linux-kernel - [RFC PATCH 1/8] mm/mmap: Teach generic_get_unmapped_area{

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Message-ID: <20240710105042.30165-2-osalvador@suse.de>
Date: Wed, 10 Jul 2024 12:50:35 +0200
From: Oscar Salvador <osalvador@...e.de>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: linux-kernel@...r.kernel.org,
	linux-mm@...ck.org,
	Muchun Song <muchun.song@...ux.dev>,
	David Hildenbrand <david@...hat.com>,
	Michal Hocko <mhocko@...e.com>,
	Donet Tom <donettom@...ux.ibm.com>,
	"Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
	Matthew Wilcox <willy@...radead.org>,
	Vlastimil Babka <vbabka@...e.cz>,
	Oscar Salvador <osalvador@...e.de>
Subject: [RFC PATCH 1/8] mm/mmap: Teach generic_get_unmapped_area{_topdown} to handle hugetlb mappings

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@...e.de>
---
 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 2b3c3a404769..1c7b0b32ff7e 100644
--- a/include/linux/hugetlb.h
+++ b/include/linux/hugetlb.h
@@ -1029,9 +1029,19 @@ 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 83b4682ec85c..09131b705e7b 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -1743,6 +1743,8 @@ generic_get_unmapped_area(struct file *filp, unsigned long addr,
 	info.length = len;
 	info.low_limit = mm->mmap_base;
 	info.high_limit = mmap_end;
+	if (filp && is_file_hugepages(filp))
+		info.align_mask = huge_page_mask_align(filp);
 	return vm_unmapped_area(&info);
 }
 
@@ -1791,6 +1793,8 @@ generic_get_unmapped_area_topdown(struct file *filp, unsigned long addr,
 	info.length = len;
 	info.low_limit = PAGE_SIZE;
 	info.high_limit = arch_get_mmap_base(addr, mm->mmap_base);
+	if (filp && is_file_hugepages(filp))
+		info.align_mask = huge_page_mask_align(filp);
 	addr = vm_unmapped_area(&info);
 
 	/*
-- 
2.45.2