[RFC PATCH rdma-next 01/10] RDMA: mr: Introduce is_pmem

[Li Zhijian <lizhijian@cn.fujitsu.com>]

We can use it to indicate whether the registering mr is associated with
a pmem/nvdimm or not.

Currently, we only assign it in rxe driver, for other device/drivers,
they should implement it if needed.

RDMA FLUSH will support the persistence feature for a pmem/nvdimm.

Signed-off-by: Li Zhijian <lizhijian@cn.fujitsu.com>
---
 drivers/infiniband/sw/rxe/rxe_mr.c | 47 ++++++++++++++++++++++++++++++
 include/rdma/ib_verbs.h            |  1 +
 2 files changed, 48 insertions(+)

diff --git a/drivers/infiniband/sw/rxe/rxe_mr.c b/drivers/infiniband/sw/rxe/rxe_mr.c
index 7c4cd19a9db2..bcd5e7afa475 100644
--- a/drivers/infiniband/sw/rxe/rxe_mr.c
+++ b/drivers/infiniband/sw/rxe/rxe_mr.c
@@ -162,6 +162,50 @@ void rxe_mr_init_dma(struct rxe_pd *pd, int access, struct rxe_mr *mr)
 	mr->type = IB_MR_TYPE_DMA;
 }
 
+// XXX: the logic is similar with mm/memory-failure.c
+static bool page_in_dev_pagemap(struct page *page)
+{
+	unsigned long pfn;
+	struct page *p;
+	struct dev_pagemap *pgmap = NULL;
+
+	pfn = page_to_pfn(page);
+	if (!pfn) {
+		pr_err("no such pfn for page %p\n", page);
+		return false;
+	}
+
+	p = pfn_to_online_page(pfn);
+	if (!p) {
+		if (pfn_valid(pfn)) {
+			pgmap = get_dev_pagemap(pfn, NULL);
+			if (pgmap)
+				put_dev_pagemap(pgmap);
+		}
+	}
+
+	return !!pgmap;
+}
+
+static bool iova_in_pmem(struct rxe_mr *mr, u64 iova, int length)
+{
+	struct page *page = NULL;
+	char *vaddr = iova_to_vaddr(mr, iova, length);
+
+	if (!vaddr) {
+		pr_err("not a valid iova %llu\n", iova);
+		return false;
+	}
+
+	page = virt_to_page(vaddr);
+	if (!page) {
+		pr_err("no such page for vaddr %p\n", vaddr);
+		return false;
+	}
+
+	return page_in_dev_pagemap(page);
+}
+
 int rxe_mr_init_user(struct rxe_pd *pd, u64 start, u64 length, u64 iova,
 		     int access, struct rxe_mr *mr)
 {
@@ -236,6 +280,9 @@ int rxe_mr_init_user(struct rxe_pd *pd, u64 start, u64 length, u64 iova,
 	set->va = start;
 	set->offset = ib_umem_offset(umem);
 
+	// iova_in_pmem must be called after set is updated
+	mr->ibmr.is_pmem = iova_in_pmem(mr, iova, length);
+
 	return 0;
 
 err_release_umem:
diff --git a/include/rdma/ib_verbs.h b/include/rdma/ib_verbs.h
index 6e9ad656ecb7..822ebb3425dc 100644
--- a/include/rdma/ib_verbs.h
+++ b/include/rdma/ib_verbs.h
@@ -1807,6 +1807,7 @@ struct ib_mr {
 	unsigned int	   page_size;
 	enum ib_mr_type	   type;
 	bool		   need_inval;
+	bool		   is_pmem;
 	union {
 		struct ib_uobject	*uobject;	/* user */
 		struct list_head	qp_entry;	/* FR */
-- 
2.31.1