[PATCH v3] mm/mempolicy,hugetlb: Checking hstate for hugetlbfs page in vma_migratable

[Li Xinhai <lixinhai.lxh@gmail.com>]

Checking hstate at early phase when isolating page, instead of during
unmap and move phase, to avoid useless isolation.

Signed-off-by: Li Xinhai <lixinhai.lxh@gmail.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
---
 include/linux/hugetlb_inline.h | 7 +++++++
 include/linux/mempolicy.h      | 5 ++---
 mm/hugetlb.c                   | 9 +++++++++
 3 files changed, 18 insertions(+), 3 deletions(-)

diff --git a/include/linux/hugetlb_inline.h b/include/linux/hugetlb_inline.h
index 0660a03..fc07139 100644
--- a/include/linux/hugetlb_inline.h
+++ b/include/linux/hugetlb_inline.h
@@ -11,6 +11,8 @@ static inline bool is_vm_hugetlb_page(struct vm_area_struct *vma)
 	return !!(vma->vm_flags & VM_HUGETLB);
 }
 
+extern bool vm_hugepage_migration_supported(struct vm_area_struct *vma);
+
 #else
 
 static inline bool is_vm_hugetlb_page(struct vm_area_struct *vma)
@@ -18,6 +20,11 @@ static inline bool is_vm_hugetlb_page(struct vm_area_struct *vma)
 	return false;
 }
 
+static inline bool vm_hugepage_migration_supported(struct vm_area_struct *vma)
+{
+	return false;
+}
+
 #endif
 
 #endif
diff --git a/include/linux/mempolicy.h b/include/linux/mempolicy.h
index 5228c62..e9ed49e 100644
--- a/include/linux/mempolicy.h
+++ b/include/linux/mempolicy.h
@@ -185,10 +185,9 @@ static inline bool vma_migratable(struct vm_area_struct *vma)
 	if (vma_is_dax(vma))
 		return false;
 
-#ifndef CONFIG_ARCH_ENABLE_HUGEPAGE_MIGRATION
-	if (vma->vm_flags & VM_HUGETLB)
+	if (is_vm_hugetlb_page(vma) &&
+		!vm_hugepage_migration_supported(vma))
 		return false;
-#endif
 
 	/*
 	 * Migration allocates pages in the highest zone. If we cannot
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index dd8737a..8ce4a98 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -1316,6 +1316,15 @@ int PageHeadHuge(struct page *page_head)
 	return get_compound_page_dtor(page_head) == free_huge_page;
 }
 
+bool vm_hugepage_migration_supported(struct vm_area_struct *vma)
+{
+	VM_BUG_ON_VMA(!is_vm_hugetlb_page(vma), vma);
+	if (hugepage_migration_supported(hstate_vma(vma)))
+		return true;
+
+	return false;
+}
+
 pgoff_t __basepage_index(struct page *page)
 {
 	struct page *page_head = compound_head(page);
-- 
1.8.3.1