Everything needed to bring the FUSE kernel protocol in line with

the Linux implementation is now in place. With this update, the
kernel can support ports that talk directly to /dev/fuse0 rather
than relying on libfuse.

sys/fusebuf.h is retained rather than introducing fuse_kernel.h

OK claudio@

lib/libfuse/fuse.c

@@ -1,4 +1,4 @@
-/* $OpenBSD: fuse.c,v 1.59 2026/03/10 16:20:57 deraadt Exp $ */
+/* $OpenBSD: fuse.c,v 1.60 2026/06/17 13:29:01 helg Exp $ */
 /*
  * Copyright (c) 2013 Sylvestre Gallon <ccna.syl@gmail.com>
  *
@@ -82,6 +82,7 @@ static struct fuse_opt fuse_lib_opts[] = {
 	FUSE_OPT_KEY("fmask=%o",		KEY_STUB),
 	FUSE_LIB_OPT("umask=",			set_mode),
 	FUSE_LIB_OPT("umask=%o",		umask),
+	FUSE_OPT_KEY("max_write=",		FUSE_OPT_KEY_KEEP),
 	FUSE_OPT_END
 };
 
@@ -98,7 +99,6 @@ static struct fuse_opt fuse_mount_opts[] = {
 	FUSE_MOUNT_OPT("fsname=%s",		fsname),
 	FUSE_MOUNT_OPT("max_read=%u",		max_read),
 	FUSE_OPT_KEY("max_readahead",		KEY_STUB),
-	FUSE_OPT_KEY("max_write",		KEY_STUB),
 	FUSE_MOUNT_OPT("noatime",		noatime),
 	FUSE_MOUNT_OPT("nonempty",		nonempty),
 	FUSE_MOUNT_OPT("-r",			rdonly),

lib/libfuse/fuse_chan.c

@@ -1,4 +1,4 @@
-/* $OpenBSD: fuse_chan.c,v 1.2 2026/01/22 11:53:31 helg Exp $ */
+/* $OpenBSD: fuse_chan.c,v 1.3 2026/06/17 13:29:01 helg Exp $ */
 /*
  * Copyright (c) 2025 Helg Bredow <helg@openbsd.org>
  *
@@ -16,6 +16,7 @@
  */
 
 #include <errno.h>
+#include <unistd.h>
 
 #include "debug.h"
 #include "fuse_private.h"
@@ -33,27 +34,9 @@ DEF(fuse_chan_fd);
 int
 fuse_chan_recv(struct fuse_chan **chp, char *buf, size_t size)
 {
-	struct fuse_chan *ch = *chp;
-	struct fusebuf *fbuf = (struct fusebuf *)buf;
-	struct iovec iov[2];
 	ssize_t n;
 
-	if (chp == NULL || *chp == NULL || buf == NULL)
+	n = read((*chp)->fd, buf, size);
-		return (-EINVAL);
-
-	/* XXX
-	 * This will change once the kernel protocol is updated to be compatible
-	 * with Linux.
-	 * buf is contiguous memory but our fbuf is separated into the header
-	 * and io structs with a pointer to the data buffer so we need to
-	 * overlay our fbuf with pointer to data buffer.
-	 */
-	iov[0].iov_base = fbuf;
-	iov[0].iov_len  = sizeof(fbuf->fb_hdr) + sizeof(fbuf->FD);
-	iov[1].iov_base = fbuf->fb_dat;
-	iov[1].iov_len  = size - (sizeof(fbuf->fb_hdr) + sizeof(fbuf->FD));
-
-	n = readv(ch->fd, iov, 2);
 	if (n == -1)
 		return (-errno);
 
@@ -67,10 +50,8 @@ fuse_chan_send(struct fuse_chan *ch, const struct iovec iov[], size_t count)
 	ssize_t n;
 
 	n = writev(ch->fd, iov, count);
-	if (n == -1) {
+	if (n == -1)
-		DPERROR(__func__);
 		return (-errno);
-	}
 
 	return (0);
 }

lib/libfuse/fuse_lowlevel.c

@@ -1,4 +1,4 @@
-/* $OpenBSD: fuse_lowlevel.c,v 1.2 2026/01/29 06:04:27 helg Exp $ */
+/* $OpenBSD: fuse_lowlevel.c,v 1.3 2026/06/17 13:29:01 helg Exp $ */
 /*
  * Copyright (c) 2025 Helg Bredow <helg@openbsd.org>
  *
@@ -16,6 +16,8 @@
  */
 
 #include <sys/uio.h>
+#include <sys/fusebuf.h>
+#include <assert.h>
 #include <errno.h>
 #include <stddef.h>
 #include <stdlib.h>
@@ -25,28 +27,48 @@
 #include "debug.h"
 #include "fuse_private.h"
 
+#if defined(__clang__) || __GNUC_PREREQ__(4, 6)
+/* confirm that constants in sys/fusebuf.h and fuse_lowlevel.h match */
+static_assert(FUSE_FATTR_MODE==FUSE_SET_ATTR_MODE, "definition mismatch");
+static_assert(FUSE_FATTR_UID==FUSE_SET_ATTR_UID, "definition mismatch");
+static_assert(FUSE_FATTR_GID==FUSE_SET_ATTR_GID, "definition mismatch");
+static_assert(FUSE_FATTR_SIZE==FUSE_SET_ATTR_SIZE, "definition mismatch");
+static_assert(FUSE_FATTR_ATIME==FUSE_SET_ATTR_ATIME, "definition mismatch");
+static_assert(FUSE_FATTR_MTIME==FUSE_SET_ATTR_MTIME, "definition mismatch");
+/* TODO: not implemented in kernel yet
+static_assert(FUSE_FATTR_ATIME_NOW==FUSE_SET_ATTR_ATIME_NOW,
+    "definition mismatch");
+static_assert(FUSE_FATTR_MTIME_NOW==FUSE_SET_ATTR_MTIME_NOW,
+    "definition mismatch");
+*/
+#endif
+
 enum {
 	KEY_HELP,
 	KEY_VERSION,
 	KEY_DEBUG
 };
 
+/* options supported by fuse_lowlevel_new */
+#define FUSE_LIB_OPT(o, m) {o, offsetof(struct fuse_session, fci.m), 1}
 static const struct fuse_opt fuse_ll_opts[] = {
+	/* core options, also supported by fuse_parse_cmdline(3) */
 	FUSE_OPT_KEY("debug",		KEY_DEBUG),
 	FUSE_OPT_KEY("-d",		KEY_DEBUG),
 	FUSE_OPT_KEY("-h",		KEY_HELP),
 	FUSE_OPT_KEY("--help",		KEY_HELP),
 	FUSE_OPT_KEY("-V",		KEY_VERSION),
 	FUSE_OPT_KEY("--version",	KEY_VERSION),
-	FUSE_OPT_KEY("max_read=",	FUSE_OPT_KEY_DISCARD),
+	/* fuse_lowlevel_new(3) options */
+	FUSE_LIB_OPT("max_write=%u",	max_write),
 	FUSE_OPT_END
 };
 
 static void
 dump_version(void)
 {
-	fprintf(stderr, "FUSE library version: %d.%d\n", FUSE_MAJOR_VERSION,
+	fprintf(stderr, "OpenBSD FUSE library version: %d.%d\n",
-	    FUSE_MINOR_VERSION);
+	    FUSE_MAJOR_VERSION, FUSE_MINOR_VERSION);
 }
 
 static void
@@ -70,12 +92,12 @@ ifuse_ll_opt_proc(void *data, const char *arg, int key,
 		break;
 	case KEY_DEBUG:
 		ifuse_debug_init();
-		return (1);
+		return (0);
 	default:
 		fprintf(stderr, "fuse: unknown option -- %s\n", arg);
 	}
 
-	return -1;
+	return (-1);
 }
 
 struct fuse_session *
@@ -89,11 +111,23 @@ fuse_lowlevel_new(struct fuse_args *fargs,
 	if (se == NULL)
 		return (NULL);
 
-	if (fuse_opt_parse(fargs, NULL, fuse_ll_opts, ifuse_ll_opt_proc) == -1) {
+	se->fci.proto_major = FUSE_KERNEL_VERSION;
+	se->fci.proto_minor = FUSE_KERNEL_MINOR_VERSION;
+	/* default that may be overridden by fargs */
+	se->fci.max_write = FUSEBUFMAXSIZE;
+
+	if (fuse_opt_parse(fargs, se, fuse_ll_opts, ifuse_ll_opt_proc) == -1) {
 		free(se);
 		return (NULL);
 	}
 
+	/* validate parsed options */
+	if (se->fci.max_write > FUSEBUFMAXSIZE) {
+		DPRINTF("libfuse: max_write %u too large, using %u instead.\n",
+		    se->fci.max_write, FUSEBUFMAXSIZE);
+		se->fci.max_write = FUSEBUFMAXSIZE;
+	}
+
 	if (llops->create && !llops->mknod)
 		DPRINTF("libfuse: WARNING: filesystem supports creating files "
 		    "but does not implement mknod. No new files can be "
@@ -113,12 +147,33 @@ fuse_lowlevel_new(struct fuse_args *fargs,
 }
 DEF(fuse_lowlevel_new);
 
+static void
+ifuse_stat2attr(const struct stat *stbuf, struct fuse_attr *attr)
+{
+	memset(attr, 0, sizeof(*attr));
+	attr->ino = stbuf->st_ino;
+	attr->size = stbuf->st_size;
+	attr->blocks = stbuf->st_blocks;
+	attr->atime = stbuf->st_atim.tv_sec;
+	attr->mtime = stbuf->st_mtim.tv_sec;
+	attr->ctime = stbuf->st_ctim.tv_sec;
+	attr->atimensec = stbuf->st_atim.tv_nsec;
+	attr->mtimensec = stbuf->st_mtim.tv_nsec;
+	attr->ctimensec = stbuf->st_ctim.tv_nsec;
+	attr->mode = stbuf->st_mode;
+	attr->nlink = stbuf->st_nlink;
+	attr->uid = stbuf->st_uid;
+	attr->gid = stbuf->st_gid;
+	attr->rdev = stbuf->st_rdev;
+	attr->blksize = stbuf->st_blksize;
+}
+
 static int
-ifuse_reply(fuse_req_t req, const char *data, const size_t data_size, int err)
+ifuse_reply(fuse_req_t req, const void *data, const size_t data_size, int err)
 {
 	struct fusebuf *fbuf;
+	struct fuse_out_header hdr;
 	struct iovec iov[2];
-	size_t fbuf_size;
 
 	/* check for sanity */
 	if (data == NULL && data_size > 0) {
@@ -128,31 +183,28 @@ ifuse_reply(fuse_req_t req, const char *data, const size_t data_size, int err)
 	}
 
 	fbuf = req->fbuf;
-	fbuf_size = sizeof(fbuf->fb_hdr) + sizeof(fbuf->FD);
 
-	fbuf->fb_err = err;
+	hdr.unique = fbuf->fb_uuid;
-	fbuf->fb_len = data_size;
+	hdr.len = sizeof(hdr) + data_size;
+	hdr.error = err;
 
-	iov[0].iov_base = fbuf;
+	iov[0].iov_base = &hdr;
-	iov[0].iov_len  = fbuf_size;
+	iov[0].iov_len  = sizeof(hdr);
 	iov[1].iov_base = (void *)data;
 	iov[1].iov_len  = data_size;
 
-	DPRINTF("errno: %d", fbuf->fb_err);
+	DPRINTF("errno: %d", err);
 
 	return fuse_chan_send(req->ch, iov, 2);
 }
 
-static int
+/*
-ifuse_reply_ok(fuse_req_t req)
+ * fuse_reply_err takes a non-negated errno but kernel expects negated errno.
-{
+ */
-	return ifuse_reply(req, NULL, 0, 0);
-}
-
 int
 fuse_reply_err(fuse_req_t req, int err)
 {
-	return ifuse_reply(req, NULL, 0, err);
+	return ifuse_reply(req, NULL, 0, -err);
 }
 DEF(fuse_reply_err);
 
@@ -173,50 +225,59 @@ DEF(fuse_reply_readlink);
 int
 fuse_reply_write(fuse_req_t req, size_t size)
 {
-	struct fusebuf *fbuf;
+	struct fuse_write_out out;
 
-	fbuf = req->fbuf;
+	memset(&out, 0, sizeof(out));
-	fbuf->fb_io_len = size;
+	out.size = size;
 
-	return ifuse_reply_ok(req);
+	return ifuse_reply(req, &out, sizeof(out), 0);
 }
 DEF(fuse_reply_write);
 
 int
 fuse_reply_attr(fuse_req_t req, const struct stat *stbuf, double attr_timeout)
 {
-	struct fusebuf *fbuf;
+	struct fuse_attr_out out;
 
-	fbuf = req->fbuf;
+	memset(&out, 0, sizeof(out));
-	fbuf->fb_attr = *stbuf;
+	ifuse_stat2attr(stbuf, &out.attr);
 
-	return ifuse_reply_ok(req);
+	return ifuse_reply(req, &out, sizeof(out), 0);
 }
 DEF(fuse_reply_attr);
 
 int
 fuse_reply_entry(fuse_req_t req, const struct fuse_entry_param *e)
 {
-	struct fusebuf *fbuf;
+	struct fuse_entry_out out;
+
+	memset(&out, 0, sizeof(out));
+	out.nodeid = e->ino;
+	out.generation = e->generation;
+	ifuse_stat2attr(&e->attr, &out.attr);
 
-	fbuf = req->fbuf;
-	fbuf->fb_attr = e->attr;
-	fbuf->fb_ino = e->ino;
 	DPRINTF("inode: %llu\t", e->ino);
 
-	return ifuse_reply_ok(req);
+	return ifuse_reply(req, &out, sizeof(out), 0);
 }
 DEF(fuse_reply_entry);
 
 int
 fuse_reply_statfs(fuse_req_t req, const struct statvfs *stbuf)
 {
-	struct fusebuf *fbuf;
+	struct fuse_statfs_out out;
 
-	fbuf = req->fbuf;
+	memset(&out, 0, sizeof(out));
-	fbuf->fb_stat = *stbuf;
+	out.st.bsize = stbuf->f_bsize;
+	out.st.frsize = stbuf->f_frsize;
+	out.st.blocks = stbuf->f_blocks;
+	out.st.bfree = stbuf->f_bfree;
+	out.st.bavail = stbuf->f_bavail;
+	out.st.files = stbuf->f_files;
+	out.st.ffree = stbuf->f_ffree;
+	out.st.namelen = stbuf->f_namemax;
 
-	return ifuse_reply_ok(req);
+	return ifuse_reply(req, &out, sizeof(out), 0);
 }
 DEF(fuse_reply_statfs);
 
@@ -240,12 +301,13 @@ DEF(fuse_reply_create);
 int
 fuse_reply_open(fuse_req_t req, const struct fuse_file_info *ffi)
 {
-	struct fusebuf *fbuf;
+	struct fuse_open_out out;
 
-	fbuf = req->fbuf;
+	memset(&out, 0, sizeof(out));
-	fbuf->fb_io_fd = ffi->fh;
+	out.fh = ffi->fh;
+	out.open_flags = ffi->flags;
 
-	return ifuse_reply_ok(req);
+	return ifuse_reply(req, &out, sizeof(out), 0);
 }
 DEF(fuse_reply_open);
 
@@ -256,22 +318,19 @@ fuse_reply_none(fuse_req_t req)
 }
 DEF(fuse_reply_none);
 
-#define GENERIC_DIRSIZ(NLEN) \
-((sizeof (struct dirent) - (MAXNAMLEN+1)) + ((NLEN+1 + 7) &~ 7))
-
 size_t
 fuse_add_direntry(fuse_req_t req, char *buf, const size_t bufsize,
      const char *name, const struct stat *stbuf, off_t off)
 {
-	struct dirent *dir;
+	struct fuse_dirent *dir;
 	size_t namelen;
 	size_t len;
 
 	if (name == NULL)
 		return (0);
 
