diff --git a/sys/fs/tarfs/tarfs_io.c b/sys/fs/tarfs/tarfs_io.c
index b957ac11ff51..87885fbb329c 100644
--- a/sys/fs/tarfs/tarfs_io.c
+++ b/sys/fs/tarfs/tarfs_io.c
@@ -1,727 +1,731 @@
 /*-
  * SPDX-License-Identifier: BSD-2-Clause
  *
  * Copyright (c) 2013 Juniper Networks, Inc.
  * Copyright (c) 2022-2023 Klara, Inc.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
  *    documentation and/or other materials provided with the distribution.
  *
  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  * SUCH DAMAGE.
  */
 
 #include "opt_tarfs.h"
 #include "opt_zstdio.h"
 
 #include <sys/param.h>
 #include <sys/systm.h>
 #include <sys/counter.h>
 #include <sys/bio.h>
 #include <sys/buf.h>
 #include <sys/malloc.h>
 #include <sys/mount.h>
 #include <sys/sysctl.h>
 #include <sys/uio.h>
 #include <sys/vnode.h>
 
 #ifdef ZSTDIO
 #define ZSTD_STATIC_LINKING_ONLY
 #include <contrib/zstd/lib/zstd.h>
 #endif
 
 #include <fs/tarfs/tarfs.h>
 #include <fs/tarfs/tarfs_dbg.h>
 
 #ifdef TARFS_DEBUG
 SYSCTL_NODE(_vfs_tarfs, OID_AUTO, zio, CTLFLAG_RD, 0,
     "Tar filesystem decompression layer");
 COUNTER_U64_DEFINE_EARLY(tarfs_zio_inflated);
 SYSCTL_COUNTER_U64(_vfs_tarfs_zio, OID_AUTO, inflated, CTLFLAG_RD,
     &tarfs_zio_inflated, "Amount of compressed data inflated.");
 COUNTER_U64_DEFINE_EARLY(tarfs_zio_consumed);
 SYSCTL_COUNTER_U64(_vfs_tarfs_zio, OID_AUTO, consumed, CTLFLAG_RD,
     &tarfs_zio_consumed, "Amount of compressed data consumed.");
 COUNTER_U64_DEFINE_EARLY(tarfs_zio_bounced);
 SYSCTL_COUNTER_U64(_vfs_tarfs_zio, OID_AUTO, bounced, CTLFLAG_RD,
     &tarfs_zio_bounced, "Amount of decompressed data bounced.");
 
 static int
 tarfs_sysctl_handle_zio_reset(SYSCTL_HANDLER_ARGS)
 {
 	unsigned int tmp;
 	int error;
 
 	tmp = 0;
 	if ((error = SYSCTL_OUT(req, &tmp, sizeof(tmp))) != 0)
 		return (error);
 	if (req->newptr != NULL) {
 		if ((error = SYSCTL_IN(req, &tmp, sizeof(tmp))) != 0)
 			return (error);
 		counter_u64_zero(tarfs_zio_inflated);
 		counter_u64_zero(tarfs_zio_consumed);
 		counter_u64_zero(tarfs_zio_bounced);
 	}
 	return (0);
 }
 
 SYSCTL_PROC(_vfs_tarfs_zio, OID_AUTO, reset,
     CTLTYPE_INT | CTLFLAG_MPSAFE | CTLFLAG_RW,
     NULL, 0, tarfs_sysctl_handle_zio_reset, "IU",
     "Reset compression counters.");
 #endif
 
 MALLOC_DEFINE(M_TARFSZSTATE, "tarfs zstate", "tarfs decompression state");
 MALLOC_DEFINE(M_TARFSZBUF, "tarfs zbuf", "tarfs decompression buffers");
 
 #define XZ_MAGIC		(uint8_t[]){ 0xfd, 0x37, 0x7a, 0x58, 0x5a }
 #define ZLIB_MAGIC		(uint8_t[]){ 0x1f, 0x8b, 0x08 }
 #define ZSTD_MAGIC		(uint8_t[]){ 0x28, 0xb5, 0x2f, 0xfd }
 
