[PATCH 5/9] imsm: fix reserved sectors for spares

[Dan Williams <dan.j.williams@intel.com>]

Different OROMs reserve different amounts of space for the migration area.
When activating a spare minimize the reserved space otherwise a valid spare
can be prevented from joining an array with a migration area smaller than
IMSM_RESERVED_SECTORS.

This may result in an array that cannot be reshaped, but that is less
surprising than not being able to rebuild a degraded array.
imsm_reserved_sectors() already reports the minimal value which adds to
the confusion when trying rebuild an array because mdadm -E indicates
that the device has enough space.

Cc: Anna Czarnowska <anna.czarnowska@intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
---
 super-intel.c |   11 ++++++++++-
 1 files changed, 10 insertions(+), 1 deletions(-)

diff --git a/super-intel.c b/super-intel.c
index 0347183..193e0d0 100644
--- a/super-intel.c
+++ b/super-intel.c
@@ -833,7 +833,16 @@ static struct extent *get_extents(struct intel_super *super, struct dl *dl)
 	struct extent *rv, *e;
 	int i;
 	int memberships = count_memberships(dl, super);
-	__u32 reservation = MPB_SECTOR_CNT + IMSM_RESERVED_SECTORS;
+	__u32 reservation;
+
+	/* trim the reserved area for spares, so they can join any array
+	 * regardless of whether the OROM has assigned sectors from the
+	 * IMSM_RESERVED_SECTORS region
+	 */
+	if (dl->index == -1)
+		reservation = MPB_SECTOR_CNT;
+	else
+		reservation = MPB_SECTOR_CNT + IMSM_RESERVED_SECTORS;
 
 	rv = malloc(sizeof(struct extent) * (memberships + 1));
 	if (!rv)