Copy stable/10@r272459 to releng/10.1 as part of
the 10.1-RELEASE process.

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

Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.

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

- Merge soft-updates journaling from projects/suj/head into head. This
brings in support for an optional intent log which eliminates the need
for background fsck on unclean shutdown.

Sponsored by: iXsystems, Yahoo!, and Juniper.
With help from: McKusick and Peter Holm

i doesn't need to be signed here, make it unsigned.

Reduce diffs with code in Perforce:
Parenthesise return values.

Clean up error reporting in block.c, so that it gives honest error strings
for the sorts of errors we run into[1]. This also gives us room to put in a
vaguely appropriate casts to silence warnings since our compiler doesn't like
when we compare ssize_t to size_t[2]. Add a cast in sblock.c[3] to silence
a warning because of signed vs. size_t hell (again). Clean up nearby
excessive parenthemutilation[4].

Reviewed by: bde [2] [3]
Suggested by: bde, many [1]
Submitted by: bde [4]

An aside about [4], bde notes that we do not check for a negative value for
the fs bsize. I'm nto going to do that in every situation we use it, one must
expect a reasonable program to pass down reasonable values. Some foot shooting
protection I will tolerate, some I will not. Also he suggests some possible
conditional improvements there, which I may take to heart.

PS: For me at least, this is now WARNS=5 clean...

If we don't know where the sblock is (e.g. filling out a blank disk), then
get it from the fs structure. Really libufs should have interfaces to generate
both what we export, and what we import, based on eachother, and this should
be full of redundant code to make sure everything is right... But really, we
don't even deal with checksums, so plenty of room to improve.

bwrite, not sbwrite, needs to open for writing and write.

Nuke dumb error reporting code, people can just use disk::d_error. Unify the
DEBUG and d_error initialisation into an ERROR macro, which can both trace and
set the d_error field. Much a more meaningful thing, I should say.

Create a new 32-bit fs_flags word in the superblock. Add code to move
the old 8-bit fs_old_flags to the new location the first time that the
filesystem is mounted by a new kernel. One of the unused flags in
fs_old_flags is used to indicate that the flags have been moved.
Leave the fs_old_flags word intact so that it will work properly if
used on an old kernel.

Change the fs_sblockloc superblock location field to be in units
of bytes instead of in units of filesystem fragments. The old units
did not work properly when the fragment size exceeeded the superblock
size (8192). Update old fs_sblockloc values at the same time that
the flags are moved.

Suggested by: BOUWSMA Barry <freebsd-misuser@netscum.dyndns.dk>
Sponsored by: DARPA & NAI Labs.

Use an error message closer to old dumpfs(8) in the case of truncated/no
superblock.

Submitted by: kkenn

Can't use it verbatim, at least I hate to, as the ", skipped" bit doesn't
make much sense in a library, to me.

Add the concept of a per-disk error string, and a function which prints it
along with the errno, if one is set.

In getino, have our DEBUG message in the unhandled case mention that it
does not know what sort of UFS filesystem this is.

Add some DEBUG(NULL)'s to function entry points.

Add libufs, a library for dealing with UFS filesystems from userland to
the build. It is here to compartmentalise functionality currently duplicated
in many notable programs in the base system. It currently handles block
reads and writes, as well as reading and writing of the filesystem superblock,
and the reading/lookup of inode data. It supports both UFS and UFS2. I
will be maintaining it, and porting programs to use it, however for now, it
is simply being built as part of world.