[PATCH RFC 21/37] mm: khugepaged: Handle metadata-enabled VMAs

[Alexandru Elisei <alexandru.elisei@xxxxxxx>]

Both madvise(MADV_COLLAPSE) and khugepaged can collapse a contiguous
THP-sized memory region mapped as PTEs into a THP. If metadata is enabled for
the VMA where the PTEs are mapped, make sure to allocate metadata storage for
the compound page that will be replacing them.

Signed-off-by: Alexandru Elisei <alexandru.elisei@xxxxxxx>
---
 arch/arm64/include/asm/memory_metadata.h | 7 +++++++
 include/asm-generic/memory_metadata.h    | 4 ++++
 mm/khugepaged.c                          | 7 +++++++
 3 files changed, 18 insertions(+)

diff --git a/arch/arm64/include/asm/memory_metadata.h b/arch/arm64/include/asm/memory_metadata.h
index 1b18e3217dd0..ade37331a5c8 100644
--- a/arch/arm64/include/asm/memory_metadata.h
+++ b/arch/arm64/include/asm/memory_metadata.h
@@ -5,6 +5,8 @@
 #ifndef __ASM_MEMORY_METADATA_H
 #define __ASM_MEMORY_METADATA_H
 
+#include <linux/mm.h>
+
 #include <asm-generic/memory_metadata.h>
 
 #include <asm/mte.h>
@@ -40,6 +42,11 @@ static inline int reserve_metadata_storage(struct page *page, int order, gfp_t g
 static inline void free_metadata_storage(struct page *page, int order)
 {
 }
+
+static inline bool vma_has_metadata(struct vm_area_struct *vma)
+{
+	return vma && (vma->vm_flags & VM_MTE);
+}
 #endif /* CONFIG_MEMORY_METADATA */
 
 #endif /* __ASM_MEMORY_METADATA_H  */
diff --git a/include/asm-generic/memory_metadata.h b/include/asm-generic/memory_metadata.h
index 111d6edc0997..35a0d6a8b5fc 100644
--- a/include/asm-generic/memory_metadata.h
+++ b/include/asm-generic/memory_metadata.h
@@ -35,6 +35,10 @@ static inline bool folio_has_metadata(struct folio *folio)
 {
 	return false;
 }
+static inline bool vma_has_metadata(struct vm_area_struct *vma)
+{
+	return false;
+}
 #endif /* !CONFIG_MEMORY_METADATA */
 
 #endif /* __ASM_GENERIC_MEMORY_METADATA_H */
diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index 78c8d5d8b628..174710d941c2 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -20,6 +20,7 @@
 #include <linux/swapops.h>
 #include <linux/shmem_fs.h>
 
+#include <asm/memory_metadata.h>
 #include <asm/tlb.h>
 #include <asm/pgalloc.h>
 #include "internal.h"
@@ -96,6 +97,7 @@ static struct kmem_cache *mm_slot_cache __read_mostly;
 
 struct collapse_control {
 	bool is_khugepaged;
+	bool has_metadata;
 
 	/* Num pages scanned per node */
 	u32 node_load[MAX_NUMNODES];
@@ -1069,6 +1071,9 @@ static int alloc_charge_hpage(struct page **hpage, struct mm_struct *mm,
 	int node = hpage_collapse_find_target_node(cc);
 	struct folio *folio;
 
+	if (cc->has_metadata)
+		gfp |= __GFP_TAGGED;
+
 	if (!hpage_collapse_alloc_page(hpage, gfp, node, &cc->alloc_nmask))
 		return SCAN_ALLOC_HUGE_PAGE_FAIL;
 
@@ -2497,6 +2502,7 @@ static unsigned int khugepaged_scan_mm_slot(unsigned int pages, int *result,
 		if (khugepaged_scan.address < hstart)
 			khugepaged_scan.address = hstart;
 		VM_BUG_ON(khugepaged_scan.address & ~HPAGE_PMD_MASK);
+		cc->has_metadata = vma_has_metadata(vma);
 
 		while (khugepaged_scan.address < hend) {
 			bool mmap_locked = true;
@@ -2838,6 +2844,7 @@ int madvise_collapse(struct vm_area_struct *vma, struct vm_area_struct **prev,
 	if (!cc)
 		return -ENOMEM;
 	cc->is_khugepaged = false;
+	cc->has_metadata = vma_has_metadata(vma);
 
 	mmgrab(mm);
 	lru_add_drain_all();
-- 
2.41.0