[PATCH v4 1/9] mm/mmap: Teach generic_get_unmapped_area{_topdown} to handle hugetlb mappings

[Oscar Salvador]

We want to stop special casing hugetlb mappings and make them go
through generic channels, so teach generic_get_unmapped_area{_topdown}
to handle those.
The main difference is that we set info.align_mask for huge mappings.

Signed-off-by: Oscar Salvador <osalvador@xxxxxxx>
---
 include/linux/hugetlb.h | 10 ++++++++++
 mm/mmap.c               |  4 ++++
 2 files changed, 14 insertions(+)

diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
index e4697539b665..368d552e4860 100644
--- a/include/linux/hugetlb.h
+++ b/include/linux/hugetlb.h
@@ -1035,9 +1035,19 @@ void hugetlb_unregister_node(struct node *node);
  */
 bool is_raw_hwpoison_page_in_hugepage(struct page *page);
 
+static inline unsigned long huge_page_mask_align(struct file *file)
+{
+	return PAGE_MASK & ~huge_page_mask(hstate_file(file));
+}
+
 #else	/* CONFIG_HUGETLB_PAGE */
 struct hstate {};
 
+static inline unsigned long huge_page_mask_align(struct file *file)
+{
+	return 0;
+}
+
 static inline struct hugepage_subpool *hugetlb_folio_subpool(struct folio *folio)
 {
 	return NULL;
diff --git a/mm/mmap.c b/mm/mmap.c
index 9c0fb43064b5..57fd5ab2abe7 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -776,6 +776,8 @@ generic_get_unmapped_area(struct file *filp, unsigned long addr,
 	info.low_limit = mm->mmap_base;
 	info.high_limit = mmap_end;
 	info.start_gap = stack_guard_placement(vm_flags);
+	if (filp && is_file_hugepages(filp))
+		info.align_mask = huge_page_mask_align(filp);
 	return vm_unmapped_area(&info);
 }
 
@@ -826,6 +828,8 @@ generic_get_unmapped_area_topdown(struct file *filp, unsigned long addr,
 	info.low_limit = PAGE_SIZE;
 	info.high_limit = arch_get_mmap_base(addr, mm->mmap_base);
 	info.start_gap = stack_guard_placement(vm_flags);
+	if (filp && is_file_hugepages(filp))
+		info.align_mask = huge_page_mask_align(filp);
 	addr = vm_unmapped_area(&info);
 
 	/*
-- 
2.46.1