-	namelen = strnlen(name, MAXNAMLEN);
+	namelen = strlen(name);
-	len = GENERIC_DIRSIZ(namelen);
+	len = FUSE_DIRENT_ALIGN(FUSE_NAME_OFFSET + namelen);
 
 	/* NULL buf is used to request size to be calculated */
 	if (buf == NULL || stbuf == NULL || req == NULL)
@@ -281,13 +340,14 @@ fuse_add_direntry(fuse_req_t req, char *buf, const size_t bufsize,
 	if (bufsize < len)
 		return (len);
 
-	dir = (struct dirent *)buf;
+	dir = (struct fuse_dirent *)buf;
-	dir->d_fileno = stbuf->st_ino;
+	memset(dir, 0, len);
-	dir->d_type = IFTODT(stbuf->st_mode);
+	dir->ino = stbuf->st_ino;
-	dir->d_reclen = len;
+	dir->type = IFTODT(stbuf->st_mode);
-	dir->d_off = off;
+	dir->off = off;
-	strlcpy(dir->d_name, name, sizeof(dir->d_name));
+	dir->namelen = namelen;
-	dir->d_namlen = strlen(dir->d_name);
+	/* name is not NUL-terminated */
+	memcpy(dir->name, name, namelen);
 
 	return (len);
 }

lib/libfuse/fuse_lowlevel.h

@@ -1,4 +1,4 @@
-/* $OpenBSD: fuse_lowlevel.h,v 1.2 2026/01/22 11:53:31 helg Exp $ */
+/* $OpenBSD: fuse_lowlevel.h,v 1.3 2026/06/17 13:29:01 helg Exp $ */
 /*
  * Copyright (c) 2025 Helg Bredow <helg@openbsd.org>
  *
@@ -126,7 +126,6 @@ void fuse_session_reset(struct fuse_session *);
 void fuse_session_process(struct fuse_session *, const char *, size_t,
     struct fuse_chan *);
 
-
 /*
  * FUSE Channel API Prototypes
  */
@@ -161,7 +160,8 @@ const struct fuse_ctx *fuse_req_ctx(fuse_req_t);
 void *fuse_req_userdata(fuse_req_t);
 
 /*
- * Bitmasks for setattr to indicate what to set.
+ * Bitmasks for setattr to indicate what to set. These must be the same
+ * as the FUSE_FATTR_* definitions in <sys/fusebuf.h>
  */
 #define FUSE_SET_ATTR_MODE	(1 << 0)
 #define FUSE_SET_ATTR_UID	(1 << 1)

lib/libfuse/fuse_ops.c

@@ -1,4 +1,4 @@
-/* $OpenBSD: fuse_ops.c,v 1.42 2026/01/29 06:04:27 helg Exp $ */
+/* $OpenBSD: fuse_ops.c,v 1.43 2026/06/17 13:29:01 helg Exp $ */
 /*
  * Copyright (c) 2013 Sylvestre Gallon <ccna.syl@gmail.com>
  *
@@ -33,7 +33,7 @@
  */
 static fuse_req_t ireq;
 
-const fuse_req_t
+fuse_req_t
 ifuse_req(void)
 {
 	return (ireq);
@@ -192,9 +192,6 @@ out:
 		fuse_reply_err(req, -err);
 }
 
-#define GENERIC_DIRSIZ(NLEN) \
-((sizeof (struct dirent) - (MAXNAMLEN+1)) + ((NLEN+1 + 7) &~ 7))
-
 /*
  * This function adds one directory entry to the buffer.
  * FUSE file systems can implement readdir in one of two ways.
@@ -265,11 +262,15 @@ ifuse_fill_readdir(void *dh, const char *name, const struct stat *stbuf,
 	/* advance buf to start of next entry and now add it for real */
 	buf = (char *) fd->buf + fd->len;
 	resid = fd->size - fd->len;
-	len = fuse_add_direntry(ifuse_req(), buf, resid, name, &attr, off);
-
 	fd->len += len;
 	fd->idx += len;
 
+	if (off)
+		fuse_add_direntry(ifuse_req(), buf, resid, name, &attr, off);
+	else
+		fuse_add_direntry(ifuse_req(), buf, resid, name, &attr,
+		    fd->idx);
+
 	return (0);
 }
 
@@ -769,23 +770,23 @@ ifuse_ops_setattr(fuse_req_t req, fuse_ino_t ino, struct stat *attr,
 	}
 
 	ictx_init(req);
-	if (flags & FUSE_FATTR_MODE) {
+	if (flags & FUSE_SET_ATTR_MODE) {
 		if (f->op.chmod)
 			err = f->op.chmod(realname, attr->st_mode);
 		else
 			err = ENOSYS;
 	}
 
-	if (!err && (flags & FUSE_FATTR_UID || flags & FUSE_FATTR_GID)) {
+	if (!err && (flags & FUSE_SET_ATTR_UID || flags & FUSE_SET_ATTR_GID)) {
-		uid = (flags & FUSE_FATTR_UID) ? attr->st_uid : (uid_t)-1;
+		uid = (flags & FUSE_SET_ATTR_UID) ? attr->st_uid : (uid_t)-1;
-		gid = (flags & FUSE_FATTR_GID) ? attr->st_gid : (gid_t)-1;
+		gid = (flags & FUSE_SET_ATTR_GID) ? attr->st_gid : (gid_t)-1;
 		if (f->op.chown)
 			err = f->op.chown(realname, uid, gid);
 		else
 			err = ENOSYS;
 	}
 
-	if (!err && (flags & FUSE_FATTR_MTIME || flags & FUSE_FATTR_ATIME)) {
+	if (!err && (flags & FUSE_SET_ATTR_MTIME || flags & FUSE_SET_ATTR_ATIME)) {
 		if (f->op.utimens) {
 			ts[0] = attr->st_atim;
 			ts[1] = attr->st_mtim;
@@ -798,7 +799,7 @@ ifuse_ops_setattr(fuse_req_t req, fuse_ino_t ino, struct stat *attr,
 			err = ENOSYS;
 	}
 
-	if (!err && (flags & FUSE_FATTR_SIZE)) {
+	if (!err && (flags & FUSE_SET_ATTR_SIZE)) {
 		if (f->op.truncate)
 			err = f->op.truncate(realname, attr->st_size);
 		else
@@ -918,16 +919,16 @@ ifuse_ops_destroy(void *userdata)
 }
 
 static void
-ifuse_ops_forget(fuse_req_t req, fuse_ino_t ino, uint64_t nlookup /* XXX */)
+ifuse_ops_forget(fuse_req_t req, fuse_ino_t ino, uint64_t nlookup)
 {
 	struct fuse *f = (struct fuse *)fuse_req_userdata(req);
 	struct fuse_vnode *vn;
 
 	vn = tree_get(&f->vnode_tree, ino);
 	if (vn != NULL)
-		unref_vn(f, vn);
+		unref_vn(f, vn, nlookup);
 
-	fuse_reply_err(req, 0);
+	fuse_reply_none(req);
 }
 
 static void

lib/libfuse/fuse_private.h

@@ -1,4 +1,4 @@
-/* $OpenBSD: fuse_private.h,v 1.28 2026/01/29 06:04:27 helg Exp $ */
+/* $OpenBSD: fuse_private.h,v 1.29 2026/06/17 13:29:01 helg Exp $ */
 /*
  * Copyright (c) 2013 Sylvestre Gallon <ccna.syl@gmail.com>
  *
@@ -58,10 +58,11 @@ SPLAY_HEAD(tree, treeentry);
 
 struct fuse_session {
 	struct fuse_lowlevel_ops llops;
-	struct fuse_chan	*chan;
+	struct fuse_conn_info fci;
-	void			*userdata;
+	struct fuse_chan *chan;
-	int			 init;
+	void *userdata;
-	int			 exit;
+	int init;
+	int exit;
 };
 
 struct fuse_chan {
@@ -122,12 +123,13 @@ struct fuse_req {
 #define FUSE_ROOT_INO ((ino_t)1)
 
 /* fuse_ops.c */
-const fuse_req_t ifuse_req(void);
+fuse_req_t ifuse_req(void);
 
 /* fuse_subr.c */
 struct fuse_vnode	*alloc_vn(struct fuse *, const char *, ino_t, ino_t);
 void			 ref_vn(struct fuse_vnode *);
-void			 unref_vn(struct fuse *, struct fuse_vnode *);
+void			 unref_vn(struct fuse *, struct fuse_vnode *,
+    const uint64_t);
 struct fuse_vnode	*get_vn_by_name_and_parent(struct fuse *, const char *,
     ino_t);
 void			remove_vnode_from_name_tree(struct fuse *,

lib/libfuse/fuse_session.c

@@ -1,4 +1,4 @@
-/* $OpenBSD: fuse_session.c,v 1.1 2026/01/22 11:53:31 helg Exp $ */
+/* $OpenBSD: fuse_session.c,v 1.2 2026/06/17 13:29:01 helg Exp $ */
 /*
  * Copyright (c) 2025 Helg Bredow <helg@openbsd.org>
  *
@@ -16,6 +16,7 @@
  */
 
 #include <sys/uio.h>
+#include <sys/fusebuf.h>
 #include <errno.h>
 #include <err.h>
 #include <stdlib.h>
@@ -83,8 +84,7 @@ int
 fuse_session_loop(struct fuse_session *se)
 {
 	struct fuse_chan *ch;
-	struct fusebuf fbuf;
+	char *buf;
-	char *buf = (char *)&fbuf;
 	size_t bufsize;
 	int err;
 
@@ -95,15 +95,25 @@ fuse_session_loop(struct fuse_session *se)
 	if (ch == NULL)
 		return (-1);
 
-	/* prepare the read and write data buffer */
+	/*
-	fbuf.fb_dat = calloc(1, FUSEBUFMAXSIZE);
+	 * Prepare the read data buffer. We need enough space for the header,
-	if (fbuf.fb_dat == NULL) {
+	 * input struct and any additional data, filenames or the buffer for
+	 * write(2). The minimum buffer size must be large enough for the
+	 * name and path parameters for FUSE_SYMLINK.
+	 */
+	if (se->fci.max_write > FUSEBUFMAXSIZE)
+		bufsize = sizeof(struct fusebuf) + FUSEBUFMAXSIZE;
+	else if (se->fci.max_write < PATH_MAX + NAME_MAX)
+		bufsize = sizeof(struct fusebuf) + PATH_MAX + NAME_MAX;
+	else
+		bufsize = sizeof(struct fusebuf) + se->fci.max_write;
+
+	buf = calloc(1, bufsize);
+	if (buf == NULL) {
 		DPERROR(__func__);
 		return (-1);
 	}
 
-	bufsize = sizeof(fbuf.fb_hdr) + sizeof(fbuf.FD) + FUSEBUFMAXSIZE;
-
 	while (!fuse_session_exited(se)) {
 		err = fuse_chan_recv(&ch, buf, bufsize);
 		if (err == -EINTR || err == -ENODEV) {
@@ -117,7 +127,7 @@ fuse_session_loop(struct fuse_session *se)
 		fuse_session_process(se, buf, bufsize, ch);
 	}
 
-	free(fbuf.fb_dat);
+	free(buf);
 	fuse_session_reset(se);
 
 	return (err == 0 ? 0 : -1);
@@ -127,20 +137,31 @@ DEF(fuse_session_loop);
 static void
 iprocess_init(fuse_req_t req)
 {
+	struct fusebuf *fbuf = req->fbuf;
 	struct fuse_session *se = req->se;
-	struct fuse_conn_info fci;
+	struct fuse_conn_info *fci = &se->fci;
+	struct fuse_init_out out;
+	uint32_t major = fbuf->in.init.major;
+	uint32_t minor = fbuf->in.init.minor;
 
 	DPRINTF("%-11s", "init");
+	DPRINTF("Kernel: %d.%d\t", major, minor);
+	DPRINTF("libfuse: %d.%d\t", fci->proto_major, fci->proto_minor);
 
-	if (se->llops.init) {
+	if (major != fci->proto_major && minor != fci->proto_minor)
-		memset(&fci, 0, sizeof(fci));
+		errx(1, "FUSE kernel protocol version mismatch");
-		fci.proto_minor = FUSE_MINOR_VERSION;
-		fci.proto_major = FUSE_MAJOR_VERSION;
 
-		se->llops.init(se->userdata, &fci);
+	if (se->llops.init)
-	}
+		se->llops.init(se->userdata, fci);
 
-	fuse_reply_err(req, 0);
+	memset(&out, 0, sizeof(out));
+	out.major = fci->proto_major;
+	out.minor = fci->proto_minor;
+	out.max_write = fci->max_write;
+
+	DPRINTF("max_write: %u\t", out.max_write);
+
+	fuse_reply_buf(req, (const char *)&out, sizeof(out));
 
 	se->init = 1;
 }
@@ -162,7 +183,7 @@ iprocess_lookup(fuse_req_t req)
 {
 	struct fusebuf *fbuf = req->fbuf;
 	struct fuse_session *se = req->se;
-	const char *name = fbuf->fb_dat;
+	const char *name = fb_dat(fbuf->hdr);
 
 	DPRINTF("%-11s", "lookup");
 	DPRINTF("inode: %llu\t", fbuf->fb_ino);
@@ -179,17 +200,13 @@ iprocess_getattr(fuse_req_t req)
 {
 	struct fusebuf *fbuf = req->fbuf;
 	struct fuse_session *se = req->se;
-	struct fuse_file_info ffi;
 
 	DPRINTF("%-11s", "getattr");
 	DPRINTF("inode: %llu\t", fbuf->fb_ino);
 
 	if (se->llops.getattr) {
-		memset(&ffi, 0, sizeof(ffi));
+		/* fuse_getattr_in is unused */
-		ffi.fh = fbuf->fb_io_fd;
+		se->llops.getattr(req, fbuf->fb_ino, NULL);
-		ffi.fh_old = ffi.fh;
-
-		se->llops.getattr(req, fbuf->fb_ino, &ffi);
 	} else
 		fuse_reply_err(req, ENOSYS);
 }
@@ -200,18 +217,28 @@ iprocess_setattr(fuse_req_t req)
 	struct fusebuf *fbuf = req->fbuf;
 	struct fuse_session *se = req->se;
 	struct fuse_file_info ffi;
-	struct stat *stbuf = &fbuf->fb_attr;
+	struct stat stbuf;
-	struct fb_io *io = fbtod(fbuf, struct fb_io *);
+	const int flags = fbuf->in.setattr.valid;
 
 	DPRINTF("%-11s", "setattr");
 	DPRINTF("inode: %llu\t", fbuf->fb_ino);
 
 	if (se->llops.setattr) {
 		memset(&ffi, 0, sizeof(ffi));
-		ffi.fh = fbuf->fb_io_fd;
+		ffi.fh = fbuf->in.setattr.fh;
 		ffi.fh_old = ffi.fh;
 
-		se->llops.setattr(req, fbuf->fb_ino, stbuf, io->fi_flags, &ffi);
+		memset(&stbuf, 0, sizeof(stbuf));
+		stbuf.st_size =  fbuf->in.setattr.size;
+		stbuf.st_atime =  fbuf->in.setattr.atime;
+		stbuf.st_mtime =  fbuf->in.setattr.mtime;
+		stbuf.st_atim.tv_nsec =  fbuf->in.setattr.atimensec;
+		stbuf.st_mtim.tv_nsec =  fbuf->in.setattr.mtimensec;
+		stbuf.st_mode =  fbuf->in.setattr.mode;
+		stbuf.st_uid =  fbuf->in.setattr.uid;
+		stbuf.st_gid =  fbuf->in.setattr.gid;
+
+		se->llops.setattr(req, fbuf->fb_ino, &stbuf, flags, &ffi);
 	} else
 		fuse_reply_err(req, ENOSYS);
 }
@@ -227,7 +254,7 @@ iprocess_opendir(fuse_req_t req)
 	DPRINTF("inode: %llu\t", fbuf->fb_ino);
 
 	memset(&ffi, 0, sizeof(ffi));
-	ffi.flags = fbuf->fb_io_flags;
+	ffi.flags = fbuf->in.open.flags;
 
 	if (se->llops.opendir)
 		se->llops.opendir(req, fbuf->fb_ino, &ffi);
@@ -244,16 +271,16 @@ iprocess_readdir(fuse_req_t req)
 
