RDMA/rtrs: Define MIN_CHUNK_SIZE

Define MIN_CHUNK_SIZE to replace the hard-coding number.
We need 4k for metadata, so MIN_CHUNK_SIZE should be at least 8k.

Link: https://lore.kernel.org/r/20210528113018.52290-7-jinpu.wang@ionos.comSigned-off-by: Gioh Kim <gi-oh.kim@ionos.com>
Signed-off-by: Jack Wang <jinpu.wang@ionos.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>

drivers/infiniband/ulp/rtrs/rtrs-pri.h

@@ -56,6 +56,7 @@ enum {
 	 * somewhere between 1 and 65536 and it depends on the system.
 	 */
 	MAX_SESS_QUEUE_DEPTH = 65536,
+	MIN_CHUNK_SIZE = 8192,
 
 	RTRS_HB_INTERVAL_MS = 5000,
 	RTRS_HB_MISSED_MAX = 5,

drivers/infiniband/ulp/rtrs/rtrs-srv.c

@@ -2165,9 +2165,9 @@ static int check_module_params(void)
 		       sess_queue_depth, 1, MAX_SESS_QUEUE_DEPTH);
 		return -EINVAL;
 	}
-	if (max_chunk_size < 4096 || !is_power_of_2(max_chunk_size)) {
+	if (max_chunk_size < MIN_CHUNK_SIZE || !is_power_of_2(max_chunk_size)) {
 		pr_err("Invalid max_chunk_size value %d, has to be >= %d and should be power of two.\n",
-		       max_chunk_size, 4096);
+		       max_chunk_size, MIN_CHUNK_SIZE);
 		return -EINVAL;
 	}