Throw const on some strings

In C, const indicates to the reader that mutation will not occur.
It can also serve as a hint about ownership.

Add const in a few places where it makes sense.

Reviewed-by: Brian Behlendorf <[email protected]>
Signed-off-by: Ryan Moeller <[email protected]>
Closes #10997 

20 files changed, 99 insertions, 108 deletions

diff --git a/include/os/freebsd/zfs/sys/zfs_ctldir.h b/include/os/freebsd/zfs/sys/zfs_ctldir.h
index 28a026603..da02863a7 100644
--- a/include/os/freebsd/zfs/sys/zfs_ctldir.h
+++ b/include/os/freebsd/zfs/sys/zfs_ctldir.h
@@ -48,7 +48,7 @@ int zfsctl_root(zfsvfs_t *, int, vnode_t **);
 void zfsctl_init(void);
 void zfsctl_fini(void);
 boolean_t zfsctl_is_node(vnode_t *);
-int zfsctl_snapshot_unmount(char *snapname, int flags);
+int zfsctl_snapshot_unmount(const char *snapname, int flags);
 int zfsctl_rename_snapshot(const char *from, const char *to);
 int zfsctl_destroy_snapshot(const char *snapname, int force);
 int zfsctl_umount_snapshots(vfs_t *, int, cred_t *);
diff --git a/include/os/freebsd/zfs/sys/zfs_dir.h b/include/os/freebsd/zfs/sys/zfs_dir.h
index f6f8ab5c4..4197e1188 100644
--- a/include/os/freebsd/zfs/sys/zfs_dir.h
+++ b/include/os/freebsd/zfs/sys/zfs_dir.h
@@ -52,11 +52,7 @@ extern int zfs_dirent_lookup(znode_t *, const char *, znode_t **, int);
 extern int zfs_link_create(znode_t *, const char *, znode_t *, dmu_tx_t *, int);
 extern int zfs_link_destroy(znode_t *, const char *, znode_t *, dmu_tx_t *, int,
     boolean_t *);
-#if 0
-extern int zfs_dirlook(vnode_t *, const char *, vnode_t **, int);
-#else
 extern int zfs_dirlook(znode_t *, const char *name, znode_t **);
-#endif
 extern void zfs_mknode(znode_t *, vattr_t *, dmu_tx_t *, cred_t *,
     uint_t, znode_t **, zfs_acl_ids_t *);
 extern void zfs_rmnode(znode_t *);
diff --git a/include/os/freebsd/zfs/sys/zfs_vnops.h b/include/os/freebsd/zfs/sys/zfs_vnops.h
index 6237372b9..587650af6 100644
--- a/include/os/freebsd/zfs/sys/zfs_vnops.h
+++ b/include/os/freebsd/zfs/sys/zfs_vnops.h
@@ -32,21 +32,21 @@ int dmu_write_pages(objset_t *os, uint64_t object, uint64_t offset,
     uint64_t size, struct vm_page **ppa, dmu_tx_t *tx);
 int dmu_read_pages(objset_t *os, uint64_t object, vm_page_t *ma, int count,
     int *rbehind, int *rahead, int last_size);
-extern int zfs_remove(znode_t *dzp, char *name, cred_t *cr, int flags);
-extern int zfs_mkdir(znode_t *dzp, char *dirname, vattr_t *vap,
+extern int zfs_remove(znode_t *dzp, const char *name, cred_t *cr, int flags);
+extern int zfs_mkdir(znode_t *dzp, const char *dirname, vattr_t *vap,
     znode_t **zpp, cred_t *cr, int flags, vsecattr_t *vsecp);
-extern int zfs_rmdir(znode_t *dzp, char *name, znode_t *cwd,
+extern int zfs_rmdir(znode_t *dzp, const char *name, znode_t *cwd,
     cred_t *cr, int flags);
 extern int zfs_setattr(znode_t *zp, vattr_t *vap, int flag, cred_t *cr);
-extern int zfs_rename(znode_t *sdzp, char *snm, znode_t *tdzp,
-    char *tnm, cred_t *cr, int flags);
+extern int zfs_rename(znode_t *sdzp, const char *snm, znode_t *tdzp,
+    const char *tnm, cred_t *cr, int flags);
 extern int zfs_symlink(znode_t *dzp, const char *name, vattr_t *vap,
     const char *link, znode_t **zpp, cred_t *cr, int flags);
 extern int zfs_link(znode_t *tdzp, znode_t *sp,
-    char *name, cred_t *cr, int flags);
+    const char *name, cred_t *cr, int flags);
 extern int zfs_space(znode_t *zp, int cmd, struct flock *bfp, int flag,
     offset_t offset, cred_t *cr);
-extern int zfs_create(znode_t *dzp, char *name, vattr_t *vap, int excl,
+extern int zfs_create(znode_t *dzp, const char *name, vattr_t *vap, int excl,
     int mode, znode_t **zpp, cred_t *cr, int flag, vsecattr_t *vsecp);
 extern int zfs_setsecattr(znode_t *zp, vsecattr_t *vsecp, int flag,
     cred_t *cr);
diff --git a/include/os/linux/zfs/sys/zfs_ctldir.h b/include/os/linux/zfs/sys/zfs_ctldir.h
index 51933bc4f..beee34979 100644
--- a/include/os/linux/zfs/sys/zfs_ctldir.h
+++ b/include/os/linux/zfs/sys/zfs_ctldir.h
@@ -60,22 +60,22 @@ extern boolean_t zfsctl_is_snapdir(struct inode *ip);
 extern int zfsctl_fid(struct inode *ip, fid_t *fidp);
 