 #ifdef ZSTDIO
 struct tarfs_zstd {
 	ZSTD_DStream *zds;
 };
 #endif
 
 /* XXX review use of curthread / uio_td / td_cred */
 
 /*
  * Reads from the tar file according to the provided uio.  If the archive
  * is compressed and raw is false, reads the decompressed stream;
  * otherwise, reads directly from the original file.  Returns 0 on success
  * and a positive errno value on failure.
  */
 int
 tarfs_io_read(struct tarfs_mount *tmp, bool raw, struct uio *uiop)
 {
 	void *rl = NULL;
 	off_t off = uiop->uio_offset;
 	size_t len = uiop->uio_resid;
 	int error;
 
 	if (raw || tmp->znode == NULL) {
 		rl = vn_rangelock_rlock(tmp->vp, off, off + len);
 		error = vn_lock(tmp->vp, LK_SHARED);
 		if (error == 0) {
 			error = VOP_READ(tmp->vp, uiop,
 			    IO_DIRECT|IO_NODELOCKED,
 			    uiop->uio_td->td_ucred);
 			VOP_UNLOCK(tmp->vp);
 		}
 		vn_rangelock_unlock(tmp->vp, rl);
 	} else {
 		error = vn_lock(tmp->znode, LK_EXCLUSIVE);
 		if (error == 0) {
 			error = VOP_READ(tmp->znode, uiop,
 			    IO_DIRECT | IO_NODELOCKED,
 			    uiop->uio_td->td_ucred);
 			VOP_UNLOCK(tmp->znode);
 		}
 	}
 	TARFS_DPF(IO, "%s(%zu, %zu) = %d (resid %zd)\n", __func__,
 	    (size_t)off, len, error, uiop->uio_resid);
 	return (error);
 }
 
 /*
  * Reads from the tar file into the provided buffer.  If the archive is
  * compressed and raw is false, reads the decompressed stream; otherwise,
  * reads directly from the original file.  Returns the number of bytes
  * read on success, 0 on EOF, and a negative errno value on failure.
  */
 ssize_t
 tarfs_io_read_buf(struct tarfs_mount *tmp, bool raw,
     void *buf, off_t off, size_t len)
 {
 	struct uio auio;
 	struct iovec aiov;
 	ssize_t res;
 	int error;
 
 	if (len == 0) {
 		TARFS_DPF(IO, "%s(%zu, %zu) null\n", __func__,
 		    (size_t)off, len);
 		return (0);
 	}
 	aiov.iov_base = buf;
 	aiov.iov_len = len;
 	auio.uio_iov = &aiov;
 	auio.uio_iovcnt = 1;
 	auio.uio_offset = off;
 	auio.uio_segflg = UIO_SYSSPACE;
 	auio.uio_rw = UIO_READ;
 	auio.uio_resid = len;
 	auio.uio_td = curthread;
 	error = tarfs_io_read(tmp, raw, &auio);
 	if (error != 0) {
 		TARFS_DPF(IO, "%s(%zu, %zu) error %d\n", __func__,
 		    (size_t)off, len, error);
 		return (-error);
 	}
 	res = len - auio.uio_resid;
 	if (res == 0 && len != 0) {
 		TARFS_DPF(IO, "%s(%zu, %zu) eof\n", __func__,
 		    (size_t)off, len);
 	} else {
 		TARFS_DPF(IO, "%s(%zu, %zu) read %zd | %*D\n", __func__,
 		    (size_t)off, len, res,
 		    (int)(res > 8 ? 8 : res), (uint8_t *)buf, " ");
 	}
 	return (res);
 }
 
 #ifdef ZSTDIO
 static void *
 tarfs_zstate_alloc(void *opaque, size_t size)
 {
 
 	(void)opaque;
 	return (malloc(size, M_TARFSZSTATE, M_WAITOK));
 }
 #endif
 
 #ifdef ZSTDIO
 static void
 tarfs_zstate_free(void *opaque, void *address)
 {
 
 	(void)opaque;
 	free(address, M_TARFSZSTATE);
 }
 #endif
 
 #ifdef ZSTDIO
 static ZSTD_customMem tarfs_zstd_mem = {
 	tarfs_zstate_alloc,
 	tarfs_zstate_free,
 	NULL,
 };
 #endif
 
