linux-kernel - [PATCH v2 3/4] mm/hugetlb: make hugetlb migration callback CMA aware

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Date:   Mon, 20 Jul 2020 13:56:17 +0900
From:   js1304@...il.com
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        kernel-team@....com, Vlastimil Babka <vbabka@...e.cz>,
        Christoph Hellwig <hch@...radead.org>,
        Roman Gushchin <guro@...com>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
        Michal Hocko <mhocko@...e.com>,
        "Aneesh Kumar K . V" <aneesh.kumar@...ux.ibm.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>
Subject: [PATCH v2 3/4] mm/hugetlb: make hugetlb migration callback CMA aware

From: Joonsoo Kim <iamjoonsoo.kim@....com>

new_non_cma_page() in gup.c requires to allocate the new page that is not
on the CMA area. new_non_cma_page() implements it by using allocation
scope APIs.

However, there is a work-around for hugetlb. Normal hugetlb page
allocation API for migration is alloc_huge_page_nodemask(). It consists
of two steps. First is dequeing from the pool. Second is, if there is no
available page on the queue, allocating by using the page allocator.

new_non_cma_page() can't use this API since first step (deque) isn't
aware of scope API to exclude CMA area. So, new_non_cma_page() exports
hugetlb internal function for the second step, alloc_migrate_huge_page(),
to global scope and uses it directly. This is suboptimal since hugetlb
pages on the queue cannot be utilized.

This patch tries to fix this situation by making the deque function on
hugetlb CMA aware. In the deque function, CMA memory is skipped if
PF_MEMALLOC_NOCMA flag is found.

Acked-by: Mike Kravetz <mike.kravetz@...cle.com>
Acked-by: Vlastimil Babka <vbabka@...e.cz>
Acked-by: Michal Hocko <mhocko@...e.com>
Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@....com>
---
 include/linux/hugetlb.h |  2 --
 mm/gup.c                |  6 +-----
 mm/hugetlb.c            | 11 +++++++++--
 3 files changed, 10 insertions(+), 9 deletions(-)

diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
index 2660b04..fb2b5aa 100644
--- a/include/linux/hugetlb.h
+++ b/include/linux/hugetlb.h
@@ -509,8 +509,6 @@ struct page *alloc_huge_page_nodemask(struct hstate *h, int preferred_nid,
 				nodemask_t *nmask, gfp_t gfp_mask);
 struct page *alloc_huge_page_vma(struct hstate *h, struct vm_area_struct *vma,
 				unsigned long address);
-struct page *alloc_migrate_huge_page(struct hstate *h, gfp_t gfp_mask,
-				     int nid, nodemask_t *nmask);
 int huge_add_to_page_cache(struct page *page, struct address_space *mapping,
 			pgoff_t idx);
 
diff --git a/mm/gup.c b/mm/gup.c
index bbd36a1..4ba822a 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -1634,11 +1634,7 @@ static struct page *new_non_cma_page(struct page *page, unsigned long private)
 		struct hstate *h = page_hstate(page);
 
 		gfp_mask = htlb_modify_alloc_mask(h, gfp_mask);
-		/*
-		 * We don't want to dequeue from the pool because pool pages will
-		 * mostly be from the CMA region.
-		 */
-		return alloc_migrate_huge_page(h, gfp_mask, nid, NULL);
+		return alloc_huge_page_nodemask(h, nid, NULL, gfp_mask);
 	}
 #endif
 	if (PageTransHuge(page)) {
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 3245aa0..d9eb923 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -29,6 +29,7 @@
 #include <linux/numa.h>
 #include <linux/llist.h>
 #include <linux/cma.h>
+#include <linux/sched/mm.h>
 
 #include <asm/page.h>
 #include <asm/tlb.h>
@@ -1036,10 +1037,16 @@ static void enqueue_huge_page(struct hstate *h, struct page *page)
 static struct page *dequeue_huge_page_node_exact(struct hstate *h, int nid)
 {
 	struct page *page;
+	bool nocma = !!(current->flags & PF_MEMALLOC_NOCMA);
+
+	list_for_each_entry(page, &h->hugepage_freelists[nid], lru) {
+		if (nocma && is_migrate_cma_page(page))
+			continue;
 
-	list_for_each_entry(page, &h->hugepage_freelists[nid], lru)
 		if (!PageHWPoison(page))
 			break;
+	}
+
 	/*
 	 * if 'non-isolated free hugepage' not found on the list,
 	 * the allocation fails.
@@ -1928,7 +1935,7 @@ static struct page *alloc_surplus_huge_page(struct hstate *h, gfp_t gfp_mask,
 	return page;
 }
 
-struct page *alloc_migrate_huge_page(struct hstate *h, gfp_t gfp_mask,
+static struct page *alloc_migrate_huge_page(struct hstate *h, gfp_t gfp_mask,
 				     int nid, nodemask_t *nmask)
 {
 	struct page *page;
-- 
2.7.4