 /* zfsctl '.zfs' functions */
-extern int zfsctl_root_lookup(struct inode *dip, char *name,
+extern int zfsctl_root_lookup(struct inode *dip, const char *name,
     struct inode **ipp, int flags, cred_t *cr, int *direntflags,
     pathname_t *realpnp);
 
 /* zfsctl '.zfs/snapshot' functions */
-extern int zfsctl_snapdir_lookup(struct inode *dip, char *name,
+extern int zfsctl_snapdir_lookup(struct inode *dip, const char *name,
     struct inode **ipp, int flags, cred_t *cr, int *direntflags,
     pathname_t *realpnp);
-extern int zfsctl_snapdir_rename(struct inode *sdip, char *sname,
-    struct inode *tdip, char *tname, cred_t *cr, int flags);
-extern int zfsctl_snapdir_remove(struct inode *dip, char *name, cred_t *cr,
-    int flags);
-extern int zfsctl_snapdir_mkdir(struct inode *dip, char *dirname, vattr_t *vap,
-    struct inode **ipp, cred_t *cr, int flags);
+extern int zfsctl_snapdir_rename(struct inode *sdip, const char *sname,
+    struct inode *tdip, const char *tname, cred_t *cr, int flags);
+extern int zfsctl_snapdir_remove(struct inode *dip, const char *name,
+    cred_t *cr, int flags);
+extern int zfsctl_snapdir_mkdir(struct inode *dip, const char *dirname,
+    vattr_t *vap, struct inode **ipp, cred_t *cr, int flags);
 extern int zfsctl_snapshot_mount(struct path *path, int flags);
-extern int zfsctl_snapshot_unmount(char *snapname, int flags);
+extern int zfsctl_snapshot_unmount(const char *snapname, int flags);
 extern int zfsctl_snapshot_unmount_delay(spa_t *spa, uint64_t objsetid,
     int delay);
 extern int zfsctl_snapdir_vget(struct super_block *sb, uint64_t objsetid,
diff --git a/include/os/linux/zfs/sys/zfs_vnops.h b/include/os/linux/zfs/sys/zfs_vnops.h
index 24a2082d3..2b41f3863 100644
--- a/include/os/linux/zfs/sys/zfs_vnops.h
+++ b/include/os/linux/zfs/sys/zfs_vnops.h
@@ -46,8 +46,8 @@ extern int zfs_write(struct inode *ip, uio_t *uio, int ioflag, cred_t *cr);
 extern int zfs_write_simple(znode_t *zp, const void *data, size_t len,
     loff_t pos, size_t *resid);
 extern int zfs_access(struct inode *ip, int mode, int flag, cred_t *cr);
-extern int zfs_lookup(znode_t *dzp, char *nm, znode_t **zpp,
-    int flags, cred_t *cr, int *direntflags, pathname_t *realpnp);
+extern int zfs_lookup(znode_t *dzp, char *nm, znode_t **zpp, int flags,
+    cred_t *cr, int *direntflags, pathname_t *realpnp);
 extern int zfs_create(znode_t *dzp, char *name, vattr_t *vap, int excl,
     int mode, znode_t **zpp, cred_t *cr, int flag, vsecattr_t *vsecp);
 extern int zfs_tmpfile(struct inode *dip, vattr_t *vapzfs, int excl,
diff --git a/include/sys/dmu.h b/include/sys/dmu.h
index d6efe2595..9c700e2d7 100644
--- a/include/sys/dmu.h
+++ b/include/sys/dmu.h
@@ -1009,7 +1009,7 @@ extern int dmu_objset_blksize(objset_t *os);
 extern int dmu_snapshot_list_next(objset_t *os, int namelen, char *name,
     uint64_t *id, uint64_t *offp, boolean_t *case_conflict);
 extern int dmu_snapshot_lookup(objset_t *os, const char *name, uint64_t *val);
-extern int dmu_snapshot_realname(objset_t *os, char *name, char *real,
+extern int dmu_snapshot_realname(objset_t *os, const char *name, char *real,
     int maxlen, boolean_t *conflict);
 extern int dmu_dir_list_next(objset_t *os, int namelen, char *name,
     uint64_t *idp, uint64_t *offp);
diff --git a/include/sys/spa.h b/include/sys/spa.h
index ddce8cc91..045431c20 100644
--- a/include/sys/spa.h
+++ b/include/sys/spa.h
@@ -768,12 +768,12 @@ extern int spa_create(const char *pool, nvlist_t *nvroot, nvlist_t *props,
 extern int spa_import(char *pool, nvlist_t *config, nvlist_t *props,
     uint64_t flags);
 extern nvlist_t *spa_tryimport(nvlist_t *tryconfig);
-extern int spa_destroy(char *pool);
+extern int spa_destroy(const char *pool);
 extern int spa_checkpoint(const char *pool);
 extern int spa_checkpoint_discard(const char *pool);
-extern int spa_export(char *pool, nvlist_t **oldconfig, boolean_t force,
+extern int spa_export(const char *pool, nvlist_t **oldconfig, boolean_t force,
     boolean_t hardforce);
-extern int spa_reset(char *pool);
+extern int spa_reset(const char *pool);
 extern void spa_async_request(spa_t *spa, int flag);
 extern void spa_async_unrequest(spa_t *spa, int flag);
 extern void spa_async_suspend(spa_t *spa);
diff --git a/include/sys/u8_textprep.h b/include/sys/u8_textprep.h
index f8b5bed6e..09ab13af2 100644
--- a/include/sys/u8_textprep.h
+++ b/include/sys/u8_textprep.h
@@ -101,7 +101,7 @@ extern int uconv_u8tou32(const uchar_t *, size_t *, uint32_t *, size_t *, int);
 #define	U8_ILLEGAL_CHAR			(-1)
 #define	U8_OUT_OF_RANGE_CHAR		(-2)
 
