[v5,4/8] hugetlb: create remove_hugetlb_page() to separate functionality

Commit Message

Mike Kravetz April 9, 2021, 8:52 p.m. UTC

The new remove_hugetlb_page() routine is designed to remove a hugetlb
page from hugetlbfs processing.  It will remove the page from the active
or free list, update global counters and set the compound page
destructor to NULL so that PageHuge() will return false for the 'page'.
After this call, the 'page' can be treated as a normal compound page or
a collection of base size pages.

update_and_free_page no longer decrements h->nr_huge_pages{_node} as
this is performed in remove_hugetlb_page.  The only functionality
performed by update_and_free_page is to free the base pages to the lower
level allocators.

update_and_free_page is typically called after remove_hugetlb_page.

remove_hugetlb_page is to be called with the hugetlb_lock held.

Creating this routine and separating functionality is in preparation for
restructuring code to reduce lock hold times.  This commit should not
introduce any changes to functionality.

Signed-off-by: Mike Kravetz <[e-mail]>
Acked-by: Michal Hocko <[e-mail]>
Reviewed-by: Miaohe Lin <[e-mail]>
Reviewed-by: Muchun Song <[e-mail]>
---
 mm/hugetlb.c | 65 ++++++++++++++++++++++++++++++++--------------------
 1 file changed, 40 insertions(+), 25 deletions(-)

Comments

Oscar Salvador April 12, 2021, 7:33 a.m. UTC | #1

On Fri, Apr 09, 2021 at 01:52:50PM -0700, Mike Kravetz wrote:
> The new remove_hugetlb_page() routine is designed to remove a hugetlb
> page from hugetlbfs processing.  It will remove the page from the active
> or free list, update global counters and set the compound page
> destructor to NULL so that PageHuge() will return false for the 'page'.
> After this call, the 'page' can be treated as a normal compound page or
> a collection of base size pages.
> 
> update_and_free_page no longer decrements h->nr_huge_pages{_node} as
> this is performed in remove_hugetlb_page.  The only functionality
> performed by update_and_free_page is to free the base pages to the lower
> level allocators.
> 
> update_and_free_page is typically called after remove_hugetlb_page.
> 
> remove_hugetlb_page is to be called with the hugetlb_lock held.
> 
> Creating this routine and separating functionality is in preparation for
> restructuring code to reduce lock hold times.  This commit should not
> introduce any changes to functionality.
> 
> Signed-off-by: Mike Kravetz <[e-mail]>
> Acked-by: Michal Hocko <[e-mail]>
> Reviewed-by: Miaohe Lin <[e-mail]>
> Reviewed-by: Muchun Song <[e-mail]>

Reviewed-by: Oscar Salvador <[e-mail]>

A "nit" below:

>  static void update_and_free_page(struct hstate *h, struct page *page)
>  {
>  	int i;
> @@ -1334,8 +1369,6 @@ static void update_and_free_page(struct hstate *h, struct page *page)

After this, update_and_free_page()'s job is to reset subpage's flags and free
the page.
Maybe we want to rename that function at some point, or maybe not as "update" might
already imply that. Just speaking out loud.

Mike Kravetz April 12, 2021, 6:03 p.m. UTC | #2

On 4/12/21 12:33 AM, Oscar Salvador wrote:
> On Fri, Apr 09, 2021 at 01:52:50PM -0700, Mike Kravetz wrote:
>> The new remove_hugetlb_page() routine is designed to remove a hugetlb
>> page from hugetlbfs processing.  It will remove the page from the active
>> or free list, update global counters and set the compound page
>> destructor to NULL so that PageHuge() will return false for the 'page'.
>> After this call, the 'page' can be treated as a normal compound page or
>> a collection of base size pages.
>>
>> update_and_free_page no longer decrements h->nr_huge_pages{_node} as
>> this is performed in remove_hugetlb_page.  The only functionality
>> performed by update_and_free_page is to free the base pages to the lower
>> level allocators.
>>
>> update_and_free_page is typically called after remove_hugetlb_page.
>>
>> remove_hugetlb_page is to be called with the hugetlb_lock held.
>>
>> Creating this routine and separating functionality is in preparation for
>> restructuring code to reduce lock hold times.  This commit should not
>> introduce any changes to functionality.
>>
>> Signed-off-by: Mike Kravetz <[e-mail]>
>> Acked-by: Michal Hocko <[e-mail]>
>> Reviewed-by: Miaohe Lin <[e-mail]>
>> Reviewed-by: Muchun Song <[e-mail]>
> 
> Reviewed-by: Oscar Salvador <[e-mail]>
> 
> A "nit" below:
> 
>>  static void update_and_free_page(struct hstate *h, struct page *page)
>>  {
>>  	int i;
>> @@ -1334,8 +1369,6 @@ static void update_and_free_page(struct hstate *h, struct page *page)
> 
> After this, update_and_free_page()'s job is to reset subpage's flags and free
> the page.
> Maybe we want to rename that function at some point, or maybe not as "update" might
> already imply that. Just speaking out loud.

Thanks Oscar,

I did not think about a name change as the routine is still "updating"
subpages before freeing.  We can certainly keep this in mind in the future,
especially if there are more functionality changes.

