Add separate field for indicating that spa is in middle of split

[mattmacy]

By default it's not possible to open a device already owned by an
active vdev. It's necessary to make an exception to this for vdev
split. The FreeBSD platform code will make an exception if
spa_is splitting is set to to true.

static int
vdev_geom_open(vdev_t *vd, uint64_t *psize, uint64_t *max_psize,
    uint64_t *logical_ashift)
{
	struct g_provider *pp;
	struct g_consumer *cp;
	int error, has_trim;
	uint16_t rate;

	/*
	 * Set the TLS to indicate downstack that we
	 * should not access zvols
	 */
	VERIFY(tsd_set(zfs_geom_probe_vdev_key, vd) == 0);

	/*
	 * We must have a pathname, and it must be absolute.
	 */
	if (vd->vdev_path == NULL || strncmp(vd->vdev_path, "/dev/", 5) != 0) {
		vd->vdev_stat.vs_aux = VDEV_AUX_BAD_LABEL;
		return (EINVAL);
	}

	/*
	 * Reopen the device if it's not currently open. Otherwise,
	 * just update the physical size of the device.
	 */
	if ((cp = vd->vdev_tsd) != NULL) {
		ASSERT(vd->vdev_reopening);
		goto skip_open;
	}

	DROP_GIANT();
	g_topology_lock();
	error = 0;

	if (vd->vdev_spa->spa_is_splitting ||
	    ((vd->vdev_prevstate == VDEV_STATE_UNKNOWN &&
	    (vd->vdev_spa->spa_load_state == SPA_LOAD_NONE ||
	    vd->vdev_spa->spa_load_state == SPA_LOAD_CREATE)))) {
		/*
		 * We are dealing with a vdev that hasn't been previously
		 * opened (since boot), and we are not loading an
		 * existing pool configuration.  This looks like a
		 * vdev add operation to a new or existing pool.
		 * Assume the user knows what he/she is doing and find
		 * GEOM provider by its name, ignoring GUID mismatches.
		 *
		 * XXPOLICY: It would be safer to only allow a device
		 *           that is unlabeled or labeled but missing
		 *           GUID information to be opened in this fashion,
		 *           unless we are doing a split, in which case we
		 *           should allow any guid.
		 */
		cp = vdev_geom_open_by_path(vd, 0);

Signed-off-by: Matt Macy mmacy@FreeBSD.org

Motivation and Context

Description

How Has This Been Tested?

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Performance enhancement (non-breaking change which improves efficiency)
• Code cleanup (non-breaking change which makes code smaller or more readable)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation (a change to man pages or other documentation)

Checklist:

• My code follows the ZFS on Linux code style requirements.
• I have updated the documentation accordingly.
• I have read the contributing document.
• I have added tests to cover my changes.
• I have run the ZFS Test Suite with this change applied.
• All commit messages are properly formatted and contain Signed-off-by.

[codecov-io]

Codecov Report

Merging #10178 into master will increase coverage by 0.29%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master   #10178      +/-   ##
==========================================
+ Coverage   78.98%   79.28%   +0.29%     
==========================================
  Files         385      385              
  Lines      122594   122596       +2     
==========================================
+ Hits        96831    97195     +364     
+ Misses      25763    25401     -362     

Flag	Coverage Δ
#kernel	79.72% <100.00%> (+0.10%)	⬆️
#user	66.07% <0.00%> (+1.12%)	⬆️

Impacted Files	Coverage Δ
module/zfs/spa.c	87.34% <100.00%> (+0.60%)	⬆️
module/lua/lmem.c	83.33% <0.00%> (-4.17%)	⬇️
module/zfs/zio_compress.c	89.74% <0.00%> (-2.57%)	⬇️
module/zfs/dsl_synctask.c	92.40% <0.00%> (-2.54%)	⬇️
lib/libzfs/libzfs_changelist.c	84.37% <0.00%> (-1.96%)	⬇️
cmd/zed/agents/fmd_api.c	88.61% <0.00%> (-1.78%)	⬇️
cmd/zed/agents/zfs_diagnosis.c	77.55% <0.00%> (-1.17%)	⬇️
module/zcommon/zfs_uio.c	87.75% <0.00%> (-1.03%)	⬇️
cmd/zed/agents/zfs_mod.c	77.55% <0.00%> (-0.67%)	⬇️
module/zfs/zfs_quota.c	86.57% <0.00%> (-0.47%)	⬇️
... and 53 more

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[ghost]

• Fixed cstyle