module/*.ko: prune .data, global .rodata

Evaluated every variable that lives in .data (and globals in .rodata)
in the kernel modules, and constified/eliminated/localised them
appropriately. This means that all read-only data is now actually
read-only data, and, if possible, at file scope. A lot of previously-
global-symbols became inlinable (and inlined!) constants. Probably
not in a big Wowee Performance Moment, but hey.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Ahelenia Ziemiańska <nabijaczleweli@nabijaczleweli.xyz>
Closes #12899

include/os/freebsd/zfs/sys/freebsd_crypto.h

@@ -88,11 +88,11 @@ void crypto_mac_final(struct hmac_ctx *ctx, void *out_data,
 	size_t out_data_size);
 
 int freebsd_crypt_newsession(freebsd_crypt_session_t *sessp,
-    struct zio_crypt_info *, crypto_key_t *);
+    const struct zio_crypt_info *, crypto_key_t *);
 void freebsd_crypt_freesession(freebsd_crypt_session_t *sessp);
 
 int freebsd_crypt_uio(boolean_t, freebsd_crypt_session_t *,
-	struct zio_crypt_info *, zfs_uio_t *, crypto_key_t *, uint8_t *,
+	const struct zio_crypt_info *, zfs_uio_t *, crypto_key_t *, uint8_t *,
 	size_t, size_t);
 
 #endif /* _ZFS_FREEBSD_CRYPTO_H */

include/os/freebsd/zfs/sys/zfs_context_os.h

@@ -48,7 +48,7 @@
 #define	cond_resched()		kern_yield(PRI_USER)
 
 #define	taskq_create_sysdc(a, b, d, e, p, dc, f) \
-	    (taskq_create(a, b, maxclsyspri, d, e, f))
+	    ((void) sizeof (dc), taskq_create(a, b, maxclsyspri, d, e, f))
 
 #define	tsd_create(keyp, destructor)    do {                 \
 		*(keyp) = osd_thread_register((destructor));         \

include/os/freebsd/zfs/sys/zfs_znode_impl.h

@@ -175,8 +175,7 @@ extern void	zfs_tstamp_update_setup_ext(struct znode *,
     uint_t, uint64_t [2], uint64_t [2], boolean_t have_tx);
 extern void zfs_znode_free(struct znode *);
 
-extern zil_replay_func_t *zfs_replay_vector[TX_MAX_TYPE];
-extern int zfsfstype;
+extern zil_replay_func_t *const zfs_replay_vector[TX_MAX_TYPE];
 
 extern int zfs_znode_parent_and_name(struct znode *zp, struct znode **dzpp,
     char *buf);

include/os/linux/spl/rpc/xdr.h

@@ -36,7 +36,8 @@ enum xdr_op {
 struct xdr_ops;
 
 typedef struct {
-	struct xdr_ops	*x_ops;	/* Let caller know xdrmem_create() succeeds */
+	const struct xdr_ops	*x_ops;
+	    /* Let caller know xdrmem_create() succeeds */
 	caddr_t		x_addr;	/* Current buffer addr */
 	caddr_t		x_addr_end;	/* End of the buffer */
 	enum xdr_op	x_op;	/* Stream direction */

include/os/linux/spl/sys/sysmacros.h

@@ -113,7 +113,6 @@
 #endif
 
 /* Missing globals */
-extern char spl_gitrev[64];
 extern unsigned long spl_hostid;
 
 /* Missing misc functions */

include/os/linux/spl/sys/taskq.h

@@ -160,7 +160,8 @@ extern taskq_t *taskq_of_curthread(void);
 #define	taskq_create_proc(name, nthreads, pri, min, max, proc, flags) \
     taskq_create(name, nthreads, pri, min, max, flags)
 #define	taskq_create_sysdc(name, nthreads, min, max, proc, dc, flags) \
-    taskq_create(name, nthreads, maxclsyspri, min, max, flags)
+	((void) sizeof (dc), \
+	    taskq_create(name, nthreads, maxclsyspri, min, max, flags))
 
 int spl_taskq_init(void);
 void spl_taskq_fini(void);

include/os/linux/zfs/sys/zfs_znode_impl.h

@@ -173,8 +173,7 @@ extern caddr_t zfs_map_page(page_t *, enum seg_rw);
 extern void zfs_unmap_page(page_t *, caddr_t);
 #endif /* HAVE_UIO_RW */
 
-extern zil_replay_func_t *zfs_replay_vector[TX_MAX_TYPE];
-extern int zfsfstype;
+extern zil_replay_func_t *const zfs_replay_vector[TX_MAX_TYPE];
 
 #ifdef	__cplusplus
 }

include/os/linux/zfs/sys/zpl.h

@@ -99,7 +99,6 @@ extern const struct inode_operations zpl_ops_root;
 
 extern const struct file_operations zpl_fops_snapdir;
 extern const struct inode_operations zpl_ops_snapdir;
-extern const struct dentry_operations zpl_dops_snapdirs;
 
 extern const struct file_operations zpl_fops_shares;
 extern const struct inode_operations zpl_ops_shares;