 	DPRINTF("%-11s", "readdir");
 	DPRINTF("inode: %llu\t", fbuf->fb_ino);
-	DPRINTF("size: %lu\t", fbuf->fb_io_len);
+	DPRINTF("size: %u\t", fbuf->in.read.size);
-	DPRINTF("offset: %llu\t", fbuf->fb_io_off);
+	DPRINTF("offset: %llu\t", fbuf->in.read.offset);
 
 	if (se->llops.readdir) {
 		memset(&ffi, 0, sizeof(ffi));
-		ffi.fh = fbuf->fb_io_fd;
+		ffi.fh = fbuf->in.read.fh;
 		ffi.fh_old = ffi.fh;
 
-		se->llops.readdir(req, fbuf->fb_ino, fbuf->fb_io_len,
+		se->llops.readdir(req, fbuf->fb_ino, fbuf->in.read.size,
-		    fbuf->fb_io_off, &ffi);
+		    fbuf->in.read.offset, &ffi);
 	} else
 		fuse_reply_err(req, ENOSYS);
 }
@@ -270,9 +297,9 @@ iprocess_releasedir(fuse_req_t req)
 
 	if (se->llops.releasedir) {
 		memset(&ffi, 0, sizeof(ffi));
-		ffi.fh = fbuf->fb_io_fd;
+		ffi.fh = fbuf->in.release.fh;
 		ffi.fh_old = ffi.fh;
-		ffi.flags = fbuf->fb_io_flags;
+		ffi.flags = fbuf->in.release.flags;
 
 		se->llops.releasedir(req, fbuf->fb_ino, &ffi);
 	} else
@@ -284,16 +311,17 @@ iprocess_mkdir(fuse_req_t req)
 {
 	struct fusebuf *fbuf = req->fbuf;
 	struct fuse_session *se = req->se;
+	const char *name = fb_dat(fbuf->in.mkdir);
 
 	DPRINTF("%-11s", "mkdir");
 	DPRINTF("inode: %llu\t", fbuf->fb_ino);
-	DPRINTF("mode: %#6o\t", fbuf->fb_io_mode);
+	DPRINTF("mode: %#6o\t", fbuf->in.mkdir.mode);
-	DPRINTF("name: %s\t", fbuf->fb_dat);
+	DPRINTF("name: %s\t", name);
 
-	if (se->llops.mkdir)
+	if (se->llops.mkdir) {
-		se->llops.mkdir(req, fbuf->fb_ino, fbuf->fb_dat,
+		req->ctx.umask = fbuf->in.mkdir.umask;
-		    fbuf->fb_io_mode);
+		se->llops.mkdir(req, fbuf->fb_ino, name, fbuf->in.mkdir.mode);
-	else
+	} else
 		fuse_reply_err(req, ENOSYS);
 }
 
@@ -302,13 +330,14 @@ iprocess_rmdir(fuse_req_t req)
 {
 	struct fusebuf *fbuf = req->fbuf;
 	struct fuse_session *se = req->se;
+	const char *name = fb_dat(fbuf->hdr);
 
 	DPRINTF("%-11s", "rmdir");
 	DPRINTF("inode: %llu\t", fbuf->fb_ino);
-	DPRINTF("name: %s\t", fbuf->fb_dat);
+	DPRINTF("name: %s\t", name);
 
 	if (se->llops.rmdir)
-		se->llops.rmdir(req, fbuf->fb_ino, fbuf->fb_dat);
+		se->llops.rmdir(req, fbuf->fb_ino, name);
 	else
 		fuse_reply_err(req, ENOSYS);
 }
@@ -318,16 +347,18 @@ iprocess_mknod(fuse_req_t req)
 {
 	struct fusebuf *fbuf = req->fbuf;
 	struct fuse_session *se = req->se;
+	const char *name = fb_dat(fbuf->in.mknod);
 
 	DPRINTF("%-11s", "mknod");
 	DPRINTF("inode: %llu\t", fbuf->fb_ino);
-	DPRINTF("mode: %#6o\t", fbuf->fb_io_mode);
+	DPRINTF("mode: %#6o\t", fbuf->in.mknod.mode);
-	DPRINTF("name: %s\t", fbuf->fb_dat);
+	DPRINTF("name: %s\t", name);
 
-	if (se->llops.mknod)
+	if (se->llops.mknod) {
-		se->llops.mknod(req, fbuf->fb_ino, fbuf->fb_dat,
+		req->ctx.umask = fbuf->in.mknod.umask;
-		    fbuf->fb_io_mode, fbuf->fb_io_rdev);
+		se->llops.mknod(req, fbuf->fb_ino, name, fbuf->in.mknod.mode,
-	else
+		    fbuf->in.mknod.rdev);
+	} else
 		fuse_reply_err(req, ENOSYS);
 }
 
@@ -342,7 +373,7 @@ iprocess_open(fuse_req_t req)
 	DPRINTF("inode: %llu\t", fbuf->fb_ino);
 
 	memset(&ffi, 0, sizeof(ffi));
-	ffi.flags = fbuf->fb_io_flags;
+	ffi.flags = fbuf->in.open.flags;
 
 	if (se->llops.open)
 		se->llops.open(req, fbuf->fb_ino, &ffi);
@@ -359,17 +390,17 @@ iprocess_read(fuse_req_t req)
 
 	DPRINTF("%-11s", "read");
 	DPRINTF("inode: %llu\t", fbuf->fb_ino);
-	DPRINTF("size: %lu\t", fbuf->fb_io_len);
+	DPRINTF("size: %u\t", fbuf->in.read.size);
-	DPRINTF("offset: %llu\t", fbuf->fb_io_off);
+	DPRINTF("offset: %llu\t", fbuf->in.read.offset);
 
 	if (se->llops.read) {
 		memset(&ffi, 0, sizeof(ffi));
-		ffi.fh = fbuf->fb_io_fd;
+		ffi.fh = fbuf->in.read.fh;
 		ffi.fh_old = ffi.fh;
-		ffi.flags = fbuf->fb_io_flags;
+		ffi.flags = fbuf->in.read.flags;
 
-		se->llops.read(req, fbuf->fb_ino, fbuf->fb_io_len,
+		se->llops.read(req, fbuf->fb_ino, fbuf->in.read.size,
-		    fbuf->fb_io_off, &ffi);
+		    fbuf->in.read.offset, &ffi);
 	} else
 		fuse_reply_err(req, ENOSYS);
 }
@@ -383,17 +414,17 @@ iprocess_write(fuse_req_t req)
 
 	DPRINTF("%-11s", "write");
 	DPRINTF("inode: %llu\t", fbuf->fb_ino);
-	DPRINTF("size: %lu\t", fbuf->fb_io_len);
+	DPRINTF("size: %u\t", fbuf->in.write.size);
-	DPRINTF("offset: %llu\t", fbuf->fb_io_off);
+	DPRINTF("offset: %llu\t", fbuf->in.write.offset);
 
 	if (se->llops.write) {
 		memset(&ffi, 0, sizeof(ffi));
-		ffi.fh = fbuf->fb_io_fd;
+		ffi.fh = fbuf->in.write.fh;
 		ffi.fh_old = ffi.fh;
-		ffi.writepage = fbuf->fb_io_flags & 1; // XXX
+		ffi.writepage = fbuf->in.write.flags & 1; // XXX
 
-		se->llops.write(req, fbuf->fb_ino, fbuf->fb_dat,
+		se->llops.write(req, fbuf->fb_ino, fb_dat(fbuf->in.write),
-		    fbuf->fb_io_len, fbuf->fb_io_off, &ffi);
+		    fbuf->in.write.size, fbuf->in.write.offset, &ffi);
 	} else
 		fuse_reply_err(req, ENOSYS);
 }
@@ -404,20 +435,18 @@ iprocess_fsync(fuse_req_t req)
 	struct fusebuf *fbuf = req->fbuf;
 	struct fuse_session *se = req->se;
 	struct fuse_file_info ffi;
+	const uint32_t fsync_flags = fbuf->in.fsync.fsync_flags & 1;
 
 	DPRINTF("%-11s", "fsync");
 	DPRINTF("inode: %llu\t", fbuf->fb_ino);
+	DPRINTF("flags: %u", fsync_flags);
 
 	if (se->llops.fsync) {
 		memset(&ffi, 0, sizeof(ffi));
-		ffi.fh = fbuf->fb_io_fd;
+		ffi.fh = fbuf->in.fsync.fh;
 		ffi.fh_old = ffi.fh;
 
-	        /*
+		se->llops.fsync(req, fbuf->fb_ino, fsync_flags, &ffi);
-	         * fdatasync(2) is just a wrapper around fsync(2) so datasync
-	         * is always false.
-	         */
-		se->llops.fsync(req, fbuf->fb_ino, 0 /* datasync */, &ffi);
 	} else
 		fuse_reply_err(req, ENOSYS);
 }
@@ -434,7 +463,7 @@ iprocess_flush(fuse_req_t req)
 
 	if (se->llops.flush) {
 		memset(&ffi, 0, sizeof(ffi));
-		ffi.fh = fbuf->fb_io_fd;
+		ffi.fh = fbuf->in.flush.fh;
 		ffi.fh_old = ffi.fh;
 		ffi.flush = 1;
 
@@ -455,9 +484,9 @@ iprocess_release(fuse_req_t req)
 
 	if (se->llops.release) {
 		memset(&ffi, 0, sizeof(ffi));
-		ffi.fh = fbuf->fb_io_fd;
+		ffi.fh = fbuf->in.release.fh;
 		ffi.fh_old = ffi.fh;
-		ffi.flags = fbuf->fb_io_flags;
+		ffi.flags = fbuf->in.release.flags;
 
 		se->llops.release(req, fbuf->fb_ino, &ffi);
 	} else
@@ -469,14 +498,16 @@ iprocess_forget(fuse_req_t req)
 {
 	struct fusebuf *fbuf = req->fbuf;
 	struct fuse_session *se = req->se;
+	const uint64_t nlookup = fbuf->in.forget.nlookup;
 
 	DPRINTF("%-11s", "forget");
 	DPRINTF("inode: %llu\t", fbuf->fb_ino);
+	DPRINTF("nlookup: %llu\t", nlookup);
 
 	if (se->llops.forget)
-		se->llops.forget(req, fbuf->fb_ino, 1 /* TODO */);
+		se->llops.forget(req, fbuf->fb_ino, nlookup);
 	else
-		fuse_reply_err(req, 0);
+		fuse_reply_none(req);
 }
 
 static void
@@ -488,9 +519,9 @@ iprocess_symlink(fuse_req_t req)
 	const char *name;
 	int len;
 
-	name = fbuf->fb_dat;
+	name = fb_dat(fbuf->hdr);
-	len = strnlen(name, fbuf->fb_len);
+	len = strlen(name);
-	target = &fbuf->fb_dat[len + 1];
+	target = &name[len + 1];
 
 	DPRINTF("%-11s", "symlink");
 	DPRINTF("inode: %llu\t", fbuf->fb_ino);
@@ -523,15 +554,16 @@ iprocess_link(fuse_req_t req)
 {
 	struct fusebuf *fbuf = req->fbuf;
 	struct fuse_session *se = req->se;
-	const char *name = fbuf->fb_dat;
+	const char *name = fb_dat(fbuf->in.link);
+	const uint64_t oldnodeid = fbuf->in.link.oldnodeid;
 
 	DPRINTF("%-11s", "link");
 	DPRINTF("inode: %llu\t", fbuf->fb_ino);
-	DPRINTF("inode: %llu\t", fbuf->fb_io_ino);
+	DPRINTF("inode: %llu\t", oldnodeid);
 	DPRINTF("name: %s\t", name);
 
 	if (se->llops.link)
-		se->llops.link(req, fbuf->fb_io_ino, fbuf->fb_ino, name);
+		se->llops.link(req, oldnodeid, fbuf->fb_ino, name);
 	else
 		fuse_reply_err(req, ENOSYS);
 }
@@ -541,13 +573,14 @@ iprocess_unlink(fuse_req_t req)
 {
 	struct fusebuf *fbuf = req->fbuf;
 	struct fuse_session *se = req->se;
+	const char *name = fb_dat(fbuf->hdr);
 
 	DPRINTF("%-11s", "unlink");
 	DPRINTF("inode: %llu\t", fbuf->fb_ino);
-	DPRINTF("name: %s\t", fbuf->fb_dat);
+	DPRINTF("name: %s\t", name);
 
 	if (se->llops.unlink)
-		se->llops.unlink(req, fbuf->fb_ino, fbuf->fb_dat);
+		se->llops.unlink(req, fbuf->fb_ino, name);
 	else
 		fuse_reply_err(req, ENOSYS);
 }
@@ -557,23 +590,23 @@ iprocess_rename(fuse_req_t req)
 {
 	struct fusebuf *fbuf = req->fbuf;
 	struct fuse_session *se = req->se;
+	const uint64_t newdir = fbuf->in.rename.newdir;
 	const char *target;
 	const char *name;
 	int len;
 
-	name = fbuf->fb_dat;
+	name = fb_dat(fbuf->in.rename);
-	len = strnlen(name, fbuf->fb_len);
+	len = strlen(name);
-	target = &fbuf->fb_dat[len + 1];
+	target = &name[len + 1];
 
 	DPRINTF("%-11s", "rename");
 	DPRINTF("inode: %llu\t", fbuf->fb_ino);
 	DPRINTF("name: %s\t", name);
-	DPRINTF("inode: %llu\t", fbuf->fb_io_ino);
+	DPRINTF("newdir: %llu\t", newdir);
 	DPRINTF("target: %s\t", target);
 
 	if (se->llops.rename)
-		se->llops.rename(req, fbuf->fb_ino, name, fbuf->fb_io_ino,
+		se->llops.rename(req, fbuf->fb_ino, name, newdir, target);
-		    target);
 	else
 		fuse_reply_err(req, ENOSYS);
 }
@@ -607,86 +640,88 @@ fuse_session_process(struct fuse_session *se, const char *buf, size_t len,
 	req.ctx.uid = fbuf->fb_uid;
 	req.ctx.gid = fbuf->fb_gid;
 	req.ctx.pid = fbuf->fb_tid;
-	req.ctx.umask = fbuf->fb_umask;
+
+	/* later set in create, mknod, mkdir */
+	req.ctx.umask = 0;
 
 	/* need to at least have the header for the next check */
-	if (len < sizeof(fbuf->fb_hdr))
+	if (len < sizeof(fbuf->hdr))
 		return;
 