 /*
  * Updates the decompression frame index, recording the current input and
  * output offsets in a new index entry, and growing the index if
  * necessary.
  */
 static void
 tarfs_zio_update_index(struct tarfs_zio *zio, off_t i, off_t o)
 {
 
 	if (++zio->curidx >= zio->nidx) {
 		if (++zio->nidx > zio->szidx) {
 			zio->szidx *= 2;
 			zio->idx = realloc(zio->idx,
 			    zio->szidx * sizeof(*zio->idx),
 			    M_TARFSZSTATE, M_ZERO | M_WAITOK);
 			TARFS_DPF(ALLOC, "%s: resized zio index\n", __func__);
 		}
 		zio->idx[zio->curidx].i = i;
 		zio->idx[zio->curidx].o = o;
 		TARFS_DPF(ZIDX, "%s: index %u = i %zu o %zu\n", __func__,
 		    zio->curidx, (size_t)zio->idx[zio->curidx].i,
 		    (size_t)zio->idx[zio->curidx].o);
 	}
 	MPASS(zio->idx[zio->curidx].i == i);
 	MPASS(zio->idx[zio->curidx].o == o);
 }
 
 /*
  * VOP_ACCESS for zio node.
  */
 static int
 tarfs_zaccess(struct vop_access_args *ap)
 {
 	struct vnode *vp = ap->a_vp;
 	struct tarfs_zio *zio = vp->v_data;
 	struct tarfs_mount *tmp = zio->tmp;
 	accmode_t accmode = ap->a_accmode;
 	int error = EPERM;
 
 	if (accmode == VREAD) {
 		error = vn_lock(tmp->vp, LK_SHARED);
 		if (error == 0) {
 			error = VOP_ACCESS(tmp->vp, accmode, ap->a_cred, ap->a_td);
 			VOP_UNLOCK(tmp->vp);
 		}
 	}
 	TARFS_DPF(ZIO, "%s(%d) = %d\n", __func__, accmode, error);
 	return (error);
 }
 
 /*
  * VOP_GETATTR for zio node.
  */
 static int
 tarfs_zgetattr(struct vop_getattr_args *ap)
 {
 	struct vattr va;
 	struct vnode *vp = ap->a_vp;
 	struct tarfs_zio *zio = vp->v_data;
 	struct tarfs_mount *tmp = zio->tmp;
 	struct vattr *vap = ap->a_vap;
 	int error = 0;
 
 	VATTR_NULL(vap);
 	error = vn_lock(tmp->vp, LK_SHARED);
 	if (error == 0) {
 		error = VOP_GETATTR(tmp->vp, &va, ap->a_cred);
 		VOP_UNLOCK(tmp->vp);
 		if (error == 0) {
 			vap->va_type = VREG;
 			vap->va_mode = va.va_mode;
 			vap->va_nlink = 1;
 			vap->va_gid = va.va_gid;
 			vap->va_uid = va.va_uid;
 			vap->va_fsid = vp->v_mount->mnt_stat.f_fsid.val[0];
 			vap->va_fileid = TARFS_ZIOINO;
 			vap->va_size = zio->idx[zio->nidx - 1].o;
 			vap->va_blocksize = vp->v_mount->mnt_stat.f_iosize;
 			vap->va_atime = va.va_atime;
 			vap->va_ctime = va.va_ctime;
 			vap->va_mtime = va.va_mtime;
 			vap->va_birthtime = tmp->root->birthtime;
 			vap->va_bytes = va.va_bytes;
 		}
 	}
 	TARFS_DPF(ZIO, "%s() = %d\n", __func__, error);
 	return (error);
 }
 