-extern int u8_validate(char *, size_t, char **, int, int *);
+extern int u8_validate(const char *, size_t, char **, int, int *);
 extern int u8_strcmp(const char *, const char *, size_t, int, size_t, int *);
 extern size_t u8_textprep_str(char *, size_t *, char *, size_t *, int, size_t,
 	int *);
diff --git a/include/sys/zfs_znode.h b/include/sys/zfs_znode.h
index d7823221e..4138f6eba 100644
--- a/include/sys/zfs_znode.h
+++ b/include/sys/zfs_znode.h
@@ -262,19 +262,20 @@ extern boolean_t zfs_get_vfs_flag_unmounted(objset_t *os);
 extern void	zfs_znode_dmu_fini(znode_t *);
 
 extern void zfs_log_create(zilog_t *zilog, dmu_tx_t *tx, uint64_t txtype,
-    znode_t *dzp, znode_t *zp, char *name, vsecattr_t *, zfs_fuid_info_t *,
-    vattr_t *vap);
+    znode_t *dzp, znode_t *zp, const char *name, vsecattr_t *,
+    zfs_fuid_info_t *, vattr_t *vap);
 extern int zfs_log_create_txtype(zil_create_t, vsecattr_t *vsecp,
     vattr_t *vap);
 extern void zfs_log_remove(zilog_t *zilog, dmu_tx_t *tx, uint64_t txtype,
-    znode_t *dzp, char *name, uint64_t foid, boolean_t unlinked);
+    znode_t *dzp, const char *name, uint64_t foid, boolean_t unlinked);
 #define	ZFS_NO_OBJECT	0	/* no object id */
 extern void zfs_log_link(zilog_t *zilog, dmu_tx_t *tx, uint64_t txtype,
-    znode_t *dzp, znode_t *zp, char *name);
+    znode_t *dzp, znode_t *zp, const char *name);
 extern void zfs_log_symlink(zilog_t *zilog, dmu_tx_t *tx, uint64_t txtype,
-    znode_t *dzp, znode_t *zp, char *name, char *link);
+    znode_t *dzp, znode_t *zp, const char *name, const char *link);
 extern void zfs_log_rename(zilog_t *zilog, dmu_tx_t *tx, uint64_t txtype,
-    znode_t *sdzp, char *sname, znode_t *tdzp, char *dname, znode_t *szp);
+    znode_t *sdzp, const char *sname, znode_t *tdzp, const char *dname,
+    znode_t *szp);
 extern void zfs_log_write(zilog_t *zilog, dmu_tx_t *tx, int txtype,
     znode_t *zp, offset_t off, ssize_t len, int ioflag,
     zil_callback_t callback, void *callback_data);
diff --git a/module/os/freebsd/zfs/zfs_ctldir.c b/module/os/freebsd/zfs/zfs_ctldir.c
index 0fe32b195..5fd367b0c 100644
--- a/module/os/freebsd/zfs/zfs_ctldir.c
+++ b/module/os/freebsd/zfs/zfs_ctldir.c
@@ -1327,7 +1327,7 @@ zfsctl_umount_snapshots(vfs_t *vfsp, int fflags, cred_t *cr)
 }
 
 int
-zfsctl_snapshot_unmount(char *snapname, int flags __unused)
+zfsctl_snapshot_unmount(const char *snapname, int flags __unused)
 {
 	vfs_t *vfsp = NULL;
 	zfsvfs_t *zfsvfs = NULL;
diff --git a/module/os/freebsd/zfs/zfs_vnops.c b/module/os/freebsd/zfs/zfs_vnops.c
index 79202b60a..31c1f81d0 100644
--- a/module/os/freebsd/zfs/zfs_vnops.c
+++ b/module/os/freebsd/zfs/zfs_vnops.c
@@ -104,14 +104,6 @@ VFS_SMR_DECLARE;
 #define	vm_page_wire_unlock(pp) vm_page_unlock(pp)
 #endif
 
-static int
-zfs_u8_validate(const char *u8str, size_t n, char **list, int flag, int *errnum)
-{
-
-	return (u8_validate(__DECONST(char *, u8str), n, list, flag, errnum));
-}
-#define	u8_validate zfs_u8_validate
-
 #ifdef DEBUG_VFS_LOCKS
 #define	VNCHECKREF(vp)				  \
 	VNASSERT((vp)->v_holdcnt > 0 && (vp)->v_usecount > 0, vp,	\
@@ -1536,8 +1528,9 @@ zfs_lookup_lock(vnode_t *dvp, vnode_t *vp, const char *name, int lkflags)
  */
 /* ARGSUSED */
 static int
-zfs_lookup(vnode_t *dvp, char *nm, vnode_t **vpp, struct componentname *cnp,
-    int nameiop, cred_t *cr, kthread_t *td, int flags, boolean_t cached)
+zfs_lookup(vnode_t *dvp, const char *nm, vnode_t **vpp,
+    struct componentname *cnp, int nameiop, cred_t *cr, kthread_t *td,
+    int flags, boolean_t cached)
 {
 	znode_t *zdp = VTOZ(dvp);
 	znode_t *zp;
@@ -1561,7 +1554,8 @@ zfs_lookup(vnode_t *dvp, char *nm, vnode_t **vpp, struct componentname *cnp,
 		}
 	}
 
-	DTRACE_PROBE2(zfs__fastpath__lookup__miss, vnode_t *, dvp, char *, nm);
+	DTRACE_PROBE2(zfs__fastpath__lookup__miss, vnode_t *, dvp,
+	    const char *, nm);
 
 	ZFS_ENTER(zfsvfs);
 	ZFS_VERIFY_ZP(zdp);
@@ -1778,7 +1772,7 @@ zfs_lookup(vnode_t *dvp, char *nm, vnode_t **vpp, struct componentname *cnp,
 
 /* ARGSUSED */
 int
-zfs_create(znode_t *dzp, char *name, vattr_t *vap, int excl, int mode,
+zfs_create(znode_t *dzp, const char *name, vattr_t *vap, int excl, int mode,
     znode_t **zpp, cred_t *cr, int flag, vsecattr_t *vsecp)
 {
 	znode_t		*zp;
@@ -1945,7 +1939,7 @@ out:
 
 /*ARGSUSED*/
 static int
-zfs_remove_(vnode_t *dvp, vnode_t *vp, char *name, cred_t *cr)
+zfs_remove_(vnode_t *dvp, vnode_t *vp, const char *name, cred_t *cr)
 {
 	znode_t		*dzp = VTOZ(dvp);
 	znode_t		*zp;
@@ -2059,13 +2053,13 @@ out:
 
 
 static int
-zfs_lookup_internal(znode_t *dzp, char *name, vnode_t **vpp,
+zfs_lookup_internal(znode_t *dzp, const char *name, vnode_t **vpp,
     struct componentname *cnp, int nameiop)
 {
 	zfsvfs_t	*zfsvfs = dzp->z_zfsvfs;
 	int error;
 
-	cnp->cn_nameptr = name;
+	cnp->cn_nameptr = __DECONST(char *, name);
 	cnp->cn_namelen = strlen(name);
 	cnp->cn_nameiop = nameiop;
 	cnp->cn_flags = ISLASTCN | SAVENAME;
@@ -2096,7 +2090,7 @@ zfs_lookup_internal(znode_t *dzp, char *name, vnode_t **vpp,
 }
 
 int
-zfs_remove(znode_t *dzp, char *name, cred_t *cr, int flags)
+zfs_remove(znode_t *dzp, const char *name, cred_t *cr, int flags)
 {
 	vnode_t *vp;
 	int error;
@@ -2131,8 +2125,8 @@ zfs_remove(znode_t *dzp, char *name, cred_t *cr, int flags)
  */
 /*ARGSUSED*/
 int
-zfs_mkdir(znode_t *dzp, char *dirname, vattr_t *vap, znode_t **zpp, cred_t *cr,
-    int flags, vsecattr_t *vsecp)
+zfs_mkdir(znode_t *dzp, const char *dirname, vattr_t *vap, znode_t **zpp,
+    cred_t *cr, int flags, vsecattr_t *vsecp)
 {
 	znode_t		*zp;
 	zfsvfs_t	*zfsvfs = dzp->z_zfsvfs;
@@ -2298,7 +2292,7 @@ zfs_mkdir(znode_t *dzp, char *dirname, vattr_t *vap, znode_t **zpp, cred_t *cr,
  */
 /*ARGSUSED*/
 static int
-zfs_rmdir_(vnode_t *dvp, vnode_t *vp, char *name, cred_t *cr)
+zfs_rmdir_(vnode_t *dvp, vnode_t *vp, const char *name, cred_t *cr)
 {
 	znode_t		*dzp = VTOZ(dvp);
 	znode_t		*zp = VTOZ(vp);
@@ -2360,7 +2354,7 @@ out:
 }
 
 int
-zfs_rmdir(znode_t *dzp, char *name, znode_t *cwd, cred_t *cr, int flags)
+zfs_rmdir(znode_t *dzp, const char *name, znode_t *cwd, cred_t *cr, int flags)
 {
 	struct componentname cn;
 	vnode_t *vp;
@@ -3934,8 +3928,8 @@ zfs_rename_(vnode_t *sdvp, vnode_t **svpp, struct componentname *scnp,
 	znode_t		*sdzp, *tdzp, *szp, *tzp;
 	zilog_t		*zilog = NULL;
 	dmu_tx_t	*tx;
-	char		*snm = scnp->cn_nameptr;
-	char		*tnm = tcnp->cn_nameptr;
+	const char	*snm = scnp->cn_nameptr;
+	const char	*tnm = tcnp->cn_nameptr;
 	int		error = 0;
 	bool	want_seqc_end __maybe_unused = false;
 
@@ -4201,7 +4195,7 @@ out:				/* original two vnodes are locked */
 }
 
 int
-zfs_rename(znode_t *sdzp, char *sname, znode_t *tdzp, char *tname,
+zfs_rename(znode_t *sdzp, const char *sname, znode_t *tdzp, const char *tname,
     cred_t *cr, int flags)
 {
 	struct componentname scn, tcn;
@@ -4360,8 +4354,7 @@ zfs_symlink(znode_t *dzp, const char *name, vattr_t *vap,
 	 */
 	(void) zfs_link_create(dzp, name, zp, tx, ZNEW);
 
