hugetlb, mempolicy: fix the mbind hugetlb migration

do_mbind migration code relies on alloc_huge_page_noerr for hugetlb
pages.  alloc_huge_page_noerr uses alloc_huge_page which is a highlevel
allocation function which has to take care of reserves, overcommit or
hugetlb cgroup accounting.  None of that is really required for the page
migration because the new page is only temporal and either will replace
the original page or it will be dropped.  This is essentially as for
other migration call paths and there shouldn't be any reason to handle
mbind in a special way.

The current implementation is even suboptimal because the migration
might fail just because the hugetlb cgroup limit is reached, or the
overcommit is saturated.

Fix this by making mbind like other hugetlb migration paths.  Add a new
migration helper alloc_huge_page_vma as a wrapper around
alloc_huge_page_nodemask with additional mempolicy handling.

alloc_huge_page_noerr has no more users and it can go.

Link: http://lkml.kernel.org/r/20180103093213.26329-7-mhocko@kernel.org
Signed-off-by: Michal Hocko <mhocko@suse.com>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Reviewed-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Andrea Reale <ar@linux.vnet.ibm.com>
Cc: Anshuman Khandual <khandual@linux.vnet.ibm.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Zi Yan <zi.yan@cs.rutgers.edu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 20 insertions, 16 deletions

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index b55886af82aa..742a929f2311 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -1674,6 +1674,25 @@ struct page *alloc_huge_page_nodemask(struct hstate *h, int preferred_nid,
 	return alloc_migrate_huge_page(h, gfp_mask, preferred_nid, nmask);
 }
 
+/* mempolicy aware migration callback */
+struct page *alloc_huge_page_vma(struct vm_area_struct *vma, unsigned long address)
+{
+	struct mempolicy *mpol;
+	nodemask_t *nodemask;
+	struct page *page;
+	struct hstate *h;
+	gfp_t gfp_mask;
+	int node;
+
+	h = hstate_vma(vma);
+	gfp_mask = htlb_alloc_mask(h);
+	node = huge_node(vma, address, gfp_mask, &mpol, &nodemask);
+	page = alloc_huge_page_nodemask(h, node, nodemask);
+	mpol_cond_put(mpol);
+
+	return page;
+}
+
 /*
  * Increase the hugetlb pool such that it can accommodate a reservation
  * of size 'delta'.
@@ -2079,20 +2098,6 @@ out_subpool_put:
 	return ERR_PTR(-ENOSPC);
 }
 
-/*
- * alloc_huge_page()'s wrapper which simply returns the page if allocation
- * succeeds, otherwise NULL. This function is called from new_vma_page(),
- * where no ERR_VALUE is expected to be returned.
- */
-struct page *alloc_huge_page_noerr(struct vm_area_struct *vma,
-				unsigned long addr, int avoid_reserve)
-{
-	struct page *page = alloc_huge_page(vma, addr, avoid_reserve);
-	if (IS_ERR(page))
-		page = NULL;
-	return page;
-}
-
 int alloc_bootmem_huge_page(struct hstate *h)
 	__attribute__ ((weak, alias("__alloc_bootmem_huge_page")));
 int __alloc_bootmem_huge_page(struct hstate *h)
diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index f604b22ebb65..96823fa07f38 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -1121,8 +1121,7 @@ static struct page *new_page(struct page *page, unsigned long start, int **x)
 	}
 
 	if (PageHuge(page)) {
-		BUG_ON(!vma);
-		return alloc_huge_page_noerr(vma, address, 1);
+		return alloc_huge_page_vma(vma, address);
 	} else if (thp_migration_supported() && PageTransHuge(page)) {
 		struct page *thp;