote: > On Tue, Jun 15, 2021 at 08:57:06PM +0800, Ding Hui wrote: >> On 2021/6/14 10:12, Naoya Horiguchi wrote: >>> @@ -1956,17 +1938,6 @@ int unpoison_memory(unsigned long pfn) >>> goto unlock_mutex; >>> } >>> - /* >>> - * unpoison_memory() can encounter thp only when the thp is being >>> - * worked by memory_failure() and the page lock is not held yet. >>> - * In such case, we yield to memory_failure() and make unpoison fail. >>> - */ >>> - if (!PageHuge(page) && PageTransHuge(page)) { >>> - unpoison_pr_info("Unpoison: Memory failure is now running on %#lx\n", >>> - pfn, &unpoison_rs); >>> - goto unlock_mutex; >>> - } >>> - >> >> if a huge page is in process of alloc or free, HUGETLB_PAGE_DTOR can be set >> after __SetPageHead() or be cleared before __ClearPageHead(), so this >> condition may be true in racy. > > Hi Ding, > > We confirm PageHWPoison() before reaching this if-block and hwpoisoned pages > are prohibited from allocation, so it seems to me that this check never > races with hugetlb allocation. > > And according to the original patch introduced this if-block (0cea3fdc416d: > "mm/hwpoison: fix race against poison thp"), this if-block intended to close > the race between memory_failure() and unpoison_memory(), so that's no longer > necessary due to mf_mutex. >
I got it and thanks for your explanation.
>> Do we need the racy test for this situation? > > I'm not sure, but I think that we need more stress/fuzz testing focusing on > this subsystem, and "unpoison vs allocation" race can be covered in the topic. > > Thank you, > Naoya Horiguchi >
-- Thanks, - Ding Hui
| |