Compile cityhash code into libzfs

Make the cityhash code compile into libzfs, in preparation for the new
"zstream" command.

Reviewed-by: Paul Dagnelie <pcd@delphix.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Matthew Ahrens <mahrens@delphix.com>
Closes #10152

module/zcommon/Makefile.in

@@ -11,6 +11,7 @@ ccflags-y := $(ZFS_MODULE_CFLAGS) $(ZFS_MODULE_CPPFLAGS)
 # Suppress unused-value warnings in sparc64 architecture headers
 ccflags-$(CONFIG_SPARC64) += -Wno-unused-value
 
+$(MODULE)-objs += cityhash.o
 $(MODULE)-objs += zfeature_common.o
 $(MODULE)-objs += zfs_comutil.o
 $(MODULE)-objs += zfs_deleg.o

module/zcommon/cityhash.c

@@ -22,7 +22,7 @@
  * Copyright (c) 2017 by Delphix. All rights reserved.
  */
 
-#include <sys/cityhash.h>
+#include <cityhash.h>
 
 #define	HASH_K1 0xb492b66fbe98f273ULL
 #define	HASH_K2 0x9ae16a3b2f90404fULL
@@ -61,3 +61,7 @@ cityhash4(uint64_t w1, uint64_t w2, uint64_t w3, uint64_t w4)
 	    a + rotate(b + HASH_K2, 18) + c, mul));
 
 }
+
+#if defined(_KERNEL)
+EXPORT_SYMBOL(cityhash4);
+#endif

module/zfs/Makefile.in

@@ -22,7 +22,6 @@ $(MODULE)-objs += bpobj.o
 $(MODULE)-objs += bptree.o
 $(MODULE)-objs += btree.o
 $(MODULE)-objs += bqueue.o
-$(MODULE)-objs += cityhash.o
 $(MODULE)-objs += dataset_kstats.o
 $(MODULE)-objs += dbuf.o
 $(MODULE)-objs += dbuf_stats.o

module/zfs/arc.c

@@ -299,7 +299,7 @@
 #include <sys/arc_impl.h>
 #include <sys/trace_zfs.h>
 #include <sys/aggsum.h>
-#include <sys/cityhash.h>
+#include <cityhash.h>
 
 #ifndef _KERNEL
 /* set with ZFS_DEBUG=watch, to enable watchpoints on frozen buffers */

module/zfs/dbuf.c

@@ -48,7 +48,7 @@
 #include <sys/callb.h>
 #include <sys/abd.h>
 #include <sys/vdev.h>
-#include <sys/cityhash.h>
+#include <cityhash.h>
 #include <sys/spa_impl.h>
 
 kstat_t *dbuf_ksp;

module/zfs/zio.c

@@ -47,7 +47,7 @@
 #include <sys/trace_zfs.h>
 #include <sys/abd.h>
 #include <sys/dsl_crypt.h>
-#include <sys/cityhash.h>
+#include <cityhash.h>
 
 /*
  * ==========================================================================