On 2025/1/20 16:46, David Hildenbrand wrote:
> On 20.01.25 08:49, David Hildenbrand wrote:
>>
>>>> if (folio_test_hugetlb(folio) && !folio_test_anon(folio)) {
>>>> struct address_space *mapping;
>>>> @@ -1572,7 +1598,7 @@ void unmap_poisoned_folio(struct folio *folio, enum ttu_flags ttu)
>>>> if (!mapping) {
>>>> pr_info("%#lx: could not lock mapping for mapped hugetlb folio\n",
>>>> folio_pfn(folio));
>>>> - return;
>>>> + return -EBUSY;
>>>> }
>>>> try_to_unmap(folio, ttu|TTU_RMAP_LOCKED);
>>>> @@ -1580,6 +1606,8 @@ void unmap_poisoned_folio(struct folio *folio, enum ttu_flags ttu)
>>>> } else {
>>>> try_to_unmap(folio, ttu);
>>>> }
>>>> +
>>>> + return folio_mapped(folio) ? -EBUSY : 0;
>>>
>>> Do we really need this return value? It's unused in do_migrate_range().
>>
>> I suggested it, because the folio_mapped() is nowadays extremely cheap.
>> It cleans up hwpoison_user_mappings() quite nicely.
>
> I'm also wondering, if in do_migrate_range(), we want to pr_warn_ratelimit() in case still mapped after the call. IIUC, we don't really expect this to happen with SYNC set.
Do you mean TTU_SYNC? It seems it's not set.
There might be a race will hit the proposed pr_warn_ratelimit():
/* Assume folio is isolated for reclaim, so memory_failure failed to handle it at first time. Then it's put back to LRU. */
do_migrate_range
folio_test_hwpoison
folio_mapped
<folio is isolated for reclaim again.>
unmap_poisoned_folio
<folio is put buck.>
pr_warn_ratelimit(folio_mapped)
But I might be miss something. And even this race is possible, it should be really hard to hit.
Thanks.
.
