diff options
| author | NeilBrown | 2015-10-22 13:20:15 +1100 |
|---|---|---|
| committer | NeilBrown | 2015-10-24 16:24:25 +1100 |
| commit | 8bce6d35b308d73cdb2ee273c95d711a55be688c (patch) | |
| tree | 01b072a83736bae1455d7bb5743d271f91cd6325 | |
| parent | c340702ca26a628832fade4f133d8160a55c29cc (diff) | |
md/raid10: fix the 'new' raid10 layout to work correctly.
In Linux 3.9 we introduce a new 'far' layout for RAID10 which was
supposed to rotate the replicas differently and so provide better
resilience. In particular it could survive more combinations of 2
drive failures.
Unfortunately. due to a coding error, this some did what was wanted,
sometimes improved less than we hoped, and sometimes - in very
unlikely circumstances - put multiple replicas on the same device so
the redundancy was harmed.
No public user-space tool has created arrays using this layout so it
is very unlikely that zero-redundancy arrays actually exist. Probably
no arrays using any form of the new layout exist. But we cannot be
certain.
So use another bit in the 'layout' number and introduce a bug-fixed
version of the layout.
Also when assembling an array, if it has a zero-redundancy layout,
give a warning.
Reported-by: Heinz Mauelshagen <heinzm@redhat.com>
Signed-off-by: NeilBrown <neilb@suse.com>
| -rw-r--r-- | drivers/md/raid10.c | 22 |
1 files changed, 20 insertions, 2 deletions
diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c index 23de2144ee13..96f365968306 100644 --- a/drivers/md/raid10.c +++ b/drivers/md/raid10.c @@ -39,6 +39,7 @@ * far_copies (stored in second byte of layout) * far_offset (stored in bit 16 of layout ) * use_far_sets (stored in bit 17 of layout ) + * use_far_sets_bugfixed (stored in bit 18 of layout ) * * The data to be stored is divided into chunks using chunksize. Each device * is divided into far_copies sections. In each section, chunks are laid out @@ -1497,6 +1498,8 @@ static void status(struct seq_file *seq, struct mddev *mddev) seq_printf(seq, " %d offset-copies", conf->geo.far_copies); else seq_printf(seq, " %d far-copies", conf->geo.far_copies); + if (conf->geo.far_set_size != conf->geo.raid_disks) + seq_printf(seq, " %d devices per set", conf->geo.far_set_size); } seq_printf(seq, " [%d/%d] [", conf->geo.raid_disks, conf->geo.raid_disks - mddev->degraded); @@ -3394,7 +3397,7 @@ static int setup_geo(struct geom *geo, struct mddev *mddev, enum geo_type new) disks = mddev->raid_disks + mddev->delta_disks; break; } - if (layout >> 18) + if (layout >> 19) return -1; if (chunk < (PAGE_SIZE >> 9) || !is_power_of_2(chunk)) @@ -3406,7 +3409,22 @@ static int setup_geo(struct geom *geo, struct mddev *mddev, enum geo_type new) geo->near_copies = nc; geo->far_copies = fc; geo->far_offset = fo; - geo->far_set_size = (layout & (1<<17)) ? disks / fc : disks; + switch (layout >> 17) { + case 0: /* original layout. simple but not always optimal */ + geo->far_set_size = disks; + break; + case 1: /* "improved" layout which was buggy. Hopefully no-one is + * actually using this, but leave code here just in case.*/ + geo->far_set_size = disks/fc; + WARN(geo->far_set_size < fc, + "This RAID10 layout does not provide data safety - please backup and create new array\n"); + break; + case 2: /* "improved" layout fixed to match documentation */ + geo->far_set_size = fc * nc; + break; + default: /* Not a valid layout */ + return -1; + } geo->chunk_mask = chunk - 1; geo->chunk_shift = ffz(~chunk); return nc*fc; |