-	zfs_log_symlink(zilog, tx, txtype, dzp, zp,
-	    __DECONST(char *, name), __DECONST(char *, link));
+	zfs_log_symlink(zilog, tx, txtype, dzp, zp, name, link);
 	*zpp = zp;
 
 	zfs_acl_ids_free(&acl_ids);
@@ -4432,7 +4425,7 @@ zfs_readlink(vnode_t *vp, uio_t *uio, cred_t *cr, caller_context_t *ct)
  */
 /* ARGSUSED */
 int
-zfs_link(znode_t *tdzp, znode_t *szp, char *name, cred_t *cr,
+zfs_link(znode_t *tdzp, znode_t *szp, const char *name, cred_t *cr,
     int flags)
 {
 	znode_t		*tzp;
diff --git a/module/os/linux/zfs/zfs_ctldir.c b/module/os/linux/zfs/zfs_ctldir.c
index 26e785a0d..c13a97712 100644
--- a/module/os/linux/zfs/zfs_ctldir.c
+++ b/module/os/linux/zfs/zfs_ctldir.c
@@ -131,7 +131,7 @@ static void zfsctl_snapshot_unmount_delay_impl(zfs_snapentry_t *se, int delay);
  * the snapshot name and provided mount point.  No reference is taken.
  */
 static zfs_snapentry_t *
-zfsctl_snapshot_alloc(char *full_name, char *full_path, spa_t *spa,
+zfsctl_snapshot_alloc(const char *full_name, const char *full_path, spa_t *spa,
     uint64_t objsetid, struct dentry *root_dentry)
 {
 	zfs_snapentry_t *se;
@@ -261,13 +261,13 @@ snapentry_compare_by_objsetid(const void *a, const void *b)
  * NULL will be returned.
  */
 static zfs_snapentry_t *
-zfsctl_snapshot_find_by_name(char *snapname)
+zfsctl_snapshot_find_by_name(const char *snapname)
 {
 	zfs_snapentry_t *se, search;
 
 	ASSERT(RW_LOCK_HELD(&zfs_snapshot_lock));
 
-	search.se_name = snapname;
+	search.se_name = (char *)snapname;
 	se = avl_find(&zfs_snapshots_by_name, &search, NULL);
 	if (se)
 		zfsctl_snapshot_hold(se);
@@ -301,7 +301,7 @@ zfsctl_snapshot_find_by_objsetid(spa_t *spa, uint64_t objsetid)
  * removed, renamed, and added back to the new correct location in the tree.
  */
 static int
-zfsctl_snapshot_rename(char *old_snapname, char *new_snapname)
+zfsctl_snapshot_rename(const char *old_snapname, const char *new_snapname)
 {
 	zfs_snapentry_t *se;
 
