tree 4bf23fcee1a1d1675339ea7e5d671dde6dd8641f
parent 5248861511d6aae4997a5aa7152824d87587b0b6
author NeilBrown <neilb@suse.de> 1165746049 -0800
committer Linus Torvalds <torvalds@woody.osdl.org> 1165773441 -0800

[PATCH] md: fix innocuous bug in raid6 stripe_to_pdidx

stripe_to_pdidx finds the index of the parity disk for a given stripe.  It
assumes raid5 in that it uses "disks-1" to determine the number of data disks.

This is incorrect for raid6 but fortunately the two usages cancel each other
out.  The only way that 'data_disks' affects the calculation of pd_idx in
raid5_compute_sector is when it is divided into the sector number.  But as
that sector number is calculated by multiplying in the wrong value of
'data_disks' the division produces the right value.

So it is innocuous but needs to be fixed.

Also change the calculation of raid_disks in compute_blocknr to make it
more obviously correct (it seems at first to always use disks-1 too).

Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>