* master:
  fs: rename from nodefs
  nodefs: make the examples package level examples
  nodefs: prefix Node interface names with Node
  zipfs: remove unused data type ZipFile
  Add TestParallelDiropsHang / emulate gvfs-udisks2-volume-monitor
  dirstream_linux: fix zero terminator search

The new naming makes clear that this is the One True API for Go-FUSE

There is a hang that appears when enabling CAP_PARALLEL_DIROPS on Linux
4.15.0: https://github.com/hanwen/go-fuse/issues/281

The hang was originally triggered by gvfs-udisks2-volume-monitor. This
test emulates what gvfs-udisks2-volume-monitor does.

On 4.15.0 kernels, the test will get stuck, and after 120 seconds you
get a kernel backtrace like this:

[ 1813.463679] INFO: task nodefs.test:2357 blocked for more than 120 seconds.
[ 1813.463685]       Not tainted 4.15.0-45-generic #48~16.04.1-Ubuntu
[ 1813.463687] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[ 1813.463689] nodefs.test     D    0  2357   2311 0x00000004
[ 1813.463691] Call Trace:
[ 1813.463709]  __schedule+0x3d6/0x8b0
[ 1813.463712]  schedule+0x36/0x80
[ 1813.463714]  schedule_preempt_disabled+0xe/0x10
[ 1813.463716]  __mutex_lock.isra.2+0x2ae/0x4e0
[ 1813.463720]  ? ___slab_alloc+0x223/0x4e0
[ 1813.463722]  ? _cond_resched+0x1a/0x50
[ 1813.463724]  __mutex_lock_slowpath+0x13/0x20
[ 1813.463725]  ? __mutex_lock_slowpath+0x13/0x20
[ 1813.463727]  mutex_lock+0x2f/0x40
[ 1813.463729]  fuse_lock_inode+0x2a/0x30
[ 1813.463732]  fuse_lookup+0x31/0x140
[ 1813.463735]  ? d_alloc_parallel+0xc1/0x4c0
[ 1813.463738]  fuse_atomic_open+0x6d/0xf0
[ 1813.463740]  path_openat+0xc5d/0x13f0
[ 1813.463744]  do_filp_open+0x99/0x110
[ 1813.463747]  ? __check_object_size+0xfc/0x1a0
[ 1813.463749]  ? __alloc_fd+0x46/0x170
[ 1813.463752]  do_sys_open+0x12d/0x290
[ 1813.463754]  ? do_sys_open+0x12d/0x290
[ 1813.463756]  SyS_openat+0x14/0x20
[ 1813.463759]  do_syscall_64+0x73/0x130
[ 1813.463762]  entry_SYSCALL_64_after_hwframe+0x3d/0xa2

The old code searched for the first non-null byte from the end of
the slice. This assumes that all bytes after the name are initialized
to zero, which does not hold true on Linux 4.15.

Instead, search for the first null byte from the start of the slice,
which is guaranteed by man(3) readdir.

Fixes https://github.com/hanwen/go-fuse/issues/287

* origin/master:
  nodefs: add Inode.IsRoot
  newunionfs: hide DELETIONS
  nodefs: fix style in doReadDir
  newunionfs: implement Readdir
  nodefs: suppress verbose output for some tests
  fuse: add FOPEN_CACHE_DIR to print registry
  newunionfs: disable umask
  nodefs: disable umask in tests
  nodefs: more renaming

This reduces the debug output from 25k lines to ~1k

* master:
  fixup! rename NodeAttr to StableAttr
  rename NodeAttr to StableAttr
  internal: fix access for root user
  tarfs: handle empty directories, handle more file types
  nodefs: add Attr to MemSymlink
  nodefs: protect dirsteam overflow with lock
  nodefs: add TestReadDirStress
  nodefs: protect against double close
  newunionfs: run PosixTest tests.
  newunionfs: symlink/readlink
  posixtest: export list of tests
  nodefs: handle unimplemented Mkdir
  newunionfs: a new unionfs implementation
  fuse: fix SupportsVersion
  nodefs: skip tests if kernel doesn't support lseek/copy_file_range
  posixtest: new package for generic file system tests
  update go modules.
  nodefs: add EntryOut to Create signature
  nodefs: add Inode.IsDir
  nodefs: implement Setattr in loopback

I saw build error when running tests:

	(neo) (z-dev) (g.env) kirr@deco:~/src/neo/src/github.com/hanwen/go-fuse$ go test ./...
	# github.com/hanwen/go-fuse/nodefs
	nodefs/inode.go:130:30: undefined: NodeAttr
	FAIL    github.com/hanwen/go-fuse/benchmark [build failed]
	...

Appeases the race detector.

This currently fails on Linux 5.0 and may be related to
https://github.com/hanwen/go-fuse/issues/287 .

1 jakob@brikett:~/go/src/github.com/hanwen/go-fuse/nodefs$ go test
21:42:47.356529 writer: Write/Writev failed, err: 2=no such file or directory. opcode: RELEASE
21:42:47.598309 writer: Write/Writev failed, err: 22=invalid argument. opcode: READDIRPLUS
21:42:47.604424 writer: Write/Writev failed, err: 22=invalid argument. opcode: READDIRPLUS
21:42:47.606073 writer: Write/Writev failed, err: 22=invalid argument. opcode: READDIRPLUS
--- FAIL: TestReadDirStress (0.36s)
    simple_test.go:270: goroutine 2 iteration 5: readdirent: input/output error
    simple_test.go:270: goroutine 1 iteration 9: readdirent: input/output error
    simple_test.go:270: goroutine 3 iteration 10: readdirent: input/output error
    simple_test.go:43: /usr/bin/fusermount: entry for /tmp/TestReadDirStress639795934/mnt not found in /etc/mtab
         (code exit status 1)

FAIL
exit status 1
FAIL	github.com/hanwen/go-fuse/nodefs	0.994s

Access file descriptors under lock, and set to -1 on close. This
avoids confusing errors if Close() is doubly called

This is based on the new nodefs API, and tests the new API for writing
a full-fledged r/w filesystem.

* origin/master: (28 commits)
  nodefs: use offset for MemRegularFile reads. Test it.
  zipfs: fix and test tarfs
  nodefs: don't tweak MemRegularFile mode
  nodefs: fix builds on darwin
  example/hello: convert hello to new nodefs API
  nodefs: add MemRegularFile.Flush
  example/statfs: use new nodefs library
  example/loopback: use new nodefs library
  nodefs: document Access
  example/zipfs: use new nodefs
  nodefs: use bridge.getattr for Access calculation
  example/multizip: use new nodefs package.
  nodefs: comment ExampleNewPersistentInode
  nodefs: add Options.DefaultPermissions
  zipfs: rewrite using new nodefs API.
  nodefs: use testMount in tests
  nodefs: don't pass root into Options.OnAdd
  nodefs: add Inode.RmAllChildren
  nodefs: various fixes
  nodefs: check that default Create returns EROFS
  ...