Patch

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index c8799a480784..773081709916 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -1326,6 +1326,41 @@  static inline void destroy_compound_gigantic_page(struct page *page,
 						unsigned int order) { }
 #endif
 
+/*
+ * Remove hugetlb page from lists, and update dtor so that page appears
+ * as just a compound page.  A reference is held on the page.
+ *
+ * Must be called with hugetlb lock held.
+ */
+static void remove_hugetlb_page(struct hstate *h, struct page *page,
+							bool adjust_surplus)
+{
+	int nid = page_to_nid(page);
+
+	VM_BUG_ON_PAGE(hugetlb_cgroup_from_page(page), page);
+	VM_BUG_ON_PAGE(hugetlb_cgroup_from_page_rsvd(page), page);
+
+	if (hstate_is_gigantic(h) && !gigantic_page_runtime_supported())
+		return;
+
+	list_del(&page->lru);
+
+	if (HPageFreed(page)) {
+		h->free_huge_pages--;
+		h->free_huge_pages_node[nid]--;
+	}
+	if (adjust_surplus) {
+		h->surplus_huge_pages--;
+		h->surplus_huge_pages_node[nid]--;
+	}
+
+	set_page_refcounted(page);
+	set_compound_page_dtor(page, NULL_COMPOUND_DTOR);
+
+	h->nr_huge_pages--;
+	h->nr_huge_pages_node[nid]--;
+}
+
 static void update_and_free_page(struct hstate *h, struct page *page)
 {
 	int i;
@@ -1334,8 +1369,6 @@  static void update_and_free_page(struct hstate *h, struct page *page)
 	if (hstate_is_gigantic(h) && !gigantic_page_runtime_supported())
 		return;
 
-	h->nr_huge_pages--;
-	h->nr_huge_pages_node[page_to_nid(page)]--;
 	for (i = 0; i < pages_per_huge_page(h);
 	     i++, subpage = mem_map_next(subpage, page, i)) {
 		subpage->flags &= ~(1 << PG_locked | 1 << PG_error |
@@ -1343,10 +1376,6 @@  static void update_and_free_page(struct hstate *h, struct page *page)
 				1 << PG_active | 1 << PG_private |
 				1 << PG_writeback);
 	}
-	VM_BUG_ON_PAGE(hugetlb_cgroup_from_page(page), page);
-	VM_BUG_ON_PAGE(hugetlb_cgroup_from_page_rsvd(page), page);
-	set_compound_page_dtor(page, NULL_COMPOUND_DTOR);
-	set_page_refcounted(page);
 	if (hstate_is_gigantic(h)) {
 		destroy_compound_gigantic_page(page, huge_page_order(h));
 		free_gigantic_page(page, huge_page_order(h));
@@ -1414,15 +1443,12 @@  static void __free_huge_page(struct page *page)
 		h->resv_huge_pages++;
 
 	if (HPageTemporary(page)) {
-		list_del(&page->lru);
-		ClearHPageTemporary(page);
+		remove_hugetlb_page(h, page, false);
 		update_and_free_page(h, page);
 	} else if (h->surplus_huge_pages_node[nid]) {
 		/* remove the page from active list */
-		list_del(&page->lru);
+		remove_hugetlb_page(h, page, true);
 		update_and_free_page(h, page);
-		h->surplus_huge_pages--;
-		h->surplus_huge_pages_node[nid]--;
 	} else {
 		arch_clear_hugepage_flags(page);
 		enqueue_huge_page(h, page);
@@ -1707,13 +1733,7 @@  static int free_pool_huge_page(struct hstate *h, nodemask_t *nodes_allowed,
 			struct page *page =
 				list_entry(h->hugepage_freelists[node].next,
 					  struct page, lru);
-			list_del(&page->lru);
-			h->free_huge_pages--;
-			h->free_huge_pages_node[node]--;
-			if (acct_surplus) {
-				h->surplus_huge_pages--;
-				h->surplus_huge_pages_node[node]--;
-			}
+			remove_hugetlb_page(h, page, acct_surplus);
 			update_and_free_page(h, page);
 			ret = 1;
 			break;
@@ -1751,7 +1771,6 @@  int dissolve_free_huge_page(struct page *page)
 	if (!page_count(page)) {
 		struct page *head = compound_head(page);
 		struct hstate *h = page_hstate(head);
-		int nid = page_to_nid(head);
 		if (h->free_huge_pages - h->resv_huge_pages == 0)
 			goto out;
 
@@ -1782,9 +1801,7 @@  int dissolve_free_huge_page(struct page *page)
 			SetPageHWPoison(page);
 			ClearPageHWPoison(head);
 		}
-		list_del(&head->lru);
-		h->free_huge_pages--;
-		h->free_huge_pages_node[nid]--;
+		remove_hugetlb_page(h, page, false);
 		h->max_huge_pages--;
 		update_and_free_page(h, head);
 		rc = 0;
@@ -2552,10 +2569,8 @@  static void try_to_free_low(struct hstate *h, unsigned long count,
 				return;
 			if (PageHighMem(page))
 				continue;
-			list_del(&page->lru);
+			remove_hugetlb_page(h, page, false);
 			update_and_free_page(h, page);
-			h->free_huge_pages--;
-			h->free_huge_pages_node[page_to_nid(page)]--;
 		}
 	}
 }