@@ -410,7 +410,7 @@ zfsctl_snapshot_unmount_delay(spa_t *spa, uint64_t objsetid, int delay)
  * and zero when unmounted.
  */
 static boolean_t
-zfsctl_snapshot_ismounted(char *snapname)
+zfsctl_snapshot_ismounted(const char *snapname)
 {
 	zfs_snapentry_t *se;
 	boolean_t ismounted = B_FALSE;
@@ -751,7 +751,7 @@ out:
  * Special case the handling of "..".
  */
 int
-zfsctl_root_lookup(struct inode *dip, char *name, struct inode **ipp,
+zfsctl_root_lookup(struct inode *dip, const char *name, struct inode **ipp,
     int flags, cred_t *cr, int *direntflags, pathname_t *realpnp)
 {
 	zfsvfs_t *zfsvfs = ITOZSB(dip);
@@ -784,7 +784,7 @@ zfsctl_root_lookup(struct inode *dip, char *name, struct inode **ipp,
  * snapshot if it exist, creating the pseudo filesystem inode as necessary.
  */
 int
-zfsctl_snapdir_lookup(struct inode *dip, char *name, struct inode **ipp,
+zfsctl_snapdir_lookup(struct inode *dip, const char *name, struct inode **ipp,
     int flags, cred_t *cr, int *direntflags, pathname_t *realpnp)
 {
 	zfsvfs_t *zfsvfs = ITOZSB(dip);
@@ -815,8 +815,8 @@ zfsctl_snapdir_lookup(struct inode *dip, char *name, struct inode **ipp,
  * to the '.zfs/snapshot' directory snapshots cannot be moved elsewhere.
  */
 int
-zfsctl_snapdir_rename(struct inode *sdip, char *snm,
-    struct inode *tdip, char *tnm, cred_t *cr, int flags)
+zfsctl_snapdir_rename(struct inode *sdip, const char *snm,
+    struct inode *tdip, const char *tnm, cred_t *cr, int flags)
 {
 	zfsvfs_t *zfsvfs = ITOZSB(sdip);
 	char *to, *from, *real, *fsname;
@@ -893,7 +893,8 @@ out:
  * the removal of the snapshot with the given name.
  */
 int
-zfsctl_snapdir_remove(struct inode *dip, char *name, cred_t *cr, int flags)
+zfsctl_snapdir_remove(struct inode *dip, const char *name, cred_t *cr,
+    int flags)
 {
 	zfsvfs_t *zfsvfs = ITOZSB(dip);
 	char *snapname, *real;
@@ -941,7 +942,7 @@ out:
  * the creation of a new snapshot with the given name.
  */
 int
-zfsctl_snapdir_mkdir(struct inode *dip, char *dirname, vattr_t *vap,
+zfsctl_snapdir_mkdir(struct inode *dip, const char *dirname, vattr_t *vap,
     struct inode **ipp, cred_t *cr, int flags)
 {
 	zfsvfs_t *zfsvfs = ITOZSB(dip);
@@ -1001,7 +1002,7 @@ exportfs_flush(void)
  * it's in use, the unmount will fail harmlessly.
  */
 int
-zfsctl_snapshot_unmount(char *snapname, int flags)
+zfsctl_snapshot_unmount(const char *snapname, int flags)
 {
 	char *argv[] = { "/usr/bin/env", "umount", "-t", "zfs", "-n", NULL,
 	    NULL };
diff --git a/module/os/linux/zfs/zfs_dir.c b/module/os/linux/zfs/zfs_dir.c
index 383657208..207a51d75 100644
--- a/module/os/linux/zfs/zfs_dir.c
+++ b/module/os/linux/zfs/zfs_dir.c
@@ -60,8 +60,9 @@
  * of names after deciding which is the appropriate lookup interface.
  */
 static int
-zfs_match_find(zfsvfs_t *zfsvfs, znode_t *dzp, char *name, matchtype_t mt,
-    boolean_t update, int *deflags, pathname_t *rpnp, uint64_t *zoid)
+zfs_match_find(zfsvfs_t *zfsvfs, znode_t *dzp, const char *name,
+    matchtype_t mt, boolean_t update, int *deflags, pathname_t *rpnp,
+    uint64_t *zoid)
 {
 	boolean_t conflict = B_FALSE;
 	int error;
@@ -139,8 +140,8 @@ zfs_match_find(zfsvfs_t *zfsvfs, znode_t *dzp, char *name, matchtype_t mt,
  *	 but return znode pointers to a single match.
  */
 int
-zfs_dirent_lock(zfs_dirlock_t **dlpp, znode_t *dzp, char *name, znode_t **zpp,
-    int flag, int *direntflags, pathname_t *realpnp)
+zfs_dirent_lock(zfs_dirlock_t **dlpp, znode_t *dzp, char *name,
+    znode_t **zpp, int flag, int *direntflags, pathname_t *realpnp)
 {
 	zfsvfs_t	*zfsvfs = ZTOZSB(dzp);
 	zfs_dirlock_t	*dl;
diff --git a/module/os/linux/zfs/zfs_vnops.c b/module/os/linux/zfs/zfs_vnops.c
index 2d104a500..0932b9b33 100644
--- a/module/os/linux/zfs/zfs_vnops.c
+++ b/module/os/linux/zfs/zfs_vnops.c
@@ -1234,8 +1234,8 @@ zfs_access(struct inode *ip, int mode, int flag, cred_t *cr)
  */
 /* ARGSUSED */
 int
-zfs_lookup(znode_t *zdp, char *nm, znode_t **zpp, int flags,
-    cred_t *cr, int *direntflags, pathname_t *realpnp)
+zfs_lookup(znode_t *zdp, char *nm, znode_t **zpp, int flags, cred_t *cr,
+    int *direntflags, pathname_t *realpnp)
 {
 	zfsvfs_t *zfsvfs = ZTOZSB(zdp);
 	int error = 0;
diff --git a/module/unicode/u8_textprep.c b/module/unicode/u8_textprep.c
index 65f555d88..be816d728 100644
--- a/module/unicode/u8_textprep.c
+++ b/module/unicode/u8_textprep.c
@@ -330,7 +330,7 @@ const uint8_t u8_valid_max_2nd_byte[0x100] = {
  * specific to UTF-8 and Unicode.
  */
 int
-u8_validate(char *u8str, size_t n, char **list, int flag, int *errnum)
+u8_validate(const char *u8str, size_t n, char **list, int flag, int *errnum)
 {
 	uchar_t *ib;
 	uchar_t *ibtail;
diff --git a/module/zfs/dmu_objset.c b/module/zfs/dmu_objset.c
index b1590d7db..af5935e23 100644
--- a/module/zfs/dmu_objset.c
+++ b/module/zfs/dmu_objset.c
@@ -2413,7 +2413,7 @@ dmu_objset_is_snapshot(objset_t *os)
 }
 
