On 4/28/21 5:26 AM, Muchun Song wrote:
> On Wed, Apr 28, 2021 at 7:47 AM Mike Kravetz <mike.kravetz@xxxxxxxxxx> wrote:
>>
>> Thanks! I will take a look at the modifications soon.
>>
>> I applied the patches to Andrew's mmotm-2021-04-21-23-03, ran some tests and
>> got the following warning. We may need to special case that call to
>> __prep_new_huge_page/free_huge_page_vmemmap from alloc_and_dissolve_huge_page
>> as it is holding hugetlb lock with IRQs disabled.
>
> Good catch. Thanks Mike. I will fix it in the next version. How about this:
>
> @@ -1618,7 +1617,8 @@ static void __prep_new_huge_page(struct hstate
> *h, struct page *page)
>
> static void prep_new_huge_page(struct hstate *h, struct page *page, int nid)
> {
> + free_huge_page_vmemmap(h, page);
> __prep_new_huge_page(page);
> spin_lock_irq(&hugetlb_lock);
> __prep_account_new_huge_page(h, nid);
> spin_unlock_irq(&hugetlb_lock);
> @@ -2429,6 +2429,7 @@ static int alloc_and_dissolve_huge_page(struct
> hstate *h, struct page *old_page,
> if (!new_page)
> return -ENOMEM;
>
> + free_huge_page_vmemmap(h, new_page);
> retry:
> spin_lock_irq(&hugetlb_lock);
> if (!PageHuge(old_page)) {
> @@ -2489,7 +2490,7 @@ static int alloc_and_dissolve_huge_page(struct
> hstate *h, struct page *old_page,
>
> free_new:
> spin_unlock_irq(&hugetlb_lock);
> - __free_pages(new_page, huge_page_order(h));
> + update_and_free_page(h, new_page, false);
>
> return ret;
> }
>
>
Another option would be to leave the prep* routines as is and only
modify alloc_and_dissolve_huge_page as follows:
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 9c617c19fc18..f8e5013a6b46 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -2420,14 +2420,15 @@ static int alloc_and_dissolve_huge_page(struct hstate *h, struct page *old_page,
/*
* Before dissolving the page, we need to allocate a new one for the
- * pool to remain stable. Using alloc_buddy_huge_page() allows us to
- * not having to deal with prep_new_huge_page() and avoids dealing of any
- * counters. This simplifies and let us do the whole thing under the
- * lock.
+ * pool to remain stable. Here, we allocate the page and 'prep' it
+ * by doing everything but actually updating counters and adding to
+ * the pool. This simplifies and let us do most of the processing
+ * under the lock.
*/
new_page = alloc_buddy_huge_page(h, gfp_mask, nid, NULL, NULL);
if (!new_page)
return -ENOMEM;
+ __prep_new_huge_page(h, new_page);
retry:
spin_lock_irq(&hugetlb_lock);
@@ -2473,7 +2474,6 @@ static int alloc_and_dissolve_huge_page(struct hstate *h, struct page *old_page,
* Reference count trick is needed because allocator gives us
* referenced page but the pool requires pages with 0 refcount.
*/
- __prep_new_huge_page(h, new_page);
__prep_account_new_huge_page(h, nid);
page_ref_dec(new_page);
enqueue_huge_page(h, new_page);
@@ -2489,7 +2489,7 @@ static int alloc_and_dissolve_huge_page(struct hstate *h, struct page *old_page,
free_new:
spin_unlock_irq(&hugetlb_lock);
- __free_pages(new_page, huge_page_order(h));
+ update_and_free_page(h, old_page, false);
return ret;
}
--
Mike Kravetz