 #ifdef ZSTDIO
 /*
  * VOP_READ for zio node, zstd edition.
  */
 static int
 tarfs_zread_zstd(struct tarfs_zio *zio, struct uio *uiop)
 {
 	void *ibuf = NULL, *obuf = NULL, *rl = NULL;
 	struct uio auio;
 	struct iovec aiov;
 	struct tarfs_mount *tmp = zio->tmp;
 	struct tarfs_zstd *zstd = zio->zstd;
 	struct thread *td = curthread;
 	ZSTD_inBuffer zib;
 	ZSTD_outBuffer zob;
 	off_t zsize;
 	off_t ipos, opos;
 	size_t ilen, olen;
 	size_t zerror;
 	off_t off = uiop->uio_offset;
 	size_t len = uiop->uio_resid;
 	size_t resid = uiop->uio_resid;
 	size_t bsize;
 	int error;
 	bool reset = false;
 
 	/* do we have to rewind? */
 	if (off < zio->opos) {
 		while (zio->curidx > 0 && off < zio->idx[zio->curidx].o)
 			zio->curidx--;
 		reset = true;
 	}
 	/* advance to the nearest index entry */
 	if (off > zio->opos) {
 		// XXX maybe do a binary search instead
 		while (zio->curidx < zio->nidx - 1 &&
 		    off >= zio->idx[zio->curidx + 1].o) {
 			zio->curidx++;
 			reset = true;
 		}
 	}
 	/* reset the decompression stream if needed */
 	if (reset) {
 		zio->ipos = zio->idx[zio->curidx].i;
 		zio->opos = zio->idx[zio->curidx].o;
 		ZSTD_resetDStream(zstd->zds);
 		TARFS_DPF(ZIDX, "%s: skipping to index %u = i %zu o %zu\n", __func__,
 		    zio->curidx, (size_t)zio->ipos, (size_t)zio->opos);
 	} else {
 		TARFS_DPF(ZIDX, "%s: continuing at i %zu o %zu\n", __func__,
 		    (size_t)zio->ipos, (size_t)zio->opos);
 	}
 
 	/*
 	 * Set up a temporary buffer for compressed data.  Use the size
 	 * recommended by the zstd library; this is usually 128 kB, but
 	 * just in case, make sure it's a multiple of the page size and no
 	 * larger than MAXBSIZE.
 	 */
 	bsize = roundup(ZSTD_CStreamOutSize(), PAGE_SIZE);
 	if (bsize > MAXBSIZE)
 		bsize = MAXBSIZE;
 	ibuf = malloc(bsize, M_TEMP, M_WAITOK);
 	zib.src = NULL;
 	zib.size = 0;
 	zib.pos = 0;
 
 	/*
 	 * Set up the decompression buffer.  If the target is not in
 	 * kernel space, we will have to set up a bounce buffer.
 	 *
 	 * TODO: to avoid using a bounce buffer, map destination pages
 	 * using vm_fault_quick_hold_pages().
 	 */
 	MPASS(zio->opos <= off);
 	MPASS(uiop->uio_iovcnt == 1);
 	MPASS(uiop->uio_iov->iov_len >= len);
 	if (uiop->uio_segflg == UIO_SYSSPACE) {
 		zob.dst = uiop->uio_iov->iov_base;
 	} else {
 		TARFS_DPF(ALLOC, "%s: allocating %zu-byte bounce buffer\n",
 		    __func__, len);
 		zob.dst = obuf = malloc(len, M_TEMP, M_WAITOK);
 	}
 	zob.size = len;
 	zob.pos = 0;
 
 	/* lock tarball */
 	rl = vn_rangelock_rlock(tmp->vp, zio->ipos, OFF_MAX);
 	error = vn_lock(tmp->vp, LK_SHARED);
 	if (error != 0) {
 		goto fail_unlocked;
 	}
 	/* check size */
 	error = vn_getsize_locked(tmp->vp, &zsize, td->td_ucred);
 	if (error != 0) {
 		goto fail;
 	}
 	if (zio->ipos >= zsize) {
 		/* beyond EOF */
 		goto fail;
 	}
 
