MFC r303799, r303800:
ext2fs: Add defines for some missing ext4 features and inode flags.

These are currently unused in our implementation and some even appear to
have not been implemented yet on linux but it is good to keep them for
reference.

Obtained from: NetBSD

Copy head@r302406 to stable/11 as part of the 11.0-RELEASE cycle.
Prune svn:mergeinfo from the new branch, as nothing has been merged
here.

Additional commits post-branch will follow.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Update superblock and inode structs for ext4.

Reviewed by: pfg

Fix comment.

Rename some directory index constants.

Directory index was introduced in ext3. We don't always use the
prefix to denote the ext2 variant they belong to but when we
do we should try to be accurate.

ext2fs: use of tab vs spaces.

Consistently use a single tab after a #define as mentioned in style(9).
Use tabs instead of space for indenting.
Fix a typo: "hash_vesion".

No functional change.

MFC after: 3 days

ext2fs: Translate the EXT4_EXTENTS and EXT4_INDEX to the inode flags.

r260545 cleared the inode flags to fix corruption problems but
we still need to pass some EXT4 flags for the ext4 read-only
mode. None of these attributes has an equivalent in FreeBSD and
are uninteresting for the system utilities so they should be
innaccessible in ext2_getattrib().

Note: we also use EXT4_HUGE_FILE but we use it directly from the
dinode structure so it is not necessary to translate it,

Suggested by: bde
MFC after: 3 days

ext2fs: add two new reserved inodes.

According to online documentation [1], Ext4 has two new "special"
inodes so add the new exclude and replica inodes.

Reference:
[1] https://ext4.wiki.kernel.org/index.php/Ext4_Disk_Layout

Reported by: Mike Ma
MFC after: 3 weeks

Add read-only support for extents in ext2fs.

Basic support for extents was implemented by Zheng Liu as part
of his Google Summer of Code in 2010. This support is read-only
at this time.

In addition to extents we also support the huge_file extension
for read-only purposes. This works nicely with the additional
support for birthtime/nanosec timestamps and dir_index that
have been added lately.

The implementation may not work for all ext4 filesystems as
it doesn't support some features that are being enabled by
default on recent linux like flex_bg. Nevertheless, the feature
should be very useful for migration or simple access in
filesystems that have been converted from ext2/3 or don't use
incompatible features.

Special thanks to Zheng Liu for his dedication and continued
work to support ext2 in FreeBSD.

Submitted by: Zheng Liu (lz@)
Reviewed by: Mike Ma, Christoph Mallon (previous version)
Sponsored by: Google Inc.
MFC after: 3 weeks

Re-sort ext2fs headers to make things easier to find.

In the ext2fs driver we have a mixture of headers:

- The ext2_ prefixed headers have strong influence from NetBSD
and are carry specific ext2/3/4 information.
- The unprefixed headers are inspired on UFS and carry implementation
specific information.

Do some small adjustments so that the information is easier to
find coming from either UFS or the NetBSD implementation.

MFC after: 3 days

ext2fs: space vs tab.

Obtained from: Christoph Mallon
MFC after: 3 days

ext2fs: Small cosmetic fixes.

Make a long macro readable and sort a header.

Obtained from: Christoph Mallon
MFC after: 3 days

Clean some 'svn:executable' properties in the tree.

Submitted by: Christoph Mallon
MFC after: 3 days

ext2fs: cleanup de dinode structure.

It was plagued with style errors and the offsets had been lost.
While here took the time to update the fields according to the
latest ext4 documentation.

Reviewed by: bde
MFC after: 3 days

More constant renaming in preparation for newer features.

We also try to make better use of the fs flags instead of
trying adapt the code according to the fs structures. In
the case of subsecond timestamps and birthtime we now
check that the feature is explicitly enabled: previously
we only checked that the reserved space was available and
silently wrote them.

This approach is much safer, especially if the filesystem
happens to use embedded inodes or support EAs.

Discussed with: Zheng Liu
MFC after: 5 days

Update some definitions or make them match NetBSD's headers.

Bring several definitions required for newer ext4 features.

Rename EXT2F_COMPAT_HTREE to EXT2F_COMPAT_DIRHASHINDEX since it
is not being used yet and the new name is more compatible with
NetBSD and Linux.

This change is purely cosmetic and has no effect on the real
code.

Obtained from: NetBSD
MFC after: 3 days

Add some basic definitions for a future htree implementation.

MFC after: 3 days

Add support for ns timestamps and birthtime to the ext2/3 driver.

When using big inodes there is sufficient space in ext3 to
keep extra resolution and birthtime (creation) timestamps.
The appropriate fields in the on-disk inode have been approved
for a long time but support for this in ext3 has not been
widely distributed.

In preparation for ext4 most linux distributions have enabled
by default such bigger inodes and some people use nanosecond
timestamps in ext3. We now support those when the inode is big
enough and while we do recognize the EXT4F_ROCOMPAT_EXTRA_ISIZE,
we maintain the extra timestamps even when they are not used.

An additional note by Bruce Evans:
We blindly accept unrepresentable tv_nsec in VOP_SETATTR(), but
all file systems have always done that. When POSIX gets around
to specifying the behaviour, it will probably require certain
rounding to the fs's resolution and not rejecting the request.
This unfortunately means that syscalls that set times can't
really tell if they succeeded without reading back the times
using stat() or similar and checking that they were set close
enough.

Reviewed by: bde
Approved by: jhb (mentor)
MFC after: 2 weeks

Update the data structures with some fields reserved for
ext4 but that can be used in ext3 mode.

Also adjust the internal inode to carry the birthtime,
like in UFS, which is starting to get some use when
big inodes are available.

Right now these are just placeholders for features
to come.

Approved by: jhb (mentor)
MFC after: 2 weeks

Various style fixes including using uint*_t instead of u_int*_t.

Submitted by: Pedro F. Giffuni giffunip at yahoo

- Move special inode constants to ext2_dinode.h and rename them to match
NetBSD.
- Add a constant for the HASJOURNAL compat flag.

PR: kern/153584
Submitted by: Pedro F. Giffuni giffunip at yahoo

Whitespace and style fixes.

Bring in the ext2fs work done by Aditya Sarawgi during and after Google Summer
of Code 2009:

- BSDL block and inode allocation policies for ext2fs. This involves the use
FFS1 style block and inode allocation for ext2fs. Preallocation was removed
since it was GPL'd.
- Make ext2fs MPSAFE by introducing locks to per-mount datastructures.
- Fixes for kern/122047 PR.
- Various small bugfixes.
- Move out of gnu/ directory.

Sponsored by: Google Inc.
Submitted by: Aditya Sarawgi <sarawgi.aditya AT SPAMFREE gmail DOT com>