Remove $FreeBSD$: two-line .h pattern

Remove /^\s*\*\n \*\s+\$FreeBSD\$$\n/

spdx: The BSD-2-Clause-FreeBSD identifier is obsolete, drop -FreeBSD

The SPDX folks have obsoleted the BSD-2-Clause-FreeBSD identifier. Catch
up to that fact and revert to their recommended match of BSD-2-Clause.

Discussed with: pfg
MFC After: 3 days
Sponsored by: Netflix

[skip ci] fix typo in comment in the fusefs tests

MFC after: 2 weeks

fusefs: coverity cleanup in the tests

Address the following defects reported by Coverity:

* Structurally dead code (CID 1404366): set m_quit before FAIL, not after

* Unchecked return value of sysctlbyname (CID 1404321)

* Unchecked return value of stat(2) (CID 1404471)

* Unchecked return value of open(2) (CID 1404402, 1404529)

* Unchecked return value of dup(2) (CID 1404478)

* Buffer overflows. These are all false positives caused by the fact that
Coverity thinks I'm using a buffer to store strings, when in fact I'm
really just using it to store a byte array that happens to be initialized
with a string. I'm changing the type from char to uint8_t in the hopes
that it will placate Coverity. (CID 1404338, 1404350, 1404367, 1404376,
1404379, 1404381, 1404388, 1404403, 1404425, 1404433, 1404434, 1404474,
1404480, 1404484, 1404503, 1404505)

* False positive file descriptor leak. I'm going to try to fix this with
Coverity modeling, but I'll also change an EXPECT to ASSERT so we don't
perform meaningless assertions after the failure. (CID 1404320, 1404324,
1404440, 1404445).

* Unannotated file descriptor leak. This will be followed up by a Coverity
modeling change. (CID 1404326, 1404334, 1404336, 1404357, 1404361,
1404372, 1404391, 1404395, 1404409, 1404430, 1404448, 1404451, 1404455,
1404457, 1404458, 1404460)

* Uninitialized variables in C++ constructors (CID 1404327, 1404346). In the
case of m_maxphys, this actually led to part of the FUSE_INIT's response
being set to stack garbage during the WriteCluster::clustering test.

* Uninitialized sun_len field in struct sockaddr_un (CID 1404330, 1404371,
1404429).

Reported by: Coverity
Reviewed by: emaste
MFC after: 3 days
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D21457

fusefs: add SVN Keywords to the test files

Reported by: SVN pre-commit hooks
MFC after: 15 days
MFC-With: r350665
Sponsored by: The FreeBSD Foundation

fusefs: fix warnings in the tests reported by GCC

Sponsored by: The FreeBSD Foundation

fusefs: annotate deliberate file descriptor leaks in the tests

closing a file descriptor causes FUSE activity that is superfluous to the
purpose of most tests, but would nonetheless require matching expectations.
Rather than do that, most tests deliberately leak file descriptors instead.
This commit moves the leakage from each test into two trivial functions:
leak and leakdir. Hopefully Coverity will only complain about those
functions and not all of their callers.

Sponsored by: The FreeBSD Foundation

fusefs: implement protocol 7.23's FUSE_WRITEBACK_CACHE option

As of protocol 7.23, fuse file systems can specify their cache behavior on a
per-mountpoint basis. If they set FUSE_WRITEBACK_CACHE in
fuse_init_out.flags, then they'll get the writeback cache. If not, then
they'll get the writethrough cache. If they set FOPEN_DIRECT_IO in every
FUSE_OPEN response, then they'll get no cache at all.

The old vfs.fusefs.data_cache_mode sysctl is ignored for servers that use
protocol 7.23 or later. However, it's retained for older servers,
especially for those running in jails that lack access to the new protocol.

This commit also fixes two other minor test bugs:
* WriteCluster:SetUp was using an uninitialized variable.
* Read.direct_io_pread wasn't verifying that the cache was actually
bypassed.

Sponsored by: The FreeBSD Foundation

fusefs: raise protocol level to 7.15

This protocol level adds two new features: the ability for the server to
store or retrieve data into/from the client's cache. But the messages
aren't defined soundly since they identify the file only by its inode,
without the generation number. So it's possible for them to modify the
wrong file's cache. Also, I don't know of any file systems in ports that
use these messages. So I'm not implementing them. I did add a (disabled)
test for the store message, however.

Sponsored by: The FreeBSD Foundation

fusefs: multiple fixes related to the write cache

* Don't always write the last page synchronously. That's not actually
required. It was probably just masking another bug that I fixed later,
possibly in r349021.

* Enable the NotifyWriteback tests now that Writeback cache is working.

* Add a test to ensure that the write cache isn't flushed synchronously when
in writeback mode.

Sponsored by: The FreeBSD Foundation

fusefs: don't require FUSE_EXPORT_SUPPORT for async invalidation

In r348560 I thought that FUSE_EXPORT_SUPPORT was required for cases where
the node to be invalidated (or the parent of the entry to be invalidated)
wasn't cached. But I realize now that that's not the case. During entry
invalidation, if the parent isn't in the vfs hash table, then it must've
been reclaimed. And since fuse_vnop_reclaim does a cache_purge, that means
the entry to be invalidated has already been removed from the namecache.
And during inode invalidation, if the inode to be invalidated isn't in the
vfs hash table, then it too must've been reclaimed. In that case it will
have no buffer cache to invalidate.

Sponsored by: The FreeBSD Foundation

fusefs: support asynchronous cache invalidation

Protocol 7.12 adds a way for the server to notify the client that it should
invalidate an inode's data cache and/or attributes. This commit implements
that mechanism. Unlike Linux's implementation, ours requires that the file
system also supports FUSE_EXPORT_SUPPORT (NFS-style lookups). Otherwise the
invalidation operation will return EINVAL.

Sponsored by: The FreeBSD Foundation

fusefs: support name cache invalidation

Protocol 7.12 adds a way for the server to notify the client that it should
invalidate an entry from its name cache. This commit implements that
mechanism.

Sponsored by: The FreeBSD Foundation