 	while (resid > 0) {
 		if (zib.pos == zib.size) {
 			/* request data from the underlying file */
 			aiov.iov_base = ibuf;
 			aiov.iov_len = bsize;
 			auio.uio_iov = &aiov;
 			auio.uio_iovcnt = 1;
 			auio.uio_offset = zio->ipos;
 			auio.uio_segflg = UIO_SYSSPACE;
 			auio.uio_rw = UIO_READ;
 			auio.uio_resid = aiov.iov_len;
 			auio.uio_td = td;
 			error = VOP_READ(tmp->vp, &auio,
 			    IO_DIRECT | IO_NODELOCKED,
 			    td->td_ucred);
 			if (error != 0)
 				goto fail;
 			TARFS_DPF(ZIO, "%s: req %zu+%zu got %zu+%zu\n", __func__,
 			    (size_t)zio->ipos, bsize,
 			    (size_t)zio->ipos, bsize - auio.uio_resid);
 			zib.src = ibuf;
 			zib.size = bsize - auio.uio_resid;
 			zib.pos = 0;
 		}
 		MPASS(zib.pos <= zib.size);
 		if (zib.pos == zib.size) {
 			TARFS_DPF(ZIO, "%s: end of file after i %zu o %zu\n", __func__,
 			    (size_t)zio->ipos, (size_t)zio->opos);
 			goto fail;
 		}
 		if (zio->opos < off) {
 			/* to be discarded */
 			zob.size = min(off - zio->opos, len);
 			zob.pos = 0;
 		} else {
 			zob.size = len;
 			zob.pos = zio->opos - off;
 		}
 		ipos = zib.pos;
 		opos = zob.pos;
 		/* decompress as much as possible */
 		zerror = ZSTD_decompressStream(zstd->zds, &zob, &zib);
 		zio->ipos += ilen = zib.pos - ipos;
 		zio->opos += olen = zob.pos - opos;
 		if (zio->opos > off)
 			resid -= olen;
 		if (ZSTD_isError(zerror)) {
 			TARFS_DPF(ZIO, "%s: inflate failed after i %zu o %zu: %s\n", __func__,
 			    (size_t)zio->ipos, (size_t)zio->opos, ZSTD_getErrorName(zerror));
 			error = EIO;
 			goto fail;
 		}
 		if (zerror == 0 && olen == 0) {
 			TARFS_DPF(ZIO, "%s: end of stream after i %zu o %zu\n", __func__,
 			    (size_t)zio->ipos, (size_t)zio->opos);
 			break;
 		}
 		if (zerror == 0) {
 			TARFS_DPF(ZIO, "%s: end of frame after i %zu o %zu\n", __func__,
 			    (size_t)zio->ipos, (size_t)zio->opos);
 			tarfs_zio_update_index(zio, zio->ipos, zio->opos);
 		}
 		TARFS_DPF(ZIO, "%s: inflated %zu\n", __func__, olen);
 #ifdef TARFS_DEBUG
 		counter_u64_add(tarfs_zio_inflated, olen);
 #endif
 	}
 fail:
 	VOP_UNLOCK(tmp->vp);
 fail_unlocked:
 	if (error == 0) {
 		if (uiop->uio_segflg == UIO_SYSSPACE) {
 			uiop->uio_resid = resid;
 		} else if (len > resid) {
 			TARFS_DPF(ALLOC, "%s: bounced %zu bytes\n", __func__,
 			    len - resid);
 			error = uiomove(obuf, len - resid, uiop);
 #ifdef TARFS_DEBUG
 			counter_u64_add(tarfs_zio_bounced, len - resid);
 #endif
 		}
 	}
 	if (obuf != NULL) {
 		TARFS_DPF(ALLOC, "%s: freeing bounce buffer\n", __func__);
 		free(obuf, M_TEMP);
 	}
 	if (rl != NULL)
 		vn_rangelock_unlock(tmp->vp, rl);
 	if (ibuf != NULL)
 		free(ibuf, M_TEMP);
 	TARFS_DPF(ZIO, "%s(%zu, %zu) = %d (resid %zd)\n", __func__,
 	    (size_t)off, len, error, uiop->uio_resid);
 #ifdef TARFS_DEBUG
 	counter_u64_add(tarfs_zio_consumed, len - uiop->uio_resid);
 #endif
 	if (error != 0) {
 		zio->curidx = 0;
 		zio->ipos = zio->idx[0].i;
 		zio->opos = zio->idx[0].o;
 		ZSTD_resetDStream(zstd->zds);
 	}
 	return (error);
 }
 #endif
 
