Update vdev_is_spacemap_addressable() for new spacemap encoding

Since the new spacemap encoding was ported to ZoL that's no longer 
a limitation. This patch updates vdev_is_spacemap_addressable() 
that was performing that check.

It also updates the appropriate test to ensure that the same 
functionality is tested.  The test does so by creating pools that 
don't have the new spacemap encoding enabled - just the checkpoint
feature. This patch also reorganizes that same tests in order to 
cut in half its memory consumption.

Reviewed by: Matt Ahrens <[email protected]>
Reviewed-by: Brian Behlendorf <[email protected]>
Signed-off-by: Serapheim Dimitropoulos <[email protected]>
Closes #8286 

1 files changed, 9 insertions, 5 deletions

diff --git a/module/zfs/vdev.c b/module/zfs/vdev.c
index 26ef5b4c5..cf49172d5 100644
--- a/module/zfs/vdev.c
+++ b/module/zfs/vdev.c
@@ -3804,13 +3804,17 @@ vdev_get_child_stat_ex(vdev_t *cvd, vdev_stat_ex_t *vsx, vdev_stat_ex_t *cvsx)
 boolean_t
 vdev_is_spacemap_addressable(vdev_t *vd)
 {
+	if (spa_feature_is_active(vd->vdev_spa, SPA_FEATURE_SPACEMAP_V2))
+		return (B_TRUE);
+
 	/*
-	 * Assuming 47 bits of the space map entry dedicated for the entry's
-	 * offset (see description in space_map.h), we calculate the maximum
-	 * address that can be described by a space map entry for the given
-	 * device.
+	 * If double-word space map entries are not enabled we assume
+	 * 47 bits of the space map entry are dedicated to the entry's
+	 * offset (see SM_OFFSET_BITS in space_map.h). We then use that
+	 * to calculate the maximum address that can be described by a
+	 * space map entry for the given device.
 	 */
-	uint64_t shift = vd->vdev_ashift + 47;
+	uint64_t shift = vd->vdev_ashift + SM_OFFSET_BITS;
 
 	if (shift >= 63) /* detect potential overflow */
 		return (B_TRUE);