 int
-dmu_snapshot_realname(objset_t *os, char *name, char *real, int maxlen,
+dmu_snapshot_realname(objset_t *os, const char *name, char *real, int maxlen,
     boolean_t *conflict)
 {
 	dsl_dataset_t *ds = os->os_dsl_dataset;
diff --git a/module/zfs/spa.c b/module/zfs/spa.c
index 532f04b91..2c70cf701 100644
--- a/module/zfs/spa.c
+++ b/module/zfs/spa.c
@@ -6225,7 +6225,7 @@ spa_tryimport(nvlist_t *tryconfig)
  * we don't sync the labels or remove the configuration cache.
  */
 static int
-spa_export_common(char *pool, int new_state, nvlist_t **oldconfig,
+spa_export_common(const char *pool, int new_state, nvlist_t **oldconfig,
     boolean_t force, boolean_t hardforce)
 {
 	spa_t *spa;
@@ -6369,7 +6369,7 @@ export_spa:
  * Destroy a storage pool.
  */
 int
-spa_destroy(char *pool)
+spa_destroy(const char *pool)
 {
 	return (spa_export_common(pool, POOL_STATE_DESTROYED, NULL,
 	    B_FALSE, B_FALSE));
@@ -6379,7 +6379,7 @@ spa_destroy(char *pool)
  * Export a storage pool.
  */
 int
-spa_export(char *pool, nvlist_t **oldconfig, boolean_t force,
+spa_export(const char *pool, nvlist_t **oldconfig, boolean_t force,
     boolean_t hardforce)
 {
 	return (spa_export_common(pool, POOL_STATE_EXPORTED, oldconfig,
@@ -6391,7 +6391,7 @@ spa_export(char *pool, nvlist_t **oldconfig, boolean_t force,
  * from the namespace in any way.
  */
 int
-spa_reset(char *pool)
+spa_reset(const char *pool)
 {
 	return (spa_export_common(pool, POOL_STATE_UNINITIALIZED, NULL,
 	    B_FALSE, B_FALSE));
diff --git a/module/zfs/zfeature.c b/module/zfs/zfeature.c
index 3757443a5..9d16fff81 100644
--- a/module/zfs/zfeature.c
+++ b/module/zfs/zfeature.c
@@ -203,7 +203,7 @@ spa_features_check(spa_t *spa, boolean_t for_write,
 			supported = B_FALSE;
 
 			if (NULL != unsup_feat) {
-				char *desc = "";
+				const char *desc = "";
 
 				if (zap_lookup(os, spa->spa_feat_desc_obj,
 				    za->za_name, 1, MAXPATHLEN, buf) == 0)
diff --git a/module/zfs/zfs_ioctl.c b/module/zfs/zfs_ioctl.c
index d2550750c..94cd1a3dc 100644
--- a/module/zfs/zfs_ioctl.c
+++ b/module/zfs/zfs_ioctl.c
@@ -270,7 +270,7 @@ static int zfs_ioc_userspace_upgrade(zfs_cmd_t *zc);
 static int zfs_ioc_id_quota_upgrade(zfs_cmd_t *zc);
 static int zfs_check_settable(const char *name, nvpair_t *property,
     cred_t *cr);
-static int zfs_check_clearable(char *dataset, nvlist_t *props,
+static int zfs_check_clearable(const char *dataset, nvlist_t *props,
     nvlist_t **errors);
 static int zfs_fill_zplprops_root(uint64_t, nvlist_t *, nvlist_t *,
     boolean_t *);
@@ -498,7 +498,7 @@ zfs_secpolicy_write_perms(const char *name, const char *perm, cred_t *cr)
  * Returns 0 for success, non-zero for access and other errors.
  */
 static int
-zfs_set_slabel_policy(const char *name, char *strval, cred_t *cr)
+zfs_set_slabel_policy(const char *name, const char *strval, cred_t *cr)
 {
 #ifdef HAVE_MLSLABEL
 	char		ds_hexsl[MAXNAMELEN];
@@ -553,7 +553,7 @@ zfs_set_slabel_policy(const char *name, char *strval, cred_t *cr)
 	 */
 	if (strcasecmp(ds_hexsl, ZFS_MLSLABEL_DEFAULT) != 0) {
 		objset_t *os;
-		static char *setsl_tag = "setsl_tag";
+		static const char *setsl_tag = "setsl_tag";
 
 		/*
 		 * Try to own the dataset; abort if there is any error,
@@ -680,7 +680,7 @@ zfs_secpolicy_send(zfs_cmd_t *zc, nvlist_t *innvl, cred_t *cr)
 {
 	dsl_pool_t *dp;
 	dsl_dataset_t *ds;
-	char *cp;
+	const char *cp;
 	int error;
 
 	/*
@@ -1443,7 +1443,7 @@ zfs_ioc_pool_create(zfs_cmd_t *zc)
 	nvlist_t *rootprops = NULL;
 	nvlist_t *zplprops = NULL;
 	dsl_crypto_params_t *dcp = NULL;
-	char *spa_name = zc->zc_name;
+	const char *spa_name = zc->zc_name;
 	boolean_t unload_wkey = B_TRUE;
 
 	if ((error = get_nvlist(zc->zc_nvlist_conf, zc->zc_nvlist_conf_size,
@@ -1997,7 +1997,7 @@ static int
 zfs_ioc_vdev_setpath(zfs_cmd_t *zc)
 {
 	spa_t *spa;
-	char *path = zc->zc_value;
+	const char *path = zc->zc_value;
 	uint64_t guid = zc->zc_guid;
 	int error;
 
@@ -2014,7 +2014,7 @@ static int
 zfs_ioc_vdev_setfru(zfs_cmd_t *zc)
 {
 	spa_t *spa;
-	char *fru = zc->zc_value;
+	const char *fru = zc->zc_value;
 	uint64_t guid = zc->zc_guid;
 	int error;
 
