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From:   Albert Huang <huangjie.albert@bytedance.com>
To:     songmuchun@bytedance.com
Cc:     "huangjie.albert" <huangjie.albert@bytedance.com>,
        Mike Kravetz <mike.kravetz@oracle.com>,
        Andrew Morton <akpm@linux-foundation.org>, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org
Subject: [PATCH] mm: hugetlb: support get/set_policy for hugetlb_vm_ops
Date:   Wed, 12 Oct 2022 16:15:25 +0800
Message-Id: <20221012081526.73067-1-huangjie.albert@bytedance.com>
MIME-Version: 1.0
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From: "huangjie.albert" <huangjie.albert@bytedance.com>

implement these two functions so that we can set the mempolicy to
the inode of the hugetlb file. This ensures that the mempolicy of
all processes sharing this huge page file is consistent.

In some scenarios where huge pages are shared:
if we need to limit the memory usage of vm within node0, so I set qemu's
mempilciy bind to node0, but if there is a process (such as virtiofsd)
shared memory with the vm, in this case. If the page fault is triggered
by virtiofsd, the allocated memory may go to node1 which  depends on
virtiofsd.

Signed-off-by: huangjie.albert <huangjie.albert@bytedance.com>
---
 mm/hugetlb.c | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 0ad53ad98e74..ed7599821655 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -4678,6 +4678,24 @@ static vm_fault_t hugetlb_vm_op_fault(struct vm_fault *vmf)
 	return 0;
 }
 
+#ifdef CONFIG_NUMA
+int hugetlb_vm_op_set_policy(struct vm_area_struct *vma, struct mempolicy *mpol)
+{
+	struct inode *inode = file_inode(vma->vm_file);
+
+	return mpol_set_shared_policy(&HUGETLBFS_I(inode)->policy, vma, mpol);
+}
+
+struct mempolicy *hugetlb_vm_op_get_policy(struct vm_area_struct *vma, unsigned long addr)
+{
+	struct inode *inode = file_inode(vma->vm_file);
+	pgoff_t index;
+
+	index = ((addr - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;
+	return mpol_shared_policy_lookup(&HUGETLBFS_I(inode)->policy, index);
+}
+#endif
+
 /*
  * When a new function is introduced to vm_operations_struct and added
  * to hugetlb_vm_ops, please consider adding the function to shm_vm_ops.
@@ -4691,6 +4709,10 @@ const struct vm_operations_struct hugetlb_vm_ops = {
 	.close = hugetlb_vm_op_close,
 	.may_split = hugetlb_vm_op_split,
 	.pagesize = hugetlb_vm_op_pagesize,
+#ifdef CONFIG_NUMA
+	.set_policy = hugetlb_vm_op_set_policy,
+	.get_policy = hugetlb_vm_op_get_policy,
+#endif
 };
 
 static pte_t make_huge_pte(struct vm_area_struct *vma, struct page *page,
-- 
2.31.1