fuse: Fix want flag conversion

32-bit conn->want flags been left to be ABI compatible to 3.10,
even though the so version was changed.
The more recent way is to use fuse_set_feature_flag(),
which will use conn->want_ext.

Given that we now have two flags (want and want_ext), we need
to convert and that brought several issues
- If the application sets conn->want, that needs to be set into
  the lower 32 bit of  conn->want_ext. As the application might
  actually unset values, it really has to be a copy and not
  just 'or' - fixed now.
- convert_to_conn_want_ext() actually needs to check for
  _modified_ conn->want and conn->want_ext
- convert_to_conn_want_ext() must consider being called from
  high and lowlevel interfact, with different want_ext_default
  and want_default values. It is only a failure, if the application
  changed both, conn->want and conn->want_ext. This function
  was failing in issue #1171, because high level fuse_fs_init()
  was changing values and then lowlevel do_init() was incorrectly
  failing on that.

This also adds a new test (test_want_conversion) and sets
values into example/{hello.c,hello_ll.c}

Also some more internal users of conn->want are converted to
fuse_{set,unset}_feature_flag().

Closes: https://github.com/libfuse/libfuse/issues/1171
Signed-off-by: Bernd Schubert <bernd@bsbernd.com>
(cherry picked from commit f68970cd235a7e14026ca0f6240428bbebe8223b)

1 files changed, 3 insertions, 0 deletions

diff --git a/test/meson.build b/test/meson.build
index 3d74b9a..5997030 100644
--- a/test/meson.build
+++ b/test/meson.build
@@ -16,6 +16,9 @@ td += executable('readdir_inode', 'readdir_inode.c',
 td += executable('release_unlink_race', 'release_unlink_race.c',
                  dependencies: [ libfuse_dep ],
                  install: false)
+td += executable('test_want_conversion', 'test_want_conversion.c',
+                 dependencies: [ libfuse_dep ],
+                 install: false)
 
 test_scripts = [ 'conftest.py', 'pytest.ini', 'test_examples.py',
                  'util.py', 'test_ctests.py', 'test_custom_io.py' ]