-	if (len < sizeof(fbuf->fb_hdr) + sizeof(fbuf->FD) + fbuf->fb_len)
+	if (len < fbuf->hdr.len)
 		return;
 
 	switch (fbuf->fb_type) {
-	case FBT_INIT:
+	case FUSE_INIT:
 		iprocess_init(&req);
 		break;
-	case FBT_DESTROY:
+	case FUSE_DESTROY:
 		iprocess_destroy(&req);
 		break;
-	case FBT_LOOKUP:
+	case FUSE_LOOKUP:
 		iprocess_lookup(&req);
 		break;
-	case FBT_GETATTR:
+	case FUSE_GETATTR:
 		iprocess_getattr(&req);
 		break;
-	case FBT_SETATTR:
+	case FUSE_SETATTR:
 		iprocess_setattr(&req);
 		break;
-	case FBT_OPENDIR:
+	case FUSE_OPENDIR:
 		iprocess_opendir(&req);
 		break;
-	case FBT_READDIR:
+	case FUSE_READDIR:
 		iprocess_readdir(&req);
 		break;
-	case FBT_RELEASEDIR:
+	case FUSE_RELEASEDIR:
 		iprocess_releasedir(&req);
 		break;
-	case FBT_MKDIR:
+	case FUSE_MKDIR:
 		iprocess_mkdir(&req);
 		break;
-	case FBT_RMDIR:
+	case FUSE_RMDIR:
 		iprocess_rmdir(&req);
 		break;
-	case FBT_MKNOD:
+	case FUSE_MKNOD:
 		iprocess_mknod(&req);
 		break;
-	case FBT_OPEN:
+	case FUSE_OPEN:
 		iprocess_open(&req);
 		break;
-	case FBT_READ:
+	case FUSE_READ:
 		iprocess_read(&req);
 		break;
-	case FBT_WRITE:
+	case FUSE_WRITE:
 		iprocess_write(&req);
 		break;
-	case FBT_FSYNC:
+	case FUSE_FSYNC:
 		iprocess_fsync(&req);
 		break;
-	case FBT_FLUSH:
+	case FUSE_FLUSH:
 		iprocess_flush(&req);
 		break;
-	case FBT_RELEASE:
+	case FUSE_RELEASE:
 		iprocess_release(&req);
 		break;
-	case FBT_RECLAIM:
+	case FUSE_FORGET:
 		iprocess_forget(&req);
 		break;
-	case FBT_SYMLINK:
+	case FUSE_SYMLINK:
 		iprocess_symlink(&req);
 		break;
-	case FBT_READLINK:
+	case FUSE_READLINK:
 		iprocess_readlink(&req);
 		break;
-	case FBT_LINK:
+	case FUSE_LINK:
 		iprocess_link(&req);
 		break;
-	case FBT_UNLINK:
+	case FUSE_UNLINK:
 		iprocess_unlink(&req);
 		break;
-	case FBT_RENAME:
+	case FUSE_RENAME:
 		iprocess_rename(&req);
 		break;
-	case FBT_STATFS:
+	case FUSE_STATFS:
 		iprocess_statfs(&req);
 		break;
 	default:

lib/libfuse/fuse_subr.c

@@ -1,4 +1,4 @@
-/* $OpenBSD: fuse_subr.c,v 1.13 2026/01/29 06:04:27 helg Exp $ */
+/* $OpenBSD: fuse_subr.c,v 1.14 2026/06/17 13:29:01 helg Exp $ */
 /*
  * Copyright (c) 2013 Sylvestre Gallon <ccna.syl@gmail.com>
  *
@@ -69,13 +69,14 @@ ref_vn(struct fuse_vnode *vn)
 }
 
 void
-unref_vn(struct fuse *f, struct fuse_vnode *vn)
+unref_vn(struct fuse *f, struct fuse_vnode *vn, const uint64_t nlookup)
 {
-	if (--vn->ref == 0) {
+	vn->ref -= nlookup;
+	if (vn->ref == 0) {
 		tree_pop(&f->vnode_tree, vn->ino);
 		remove_vnode_from_name_tree(f, vn);
 		if (vn->parent != NULL)
-			unref_vn(f, vn->parent);
+			unref_vn(f, vn->parent, 1);
 		free(vn);
 	}
 }

sys/miscfs/fuse/fuse_device.c

@@ -1,4 +1,4 @@
-/* $OpenBSD: fuse_device.c,v 1.49 2026/01/22 11:53:31 helg Exp $ */
+/* $OpenBSD: fuse_device.c,v 1.50 2026/06/17 13:29:01 helg Exp $ */
 /*
  * Copyright (c) 2012-2013 Sylvestre Gallon <ccna.syl@gmail.com>
  *
@@ -303,7 +303,6 @@ fuseread(dev_t dev, struct uio *uio, int ioflag)
 {
 	struct fuse_d *fd;
 	struct fusebuf *fbuf;
-	struct fb_hdr hdr;
 	int error = 0;
 
 	fd = fuse_lookup(minor(dev));
@@ -342,20 +341,16 @@ fuseread(dev_t dev, struct uio *uio, int ioflag)
 	}
 
 	/* We get the whole fusebuf or nothing */
-	if (uio->uio_resid < sizeof(fbuf->fb_hdr) + sizeof(fbuf->FD) +
+	if (uio->uio_resid < sizeof(fbuf->hdr) + fbuf->op_in_len +
 	    fbuf->fb_len) {
 		error = EINVAL;
 		goto end;
 	}
 
-	/* Do not send kernel pointers */
+	error = uiomove(&fbuf->hdr, sizeof(fbuf->hdr), uio);
-	memcpy(&hdr.fh_next, &fbuf->fb_next, sizeof(fbuf->fb_next));
-	memset(&fbuf->fb_next, 0, sizeof(fbuf->fb_next));
-
-	error = uiomove(&fbuf->fb_hdr, sizeof(fbuf->fb_hdr), uio);
 	if (error)
 		goto end;
-	error = uiomove(&fbuf->FD, sizeof(fbuf->FD), uio);
+	error = uiomove(&fbuf->op, fbuf->op_in_len, uio);
 	if (error)
 		goto end;
 	if (fbuf->fb_len > 0) {
@@ -367,8 +362,6 @@ fuseread(dev_t dev, struct uio *uio, int ioflag)
 #ifdef FUSE_DEBUG
 	fuse_dump_buff((char *)fbuf, sizeof(struct fusebuf));
 #endif
-	/* Restore kernel pointers */
-	memcpy(&fbuf->fb_next, &hdr.fh_next, sizeof(fbuf->fb_next));
 
 	free(fbuf->fb_dat, M_FUSEFS, fbuf->fb_len);
 	fbuf->fb_dat = NULL;
@@ -376,6 +369,13 @@ fuseread(dev_t dev, struct uio *uio, int ioflag)
 	/* Move the fbuf to the wait queue */
 	SIMPLEQ_REMOVE_HEAD(&fd->fd_fbufs_in, fb_next);
 	stat_fbufs_in--;
+
+	/* FUSE_FORGET has no response */
+	if (fbuf->fb_type == FUSE_FORGET) {
+		fb_delete(fbuf);
+		goto end;
+ 	}
+
 	SIMPLEQ_INSERT_TAIL(&fd->fd_fbufs_wait, fbuf, fb_next);
 	stat_fbufs_wait++;
 
@@ -391,37 +391,35 @@ fusewrite(dev_t dev, struct uio *uio, int ioflag)
 	struct fusebuf *lastfbuf;
 	struct fuse_d *fd;
 	struct fusebuf *fbuf;
-	struct fb_hdr hdr;
+	struct fuse_out_header hdr;
 	int error = 0;
 
 	fd = fuse_lookup(minor(dev));
 	if (fd == NULL)
-		return (ENXIO);
+		return (ENODEV);
 
-	/* Check for sanity - must receive more than just the header */
+	/* Check for sanity - must receive at least the header */
-	if (uio->uio_resid <= sizeof(hdr)) {
+	if (uio->uio_resid < sizeof(hdr)) {
 		error = EINVAL;
 		goto out;
 	}
 
+	/* Read the header */
 	if ((error = uiomove(&hdr, sizeof(hdr), uio)) != 0)
 		goto out;
 
-	/* Check for sanity */
+	/*
-	if (hdr.fh_len > FUSEBUFMAXSIZE) {
+	 * A unique value of zero means daemon is notifying us and hdr.error
-		error = EINVAL;
+	 * contains notification type. Currently unsupported.
-		goto out;
+	 */
-	}
+	if (hdr.unique == 0) {
-
+		error = 0;
-	/* We get the whole fusebuf or nothing */
-	if (uio->uio_resid != sizeof(fbuf->FD) + hdr.fh_len) {
-		error = EINVAL;
 		goto out;
 	}
 
 	/* looking for uuid in fd_fbufs_wait */
 	SIMPLEQ_FOREACH(fbuf, &fd->fd_fbufs_wait, fb_next) {
-		if (fbuf->fb_uuid == hdr.fh_uuid)
+		if (fbuf->fb_uuid == hdr.unique)
 			break;
 
 		lastfbuf = fbuf;
@@ -432,49 +430,93 @@ fusewrite(dev_t dev, struct uio *uio, int ioflag)
 	}
 
 	/* Update fb_hdr */
-	fbuf->fb_len = hdr.fh_len;
+	fbuf->fb_err = -hdr.error;
-	fbuf->fb_err = hdr.fh_err;
-	fbuf->fb_ino = hdr.fh_ino;
 
-	/* Check for corrupted fbufs */
+	/* Don't expect out struct or data if there was an error */
-	if ((fbuf->fb_len && fbuf->fb_err) || fbuf->fb_len > fbuf->fb_io_len ||
+	if (fbuf->fb_err) {
-	    SIMPLEQ_EMPTY(&fd->fd_fbufs_wait)) {
+		if (uio->uio_resid > 0) {
-		printf("fuse: dropping corrupted fusebuf: %zu: %zu: %d\n",
+			error = EINVAL;
-		    fbuf->fb_io_len, fbuf->fb_len, fbuf->fb_err);
+			fbuf->fb_err = EIO;
+		}
+ 		goto end;
+ 	}
+
+	/* get operation output */
+	if (fbuf->op_out_len > 0) {
+		if ((error = uiomove(&fbuf->op, fbuf->op_out_len, uio)) != 0) {
+			fbuf->fb_err = error;
+			goto end;
+		}
+	}
+
+	/* Calculate the length of the data buffer to expect */
+	if (fbuf->op_out_buf) {
+		fbuf->fb_len = hdr.len - sizeof(hdr) - fbuf->op_out_len;
+		if (fbuf->fb_len > fd->fd_fmp->max_read || fbuf->fb_len < 0) {
+			printf("fuse: invalid fusebuf read size: %llu "
+			    "opcode=%d\n", fbuf->fb_len, fbuf->fb_type);
+			error = EINVAL;
+			fbuf->fb_err = EIO;
+			goto end;
+		}
+	} else
+		fbuf->fb_len = 0;
+
+	/* validate remaining data */
+	if (uio->uio_resid != fbuf->fb_len) {
 		error = EINVAL;
 		fbuf->fb_err = EIO;
 		goto end;
 	}
 
-	/* Get the missing data from the fbuf */
-	error = uiomove(&fbuf->FD, sizeof(fbuf->FD), uio);
-	if (error)
-		return error;
-
-	fbuf->fb_dat = NULL;
 	if (fbuf->fb_len > 0) {
-		fbuf->fb_dat = malloc(fbuf->fb_len, M_FUSEFS,
+		fbuf->fb_dat = malloc(fbuf->fb_len, M_FUSEFS, M_WAITOK);
-		    M_WAITOK | M_ZERO);
+		if ((error = uiomove(fbuf->fb_dat, fbuf->fb_len, uio)) != 0) {
-		error = uiomove(fbuf->fb_dat, fbuf->fb_len, uio);
-		if (error) {
 			free(fbuf->fb_dat, M_FUSEFS, fbuf->fb_len);
 			fbuf->fb_dat = NULL;
+			fbuf->fb_err = error;
 			goto end;
 		}
 	}
 
-#ifdef FUSE_DEBUG
+	if (fbuf->fb_type == FUSE_INIT && fbuf->fb_err == 0) {
-	fuse_dump_buff((char *)fbuf, sizeof(struct fusebuf));
+		/*
-#endif
+		 * We don't support userspace with a smaller major version and
-
+		 * it's up to userspace implementations to fall back to our
-	switch (fbuf->fb_type) {
+	 	 * version if they are capable of a later version.
-	case FBT_INIT:
+	 	 */
+		if (fbuf->op.out.init.major != FUSE_KERNEL_VERSION) {
+			printf("fuse: unsupported major version: %d.%d\n",
+ 			    fbuf->op.out.init.major, fbuf->op.out.init.minor);
+			error = EINVAL;
+			goto end;
+		}
+		/*
+		 * If the major versions match then both shall use the smallest
+ 		 * of the two minor versions for communication. 7.9 is the
+		 * smallest version less than what we support where the ABI has
+		 * not changed. Supporting an earlier version would require
+		 * conditional handling of some FUSE input arguments. If the
+		 * daemon supports a later version then it must fall back to
+		 * ours.
+		 */
+		if (fbuf->op.out.init.minor < 9) {
+			printf("fuse: unsupported minor version: %d.%d\n",
+ 			    fbuf->op.out.init.major, fbuf->op.out.init.minor);
+			error = EINVAL;
+			goto end;
+		}
+		/*
+		 * max_write determines the size of buffer to send to the file
+		 * system daemon when writing so ensure that it's sane.
+		 */
+		fd->fd_fmp->max_write = MIN(fbuf->op.out.init.max_write,
+		    FUSEBUFMAXSIZE);
+		if (fd->fd_fmp->max_write == 0)
+			fd->fd_fmp->max_write = FUSEBUFMAXSIZE;
 		fd->fd_fmp->sess_init = 1;
-		break ;
+ 	}
-	case FBT_DESTROY:
+
-		fd->fd_fmp = NULL;
-		break ;
-	}
 end:
 	/* Remove the fbuf from the wait queue */
 	if (fbuf == SIMPLEQ_FIRST(&fd->fd_fbufs_wait))
@@ -488,7 +530,7 @@ end:
 	 * FBT_INIT doesn't expect a response. Otherwise let the VFS
 	 * syscall that is waiting on this fbuf know the reponse is ready.
 	 */
-	if (fbuf->fb_type == FBT_INIT)
+	if (fbuf->fb_type == FUSE_INIT)
 		fb_delete(fbuf);
 	else
 		wakeup(fbuf);

sys/miscfs/fuse/fuse_file.c

@@ -1,4 +1,4 @@
-/* $OpenBSD: fuse_file.c,v 1.10 2024/10/31 13:55:21 claudio Exp $ */
+/* $OpenBSD: fuse_file.c,v 1.11 2026/06/17 13:29:01 helg Exp $ */
 /*
  * Copyright (c) 2012-2013 Sylvestre Gallon <ccna.syl@gmail.com>
  *
@@ -36,8 +36,8 @@ fusefs_file_open(struct fusefs_mnt *fmp, struct fusefs_node *ip,
 		return (0);
 
 	fbuf = fb_setup(0, ip->i_number,
-	    ((isdir) ? FBT_OPENDIR : FBT_OPEN), p);
+	    ((isdir) ? FUSE_OPENDIR : FUSE_OPEN), p);
-	fbuf->fb_io_flags = flags;
+	fbuf->op.in.open.flags = flags;
 
 	error = fb_queue(fmp->dev, fbuf);
 	if (error) {
@@ -45,7 +45,7 @@ fusefs_file_open(struct fusefs_mnt *fmp, struct fusefs_node *ip,
 		return (error);
 	}
 
-	ip->fufh[fufh_type].fh_id = fbuf->fb_io_fd;
+	ip->fufh[fufh_type].fh_id = fbuf->op.out.open.fh;
 	ip->fufh[fufh_type].fh_type = fufh_type;
 
 	fb_delete(fbuf);
@@ -61,13 +61,13 @@ fusefs_file_close(struct fusefs_mnt *fmp, struct fusefs_node * ip,
 
 	if (fmp->sess_init) {
 		fbuf = fb_setup(0, ip->i_number,
-		    ((isdir) ? FBT_RELEASEDIR : FBT_RELEASE), p);
+		    ((isdir) ? FUSE_RELEASEDIR : FUSE_RELEASE), p);
-		fbuf->fb_io_fd  = ip->fufh[fufh_type].fh_id;
+		fbuf->op.in.release.fh  = ip->fufh[fufh_type].fh_id;
-		fbuf->fb_io_flags = flags;
+		fbuf->op.in.release.flags = flags;
 
 		error = fb_queue(fmp->dev, fbuf);
 		if (error && (error != ENOSYS))
-			printf("fusefs: file error %d\n", error);
+			printf("fusefs: file close error: %d\n", error);
 
 		fb_delete(fbuf);
 	}

sys/miscfs/fuse/fuse_lookup.c

@@ -1,4 +1,4 @@
-/* $OpenBSD: fuse_lookup.c,v 1.23 2026/01/22 11:53:31 helg Exp $ */
+/* $OpenBSD: fuse_lookup.c,v 1.24 2026/06/17 13:29:01 helg Exp $ */
 /*
  * Copyright (c) 2012-2013 Sylvestre Gallon <ccna.syl@gmail.com>
  *
@@ -82,7 +82,7 @@ fusefs_lookup(void *v)
 
