11182 loader: Distinguish between "no partition" and "choose best partition" with a constant.

Review Request #1961 — Created June 3, 2019 and submitted


The values of the d_slice and d_partition fields of a disk_devdesc have a
few values with special meanings in the disk_open() routine. Through various
evolutions of the loader code over time, a d_partition value of -1 has
meant both "use the first ufs partition found in the bsd label" and "don't
open a bsd partition at all, open the raw slice."

This defines a new special value of -2 to mean open the raw slice, and it
gives symbolic names to all the special values used in d_slice and
d_partition, and adjusts all existing uses of those fields to use the new

The phab review for this timed out without being accepted, but I'm still
citing it below because there is useful commentary there.

Differential Revision:	https://reviews.freebsd.org/D19262

Restore the ability to open a raw disk or partition in loader(8).

The disk_open() function searches for "the best partition" when slice and
partition information is not provided as part of the device name.  As of
r345477 the slice and partition fields of a disk_devdesc are initialized to
D_SLICEWILD and D_PARTWILD; in the past they were initialized to -1, which
was sometimes interpreted as meaning 'wildcard' and sometimes as 'open the
raw partition' depending on the context.  So as an unintended side effect of
r345477 it became basically impossible to ever open a disk or partition
without doing the 'best partition' search.  One visible effect of that was
the inability to open the raw disk to read the partition table correctly in
zfs_probe_dev(), leading to failures to find the zfs pool unless it was on
the first partition.

Now instead of always initializing slice and partition to wildcards, the
disk_parsedev() function initializes them based on the presence of a
path/file name following the device.  If there is any path or filename
following the ':' that ends the device name, then slice and partition are
initialized to D_SLICEWILD and D_PARTWILD.  If there is nothing after the
':' then it is considered to be a request to open the raw device or
partition itself (not a file stored within it), and the fields are
initialized to D_SLICENONE and D_PARTNONE.

With this change in place, all the tests in src/tools/boot are succesful
again, including the recently-added cases of booting from a zfs pool on
a partition other than slice 1 of the device.

Use D_PARTISGPT rather than bare 255

These three cases dovetail with other places in the code where we use
or set D_PARTISGPT when we mean that the partitioning scheme is
GPT. Use this #define to make the code easier to undertand.

Reviewed by: tsoome@
Differential Revision: https://reviews.freebsd.org/D20122

use local partdev device descriptor to read disk global partition table.

Check if we have VTOC at the start of the disk.

In case the D_PARTISGPT was used with non-GPT table, use D_PARTWILD to allow
the autodetection code to work - D_PARTNONE means we should open raw MBR

/code/illumos-gate/usr/src/tools/proto/root_i386-nd/opt/onbld/bin/i386/smatch: ../../common/disk.c:310 disk_open() warn: was && intended here instead of ||?
/code/illumos-gate/usr/src/tools/proto/root_i386-nd/opt/onbld/bin/i386/smatch: ../../common/disk.c:327 disk_open() warn: was && intended here instead of ||?

  1. Ship It!
  1. Ship It!
Review request changed

Status: Closed (submitted)