 /*
  * VOP_READ for zio node.
  */
 static int
 tarfs_zread(struct vop_read_args *ap)
 {
+#if defined(TARFS_DEBUG) || defined(ZSTDIO)
 	struct vnode *vp = ap->a_vp;
 	struct tarfs_zio *zio = vp->v_data;
 	struct uio *uiop = ap->a_uio;
+#endif
 #ifdef TARFS_DEBUG
 	off_t off = uiop->uio_offset;
 	size_t len = uiop->uio_resid;
 #endif
 	int error;
 
 	TARFS_DPF(ZIO, "%s(%zu, %zu)\n", __func__,
 	    (size_t)off, len);
 #ifdef ZSTDIO
 	if (zio->zstd != NULL) {
 		error = tarfs_zread_zstd(zio, uiop);
 	} else
 #endif
 		error = EFTYPE;
 	TARFS_DPF(ZIO, "%s(%zu, %zu) = %d (resid %zd)\n", __func__,
 	    (size_t)off, len, error, uiop->uio_resid);
 	return (error);
 }
 
 /*
  * VOP_RECLAIM for zio node.
  */
 static int
 tarfs_zreclaim(struct vop_reclaim_args *ap)
 {
 	struct vnode *vp = ap->a_vp;
 
 	TARFS_DPF(ZIO, "%s(%p)\n", __func__, vp);
 	vp->v_data = NULL;
 	vnode_destroy_vobject(vp);
 	cache_purge(vp);
 	return (0);
 }
 
 /*
  * VOP_STRATEGY for zio node.
  */
 static int
 tarfs_zstrategy(struct vop_strategy_args *ap)
 {
 	struct uio auio;
 	struct iovec iov;
 	struct vnode *vp = ap->a_vp;
 	struct buf *bp = ap->a_bp;
 	off_t off;
 	size_t len;
 	int error;
 
 	iov.iov_base = bp->b_data;
 	iov.iov_len = bp->b_bcount;
 	off = bp->b_iooffset;
 	len = bp->b_bcount;
 	bp->b_resid = len;
 	auio.uio_iov = &iov;
 	auio.uio_iovcnt = 1;
 	auio.uio_offset = off;
 	auio.uio_resid = len;
 	auio.uio_segflg = UIO_SYSSPACE;
 	auio.uio_rw = UIO_READ;
 	auio.uio_td = curthread;
 	error = VOP_READ(vp, &auio, IO_DIRECT | IO_NODELOCKED, bp->b_rcred);
 	bp->b_flags |= B_DONE;
 	if (error != 0) {
 		bp->b_ioflags |= BIO_ERROR;
 		bp->b_error = error;
 	}
 	return (0);
 }
 
 static struct vop_vector tarfs_znodeops = {
 	.vop_default =		&default_vnodeops,
 
 	.vop_access =		tarfs_zaccess,
 	.vop_getattr =		tarfs_zgetattr,
 	.vop_read =		tarfs_zread,
 	.vop_reclaim =		tarfs_zreclaim,
 	.vop_strategy =		tarfs_zstrategy,
 };
 VFS_VOP_VECTOR_REGISTER(tarfs_znodeops);
 
 /*
  * Initializes the decompression layer.
  */
 static struct tarfs_zio *
 tarfs_zio_init(struct tarfs_mount *tmp, off_t i, off_t o)
 {
 	struct tarfs_zio *zio;
 	struct vnode *zvp;
 
 	zio = malloc(sizeof(*zio), M_TARFSZSTATE, M_ZERO | M_WAITOK);
 	TARFS_DPF(ALLOC, "%s: allocated zio\n", __func__);
 	zio->tmp = tmp;
 	zio->szidx = 128;
 	zio->idx = malloc(zio->szidx * sizeof(*zio->idx), M_TARFSZSTATE,
 	    M_ZERO | M_WAITOK);
 	zio->curidx = 0;
 	zio->nidx = 1;
 	zio->idx[zio->curidx].i = zio->ipos = i;
 	zio->idx[zio->curidx].o = zio->opos = o;
 	tmp->zio = zio;
 	TARFS_DPF(ALLOC, "%s: allocated zio index\n", __func__);
 	getnewvnode("tarfsz", tmp->vfs, &tarfs_znodeops, &zvp);
 	zvp->v_data = zio;
 	zvp->v_type = VREG;
 	zvp->v_mount = tmp->vfs;
 	vn_set_state(zvp, VSTATE_CONSTRUCTED);
 	tmp->znode = zvp;
 	TARFS_DPF(ZIO, "%s: created zio node\n", __func__);
 	return (zio);
 }
 