 		/* got a real entry */
 		fbuf = fb_setup(cnp->cn_namelen + 1, dp->i_number,
-		    FBT_LOOKUP, p);
+		    FUSE_LOOKUP, p);
 
 		memcpy(fbuf->fb_dat, cnp->cn_nameptr, cnp->cn_namelen);
 		fbuf->fb_dat[cnp->cn_namelen] = '\0';
@@ -119,8 +119,8 @@ fusefs_lookup(void *v)
 			return (ENOENT);
 		}
 
-		nid = fbuf->fb_ino;
+		nid = fbuf->op.out.entry.nodeid;
-		nvtype = IFTOVT(fbuf->fb_attr.st_mode);
+		nvtype = IFTOVT(fbuf->op.out.entry.attr.mode);
 		fb_delete(fbuf);
 
 		/*
@@ -159,6 +159,7 @@ fusefs_lookup(void *v)
 			goto reclaim;
 
 		tdp->v_type = nvtype;
+		VTOI(tdp)->i_parent_cache = dp->i_number;
 		*vpp = tdp;
 		cnp->cn_flags |= SAVENAME;
 
@@ -193,6 +194,9 @@ fusefs_lookup(void *v)
 		}
 		*vpp = tdp;
 
+		/* Didn't actually make a call but vget increments lookup */
+		VTOI(tdp)->nlookup--;
+
 	} else if (nid == dp->i_number) {
 		vref(vdp);
 		*vpp = vdp;
@@ -203,6 +207,7 @@ fusefs_lookup(void *v)
 			goto reclaim;
 
 		tdp->v_type = nvtype;
+		VTOI(tdp)->i_parent_cache = dp->i_number;
 
 		/*
 		 * Cache the parent if it's a directory so that we can resolve
@@ -222,11 +227,10 @@ fusefs_lookup(void *v)
 	return (error);
 
 reclaim:
-	if (nid != dp->i_number && nid != FUSE_ROOTINO) {
+	if (nid != dp->i_number && nid != FUSE_ROOT_ID) {
-		fbuf = fb_setup(0, nid, FBT_RECLAIM, p);
+		fbuf = fb_setup(0, nid, FUSE_FORGET, p);
-		if (fb_queue(fmp->dev, fbuf))
+		fbuf->op.in.forget.nlookup = 1;
-			printf("fusefs: libfuse vnode reclaim failed\n");
+		fuse_device_queue_fbuf(fmp->dev, fbuf); /* no response */
-		fb_delete(fbuf);
 	}
 	return (error);
 }

sys/miscfs/fuse/fuse_vfsops.c

@@ -1,4 +1,4 @@
-/* $OpenBSD: fuse_vfsops.c,v 1.49 2025/09/20 13:53:36 mpi Exp $ */
+/* $OpenBSD: fuse_vfsops.c,v 1.50 2026/06/17 13:29:01 helg Exp $ */
 /*
  * Copyright (c) 2012-2013 Sylvestre Gallon <ccna.syl@gmail.com>
  *
@@ -68,7 +68,7 @@ const struct vfsops fusefs_vfsops = {
 
 struct pool fusefs_fbuf_pool;
 
-#define PENDING 2	/* FBT_INIT reply not yet received */
+#define PENDING 2	/* FUSE_INIT reply not yet received */
 
 int
 fusefs_mount(struct mount *mp, const char *path, void *data,
@@ -111,6 +111,12 @@ fusefs_mount(struct mount *mp, const char *path, void *data,
 	else
 		fmp->max_read = FUSEBUFMAXSIZE;
 
+	/*
+	 * Initialise to a safe value just to be sure. This will be
+	 * overwritten when the file system responds to FUSE_INIT.
+	 */
+	fmp->max_write = BLKDEV_IOSIZE;
+
 	fmp->allow_other = args->allow_other;
 
 	mp->mnt_data = fmp;
@@ -124,7 +130,11 @@ fusefs_mount(struct mount *mp, const char *path, void *data,
 	strlcpy(mp->mnt_stat.f_mntfromspec, "fusefs", MNAMELEN);
 
 	fuse_device_set_fmp(fmp, 1);
-	fbuf = fb_setup(0, 0, FBT_INIT, p);
+	fbuf = fb_setup(0, 0, FUSE_INIT, p);
+	fbuf->op.in.init.major = FUSE_KERNEL_VERSION;
+	fbuf->op.in.init.minor = FUSE_KERNEL_MINOR_VERSION;
+	fbuf->op.in.init.max_readahead = 0;
+	fbuf->op.in.init.flags = 0; /* OpenBSD supports nothing... */
 
 	/* cannot tsleep on mount */
 	fuse_device_queue_fbuf(fmp->dev, fbuf);
@@ -157,7 +167,7 @@ fusefs_unmount(struct mount *mp, int mntflags, struct proc *p)
 		return (error);
 
 	if (fmp->sess_init && fmp->sess_init != PENDING) {
-		fbuf = fb_setup(0, 0, FBT_DESTROY, p);
+		fbuf = fb_setup(0, 0, FUSE_DESTROY, p);
 
 		error = fb_queue(fmp->dev, fbuf);
 
@@ -182,7 +192,7 @@ fusefs_root(struct mount *mp, struct vnode **vpp)
 	struct vnode *nvp;
 	int error;
 
-	if ((error = VFS_VGET(mp, FUSE_ROOTINO, &nvp)) != 0)
+	if ((error = VFS_VGET(mp, FUSE_ROOT_ID, &nvp)) != 0)
 		return (error);
 
 	nvp->v_type = VDIR;
@@ -214,10 +224,10 @@ fusefs_statfs(struct mount *mp, struct statfs *sbp, struct proc *p)
 	copy_statfs_info(sbp, mp);
 
 	/*
-	 * Both FBT_INIT and FBT_STATFS are sent to the FUSE file system
+	 * Both FUSE_INIT and FUSE_STATFS are sent to the FUSE file system
 	 * daemon when it is mounted. However, the daemon is the process
 	 * that called mount(2) so to prevent a deadlock return dummy
-	 * values until the response to FBT_INIT init is received. All
+	 * values until the response to FUSE_INIT init is received. All
 	 * other VFS syscalls are queued.
 	 */
 	if (!fmp->sess_init || fmp->sess_init == PENDING) {
@@ -231,7 +241,7 @@ fusefs_statfs(struct mount *mp, struct statfs *sbp, struct proc *p)
 		sbp->f_iosize = 0;
 		sbp->f_namemax = 0;
 	} else {
-		fbuf = fb_setup(0, FUSE_ROOTINO, FBT_STATFS, p);
+		fbuf = fb_setup(0, FUSE_ROOT_ID, FUSE_STATFS, p);
 
 		error = fb_queue(fmp->dev, fbuf);
 
@@ -240,15 +250,25 @@ fusefs_statfs(struct mount *mp, struct statfs *sbp, struct proc *p)
 			return (error);
 		}
 
-		sbp->f_bavail = fbuf->fb_stat.f_bavail;
+		sbp->f_blocks = fbuf->op.out.statfs.st.blocks;
-		sbp->f_bfree = fbuf->fb_stat.f_bfree;
+		sbp->f_bfree = fbuf->op.out.statfs.st.bfree;
-		sbp->f_blocks = fbuf->fb_stat.f_blocks;
+		sbp->f_bavail = fbuf->op.out.statfs.st.bavail;
-		sbp->f_files = fbuf->fb_stat.f_files;
+		sbp->f_files = fbuf->op.out.statfs.st.files;
-		sbp->f_ffree = fbuf->fb_stat.f_ffree;
+		sbp->f_ffree = fbuf->op.out.statfs.st.ffree;
-		sbp->f_favail = fbuf->fb_stat.f_favail;
+		sbp->f_favail = fbuf->op.out.statfs.st.ffree;
-		sbp->f_bsize = fbuf->fb_stat.f_frsize;
+		sbp->f_bsize = fbuf->op.out.statfs.st.frsize;
-		sbp->f_iosize = fbuf->fb_stat.f_bsize;
+		sbp->f_namemax = fbuf->op.out.statfs.st.namelen;
-		sbp->f_namemax = fbuf->fb_stat.f_namemax;
+		sbp->f_iosize = fbuf->op.out.statfs.st.bsize;
+
+		/*
+		 * Programs use this to allocate an i/o buffer so ensure it's
+		 * sane.
+		 *
+		 * XXX Should this be larger?
+		 */
+		if (sbp->f_iosize > BLKDEV_IOSIZE)
+			sbp->f_iosize = BLKDEV_IOSIZE;
+
 		fb_delete(fbuf);
 	}
 
@@ -276,8 +296,10 @@ retry:
 	/*
 	 * check if vnode is in hash.
 	 */
-	if ((*vpp = fuse_ihashget(fmp->dev, ino)) != NULL)
+	if ((*vpp = fuse_ihashget(fmp->dev, ino)) != NULL) {
+		VTOI(*vpp)->nlookup++;
 		return (0);
+	}
 
 	/*
 	 * if not create it
@@ -295,6 +317,7 @@ retry:
 	ip->i_vnode = nvp;
 	ip->i_dev = fmp->dev;
 	ip->i_number = ino;
+	ip->nlookup = 1;
 
 	for (i = 0; i < FUFH_MAXTYPE; i++)
 		ip->fufh[i].fh_type = FUFH_INVALID;
@@ -311,7 +334,7 @@ retry:
 
 	ip->i_ump = fmp;
 
-	if (ino == FUSE_ROOTINO)
+	if (ino == FUSE_ROOT_ID)
 		nvp->v_flag |= VROOT;
 	else {
 		/*

sys/miscfs/fuse/fuse_vnops.c

@@ -1,4 +1,4 @@
-/* $OpenBSD: fuse_vnops.c,v 1.76 2026/01/29 06:04:27 helg Exp $ */
+/* $OpenBSD: fuse_vnops.c,v 1.77 2026/06/17 13:29:01 helg Exp $ */
 /*
  * Copyright (c) 2012-2013 Sylvestre Gallon <ccna.syl@gmail.com>
  *
@@ -20,6 +20,7 @@
 #include <sys/dirent.h>
 #include <sys/fcntl.h>
 #include <sys/file.h>
+#include <sys/filedesc.h>
 #include <sys/lockf.h>
 #include <sys/malloc.h>
 #include <sys/mount.h>
@@ -329,8 +330,8 @@ fusefs_close(void *v)
 	if (ip->fufh[fufh_type].fh_type == FUFH_INVALID)
 		return (EBADF);
 
-	fbuf = fb_setup(0, ip->i_number, FBT_FLUSH, ap->a_p);
+	fbuf = fb_setup(0, ip->i_number, FUSE_FLUSH, ap->a_p);
-	fbuf->fb_io_fd = ip->fufh[fufh_type].fh_id;
+	fbuf->op.in.flush.fh = ip->fufh[fufh_type].fh_id;
 	error = fb_queue(fmp->dev, fbuf);
 	fb_delete(fbuf);
 	if (error == ENOSYS) {
@@ -405,7 +406,7 @@ fusefs_getattr(void *v)
 	struct ucred *cred = p->p_ucred;
 	struct fusefs_node *ip;
 	struct fusebuf *fbuf;
-	struct stat *st;
+	struct fuse_attr *st;
 	int error = 0;
 
 	ip = VTOI(vp);
@@ -423,7 +424,7 @@ fusefs_getattr(void *v)
 			vap->va_mode = S_IRUSR | S_IXUSR;
 		else
 			vap->va_mode = S_IRWXU;
-		vap->va_nlink = 1;
+		vap->va_nlink = 2;
 		vap->va_uid = fmp->mp->mnt_stat.f_owner;
 		vap->va_gid = fmp->mp->mnt_stat.f_owner;
 		vap->va_fsid = fmp->mp->mnt_stat.f_fsid.val[0];
@@ -441,7 +442,7 @@ fusefs_getattr(void *v)
 	if (!fmp->sess_init)
 		return (ENXIO);
 
-	fbuf = fb_setup(0, ip->i_number, FBT_GETATTR, p);
+	fbuf = fb_setup(0, ip->i_number, FUSE_GETATTR, p);
 
 	error = fb_queue(fmp->dev, fbuf);
 	if (error) {
@@ -449,31 +450,36 @@ fusefs_getattr(void *v)
 		return (error);
 	}
 
-	st = &fbuf->fb_attr;
+	st = &fbuf->op.out.attr.attr;
 
 	/* opendir(3) expects blocksize to be greater than zero. */
-	if (st->st_blksize == 0)
+	if (st->blksize == 0)
-		st->st_blksize = S_BLKSIZE;
+		st->blksize = S_BLKSIZE;
+	else if (st->blksize > BLKDEV_IOSIZE)
+		st->blksize = BLKDEV_IOSIZE;
 
 	/* calculate blocks of held disk space if fs didn't do it */
-	if (st->st_blocks == 0 && st->st_size > 0)
+	if (st->blocks == 0 && st->size > 0)
-		st->st_blocks = (st->st_size + S_BLKSIZE - 1) / S_BLKSIZE;
+		st->blocks = (st->size + S_BLKSIZE - 1) / S_BLKSIZE;
 
 	memset(vap, 0, sizeof(*vap));
-	vap->va_type = IFTOVT(st->st_mode);
+	vap->va_type = IFTOVT(st->mode);
-	vap->va_mode = st->st_mode & ~S_IFMT;
+	vap->va_mode = st->mode & ~S_IFMT;
-	vap->va_nlink = st->st_nlink;
+	vap->va_nlink = st->nlink;
-	vap->va_uid = st->st_uid;
+	vap->va_uid = st->uid;
-	vap->va_gid = st->st_gid;
+	vap->va_gid = st->gid;
 	vap->va_fsid = fmp->mp->mnt_stat.f_fsid.val[0];
-	vap->va_fileid = st->st_ino;
+	vap->va_fileid = st->ino;
-	vap->va_size = st->st_size;
+	vap->va_size = st->size;
-	vap->va_blocksize = st->st_blksize;
+	vap->va_blocksize = st->blksize;
-	vap->va_atime = st->st_atim;
+	vap->va_atime.tv_sec = st->atime;
-	vap->va_mtime = st->st_mtim;
+	vap->va_atime.tv_nsec = st->atimensec;
-	vap->va_ctime = st->st_ctim;
+	vap->va_mtime.tv_sec = st->mtime;
-	vap->va_rdev = st->st_rdev;
+	vap->va_mtime.tv_nsec = st->mtimensec;
-	vap->va_bytes = st->st_blocks * S_BLKSIZE;
+	vap->va_ctime.tv_sec = st->ctime;
+	vap->va_ctime.tv_nsec = st->ctimensec;
+	vap->va_rdev = st->rdev;
+	vap->va_bytes = st->blocks * S_BLKSIZE;
 
 	fb_delete(fbuf);
 	return (error);
@@ -490,7 +496,6 @@ fusefs_setattr(void *v)
 	struct proc *p = ap->a_p;
 	struct fusefs_mnt *fmp;
 	struct fusebuf *fbuf;
-	struct fb_io *io;
 	int error = 0;
 
 	fmp = (struct fusefs_mnt *)ip->i_ump;
@@ -516,17 +521,16 @@ fusefs_setattr(void *v)
 	if (fmp->undef_op & UNDEF_SETATTR)
 		return (ENOSYS);
 
-	fbuf = fb_setup(sizeof(*io), ip->i_number, FBT_SETATTR, p);
+	fbuf = fb_setup(0, ip->i_number, FUSE_SETATTR, p);
-	io = fbtod(fbuf, struct fb_io *);
+	fbuf->op.in.setattr.valid = 0;
-	io->fi_flags = 0;
 
 	if (vap->va_uid != (uid_t)VNOVAL) {
 		if (vp->v_mount->mnt_flag & MNT_RDONLY) {
 			error = EROFS;
 			goto out;
 		}
-		fbuf->fb_attr.st_uid = vap->va_uid;
+		fbuf->op.in.setattr.uid |= vap->va_uid;
-		io->fi_flags |= FUSE_FATTR_UID;
+		fbuf->op.in.setattr.valid |= FUSE_FATTR_UID;
 	}
 
 	if (vap->va_gid != (gid_t)VNOVAL) {
@@ -534,8 +538,8 @@ fusefs_setattr(void *v)
 			error = EROFS;
 			goto out;
 		}
-		fbuf->fb_attr.st_gid = vap->va_gid;
+		fbuf->op.in.setattr.gid |= vap->va_gid;
-		io->fi_flags |= FUSE_FATTR_GID;
+		fbuf->op.in.setattr.valid |= FUSE_FATTR_GID;
 	}
 
 	if (vap->va_size != VNOVAL) {
@@ -559,8 +563,8 @@ fusefs_setattr(void *v)
 			break;
 		}
 
