imsm: fix reserved sectors for spares

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>
Signed-off-by: NeilBrown <neilb@suse.de>

diff --git a/super-intel.c b/super-intel.c
index 034718376c219ed1da5dbeae45ed7396427d4b42..193e0d04804d83f663a0a6ddbf00028bdf131870 100644 (file)
--- 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)