binderfs: port to new mount api

binderfs: port to new mount api

When I first wrote binderfs the new mount api had not yet landed. Now
that it has been around for a little while and a bunch of filesystems
have already been ported we should do so too. When Al sent his
mount-api-conversion pr he requested that binderfs (and a few others) be
ported separately. It's time we port binderfs. We can make use of the
new option parser, get nicer infrastructure and it will be easier if we
ever add any new mount options.

This survives testing with the binderfs selftests:

for i in `seq 1 1000`; do ./binderfs_test; done

including the new stress tests I sent out for review today:

 TAP version 13
 1..1
 # selftests: filesystems/binderfs: binderfs_test
 # [==========] Running 3 tests from 1 test cases.
 # [ RUN      ] global.binderfs_stress
 # [  XFAIL!  ] Tests are not run as root. Skipping privileged tests
 # [==========] Running 3 tests from 1 test cases.
 # [ RUN      ] global.binderfs_stress
 # [       OK ] global.binderfs_stress
 # [ RUN      ] global.binderfs_test_privileged
 # [       OK ] global.binderfs_test_privileged
 # [ RUN      ] global.binderfs_test_unprivileged
 # # Allocated new binder device with major 243, minor 4, and name my-binder
 # # Detected binder version: 8
 # [==========] Running 3 tests from 1 test cases.
 # [ RUN      ] global.binderfs_stress
 # [       OK ] global.binderfs_stress
 # [ RUN      ] global.binderfs_test_privileged
 # [       OK ] global.binderfs_test_privileged
 # [ RUN      ] global.binderfs_test_unprivileged
 # [       OK ] global.binderfs_test_unprivileged
 # [==========] 3 / 3 tests passed.
 # [  PASSED  ]
 ok 1 selftests: filesystems/binderfs: binderfs_test

Cc: Todd Kjos <tkjos@google.com>
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20200313153427.141789-1-christian.brauner@ubuntu.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>