fusefs: attempt to support servers as old as protocol 7.4

Previously we allowed servers as old as 7.1 to connect (there never was a
7.0).  However, we wrongly assumed a few things about protocols older than
7.8.  This commit attempts to support servers as old as 7.4 but no older.  I
added no new tests because I'm not sure there actually _are_ any servers
this old in the wild.

Sponsored by:	The FreeBSD Foundation

2 files changed, 25 insertions, 11 deletions

diff --git a/sys/fs/fuse/fuse_internal.c b/sys/fs/fuse/fuse_internal.c
index ee1231b132ff..7eecad182b8a 100644
--- a/sys/fs/fuse/fuse_internal.c
+++ b/sys/fs/fuse/fuse_internal.c
@@ -896,20 +896,21 @@ fuse_internal_init_callback(struct fuse_ticket *tick, struct uio *uio)
 	}
 	fiio = fticket_resp(tick)->base;
 
-	/* XXX: Do we want to check anything further besides this? */
-	if (fiio->major < 7) {
+	data->fuse_libabi_major = fiio->major;
+	data->fuse_libabi_minor = fiio->minor;
+	if (!fuse_libabi_geq(data, 7, 4)) {
+		/* 
+		 * With a little work we could support servers as old as 7.1.
+		 * But there would be little payoff.
+		 */
 		SDT_PROBE2(fusefs, , internal, trace, 1,
 			"userpace version too low");
 		err = EPROTONOSUPPORT;
 		goto out;
 	}
-	data->fuse_libabi_major = fiio->major;
-	data->fuse_libabi_minor = fiio->minor;
 
 	if (fuse_libabi_geq(data, 7, 5)) {
 		if (fticket_resp(tick)->len == sizeof(struct fuse_init_out)) {
-			data->max_readahead_blocks = fiio->max_readahead /
-				maxbcachebuf;
 			data->max_write = fiio->max_write;
 			if (fiio->flags & FUSE_ASYNC_READ)
 				data->dataflags |= FSESS_ASYNC_READ;
@@ -929,10 +930,21 @@ fuse_internal_init_callback(struct fuse_ticket *tick, struct uio *uio)
 			err = EINVAL;
 		}
 	} else {
-		/* Old fix values */
+		/* Old fixed values */
 		data->max_write = 4096;
 	}
 
+	if (fuse_libabi_geq(data, 7, 6))
+		data->max_readahead_blocks = fiio->max_readahead / maxbcachebuf;
+
+	if (!fuse_libabi_geq(data, 7, 7))
+		fsess_set_notimpl(data->mp, FUSE_INTERRUPT);
+
+	if (!fuse_libabi_geq(data, 7, 8)) {
+		fsess_set_notimpl(data->mp, FUSE_BMAP);
+		fsess_set_notimpl(data->mp, FUSE_DESTROY);
+	}
+
 out:
 	if (err) {
 		fdata_set_dead(data);
diff --git a/sys/fs/fuse/fuse_vfsops.c b/sys/fs/fuse/fuse_vfsops.c
index 64d7ccc7600c..f64b69164e5f 100644
--- a/sys/fs/fuse/fuse_vfsops.c
+++ b/sys/fs/fuse/fuse_vfsops.c
@@ -493,11 +493,13 @@ fuse_vfsop_unmount(struct mount *mp, int mntflags)
 	if (fdata_get_dead(data)) {
 		goto alreadydead;
 	}
-	fdisp_init(&fdi, 0);
-	fdisp_make(&fdi, FUSE_DESTROY, mp, 0, td, NULL);
+	if (fsess_isimpl(mp, FUSE_DESTROY)) {
+		fdisp_init(&fdi, 0);
+		fdisp_make(&fdi, FUSE_DESTROY, mp, 0, td, NULL);
 
-	err = fdisp_wait_answ(&fdi);
-	fdisp_destroy(&fdi);
+		(void)fdisp_wait_answ(&fdi);
+		fdisp_destroy(&fdi);
+	}
 
 	fdata_set_dead(data);