userlandfs: Support mapping FUSE files to memory

- Create a file cache for FUSE mounted files on open to allow
memory mapping these files unless direct_io is specified.
- Implement DoIO for FUSE mounted files.

This patch enables files mounted through FUSE filesystems such as
sshfs or vmhgfs to be `mmap`ed, allowing remotely cross-compiled
executables to be directly run on Haiku.

Change-Id: I364b8225eae5b1d586280c2b3301fb661581caed
Reviewed-on: https://review.haiku-os.org/c/haiku/+/6277
Tested-by: Automation <automation@haiku-os.org>
Reviewed-by: Adrien Destugues <pulkomandy@pulkomandy.tk>

headers/private/kernel/util/OpenHashTable.h, Hugo's version, is a bit nicer than
Tracker's OpenHashTable.h which it should eventually replace. We've renamed the
class to BOpenHashTable and changed the interface slightly so that HashTableLink
became superfluous.
Adapted all the code that used it. Since the OpenHashTables no longer clash,
this should fix the GCC4 build.


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@31791 a95241bf-73f2-0310-859d-f6bbb57e9c96

* Removed WriteFSInfo(). It's used only for changing the volume name and we
can't implement that with the FUSE interface.
* We now mark nodes dirty after a write operation.
* Implemented Sync() by fsync()ing all dirty nodes.


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@29746 a95241bf-73f2-0310-859d-f6bbb57e9c96

* Preparations for write support: Added a locking to the existing hooks. We
need to make sure that the paths of nodes don't change while we're meddling
with them. We read-lock the directories up to the root directory for that
purpose.
* Added missing locking for directory and attribute directory cookies.
We have to do that, since concurrent readdir()s on the same dir handle are
possible and we write-access the cookie data in such a case.


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@29687 a95241bf-73f2-0310-859d-f6bbb57e9c96

Forgot to add in my previous commit. Defines the FUSEEntry, FUSENode structs
and the respective hash table definitions.


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@29622 a95241bf-73f2-0310-859d-f6bbb57e9c96

headers/private/kernel/util/OpenHashTable.h, Hugo's version, is a bit nicer than
Tracker's OpenHashTable.h which it should eventually replace. We've renamed the
class to BOpenHashTable and changed the interface slightly so that HashTableLink
became superfluous.
Adapted all the code that used it. Since the OpenHashTables no longer clash,
this should fix the GCC4 build.


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@31791 a95241bf-73f2-0310-859d-f6bbb57e9c96

* Removed WriteFSInfo(). It's used only for changing the volume name and we
can't implement that with the FUSE interface.
* We now mark nodes dirty after a write operation.
* Implemented Sync() by fsync()ing all dirty nodes.


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@29746 a95241bf-73f2-0310-859d-f6bbb57e9c96

* Preparations for write support: Added a locking to the existing hooks. We
need to make sure that the paths of nodes don't change while we're meddling
with them. We read-lock the directories up to the root directory for that
purpose.
* Added missing locking for directory and attribute directory cookies.
We have to do that, since concurrent readdir()s on the same dir handle are
possible and we write-access the cookie data in such a case.


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@29687 a95241bf-73f2-0310-859d-f6bbb57e9c96

Forgot to add in my previous commit. Defines the FUSEEntry, FUSENode structs
and the respective hash table definitions.


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@29622 a95241bf-73f2-0310-859d-f6bbb57e9c96