 /*
  * Initializes the I/O layer, including decompression if the signature of
  * a supported compression format is detected.  Returns 0 on success and a
  * positive errno value on failure.
  */
 int
 tarfs_io_init(struct tarfs_mount *tmp)
 {
 	uint8_t *block;
+#ifdef ZSTDIO
 	struct tarfs_zio *zio = NULL;
+#endif
 	ssize_t res;
 	int error = 0;
 
 	block = malloc(tmp->iosize, M_TEMP, M_ZERO | M_WAITOK);
 	res = tarfs_io_read_buf(tmp, true, block, 0, tmp->iosize);
 	if (res < 0) {
 		return (-res);
 	}
 	if (memcmp(block, XZ_MAGIC, sizeof(XZ_MAGIC)) == 0) {
 		printf("xz compression not supported\n");
 		error = EOPNOTSUPP;
 		goto bad;
 	} else if (memcmp(block, ZLIB_MAGIC, sizeof(ZLIB_MAGIC)) == 0) {
 		printf("zlib compression not supported\n");
 		error = EOPNOTSUPP;
 		goto bad;
 	} else if (memcmp(block, ZSTD_MAGIC, sizeof(ZSTD_MAGIC)) == 0) {
 #ifdef ZSTDIO
 		zio = tarfs_zio_init(tmp, 0, 0);
 		zio->zstd = malloc(sizeof(*zio->zstd), M_TARFSZSTATE, M_WAITOK);
 		zio->zstd->zds = ZSTD_createDStream_advanced(tarfs_zstd_mem);
 		(void)ZSTD_initDStream(zio->zstd->zds);
 #else
 		printf("zstd compression not supported\n");
 		error = EOPNOTSUPP;
 		goto bad;
 #endif
 	}
 bad:
 	free(block, M_TEMP);
 	return (error);
 }
 
 /*
  * Tears down the decompression layer.
  */
 static int
 tarfs_zio_fini(struct tarfs_mount *tmp)
 {
 	struct tarfs_zio *zio = tmp->zio;
 	int error = 0;
 
 	if (tmp->znode != NULL) {
 		error = vn_lock(tmp->znode, LK_EXCLUSIVE);
 		if (error != 0) {
 			TARFS_DPF(ALLOC, "%s: failed to lock znode", __func__);
 			return (error);
 		}
 		tmp->znode->v_mount = NULL;
 		vgone(tmp->znode);
 		vput(tmp->znode);
 		tmp->znode = NULL;
 	}
 #ifdef ZSTDIO
 	if (zio->zstd != NULL) {
 		TARFS_DPF(ALLOC, "%s: freeing zstd state\n", __func__);
 		ZSTD_freeDStream(zio->zstd->zds);
 		free(zio->zstd, M_TARFSZSTATE);
 	}
 #endif
 	if (zio->idx != NULL) {
 		TARFS_DPF(ALLOC, "%s: freeing index\n", __func__);
 		free(zio->idx, M_TARFSZSTATE);
 	}
 	TARFS_DPF(ALLOC, "%s: freeing zio\n", __func__);
 	free(zio, M_TARFSZSTATE);
 	tmp->zio = NULL;
 	return (error);
 }
 
 /*
  * Tears down the I/O layer, including the decompression layer if
  * applicable.
  */
 int
 tarfs_io_fini(struct tarfs_mount *tmp)
 {
 	int error = 0;
 
 	if (tmp->zio != NULL) {
 		error = tarfs_zio_fini(tmp);
 	}
 	return (error);
 }