- Copy stable/10 (r259064) to releng/10.0 as part of the
10.0-RELEASE cycle.
- Update __FreeBSD_version [1]
- Set branch name to -RC1

[1] 10.0-CURRENT __FreeBSD_version value ended at '55', so
start releng/10.0 at '100' so the branch is started with
a value ending in zero.

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

In r243868, the error message buffer errmsg have been changed from
an on-stack array to a pointer and therefore sizeof(errmsg) would
become 4 or 8 bytes depending on the architecture.

Fix this by using ERRMSGL in place of sizeof().

Submitted by: J David <j.david.lists@gmail.com>
MFC after: 3 days
Approved by: re (kib)

Add a tunable for the default timeout.

Changes to allow using BOOTP_NFSROOT and mounting an nfs root filesystem
other than the one specified by the BOOTP server. This configures NFS
using the BOOTP protocol while also respecting other root-path options such
as setting vfs.root.mountfrom in the environment or using the RB_DFLTROOT
boot option. It allows you to override the root path provided by the
server, or to supply a root path when the server provides IP configuration
but no root path info.

This maintains the historical BOOTP_NFSROOT behavior of panicking on a
failure to mount the root path provided by the server, unless you've
provided an alternative via the ROOTDEVNAME kernel option or by setting
vfs.root.mountfrom. The behavior of panicking when given no other options
is preserved because it amounts to a bit of a retry loop that could
eventually recover from a transient network or server problem.

The user can now override the root path from loader(8) even if the
kernel is compiled with BOOTP_NFSROOT. If vfs.root.mountfrom is set in
the environment it is used unconditionally -- it always overrides the
BOOTP info. If it begins with [old]nfs: then the BOOTP code uses it
instead of the server-provided info. If it specifies some other
filesystem then the bootp code will not panic like it used to and the code
in vfs_mountroot.c will invoke the right filesystem to do the mount.

If the kernel is compiled with the ROOTDEVNAME option, then that name is
used by the BOOTP code if either
* The server doesn't provide a pathname.
* The boothowto flags include RB_DFLTROOT.
The latter allows the user to compile in alternate path in ROOTDEVNAME
such as ufs:/dev/da0s1a and boot from that path by setting
boot_dftlroot=1 in loader(8) or using the '-r' option in boot(8).

The one thing not provided here is automatic failover from a
server-provided path to a compiled-in one without the user manually
requesting that. The code just isn't currently structured in a way that
makes that possible with a lot of rewrite. I think the ability to set
vfs.root.mountfrom and to use ROOTDEVNAME automatically when the server
doesn't provide a name covers the most common needs.

A set of patches submitted by Lars Eggert provided the part I couldn't
figure out by myself when I tried to do this last year; many thanks.

Reviewed by: rodrigc

post mountroot event after a real/final root is mounted

not every time an intermediate root (including the first devfs) is
mounted.
This is also consistent with waking up via root_mount_complete.

Reviewed by: jhb
MFC after: 13 days

Do not allocate buffer of the 255 bytes length on the stack.

Reported and tested by: sig6247@gmail.com
MFC after: 1 week

Remove the support for using non-mpsafe filesystem modules.

In particular, do not lock Giant conditionally when calling into the
filesystem module, remove the VFS_LOCK_GIANT() and related
macros. Stop handling buffers belonging to non-mpsafe filesystems.

The VFS_VERSION is bumped to indicate the interface change which does
not result in the interface signatures changes.

Conducted and reviewed by: attilio
Tested by: pho

Fix found places where uio_resid is truncated to int.

Add the sysctl debug.iosize_max_clamp, enabled by default. Setting the
sysctl to zero allows to perform the SSIZE_MAX-sized i/o requests from
the usermode.

Discussed with: bde, das (previous versions)
MFC after: 1 month

replace uses of libkern gets with cngets

MFC after: 2 months

Don't terminate the interactive root mount prompt on mount failure.
This restores the previous behaviour. While here, match '?' and '.'
inputs exactly and improve the error message.

Requested by: avg@
Derived from a patch by: Arnaud Lacombe <lacombar@gmail.com>

Include sys/sbuf.h directly.

Make RB_CDROM work. This should probably check for a disc in cd1 and acd1
as well.

Add support for asterisk characters when filling in the GELI password
during boot.

Change the last argument of gets() to indicate a visibility flag and add
definitions for the numerical constants. Except for the value 2, gets()
will behave exactly the same, so existing consumers shouldn't break. We
only use it in two places, though.

Submitted by: lme (older version)

ZFS pool name is not a real device in devfs. Do not wait for
device appear when mounting root from ZFS.

Reviewed by: marcel
Approved by: mav (mentor)

Re-implement the root mount logic using a recursive approach, whereby each
root file system (starting with devfs and a synthesized configuration) can
contain directives for mounting another file system as root. The old root
file system is re-mounted under the new root file system (with /.mount or
/mnt as the mount point) to allow access to the underlying file system.

The configuration allows for creating vnode-backed memory disks that can
subsequently be mounted as root. This allows for an efficient and low-
cost way to distribute and boot FreeBSD software images that reside on
some storage media.

When trying a mount, the kernel will wait for the device in question to
arrive. The timeout is configurable and is part of the configuration.
This allows arbitrarily complex GEOM configurations to be constructed
on the fly.

A side-effect of this change is that all root specifications, whether
compiled into the kernel or typed at the prompt can contain root mount
options.

Split the root mount logic from the (generic) mount code and move
it (the root mount code) into a new file called vfs_mountroot.c

The split is almost trivial, as the code is almost perfectly
non-intertwined. The only adjustment needed was to move the UMA
zone allocation out of vfs_mountroot() [in vfs_mountroot.c] and
into vfs_mount.c, where it had to be done as a SYSINIT [see
vfs_mount_init()].

There are no functional changes with this commit.