-		fbuf->fb_attr.st_size = vap->va_size;
+		fbuf->op.in.setattr.size |= vap->va_size;
-		io->fi_flags |= FUSE_FATTR_SIZE;
+		fbuf->op.in.setattr.valid |= FUSE_FATTR_SIZE;
 	}
 
 	if (vap->va_atime.tv_nsec != VNOVAL) {
@@ -568,8 +572,9 @@ fusefs_setattr(void *v)
 			error = EROFS;
 			goto out;
 		}
-		fbuf->fb_attr.st_atim = vap->va_atime;
+		fbuf->op.in.setattr.atime = vap->va_atime.tv_sec;
-		io->fi_flags |= FUSE_FATTR_ATIME;
+		fbuf->op.in.setattr.atimensec = vap->va_atime.tv_nsec;
+		fbuf->op.in.setattr.valid |= FUSE_FATTR_ATIME;
 	}
 
 	if (vap->va_mtime.tv_nsec != VNOVAL) {
@@ -577,8 +582,9 @@ fusefs_setattr(void *v)
 			error = EROFS;
 			goto out;
 		}
-		fbuf->fb_attr.st_mtim = vap->va_mtime;
+		fbuf->op.in.setattr.mtime = vap->va_mtime.tv_sec;
-		io->fi_flags |= FUSE_FATTR_MTIME;
+		fbuf->op.in.setattr.mtimensec = vap->va_mtime.tv_nsec;
+		fbuf->op.in.setattr.valid |= FUSE_FATTR_MTIME;
 	}
 	/* XXX should set a flag if (vap->va_vaflags & VA_UTIMES_CHANGE) */
 
@@ -599,11 +605,11 @@ fusefs_setattr(void *v)
 			goto out;
 		}
 
-		fbuf->fb_attr.st_mode = vap->va_mode & ALLPERMS;
+		fbuf->op.in.setattr.mode = vap->va_mode & ALLPERMS;
-		io->fi_flags |= FUSE_FATTR_MODE;
+		fbuf->op.in.setattr.valid |= FUSE_FATTR_MODE;
 	}
 
-	if (!io->fi_flags) {
+	if (!fbuf->op.in.setattr.valid) {
 		goto out;
 	}
 
@@ -667,9 +673,9 @@ fusefs_link(void *v)
 	}
 
 	fbuf = fb_setup(cnp->cn_namelen + 1, dip->i_number,
-	    FBT_LINK, p);
+	    FUSE_LINK, p);
 
-	fbuf->fb_io_ino = ip->i_number;
+	fbuf->op.in.link.oldnodeid = ip->i_number;
 	memcpy(fbuf->fb_dat, cnp->cn_nameptr, cnp->cn_namelen);
 	fbuf->fb_dat[cnp->cn_namelen] = '\0';
 
@@ -728,7 +734,7 @@ fusefs_symlink(void *v)
 	len = strlen(target) + 1;
 
 	fbuf = fb_setup(len + cnp->cn_namelen + 1, dp->i_number,
-	    FBT_SYMLINK, p);
+	    FUSE_SYMLINK, p);
 
 	memcpy(fbuf->fb_dat, cnp->cn_nameptr, cnp->cn_namelen);
 	fbuf->fb_dat[cnp->cn_namelen] = '\0';
@@ -743,7 +749,15 @@ fusefs_symlink(void *v)
 		goto bad;
 	}
 
-	if ((error = VFS_VGET(fmp->mp, fbuf->fb_ino, &tdp))) {
+	/* symlink returns a fuse_entry_out with the ino of the new link */
+	if (fbuf->op.out.entry.nodeid == 0 ||
+	    fbuf->op.out.entry.nodeid == FUSE_ROOT_ID) {
+		error = EIO;
+		fb_delete(fbuf);
+		goto bad;
+	}
+
+	if ((error = VFS_VGET(fmp->mp, fbuf->op.out.entry.nodeid, &tdp))) {
 		fb_delete(fbuf);
 		goto bad;
 	}
@@ -767,16 +781,20 @@ fusefs_readdir(void *v)
 	struct fusefs_node *ip;
 	struct fusefs_mnt *fmp;
 	struct fusebuf *fbuf;
-	struct dirent *dp;
+	struct fuse_dirent *fdp;
-	char *edp;
+	struct dirent de;
 	struct vnode *vp;
 	struct proc *p;
 	struct uio *uio;
+	size_t read_size;
+	uint32_t fresid;
+	off_t foffset, freclen;
 	int error = 0, eofflag = 0, diropen = 0;
 
 	vp = ap->a_vp;
 	uio = ap->a_uio;
 	p = uio->uio_procp;
+	foffset = uio->uio_offset;
 
 	ip = VTOI(vp);
 	fmp = (struct fusefs_mnt *)ip->i_ump;
@@ -784,31 +802,35 @@ fusefs_readdir(void *v)
 	if (!fmp->sess_init)
 		return (ENXIO);
 
+	/*
+	 * Some file systems expect that the kernel always uses the same
+	 * read buffer size. In the event that uio_resid is a multiple of
+	 * max_read, we need to ensure that we use a consistent buffer size
+	 * in the loop.
+	 */
+	read_size = MIN(uio->uio_resid, fmp->max_read);
+
 	/*
 	 * Basic check to ensure buffer is large enough for at least one
 	 * dirent with maximum allowed name length.
 	 */
-	if (uio->uio_resid < sizeof(struct dirent))
+	if (read_size < sizeof(struct dirent))
 		return (EINVAL);
 
 	if (ip->fufh[FUFH_RDONLY].fh_type == FUFH_INVALID) {
 		error = fusefs_file_open(fmp, ip, FUFH_RDONLY, O_RDONLY, 1, p);
 		if (error)
 			return (error);
-
+		else
-		diropen = 1;
+			diropen = 1;
 	}
 
-	while (uio->uio_resid > 0) {
+	/* loop until we run out of buffer space */
-		fbuf = fb_setup(0, ip->i_number, FBT_READDIR, p);
+	while (!error && uio->uio_resid >= read_size) {
-
+		fbuf = fb_setup(0, ip->i_number, FUSE_READDIR, p);
-		fbuf->fb_io_fd = ip->fufh[FUFH_RDONLY].fh_id;
+		fbuf->op.in.read.fh = ip->fufh[FUFH_RDONLY].fh_id;
-		fbuf->fb_io_off = uio->uio_offset;
+		fbuf->op.in.read.offset = foffset;
-		fbuf->fb_io_len = MIN(uio->uio_resid, fmp->max_read);
+		fbuf->op.in.read.size = read_size;
-
-		/* might not have enough space for another dirent */
-		if (fbuf->fb_io_len < sizeof(struct dirent))
-			break;
 
 		error = fb_queue(fmp->dev, fbuf);
 		if (error) {
@@ -816,58 +838,78 @@ fusefs_readdir(void *v)
 			break;
 		}
 
-		/* ack end of readdir */
+		/*
+		 * Ack end of readdir. Only used by getcwd(3), getdents(3)
+		 * relies on a repeat call that returns no entries.
+		 */
 		if (fbuf->fb_len == 0) {
 			eofflag = 1;
 			fb_delete(fbuf);
 			break;
 		}
 
-		/* validate the returned dirents */
+		/* validate and convert the returned dirents */
-		dp = (struct dirent *)fbuf->fb_dat;
+		fresid = fbuf->fb_len;
-		edp = fbuf->fb_dat + fbuf->fb_len;
+		fdp = (struct fuse_dirent *)fbuf->fb_dat;
-		while ((char *)dp < edp) {
+
+		while (uio->uio_resid > 0 && fresid > FUSE_NAME_OFFSET) {
+
+			/* get the size of the FUSE dirent */
+			freclen = FUSE_DIRENT_SIZE(fdp);
+
 			/* check for partial dirent */
-			if ((char *)dp + offsetof(struct dirent, d_name) >= edp
+			if (fresid < freclen)
-			    || dp->d_reclen <= offsetof(struct dirent, d_name)
+				break;
-			    || (char *)dp + dp->d_reclen > edp) {
+
-				error = EINVAL;
+			/* check for sane name length */
+			if (fdp->namelen == 0 || fdp->namelen > MAXNAMLEN) {
+				error = EIO;
 				break;
 			}
-			/* check name doesn't extend past end of dirent */
-			if (dp->d_namlen + offsetof(struct dirent, d_name) >=
-			    dp->d_reclen) {
-				error = EINVAL;
-				break;
-			}
-			/*
-			 * If name doesn't extend to end of dirent then set
-			 * remaining space to NULL. This is not usually the
-			 * case but we can't trust userspace.
-			 */
-			memset(dp->d_name + dp->d_namlen, 0, dp->d_reclen -
-			    dp->d_namlen - offsetof(struct dirent, d_name));
 
 			/* check for illegal character in file name */
-			if (memchr(dp->d_name, '/', dp->d_namlen) != NULL) {
+			if (memchr(fdp->name, '/', fdp->namelen) != NULL) {
-				error = EINVAL;
+				error = EIO;
 				break;
 			}
-			dp = (struct dirent *)((char *)dp + dp->d_reclen);
-		}
-		if (error) {
-			fb_delete(fbuf);
-			break;
-		}
 
-		if ((error = uiomove(fbuf->fb_dat, fbuf->fb_len, uio))) {
+			/* copy FUSE dirent into struct dirent */
-			fb_delete(fbuf);
+			memset(&de, 0, sizeof(de));
-			break;
+			de.d_namlen = fdp->namelen;
+			de.d_reclen = DIRENT_RECSIZE(de.d_namlen);
+			if (uio->uio_resid < de.d_reclen)
+				goto out;
+			/*
+			 * d_off is used by telldir, seekdir, readdir libc
+			 * functions and expect the file system's offset. This
+			 * will be passed back to this function so needs to be
+			 * the FUSE offset.
+			 */
+			de.d_off = fdp->off;
+			de.d_fileno = fdp->ino;
+			de.d_type = fdp->type;
+			memcpy(de.d_name, fdp->name, de.d_namlen);
+			/* pad with NUL */
+			/* XXX necessary if we memset 0 above?
+			 * or is this better? */
+			memset(de.d_name + de.d_namlen, 0, de.d_reclen
+			    - de.d_namlen - offsetof(struct dirent, d_name));
+
+			if ((error = uiomove(&de, de.d_reclen, uio)))
+				break;
+
+			/* advance to next FUSE dirent */
+			fresid -= freclen;
+			foffset = fdp->off;
+			fdp = (struct fuse_dirent *)((char *)fdp + freclen);
 		}
 
 		fb_delete(fbuf);
 	}
 
+out:
+	uio->uio_offset = foffset;
+
 	if (!error && ap->a_eofflag != NULL)
 		*ap->a_eofflag = eofflag;
 
@@ -949,11 +991,7 @@ fusefs_readlink(void *v)
 	if (fmp->undef_op & UNDEF_READLINK)
 		return (ENOSYS);
 
-	fbuf = fb_setup(0, ip->i_number, FBT_READLINK, p);
+	fbuf = fb_setup(0, ip->i_number, FUSE_READLINK, p);
-
-	fbuf->fb_io_off = uio->uio_offset;
-	fbuf->fb_io_len = MIN(uio->uio_resid, fmp->max_read);
-
 	error = fb_queue(fmp->dev, fbuf);
 
 	if (error) {
@@ -991,7 +1029,7 @@ fusefs_reclaim(void *v)
 	struct fusefs_filehandle *fufh = NULL;
 	struct fusefs_mnt *fmp;
 	struct fusebuf *fbuf;
-	int type, error = 0;
+	int type;
 
 	fmp = (struct fusefs_mnt *)ip->i_ump;
 
@@ -1008,12 +1046,11 @@ fusefs_reclaim(void *v)
 	/*
 	 * If the fuse connection is opened ask libfuse to free the vnodes.
 	 */
-	if (fmp->sess_init && ip->i_number != FUSE_ROOTINO) {
+	if (fmp->sess_init && ip->i_number != FUSE_ROOT_ID) {
-		fbuf = fb_setup(0, ip->i_number, FBT_RECLAIM, p);
+		fbuf = fb_setup(0, ip->i_number, FUSE_FORGET, p);
-		error = fb_queue(fmp->dev, fbuf);
+		fbuf->op.in.forget.nlookup = ip->nlookup;
-		if (error)
+		fuse_device_queue_fbuf(fmp->dev, fbuf);
-			printf("fusefs: vnode reclaim failed: %d\n", error);
+		/* FUSE_FORGET has no response */
-		fb_delete(fbuf);
 	}
 
 	/*
@@ -1074,9 +1111,10 @@ fusefs_create(void *v)
 	}
 
 	fbuf = fb_setup(cnp->cn_namelen + 1, ip->i_number,
-	    FBT_MKNOD, p);
+	    FUSE_MKNOD, p);
 
-	fbuf->fb_io_mode = mode;
+	fbuf->op.in.mknod.mode = mode;
+	fbuf->op.in.mknod.umask = p->p_p->ps_fd->fd_cmask;
 
 	memcpy(fbuf->fb_dat, cnp->cn_nameptr, cnp->cn_namelen);
 	fbuf->fb_dat[cnp->cn_namelen] = '\0';
@@ -1089,10 +1127,17 @@ fusefs_create(void *v)
 		goto out;
 	}
 
-	if ((error = VFS_VGET(fmp->mp, fbuf->fb_ino, &tdp)))
+	/* mknod returns a fuse_entry_out with the ino of the new file */
+	if (fbuf->op.out.entry.nodeid == 0 ||
+	    fbuf->op.out.entry.nodeid == FUSE_ROOT_ID) {
+		error = EIO;
+		goto out;
+	}
+
+	if ((error = VFS_VGET(fmp->mp, fbuf->op.out.entry.nodeid, &tdp)))
 		goto out;
 
-	tdp->v_type = IFTOVT(fbuf->fb_attr.st_mode);
+	tdp->v_type = VREG;
 
 	*vpp = tdp;
 	VN_KNOTE(ap->a_dvp, NOTE_WRITE);
@@ -1131,11 +1176,12 @@ fusefs_mknod(void *v)
 	}
 
 	fbuf = fb_setup(cnp->cn_namelen + 1, ip->i_number,
-	    FBT_MKNOD, p);
+	    FUSE_MKNOD, p);
 
-	fbuf->fb_io_mode = MAKEIMODE(vap->va_type, vap->va_mode);
+	fbuf->op.in.mknod.mode = MAKEIMODE(vap->va_type, vap->va_mode);
+	fbuf->op.in.mknod.umask = p->p_p->ps_fd->fd_cmask;
 	if (vap->va_rdev != VNOVAL)
-		fbuf->fb_io_rdev = vap->va_rdev;
+		fbuf->op.in.mknod.rdev = vap->va_rdev;
 
 	memcpy(fbuf->fb_dat, cnp->cn_nameptr, cnp->cn_namelen);
 	fbuf->fb_dat[cnp->cn_namelen] = '\0';
@@ -1148,10 +1194,21 @@ fusefs_mknod(void *v)
 		goto out;
 	}
 
-	if ((error = VFS_VGET(fmp->mp, fbuf->fb_ino, &tdp)))
+	/* mknod returns a fuse_entry_out with the ino of the new file */
+	if (fbuf->op.out.entry.nodeid == 0 ||
+	    fbuf->op.out.entry.nodeid == FUSE_ROOT_ID) {
+		error = EIO;
+		goto out;
+	}
+
+	if ((error = VFS_VGET(fmp->mp, fbuf->op.out.entry.nodeid, &tdp)))
 		goto out;
 