@@ -2351,8 +2351,7 @@ zfs_prop_set_userquota(const char *dsname, nvpair_t *pair)
 	const char *propname = nvpair_name(pair);
 	uint64_t *valary;
 	unsigned int vallen;
-	const char *domain;
-	char *dash;
+	const char *dash, *domain;
 	zfs_userquota_prop_t type;
 	uint64_t rid;
 	uint64_t quota;
@@ -2405,7 +2404,7 @@ zfs_prop_set_special(const char *dsname, zprop_source_t source,
 	const char *propname = nvpair_name(pair);
 	zfs_prop_t prop = zfs_name_to_prop(propname);
 	uint64_t intval = 0;
-	char *strval = NULL;
+	const char *strval = NULL;
 	int err = -1;
 
 	if (prop == ZPROP_INVAL) {
@@ -2531,7 +2530,7 @@ zfs_set_prop_nvlist(const char *dsname, zprop_source_t source, nvlist_t *nvl,
 	nvpair_t *propval;
 	int rv = 0;
 	uint64_t intval;
-	char *strval;
+	const char *strval;
 
 	nvlist_t *genericnvl = fnvlist_alloc();
 	nvlist_t *retrynvl = fnvlist_alloc();
@@ -3349,7 +3348,7 @@ zfs_ioc_clone(const char *fsname, nvlist_t *innvl, nvlist_t *outnvl)
 {
 	int error = 0;
 	nvlist_t *nvprops = NULL;
-	char *origin_name;
+	const char *origin_name;
 
 	origin_name = fnvlist_lookup_string(innvl, "origin");
 	(void) nvlist_lookup_nvlist(innvl, "props", &nvprops);
@@ -3475,10 +3474,10 @@ static const zfs_ioc_key_t zfs_keys_log_history[] = {
 static int
 zfs_ioc_log_history(const char *unused, nvlist_t *innvl, nvlist_t *outnvl)
 {
-	char *message;
+	const char *message;
+	char *poolname;
 	spa_t *spa;
 	int error;
-	char *poolname;
 
 	/*
 	 * The poolname in the ioctl is not set, we get it from the TSD,
@@ -3574,7 +3573,7 @@ zfs_unmount_snap(const char *snapname)
 	if (strchr(snapname, '@') == NULL)
 		return;
 
-	(void) zfsctl_snapshot_unmount((char *)snapname, MNT_FORCE);
+	(void) zfsctl_snapshot_unmount(snapname, MNT_FORCE);
 }
 
 /* ARGSUSED */
@@ -4617,7 +4616,7 @@ zfs_check_settable(const char *dsname, nvpair_t *pair, cred_t *cr)
  * pointed at by errlist is NULL.
  */
 static int
-zfs_check_clearable(char *dataset, nvlist_t *props, nvlist_t **errlist)
+zfs_check_clearable(const char *dataset, nvlist_t *props, nvlist_t **errlist)
 {
 	zfs_cmd_t *zc;
 	nvpair_t *pair, *next_pair;
diff --git a/module/zfs/zfs_log.c b/module/zfs/zfs_log.c
index fb44007fe..4bb529f78 100644
--- a/module/zfs/zfs_log.c
+++ b/module/zfs/zfs_log.c
@@ -299,7 +299,7 @@ zfs_xattr_owner_unlinked(znode_t *zp)
  */
 void
 zfs_log_create(zilog_t *zilog, dmu_tx_t *tx, uint64_t txtype,
-    znode_t *dzp, znode_t *zp, char *name, vsecattr_t *vsecp,
+    znode_t *dzp, znode_t *zp, const char *name, vsecattr_t *vsecp,
     zfs_fuid_info_t *fuidp, vattr_t *vap)
 {
 	itx_t *itx;
@@ -413,7 +413,7 @@ zfs_log_create(zilog_t *zilog, dmu_tx_t *tx, uint64_t txtype,
  */
 void
 zfs_log_remove(zilog_t *zilog, dmu_tx_t *tx, uint64_t txtype,
-    znode_t *dzp, char *name, uint64_t foid, boolean_t unlinked)
+    znode_t *dzp, const char *name, uint64_t foid, boolean_t unlinked)
 {
 	itx_t *itx;
 	lr_remove_t *lr;
@@ -448,7 +448,7 @@ zfs_log_remove(zilog_t *zilog, dmu_tx_t *tx, uint64_t txtype,
  */
 void
 zfs_log_link(zilog_t *zilog, dmu_tx_t *tx, uint64_t txtype,
-    znode_t *dzp, znode_t *zp, char *name)
+    znode_t *dzp, znode_t *zp, const char *name)
 {
 	itx_t *itx;
 	lr_link_t *lr;
@@ -471,7 +471,7 @@ zfs_log_link(zilog_t *zilog, dmu_tx_t *tx, uint64_t txtype,
  */
 void
 zfs_log_symlink(zilog_t *zilog, dmu_tx_t *tx, uint64_t txtype,
-    znode_t *dzp, znode_t *zp, char *name, char *link)
+    znode_t *dzp, znode_t *zp, const char *name, const char *link)
 {
 	itx_t *itx;
 	lr_create_t *lr;
@@ -502,8 +502,8 @@ zfs_log_symlink(zilog_t *zilog, dmu_tx_t *tx, uint64_t txtype,
  * Handles TX_RENAME transactions.
  */
 void
-zfs_log_rename(zilog_t *zilog, dmu_tx_t *tx, uint64_t txtype,
-    znode_t *sdzp, char *sname, znode_t *tdzp, char *dname, znode_t *szp)
+zfs_log_rename(zilog_t *zilog, dmu_tx_t *tx, uint64_t txtype, znode_t *sdzp,
+    const char *sname, znode_t *tdzp, const char *dname, znode_t *szp)
 {
 	itx_t *itx;
 	lr_rename_t *lr;