[RFC PATCH v3 3/5] mm, thp: add bpf thp hook to determine thp reclaimer

[Yafang Shao <laoar.shao@gmail.com>]

A new hook, bpf_thp_gfp_mask(), is introduced to determine whether memory
reclamation is being performed by the current task or by kswapd.

Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
---
 include/linux/huge_mm.h | 5 +++++
 mm/huge_memory.c        | 5 +++++
 2 files changed, 10 insertions(+)

diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
index db2eadd3f65b..6a40ebf25f5c 100644
--- a/include/linux/huge_mm.h
+++ b/include/linux/huge_mm.h
@@ -198,6 +198,11 @@ static inline int bpf_thp_allocator(unsigned long vm_flags,
 	return THP_ALLOC_KHUGEPAGED | THP_ALLOC_CURRENT;
 }
 
+static inline gfp_t bpf_thp_gfp_mask(bool vma_madvised)
+{
+	return 0;
+}
+
 static inline int highest_order(unsigned long orders)
 {
 	return fls_long(orders) - 1;
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index d3e66136e41a..81c1711d13fa 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1280,6 +1280,11 @@ static vm_fault_t __do_huge_pmd_anonymous_page(struct vm_fault *vmf)
 gfp_t vma_thp_gfp_mask(struct vm_area_struct *vma)
 {
 	const bool vma_madvised = vma && (vma->vm_flags & VM_HUGEPAGE);
+	gfp_t gfp_mask;
+
+	gfp_mask = bpf_thp_gfp_mask(vma_madvised);
+	if (gfp_mask)
+		return gfp_mask;
 
 	/* Always do synchronous compaction */
 	if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags))
-- 
2.43.5