-	tdp->v_type = IFTOVT(fbuf->fb_attr.st_mode);
+	/*
+	 * Don't trust the type returned by the file system and assume it
+	 * created what it was asked.
+	 */
+	tdp->v_type = vap->va_type;
 
 	*vpp = tdp;
 	VN_KNOTE(ap->a_dvp, NOTE_WRITE);
@@ -1194,12 +1251,12 @@ fusefs_read(void *v)
 		return (EINVAL);
 
 	while (uio->uio_resid > 0) {
-		fbuf = fb_setup(0, ip->i_number, FBT_READ, p);
+		fbuf = fb_setup(0, ip->i_number, FUSE_READ, p);
 
 		size = MIN(uio->uio_resid, fmp->max_read);
-		fbuf->fb_io_fd = fusefs_fd_get(ip, FUFH_RDONLY);
+		fbuf->op.in.read.fh = fusefs_fd_get(ip, FUFH_RDONLY);
-		fbuf->fb_io_off = uio->uio_offset;
+		fbuf->op.in.read.offset = uio->uio_offset;
-		fbuf->fb_io_len = size;
+		fbuf->op.in.read.size = size;
 
 		error = fb_queue(fmp->dev, fbuf);
 
@@ -1240,6 +1297,15 @@ fusefs_write(void *v)
 	ip = VTOI(vp);
 	fmp = (struct fusefs_mnt *)ip->i_ump;
 
+	/*
+	 * XXX
+	 * fmp->max_write will not be set to the value wanted by the file
+	 * system if sess_init == PENDING. It is not currently possible for
+	 * this to be the case since a write operation cannot take place on
+	 * a vnode until after VOP_LOOKUP(9) has successfully returned. At
+	 * which point, the file system must have responded to FUSE_INIT and
+	 * sess_init will be 1 and max_write will be correctly set.
+	 */
 	if (!fmp->sess_init)
 		return (ENXIO);
 	if (uio->uio_resid == 0)
@@ -1253,12 +1319,12 @@ fusefs_write(void *v)
 	}
 
 	while (uio->uio_resid > 0) {
-		len = MIN(uio->uio_resid, fmp->max_read);
+		len = MIN(uio->uio_resid, fmp->max_write);
-		fbuf = fb_setup(len, ip->i_number, FBT_WRITE, p);
+		fbuf = fb_setup(len, ip->i_number, FUSE_WRITE, p);
 
-		fbuf->fb_io_fd = fusefs_fd_get(ip, FUFH_WRONLY);
+		fbuf->op.in.write.fh = fusefs_fd_get(ip, FUFH_WRONLY);
-		fbuf->fb_io_off = uio->uio_offset;
+		fbuf->op.in.write.offset = uio->uio_offset;
-		fbuf->fb_io_len = len;
+		fbuf->op.in.write.size = len;
 
 		if ((error = uiomove(fbuf->fb_dat, len, uio))) {
 			printf("fusefs: uio error %i\n", error);
@@ -1270,8 +1336,8 @@ fusefs_write(void *v)
 		if (error)
 			break;
 
-		diff = len - fbuf->fb_io_len;
+		diff = len - fbuf->op.out.write.size;
-		if (fbuf->fb_io_len > len) {
+		if (fbuf->op.out.write.size > len) {
 			error = EINVAL;
 			break;
 		}
@@ -1382,14 +1448,14 @@ abortit:
 	}
 
 	fbuf = fb_setup(fcnp->cn_namelen + tcnp->cn_namelen + 2,
-	    dp->i_number, FBT_RENAME, p);
+	    dp->i_number, FUSE_RENAME, p);
 
 	memcpy(fbuf->fb_dat, fcnp->cn_nameptr, fcnp->cn_namelen);
 	fbuf->fb_dat[fcnp->cn_namelen] = '\0';
 	memcpy(fbuf->fb_dat + fcnp->cn_namelen + 1, tcnp->cn_nameptr,
 	    tcnp->cn_namelen);
 	fbuf->fb_dat[fcnp->cn_namelen + tcnp->cn_namelen + 1] = '\0';
-	fbuf->fb_io_ino = VTOI(tdvp)->i_number;
+	fbuf->op.in.rename.newdir = VTOI(tdvp)->i_number;
 
 	error = fb_queue(fmp->dev, fbuf);
 
@@ -1449,9 +1515,10 @@ fusefs_mkdir(void *v)
 	}
 
 	fbuf = fb_setup(cnp->cn_namelen + 1, ip->i_number,
-	    FBT_MKDIR, p);
+	    FUSE_MKDIR, p);
 
-	fbuf->fb_io_mode = MAKEIMODE(vap->va_type, vap->va_mode);
+	fbuf->op.in.mkdir.mode = MAKEIMODE(vap->va_type, vap->va_mode);
+	fbuf->op.in.mkdir.umask = p->p_p->ps_fd->fd_cmask;
 	memcpy(fbuf->fb_dat, cnp->cn_nameptr, cnp->cn_namelen);
 	fbuf->fb_dat[cnp->cn_namelen] = '\0';
 
@@ -1464,12 +1531,19 @@ fusefs_mkdir(void *v)
 		goto out;
 	}
 
-	if ((error = VFS_VGET(fmp->mp, fbuf->fb_ino, &tdp))) {
+	/* mkdir returns a fuse_entry_out with the ino of the new directory */
+	if (fbuf->op.out.entry.nodeid == 0 ||
+	    fbuf->op.out.entry.nodeid == FUSE_ROOT_ID) {
+		error = EIO;
+		goto out;
+	}
+
+	if ((error = VFS_VGET(fmp->mp, fbuf->op.out.entry.nodeid, &tdp))) {
 		fb_delete(fbuf);
 		goto out;
 	}
 
-	tdp->v_type = IFTOVT(fbuf->fb_attr.st_mode);
+	tdp->v_type = VDIR;
 
 	*vpp = tdp;
 	VN_KNOTE(ap->a_dvp, NOTE_WRITE | NOTE_LINK);
@@ -1517,7 +1591,7 @@ fusefs_rmdir(void *v)
 	VN_KNOTE(dvp, NOTE_WRITE | NOTE_LINK);
 
 	fbuf = fb_setup(cnp->cn_namelen + 1, dp->i_number,
-	    FBT_RMDIR, p);
+	    FUSE_RMDIR, p);
 	memcpy(fbuf->fb_dat, cnp->cn_nameptr, cnp->cn_namelen);
 	fbuf->fb_dat[cnp->cn_namelen] = '\0';
 
@@ -1575,7 +1649,7 @@ fusefs_remove(void *v)
 	}
 
 	fbuf = fb_setup(cnp->cn_namelen + 1, dp->i_number,
-	    FBT_UNLINK, p);
+	    FUSE_UNLINK, p);
 	memcpy(fbuf->fb_dat, cnp->cn_nameptr, cnp->cn_namelen);
 	fbuf->fb_dat[cnp->cn_namelen] = '\0';
 
@@ -1674,8 +1748,14 @@ fusefs_fsync(void *v)
 		if (fufh->fh_type == FUFH_WRONLY ||
 		    fufh->fh_type == FUFH_RDWR) {
 
-			fbuf = fb_setup(0, ip->i_number, FBT_FSYNC, p);
+			fbuf = fb_setup(0, ip->i_number, FUSE_FSYNC, p);
-			fbuf->fb_io_fd = fufh->fh_id;
+			fbuf->op.in.fsync.fh = fufh->fh_id;
+
+			/*
+			 * fdatasync(2) is just a wrapper around fsync(2) so
+			 * datasync is always false.
+			 */
+			fbuf->op.in.fsync.fsync_flags = 0;
 
 			/* Always behave as if ap->a_waitfor = MNT_WAIT. */
 			error = fb_queue(fmp->dev, fbuf);

sys/miscfs/fuse/fusebuf.c

@@ -1,4 +1,4 @@
-/* $OpenBSD: fusebuf.c,v 1.18 2021/03/11 13:31:35 jsg Exp $ */
+/* $OpenBSD: fusebuf.c,v 1.19 2026/06/17 13:29:01 helg Exp $ */
 /*
  * Copyright (c) 2012-2013 Sylvestre Gallon <ccna.syl@gmail.com>
  *
@@ -35,7 +35,82 @@ fb_setup(size_t len, ino_t ino, int op, struct proc *p)
 {
 	struct fusebuf *fbuf;
 
-	fbuf = pool_get(&fusefs_fbuf_pool, PR_WAITOK | PR_ZERO);
+	KASSERT(len <= FUSEBUFMAXSIZE);
+
+ 	fbuf = pool_get(&fusefs_fbuf_pool, PR_WAITOK | PR_ZERO);
+
+	fbuf->op_in_len = 0;
+	fbuf->op_out_len = 0;
+	fbuf->op_out_buf = 0;
+	switch(op) {
+		case FUSE_GETATTR:
+			fbuf->op_in_len = sizeof(struct fuse_getattr_in);
+			fbuf->op_out_len = sizeof(struct fuse_attr_out);
+			break;
+		case FUSE_SETATTR:
+			fbuf->op_in_len = sizeof(struct fuse_setattr_in);
+			fbuf->op_out_len = sizeof(struct fuse_attr_out);
+			break;
+		case FUSE_READLINK:
+			fbuf->op_out_buf = 1;
+			break;
+		case FUSE_FLUSH:
+			fbuf->op_in_len = sizeof(struct fuse_flush_in);
+			break;
+		case FUSE_INIT:
+			fbuf->op_in_len = sizeof(struct fuse_init_in);
+			fbuf->op_out_len = sizeof(struct fuse_init_out);
+			break;
+		case FUSE_OPEN:
+		case FUSE_OPENDIR:
+			fbuf->op_in_len = sizeof(struct fuse_open_in);
+			fbuf->op_out_len = sizeof(struct fuse_open_out);
+			break;
+		case FUSE_READ:
+		case FUSE_READDIR:
+			fbuf->op_in_len = sizeof(struct fuse_read_in);
+			fbuf->op_out_buf = 1;
+			break;
+		case FUSE_MKDIR:
+			fbuf->op_in_len = sizeof(struct fuse_mkdir_in);
+			fbuf->op_out_len = sizeof(struct fuse_entry_out);
+			break;
+		case FUSE_MKNOD:
+			fbuf->op_in_len = sizeof(struct fuse_mknod_in);
+			fbuf->op_out_len = sizeof(struct fuse_entry_out);
+			break;
+		case FUSE_FSYNC:
+			fbuf->op_in_len = sizeof(struct fuse_fsync_in);
+			break;
+		case FUSE_RENAME:
+			fbuf->op_in_len = sizeof(struct fuse_rename_in);
+			break;
+		case FUSE_LINK:
+			fbuf->op_in_len = sizeof(struct fuse_link_in);
+			fbuf->op_out_len = sizeof(struct fuse_entry_out);
+			break;
+		case FUSE_SYMLINK:
+			fbuf->op_out_len = sizeof(struct fuse_entry_out);
+			break;
+		case FUSE_RELEASE:
+		case FUSE_RELEASEDIR:
+			fbuf->op_in_len = sizeof(struct fuse_release_in);
+			break;
+		case FUSE_WRITE:
+			fbuf->op_in_len = sizeof(struct fuse_write_in);
+			fbuf->op_out_len = sizeof(struct fuse_write_out);
+			break;
+		case FUSE_FORGET:
+			fbuf->op_in_len = sizeof(struct fuse_forget_in);
+			break;
+		case FUSE_LOOKUP:
+			fbuf->op_out_len = sizeof(struct fuse_entry_out);
+			break;
+		case FUSE_STATFS:
+			fbuf->op_out_len = sizeof(struct fuse_statfs_out);
+			break;
+	}
+	fbuf->hdr.len = sizeof(fbuf->hdr) + fbuf->op_in_len + len;
 	fbuf->fb_len = len;
 	fbuf->fb_err = 0;
 	arc4random_buf(&fbuf->fb_uuid, sizeof fbuf->fb_uuid);
@@ -48,7 +123,6 @@ fb_setup(size_t len, ino_t ino, int op, struct proc *p)
 	fbuf->fb_tid = p->p_tid + THREAD_PID_OFFSET;
 	fbuf->fb_uid = p->p_ucred->cr_uid;
 	fbuf->fb_gid = p->p_ucred->cr_gid;
-	fbuf->fb_umask = p->p_p->ps_fd->fd_cmask;
 	if (len == 0)
 		fbuf->fb_dat = NULL;
 	else

sys/miscfs/fuse/fusefs.h

@@ -1,4 +1,4 @@
-/* $OpenBSD: fusefs.h,v 1.15 2025/09/08 17:25:46 helg Exp $ */
+/* $OpenBSD: fusefs.h,v 1.16 2026/06/17 13:29:01 helg Exp $ */
 /*
  * Copyright (c) 2012-2013 Sylvestre Gallon <ccna.syl@gmail.com>
  *
@@ -41,6 +41,7 @@ struct fusefs_mnt {
 	struct mount *mp;
 	uint32_t undef_op;
 	int max_read;
+	int max_write;
 	int sess_init;
 	int allow_other;
 	dev_t dev;
@@ -74,11 +75,6 @@ void fuse_device_cleanup(dev_t);
 void fuse_device_queue_fbuf(dev_t, struct fusebuf *);
 void fuse_device_set_fmp(struct fusefs_mnt *, int);
 
-/*
- * The root inode is the root of the file system.  Inode 0 can't be used for
- * normal purposes.
- */
-#define	FUSE_ROOTINO ((ino_t)1)
 #define VFSTOFUSEFS(mp)	((struct fusefs_mnt *)((mp)->mnt_data))
 
 #endif /* _KERNEL */

sys/miscfs/fuse/fusefs_node.h

@@ -1,4 +1,4 @@
-/* $OpenBSD: fusefs_node.h,v 1.6 2026/01/22 11:53:31 helg Exp $ */
+/* $OpenBSD: fusefs_node.h,v 1.7 2026/06/17 13:29:01 helg Exp $ */
 /*
  * Copyright (c) 2012-2013 Sylvestre Gallon <ccna.syl@gmail.com>
  *
@@ -49,6 +49,9 @@ struct fusefs_node {
 
 	/** meta **/
 	off_t			 filesize;
+
+	/** lookup count needed by FUSE_FORGET **/
+	uint64_t		 nlookup;
 };
 
 #ifdef ITOV

sys/sys/fusebuf.h

@@ -1,4 +1,4 @@
-/* $OpenBSD: fusebuf.h,v 1.16 2025/09/06 06:15:52 helg Exp $ */
+/* $OpenBSD: fusebuf.h,v 1.17 2026/06/17 13:29:01 helg Exp $ */
 /*
  * Copyright (c) 2013 Sylvestre Gallon
  * Copyright (c) 2013 Martin Pieuchot
@@ -19,36 +19,25 @@
 #ifndef _SYS_FUSEBUF_H_
 #define _SYS_FUSEBUF_H_
 
+#include <sys/stdint.h>
+
 /*
  * Maximum size of the read or write buffer sent from the kernel for VFS
  * syscalls: read, readdir, readlink, write.
  */
 #define FUSEBUFMAXSIZE	(4096*1024)
 
-/* header at beginning of each fusebuf: */
+/** Linux FUSE kernel interface major version we somewhat emulate. */
-struct fb_hdr {
+#define FUSE_KERNEL_VERSION 7
-	SIMPLEQ_ENTRY(fusebuf)	fh_next;	/* next buffer in chain */
-	size_t			fh_len;		/* Amount of data */
-	int			fh_err;		/* errno to pass back */
-	int			fh_type;	/* type of data */
-	ino_t			fh_ino;		/* Inode of this fusebuf */
-	uint64_t		fh_uuid;	/* Uuid to track the answer */
-	pid_t			fh_tid;		/* calling proc thread id */
-	uid_t			fh_uid;		/* calling proc uid */
-	gid_t			fh_gid;		/* calling proc gid */
-	mode_t			fh_umask;	/* calling proc umask */
-};
 
