tree 480fe9fd2e9cd0884b375351c4db98a9dfb21aac
parent 9a3152ab024867100f2f50d124b998d05fb1c3f6
author Jonathan Brassow <jbrassow@redhat.com> 1361413690 +1100
committer NeilBrown <neilb@suse.de> 1361840136 +1100

DM RAID: Add support for MD's RAID10 "far" and "offset" algorithms

DM RAID:  Add support for MD's RAID10 "far" and "offset" algorithms

Until now, dm-raid.c only supported the "near" algorthm of MD's RAID10
implementation.  This patch adds support for the "far" and "offset"
algorithms, but only with the improved redundancy that is brought with
the introduction of the 'use_far_sets' bit, which shifts copied stripes
according to smaller sets vs the entire array.  That is, the 17th bit
of the 'layout' variable that defines the RAID10 implementation will
always be set.   (More information on how the 'layout' variable selects
the RAID10 algorithm can be found in the opening comments of
drivers/md/raid10.c.)

Signed-off-by: Jonathan Brassow <jbrassow@redhat.com>
Signed-off-by: NeilBrown <neilb@suse.de>