RDMA/rxe: Replace rxe_map and rxe_phys_buf by xarray

Replace struct rxe-phys_buf and struct rxe_map by struct xarray
in rxe_verbs.h. This allows using rcu locking on reads for
the memory maps stored in each mr.

This is based off of a sketch of a patch from Jason Gunthorpe in the
link below. Some changes were needed to make this work. It applies
cleanly to the current for-next and passes the pyverbs, perftest
and the same blktests test cases which run today.

Link: https://lore.kernel.org/r/20230119235936.19728-7-rpearsonhpe@gmail.com
Link: https://lore.kernel.org/linux-rdma/Y3gvZr6%2FNCii9Avy@nvidia.com/Co-developed-by: Jason Gunthorpe <jgg@nvidia.com>
Signed-off-by: Bob Pearson <rpearsonhpe@gmail.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>

drivers/infiniband/sw/rxe/rxe_loc.h

@@ -64,9 +64,9 @@ void rxe_mr_init_dma(int access, struct rxe_mr *mr);
 int rxe_mr_init_user(struct rxe_dev *rxe, u64 start, u64 length, u64 iova,
 		     int access, struct rxe_mr *mr);
 int rxe_mr_init_fast(int max_pages, struct rxe_mr *mr);
-int rxe_flush_pmem_iova(struct rxe_mr *mr, u64 iova, int length);
-int rxe_mr_copy(struct rxe_mr *mr, u64 iova, void *addr, int length,
-		enum rxe_mr_copy_dir dir);
+int rxe_flush_pmem_iova(struct rxe_mr *mr, u64 iova, unsigned int length);
+int rxe_mr_copy(struct rxe_mr *mr, u64 iova, void *addr,
+		unsigned int length, enum rxe_mr_copy_dir dir);
 int copy_data(struct rxe_pd *pd, int access, struct rxe_dma_info *dma,
 	      void *addr, int length, enum rxe_mr_copy_dir dir);
 int rxe_map_mr_sg(struct ib_mr *ibmr, struct scatterlist *sg,

drivers/infiniband/sw/rxe/rxe_verbs.h

@@ -283,17 +283,6 @@ enum rxe_mr_lookup_type {
 	RXE_LOOKUP_REMOTE,
 };
 
-#define RXE_BUF_PER_MAP		(PAGE_SIZE / sizeof(struct rxe_phys_buf))
-
-struct rxe_phys_buf {
-	u64      addr;
-	u64      size;
-};
-
-struct rxe_map {
-	struct rxe_phys_buf	buf[RXE_BUF_PER_MAP];
-};
-
 static inline int rkey_is_mw(u32 rkey)
 {
 	u32 index = rkey >> 8;
@@ -311,22 +300,16 @@ struct rxe_mr {
 	u32			rkey;
 	enum rxe_mr_state	state;
 	int			access;
+	atomic_t		num_mw;
 
 	unsigned int		page_offset;
 	unsigned int		page_shift;
 	u64			page_mask;
-	int			map_shift;
-	int			map_mask;
 
 	u32			num_buf;
 	u32			nbuf;
 
-	u32			max_buf;
-	u32			num_map;
-
-	atomic_t		num_mw;
-
-	struct rxe_map		**map;
+	struct xarray		page_list;
 };
 
 static inline unsigned int mr_page_size(struct rxe_mr *mr)