-/* header for fuse file operations (like read/write/mkdir): */
+/** Linux FUSE kernel interface minor version we somewhat emulate. */
-struct fb_io {
+#define FUSE_KERNEL_MINOR_VERSION 19
-	uint64_t	fi_fd;		/* fd where the io is performed */
+
-	ino_t           fi_ino;		/* ino for the io */
+/*
-	off_t		fi_off;		/* offset for the io */
+ * The root inode is the root of the mounted FUSE file system.
-	size_t		fi_len;		/* Length of data */
+ * Also note that inode 0 can't be used for normal purposes.
-	mode_t		fi_mode;	/* mode for fd */
+ */
-	uint32_t	fi_flags;	/* flags on transfer */
+#define FUSE_ROOT_ID ((ino_t)1)
-	dev_t		fi_rdev;	/* dev for mknod */
-};
 
 /*
  * An operation is issued by the kernel through fuse(4) when the
@@ -62,43 +51,6 @@ struct fb_io {
  * When the userland file system answers to this operation it uses
  * the same ID (fh_uuid).
  */
-struct fusebuf {
-	struct fb_hdr	fb_hdr;
-	union {
-		struct statvfs	FD_stat;	/* vfs statfs */
-		struct stat	FD_attr;	/* for attr vnops */
-		struct fb_io	FD_io;		/* for file io vnops */
-	} FD;
-	uint8_t *fb_dat;			/* data's */
-};
-
-#define fb_next		fb_hdr.fh_next
-#define fb_len		fb_hdr.fh_len
-#define fb_err		fb_hdr.fh_err
-#define fb_type		fb_hdr.fh_type
-#define fb_ino		fb_hdr.fh_ino
-#define fb_uuid		fb_hdr.fh_uuid
-#define fb_tid		fb_hdr.fh_tid
-#define fb_uid		fb_hdr.fh_uid
-#define fb_gid		fb_hdr.fh_gid
-#define fb_umask	fb_hdr.fh_umask
-
-#define fb_stat		FD.FD_stat
-#define fb_attr		FD.FD_attr
-#define fb_io_fd	FD.FD_io.fi_fd
-#define fb_io_ino	FD.FD_io.fi_ino
-#define fb_io_off	FD.FD_io.fi_off
-#define fb_io_len	FD.FD_io.fi_len
-#define fb_io_mode	FD.FD_io.fi_mode
-#define fb_io_flags	FD.FD_io.fi_flags
-#define fb_io_rdev	FD.FD_io.fi_rdev
-
-/*
- * Macros for type conversion
- * fbtod(fb,t) -	convert fusebuf pointer to data pointer of correct
- *			type
- */
-#define	fbtod(fb,t)	((t)((fb)->fb_dat))
 
 /* flags needed by setattr */
 #define FUSE_FATTR_MODE		(1 << 0)
@@ -107,42 +59,368 @@ struct fusebuf {
 #define FUSE_FATTR_SIZE		(1 << 3)
 #define FUSE_FATTR_ATIME	(1 << 4)
 #define FUSE_FATTR_MTIME	(1 << 5)
-#define FUSE_FATTR_FH		(1 << 6)
 
 /* fusebuf types */
-#define	FBT_LOOKUP	0
+#define FUSE_LOOKUP	1
-#define FBT_GETATTR	1
+#define FUSE_GETATTR	3
-#define FBT_SETATTR	2
+#define FUSE_SETATTR	4
-#define FBT_READLINK	3
+#define FUSE_READLINK	5
-#define FBT_SYMLINK	4
+#define FUSE_SYMLINK	6
-#define FBT_MKNOD	5
+#define FUSE_MKNOD	8
-#define FBT_MKDIR	6
+#define FUSE_MKDIR	9
-#define FBT_UNLINK	7
+#define FUSE_UNLINK	10
-#define FBT_RMDIR	8
+#define FUSE_RMDIR	11
-#define FBT_RENAME	9
+#define FUSE_RENAME	12
-#define FBT_LINK	10
+#define FUSE_LINK	13
-#define FBT_OPEN	11
+#define FUSE_OPEN	14
-#define FBT_READ	12
+#define FUSE_READ	15
-#define FBT_WRITE	13
+#define FUSE_WRITE	16
-#define FBT_STATFS	14
+#define FUSE_STATFS	17
-#define FBT_RELEASE	16
+#define FUSE_RELEASE	18
-#define FBT_FSYNC	17
+#define FUSE_FSYNC	20
-#define FBT_FLUSH	18
+#define FUSE_FLUSH	25
-#define FBT_INIT	19
+#define FUSE_INIT	26
-#define FBT_OPENDIR	20
+#define FUSE_OPENDIR	27
-#define FBT_READDIR	21
+#define FUSE_READDIR	28
-#define FBT_RELEASEDIR	22
+#define FUSE_RELEASEDIR	29
-#define FBT_FSYNCDIR	23
+#define FUSE_DESTROY	38
-#define FBT_ACCESS	24
+#define FUSE_FORGET	2
-#define FBT_DESTROY	26
+
-#define FBT_RECLAIM	27
+struct fuse_attr {
+	uint64_t	ino;
+	uint64_t	size;
+	uint64_t	blocks;
+	uint64_t	atime;
+	uint64_t	mtime;
+	uint64_t	ctime;
+	uint32_t	atimensec;
+	uint32_t	mtimensec;
+	uint32_t	ctimensec;
+	uint32_t	mode;
+	uint32_t	nlink;
+	uint32_t	uid;
+	uint32_t	gid;
+	uint32_t	rdev;
+	uint32_t	blksize;
+	uint32_t	padding;
+};
+
+
+struct fuse_entry_out {
+	uint64_t	nodeid;			/* Inode number */
+	uint64_t	generation;		/* Not implemented */
+	uint64_t	entry_valid;		/* Not implemented */
+	uint64_t	attr_valid;		/* Not implemented */
+	uint32_t	entry_valid_nsec;	/* Not implemented */
+	uint32_t	attr_valid_nsec;	/* Not implemented */
+	struct		fuse_attr attr;
+};
+
+struct fuse_forget_in {
+	uint64_t	nlookup;
+};
+
+struct fuse_getattr_in {
+	uint32_t	getattr_flags;		/* Not implemented */
+	uint32_t	dummy;
+	uint64_t	fh;			/* Not implemented */
+};
+
+struct fuse_attr_out {
+	uint64_t	attr_valid;		/* Not implemented */
+	uint32_t	attr_valid_nsec;	/* Not implemented */
+	uint32_t	dummy;
+	struct		fuse_attr attr;
+};
+
+struct fuse_mknod_in {
+	uint32_t	mode;
+	uint32_t	rdev;
+	uint32_t	umask;
+	uint32_t	padding;
+};
+
+struct fuse_mkdir_in {
+	uint32_t	mode;
+	uint32_t	umask;
+};
+
+struct fuse_rename_in {
+	uint64_t	newdir;
+};
+
+struct fuse_link_in {
+	uint64_t	oldnodeid;
+};
+
+struct fuse_setattr_in {
+	uint32_t	valid;
+	uint32_t	padding;
+	uint64_t	fh;
+	uint64_t	size;
+	uint64_t	lock_owner;
+	uint64_t	atime;
+	uint64_t	mtime;
+	uint64_t	unused2;
+	uint32_t	atimensec;
+	uint32_t	mtimensec;
+	uint32_t	unused3;
+	uint32_t	mode;
+	uint32_t	unused4;
+	uint32_t	uid;
+	uint32_t	gid;
+	uint32_t	unused5;
+};
+
+struct fuse_open_in {
+	uint32_t	flags;
+	uint32_t	unused;
+};
+
+struct fuse_open_out {
+	uint64_t	fh;
+	uint32_t	open_flags;
+	uint32_t	padding;
+};
+
+struct fuse_release_in {
+	uint64_t	fh;
+	uint32_t	flags;
+	uint32_t	release_flags;
+	uint64_t	lock_owner;
+};
+
+struct fuse_flush_in {
+	uint64_t	fh;
+	uint32_t	unused;
+	uint32_t	padding;
+	uint64_t	lock_owner;
+};
+
+struct fuse_read_in {
+	uint64_t	fh;
+	uint64_t	offset;
+	uint32_t	size;
+	uint32_t	read_flags;
+	uint64_t	lock_owner;
+	uint32_t	flags;
+	uint32_t	padding;
+};
+
+struct fuse_write_in {
+	uint64_t	fh;
+	uint64_t	offset;
+	uint32_t	size;
+	uint32_t	write_flags;
+	uint64_t	lock_owner;
+	uint32_t	flags;
+	uint32_t	padding;
+};
+
+struct fuse_write_out {
+	uint32_t	size;
+	uint32_t	padding;
+};
+
+struct fuse_kstatfs {
+	uint64_t	blocks;
+	uint64_t	bfree;
+	uint64_t	bavail;
+	uint64_t	files;
+	uint64_t	ffree;
+	uint32_t	bsize;
+	uint32_t	namelen;
+	uint32_t	frsize;
+	uint32_t	padding;
+	uint32_t	spare[6];
+};
+
+struct fuse_statfs_out {
+	struct		fuse_kstatfs st;
+};
+
+struct fuse_fsync_in {
+	uint64_t	fh;
+	uint32_t	fsync_flags;		//XXX
+	uint32_t	padding;
+};
+
+struct fuse_init_in {
+	uint32_t	major;
+	uint32_t	minor;
+	uint32_t	max_readahead;
+	uint32_t	flags;
+};
+
+struct fuse_init_out {
+	uint32_t	major;
+	uint32_t	minor;
+	uint32_t	max_readahead;		/* Not implemented */
+	uint32_t	flags;			/* Not implemented */
+	uint16_t   	max_background;		/* Not implemented */
+	uint16_t   	congestion_threshold;	/* Not implemented */
+	uint32_t	max_write;
+};
+
+struct fuse_in_header {
+	uint32_t	len;
+	uint32_t	opcode;
+	uint64_t	unique;
+	uint64_t	nodeid;
+	uint32_t	uid;
+	uint32_t	gid;
+	uint32_t	pid;
+	uint32_t	padding;
+};
+
+struct fuse_out_header {
+	uint32_t	len;
+	int32_t		error;
+	uint64_t	unique;
+};
+
+struct fuse_dirent {
+	uint64_t	ino;
+	uint64_t	off;
+	uint32_t	namelen;
+	uint32_t	type;
+	char		name[];			/* unterminated string */
+};
+
+#define FUSE_NAME_OFFSET offsetof(struct fuse_dirent, name)
+#define FUSE_DIRENT_ALIGN(x) \
+	(((x) + sizeof(uint64_t) - 1) & ~(sizeof(uint64_t) - 1))
+#define FUSE_DIRENT_SIZE(d) \
+	FUSE_DIRENT_ALIGN(FUSE_NAME_OFFSET + (d)->namelen)
 
 #ifdef _KERNEL
 
+/*
+ * An operation is issued by the kernel through fuse(4) when the
+ * userland file system needs to execute an action (mkdir(2),
+ * link(2), etc).
+ *
+ * When the userland file system answers to this operation it uses
+ * the same ID (fb_uuid).
+ */
+struct fusebuf {
+	SIMPLEQ_ENTRY(fusebuf)	next;		/* next buffer in chain */
+	struct fuse_in_header	hdr;
+	int32_t			error;		/* error returned by daemon */
+	size_t			op_in_len;	/* size of input */
+	size_t			op_out_len;	/* size of output */
+	uint8_t			op_out_buf;	/* whether to expect data */
+	union {
+		union {
+			struct fuse_forget_in	forget;
+			struct fuse_getattr_in	getattr;
+			struct fuse_setattr_in	setattr;
+			struct fuse_mknod_in	mknod;
+			struct fuse_mkdir_in	mkdir;
+			struct fuse_rename_in	rename;
+			struct fuse_link_in	link;
+			struct fuse_open_in	open;
+			struct fuse_read_in	read;
+			struct fuse_write_in	write;
+			struct fuse_release_in	release;
+			struct fuse_fsync_in	fsync;
+			struct fuse_flush_in	flush;
+			struct fuse_init_in	init;
+		} in;
+		union {
+			struct fuse_entry_out	entry;
+			struct fuse_attr_out	attr;
+			struct fuse_open_out	open;
+			struct fuse_write_out	write;
+			struct fuse_statfs_out	statfs;
+			struct fuse_init_out	init;
+		} out;
+	} op;
+	uint64_t dat_len;
+	uint8_t *dat;
+};
+
+#define fb_dat		dat
+#define fb_next		next
+#define fb_err		error
+#define fb_len		dat_len
+#define fb_type		hdr.opcode
+#define fb_uuid		hdr.unique
+#define fb_ino		hdr.nodeid
+#define fb_tid		hdr.pid
+#define fb_uid		hdr.uid
+#define fb_gid		hdr.gid
+
 /* fusebuf prototypes */
 struct	fusebuf *fb_setup(size_t, ino_t, int, struct proc *);
 int	fb_queue(dev_t, struct fusebuf *);
 void	fb_delete(struct fusebuf *);
 
+#else /* _KERNEL */
+
+/*
+ * Userland fusebuf more directly maps to the protocol binary layout for each
+ * file operation request (input). This consists of a header followed by an
+ * optional input struct with data immediately following either the header or
+ * input struct.
+ *
+ * FUSE_LOOKUP:		hdr, 		dat (filename)
+ * FUSE_GETATTR:	hdr, getattr
+ * FUSE_SETATTR:	hdr, setattr
+ * FUSE_READLINK:	hdr
+ * FUSE_SYMLINK:	hdr, 		dat (source\0target)
+ * FUSE_MKNOD:		hdr, mknod, 	dat (filename)
+ * FUSE_MKDIR:		hdr, mkdir, 	dat (dirname)
+ * FUSE_UNLINK:		hdr, 		dat (filename)
+ * FUSE_RMDIR:		hdr, 		dat (dirname)
+ * FUSE_RENAME:		hdr, rename, 	dat (oldname\0newname)
+ * FUSE_LINK:		hdr, 		dat (source\0target)
+ * FUSE_OPEN:		hdr, open
+ * FUSE_READ:		hdr, read
+ * FUSE_WRITE:		hdr, write, 	dat
+ * FUSE_STATFS:		hdr, statfs
+ * FUSE_RELEASE:	hdr, release
+ * FUSE_FSYNC:		hdr, fsync
+ * FUSE_FLUSH:		hdr, flush
+ * FUSE_INIT:		hdr, init
+ * FUSE_OPENDIR:	hdr, open
+ * FUSE_READDIR:	hdr, read
+ * FUSE_RELEASEDIR:	hdr, release
+ * FUSE_DESTROY:	hdr
+ * FUSE_FORGET:		hdr, forget
+ */
+struct fusebuf {
+	struct fuse_in_header hdr;
+	union {
+		struct fuse_forget_in	forget;
+		struct fuse_getattr_in	getattr;
+		struct fuse_setattr_in	setattr;
+		struct fuse_mknod_in	mknod;
+		struct fuse_mkdir_in	mkdir;
+		struct fuse_rename_in	rename;
+		struct fuse_link_in	link;
+		struct fuse_open_in	open;
+		struct fuse_read_in	read;
+		struct fuse_write_in	write;
+		struct fuse_release_in	release;
+		struct fuse_fsync_in	fsync;
+		struct fuse_flush_in	flush;
+		struct fuse_init_in	init;
+	} in;
+};
+
+#define fb_type	hdr.opcode
+#define fb_uuid	hdr.unique
+#define fb_ino	hdr.nodeid
+#define fb_tid	hdr.pid
+#define fb_uid	hdr.uid
+#define fb_gid	hdr.gid
+
+/*
+ * Macro to get the additional data for operations that have it.
+ * The data starts immediately after the related input struct.
+ */
+#define fb_dat(in) (((char *)&(in)) + sizeof(in))
+
 #endif /* _KERNEL */
 #endif /* _SYS_FUSEBUF_H_ */