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>

4 files changed, 80 insertions, 37 deletions

diff --git a/fs/exofs/Kconfig.ore b/fs/exofs/Kconfig.ore
index 1ca7fb7b6ba8..2daf2329c28d 100644
--- a/fs/exofs/Kconfig.ore
+++ b/fs/exofs/Kconfig.ore
@@ -9,4 +9,6 @@ config ORE
         tristate
         depends on EXOFS_FS || PNFS_OBJLAYOUT
         select ASYNC_XOR
+        select RAID6_PQ
+        select ASYNC_PQ
         default SCSI_OSD_ULD
diff --git a/fs/exofs/ore.c b/fs/exofs/ore.c
index 0e2a8353f7cc..cfc0205d62c4 100644
--- a/fs/exofs/ore.c
+++ b/fs/exofs/ore.c
@@ -58,9 +58,12 @@ int ore_verify_layout(unsigned total_comps, struct ore_layout *layout)
                 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 @@ int ore_verify_layout(unsigned total_comps, struct ore_layout *layout)
                 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 @@ void ore_calc_stripe_info(struct ore_layout *layout, u64 file_offset,
 
                 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 @@ out:	/* we fail the complete unit on an error eg don't advance
         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 @@ static int _prepare_for_striping(struct ore_io_state *ios)
         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 @@ static int _prepare_for_striping(struct ore_io_state *ios)
 
         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 @@ static int _prepare_for_striping(struct ore_io_state *ios)
                                 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 @@ static int _prepare_for_striping(struct ore_io_state *ios)
                                 /* 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 @@ static int _prepare_for_striping(struct ore_io_state *ios)
                         /* Next stripe, start fresh */
                         si->cur_comp = 0;
                         si->cur_pg = 0;
+                        si->obj_offset += cur_len;
+                        si->unit_off = 0;
                 }
         }
 out:
diff --git a/fs/exofs/ore_raid.c b/fs/exofs/ore_raid.c
index d58a952e28bc..7f20f25c232c 100644
--- a/fs/exofs/ore_raid.c
+++ b/fs/exofs/ore_raid.c
@@ -218,20 +218,28 @@ static unsigned _sp2d_max_pg(struct __stripe_pages_2d *sp2d)
 static void _gen_xor_unit(struct __stripe_pages_2d *sp2d)
 {
         unsigned p;
+        unsigned tx_flags = ASYNC_TX_ACK;
+
+        if (sp2d->parity == 1)
+                tx_flags |= ASYNC_TX_XOR_ZERO_DST;
+
         for (p = 0; p < sp2d->pages_in_unit; p++) {
                 struct __1_page_stripe *_1ps = &sp2d->_1p_stripes[p];
 
                 if (!_1ps->write_count)
                         continue;
 
-                init_async_submit(&_1ps->submit,
-                        ASYNC_TX_XOR_ZERO_DST | ASYNC_TX_ACK,
+                init_async_submit(&_1ps->submit, tx_flags,
                         NULL, NULL, NULL, (addr_conv_t *)_1ps->scribble);
 
-                /* TODO: raid6 */
-                _1ps->tx = async_xor(_1ps->pages[sp2d->data_devs], _1ps->pages,
-                                     0, sp2d->data_devs, PAGE_SIZE,
-                                     &_1ps->submit);
+                if (sp2d->parity == 1)
+                        _1ps->tx = async_xor(_1ps->pages[sp2d->data_devs],
+                                                _1ps->pages, 0, sp2d->data_devs,
+                                                PAGE_SIZE, &_1ps->submit);
+                else /* parity == 2 */
+                        _1ps->tx = async_gen_syndrome(_1ps->pages, 0,
+                                                sp2d->data_devs + sp2d->parity,
+                                                PAGE_SIZE, &_1ps->submit);
         }
 
         for (p = 0; p < sp2d->pages_in_unit; p++) {
@@ -616,7 +624,7 @@ static int _read_4_write_execute(struct ore_io_state *ios)
 int _ore_add_parity_unit(struct ore_io_state *ios,
                             struct ore_striping_info *si,
                             struct ore_per_dev_state *per_dev,
-                            unsigned cur_len)
+                            unsigned cur_len, bool do_xor)
 {
         if (ios->reading) {
                 if (per_dev->cur_sg >= ios->sgs_per_dev) {
@@ -641,9 +649,11 @@ int _ore_add_parity_unit(struct ore_io_state *ios,
                         /* If first stripe, Read in all read4write pages
                          * (if needed) before we calculate the first parity.
                          */
-                        _read_4_write_first_stripe(ios);
+                        if (do_xor)
+                                _read_4_write_first_stripe(ios);
                 }
-                if (!cur_len) /* If last stripe r4w pages of last stripe */
+                if (!cur_len && do_xor)
+                        /* If last stripe r4w pages of last stripe */
                         _read_4_write_last_stripe(ios);
                 _read_4_write_execute(ios);
 
@@ -655,7 +665,7 @@ int _ore_add_parity_unit(struct ore_io_state *ios,
                         ++(ios->cur_par_page);
                 }
 
-                BUG_ON(si->cur_comp != sp2d->data_devs);
+                BUG_ON(si->cur_comp < sp2d->data_devs);
                 BUG_ON(si->cur_pg + num_pages > sp2d->pages_in_unit);
 
                 ret = _ore_add_stripe_unit(ios,  &array_start, 0, pages,
@@ -663,9 +673,10 @@ int _ore_add_parity_unit(struct ore_io_state *ios,
                 if (unlikely(ret))
                         return ret;
 
-                /* TODO: raid6 if (last_parity_dev) */
-                _gen_xor_unit(sp2d);
-                _sp2d_reset(sp2d, ios->r4w, ios->private);
+                if (do_xor) {
+                        _gen_xor_unit(sp2d);
+                        _sp2d_reset(sp2d, ios->r4w, ios->private);
+                }
         }
         return 0;
 }
diff --git a/fs/exofs/ore_raid.h b/fs/exofs/ore_raid.h
index d365bda6beef..cf6375d82129 100644
--- a/fs/exofs/ore_raid.h
+++ b/fs/exofs/ore_raid.h
@@ -38,7 +38,8 @@ void _ore_free_raid_stuff(struct ore_io_state *ios);
 void _ore_add_sg_seg(struct ore_per_dev_state *per_dev, unsigned cur_len,
                  bool not_last);
 int _ore_add_parity_unit(struct ore_io_state *ios, struct ore_striping_info *si,
-                     struct ore_per_dev_state *per_dev, unsigned cur_len);
+                     struct ore_per_dev_state *per_dev, unsigned cur_len,
+                     bool do_xor);
 void _ore_add_stripe_page(struct __stripe_pages_2d *sp2d,
                        struct ore_striping_info *si, struct page *page);
 static inline void _add_stripe_page(struct __stripe_pages_2d *sp2d,