ore: Support for raid 6
This simple patch adds support for raid6 to the ORE.
Most operations and calculations where already for the general
case. Only things left:
* call async_gen_syndrome() in the case of raid6
(NOTE that the raid6 math is the one supported by the Linux Kernel
see: crypto/async_tx/async_pq.c)
* call _ore_add_parity_unit() twice with only last call generating
the redundancy pages.
* Fix couple BUGS in old code
a. In reads when parity==2 it can happen that per_dev->length=0
but per_dev->offset was set and adjusted by _ore_add_sg_seg().
Don't let it be overwritten.
b. The all 'cur_comp > starting_dev' thing to determine if:
"per_dev->offset is in the current stripe number or the
next one."
Was a complete raid5/4 accident. When parity==2 this is not
at all true usually. All we need to do is increment si->ob_offset
once we pass by the first parity device.
(This also greatly simplifies the code, amen)
c. Calculation of si->dev rotation can overflow when parity==2.
* Then last enable raid6 in ore_verify_layout()
I want to deeply thank Daniel Gryniewicz who found first all the
bugs in the old raid code, and inspired these patches:
Inspired-by Daniel Gryniewicz <dang@linuxbox.com>
Signed-off-by: Boaz Harrosh <bharrosh@panasas.com>
diff --git a/fs/exofs/ore.c b/fs/exofs/ore.c
index 0e2a835..cfc0205 100644
--- a/fs/exofs/ore.c
+++ b/fs/exofs/ore.c
@@ -58,9 +58,12 @@
layout->parity = 1;
break;
case PNFS_OSD_RAID_PQ:
+ layout->parity = 2;
+ break;
case PNFS_OSD_RAID_4:
default:
- ORE_ERR("Only RAID_0/5 for now\n");
+ ORE_ERR("Only RAID_0/5/6 for now received-enum=%d\n",
+ layout->raid_algorithm);
return -EINVAL;
}
if (0 != (layout->stripe_unit & ~PAGE_MASK)) {
@@ -112,6 +115,8 @@
layout->max_io_length /= stripe_length;
layout->max_io_length *= stripe_length;
}
+ ORE_DBGMSG("max_io_length=0x%lx\n", layout->max_io_length);
+
return 0;
}
EXPORT_SYMBOL(ore_verify_layout);
@@ -561,7 +566,8 @@
si->par_dev = (group_width + group_width - parity - RxP) %
group_width + first_dev;
- si->dev = (group_width + C - RxP) % group_width + first_dev;
+ si->dev = (group_width + group_width + C - RxP) %
+ group_width + first_dev;
si->bytes_in_stripe = U;
si->first_stripe_start = M * S + G * T + N * U;
} else {
@@ -651,6 +657,43 @@
return ret;
}
+static int _add_parity_units(struct ore_io_state *ios,
+ struct ore_striping_info *si,
+ unsigned dev, unsigned first_dev,
+ unsigned mirrors_p1, unsigned devs_in_group,
+ unsigned cur_len)
+{
+ unsigned do_parity;
+ int ret = 0;
+
+ for (do_parity = ios->layout->parity; do_parity; --do_parity) {
+ struct ore_per_dev_state *per_dev;
+
+ per_dev = &ios->per_dev[dev - first_dev];
+ if (!per_dev->length && !per_dev->offset) {
+ /* Only/always the parity unit of the first
+ * stripe will be empty. So this is a chance to
+ * initialize the per_dev info.
+ */
+ per_dev->dev = dev;
+ per_dev->offset = si->obj_offset - si->unit_off;
+ }
+
+ ret = _ore_add_parity_unit(ios, si, per_dev, cur_len,
+ do_parity == 1);
+ if (unlikely(ret))
+ break;
+
+ if (do_parity != 1) {
+ dev = ((dev + mirrors_p1) % devs_in_group) + first_dev;
+ si->cur_comp = (si->cur_comp + 1) %
+ ios->layout->group_width;
+ }
+ }
+
+ return ret;
+}
+
static int _prepare_for_striping(struct ore_io_state *ios)
{
struct ore_striping_info *si = &ios->si;
@@ -660,7 +703,6 @@
unsigned devs_in_group = group_width * mirrors_p1;
unsigned dev = si->dev;
unsigned first_dev = dev - (dev % devs_in_group);
- unsigned dev_order;
unsigned cur_pg = ios->pages_consumed;
u64 length = ios->length;
int ret = 0;
@@ -672,14 +714,13 @@
BUG_ON(length > si->length);
- dev_order = si->cur_comp;
-
while (length) {
struct ore_per_dev_state *per_dev =
&ios->per_dev[dev - first_dev];
unsigned cur_len, page_off = 0;
- if (!per_dev->length) {
+ if (!per_dev->length && !per_dev->offset) {
+ /* First time initialize the per_dev info. */
per_dev->dev = dev;
if (dev == si->dev) {
WARN_ON(dev == si->par_dev);
@@ -688,13 +729,7 @@
page_off = si->unit_off & ~PAGE_MASK;
BUG_ON(page_off && (page_off != ios->pgbase));
} else {
- if (si->cur_comp > dev_order)
- per_dev->offset =
- si->obj_offset - si->unit_off;
- else /* si->cur_comp < dev_order */
- per_dev->offset =
- si->obj_offset + stripe_unit -
- si->unit_off;
+ per_dev->offset = si->obj_offset - si->unit_off;
cur_len = stripe_unit;
}
} else {
@@ -721,20 +756,12 @@
/* If last stripe operate on parity comp */
si->cur_comp = group_width - ios->layout->parity;
}
- per_dev = &ios->per_dev[dev - first_dev];
- if (!per_dev->length) {
- /* Only/always the parity unit of the first
- * stripe will be empty. So this is a chance to
- * initialize the per_dev info.
- */
- per_dev->dev = dev;
- per_dev->offset = si->obj_offset - si->unit_off;
- }
/* In writes cur_len just means if it's the
* last one. See _ore_add_parity_unit.
*/
- ret = _ore_add_parity_unit(ios, si, per_dev,
+ ret = _add_parity_units(ios, si, dev, first_dev,
+ mirrors_p1, devs_in_group,
ios->sp2d ? length : cur_len);
if (unlikely(ret))
goto out;
@@ -746,6 +773,8 @@
/* Next stripe, start fresh */
si->cur_comp = 0;
si->cur_pg = 0;
+ si->obj_offset += cur_len;
+ si->unit_off = 0;
}
}
out: