Make fuse3 support optional and document.

The experimental fuse3 support is not complete yet, and fuse3 is new and
still difficult to install on some platforms.

Make it optional at compile time, and default to off.

Signed-off-by: Justin Husted <sigstop@gmail.com>

INSTALL

@@ -1,3 +1,4 @@
+-- Getting started --
 
 Dependencies:
 
@@ -20,3 +21,32 @@ On debian, you can install these with
         uuid-dev zlib1g-dev valgrind
 
 Then, just make && make install
+
+
+-- Experimental features --
+
+Experimental fuse support is currently disabled by default. Fuse support is at
+an early stage and may corrupt your filesystem, so it should only be used for
+testing. To enable, you'll also need to add:
+
+* libfuse3
+
+On debian:
+    apt install -y libfuse3-dev
+
+Then, make using the BCACHEFS_FUSE environment variable:
+
+BCACHEFS_FUSE=1 make &&
+
+
+-- Tests --
+
+Some tests are available to validate the "bcachefs" binary.  The tests depend
+on python3 pytest.
+
+On debian:
+   apt install -u python3-pytest
+
+Then, you can run the tests via:
+
+   make check

Makefile

@@ -38,7 +38,11 @@ ifdef D
 	CFLAGS+=-DCONFIG_BCACHEFS_DEBUG=y
 endif
 
-PKGCONFIG_LIBS="blkid uuid liburcu libsodium zlib liblz4 libzstd fuse3"
+PKGCONFIG_LIBS="blkid uuid liburcu libsodium zlib liblz4 libzstd"
+ifdef BCACHEFS_FUSE
+	PKGCONFIG_LIBS+="fuse3"
+	CFLAGS+=-DBCACHEFS_FUSE
+endif
 
 PKGCONFIG_CFLAGS:=$(shell $(PKG_CONFIG) --cflags $(PKGCONFIG_LIBS))
 ifeq (,$(PKGCONFIG_CFLAGS))

bcachefs.c

@@ -203,8 +203,10 @@ int main(int argc, char *argv[])
 	if (!strcmp(cmd, "setattr"))
 		return cmd_setattr(argc, argv);
 
+#ifdef BCACHEFS_FUSE
 	if (!strcmp(cmd, "fusemount"))
 		return cmd_fusemount(argc, argv);
+#endif
 
 	if (!strcmp(cmd, "--help")) {
 		usage();

cmd_fusemount.c

@@ -1,3 +1,5 @@
+#ifdef BCACHEFS_FUSE
+
 #include <errno.h>
 #include <float.h>
 #include <getopt.h>
@@ -1262,3 +1264,5 @@ out:
 
 	return ret ? 1 : 0;
 }
+
+#endif /* BCACHEFS_FUSE */

tests/test_fuse.py

@@ -2,9 +2,13 @@
 #
 # Tests of the fuse mount functionality.
 
+import pytest
 import os
 import util
 
+pytestmark = pytest.mark.skipif(
+    not util.have_fuse(), reason="bcachefs not built with fuse support.")
+
 def test_mount(bfuse):
     bfuse.mount()
     bfuse.unmount()

tests/util.py

@@ -4,6 +4,7 @@ import os
 import pytest
 import re
 import subprocess
+import sys
 import tempfile
 import threading
 import time
@@ -208,3 +209,7 @@ class BFuse(threading.Thread):
         assert self.returncode == 0
         assert len(self.stdout) > 0
         assert len(self.stderr) == 0
+
+def have_fuse():
+    res = run(BCH_PATH, 'fusemount', valgrind=False)
+    return "Please supply a mountpoint." in res.stdout