ARM: dts: sun8i: r40: Remove fallback display engine compatible

[linux/fpc-iii.git] / fs / exofs / ore_raid.c

/*
 * Copyright (C) 2011
 * Boaz Harrosh <ooo@electrozaur.com>
 *
 * This file is part of the objects raid engine (ore).
 *
 * It is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as published
 * by the Free Software Foundation.
 *
 * You should have received a copy of the GNU General Public License
 * along with "ore". If not, write to the Free Software Foundation, Inc:
 *      "Free Software Foundation <info@fsf.org>"
 */

#include <linux/gfp.h>
#include <linux/async_tx.h>

#include "ore_raid.h"

#undef ORE_DBGMSG2
#define ORE_DBGMSG2 ORE_DBGMSG

static struct page *_raid_page_alloc(void)
{
        return alloc_page(GFP_KERNEL);
}

static void _raid_page_free(struct page *p)
{
        __free_page(p);
}

/* This struct is forward declare in ore_io_state, but is private to here.
 * It is put on ios->sp2d for RAID5/6 writes only. See _gen_xor_unit.
 *
 * __stripe_pages_2d is a 2d array of pages, and it is also a corner turn.
 * Ascending page index access is sp2d(p-minor, c-major). But storage is
 * sp2d[p-minor][c-major], so it can be properlly presented to the async-xor
 * API.
 */
struct __stripe_pages_2d {
        /* Cache some hot path repeated calculations */
        unsigned parity;
        unsigned data_devs;
        unsigned pages_in_unit;

        bool needed ;

        /* Array size is pages_in_unit (layout->stripe_unit / PAGE_SIZE) */
        struct __1_page_stripe {
                bool alloc;
                unsigned write_count;
                struct async_submit_ctl submit;
                struct dma_async_tx_descriptor *tx;

                /* The size of this array is data_devs + parity */
                struct page **pages;
                struct page **scribble;
                /* bool array, size of this array is data_devs */
                char *page_is_read;
        } _1p_stripes[];
};

/* This can get bigger then a page. So support multiple page allocations
 * _sp2d_free should be called even if _sp2d_alloc fails (by returning
 * none-zero).
 */
static int _sp2d_alloc(unsigned pages_in_unit, unsigned group_width,
                       unsigned parity, struct __stripe_pages_2d **psp2d)
{
        struct __stripe_pages_2d *sp2d;
        unsigned data_devs = group_width - parity;

        /*
         * Desired allocation layout is, though when larger than PAGE_SIZE,
         * each struct __alloc_1p_arrays is separately allocated:

        struct _alloc_all_bytes {
                struct __alloc_stripe_pages_2d {
                        struct __stripe_pages_2d sp2d;
                        struct __1_page_stripe _1p_stripes[pages_in_unit];
                } __asp2d;
                struct __alloc_1p_arrays {
                        struct page *pages[group_width];
                        struct page *scribble[group_width];
                        char page_is_read[data_devs];
                } __a1pa[pages_in_unit];
        } *_aab;

        struct __alloc_1p_arrays *__a1pa;
        struct __alloc_1p_arrays *__a1pa_end;

        */

        char *__a1pa;
        char *__a1pa_end;

        const size_t sizeof_stripe_pages_2d =
                sizeof(struct __stripe_pages_2d) +
                sizeof(struct __1_page_stripe) * pages_in_unit;
        const size_t sizeof__a1pa =
                ALIGN(sizeof(struct page *) * (2 * group_width) + data_devs,
                      sizeof(void *));
        const size_t sizeof__a1pa_arrays = sizeof__a1pa * pages_in_unit;
        const size_t alloc_total = sizeof_stripe_pages_2d +
                                   sizeof__a1pa_arrays;

        unsigned num_a1pa, alloc_size, i;

        /* FIXME: check these numbers in ore_verify_layout */
        BUG_ON(sizeof_stripe_pages_2d > PAGE_SIZE);
        BUG_ON(sizeof__a1pa > PAGE_SIZE);

        /*
         * If alloc_total would be larger than PAGE_SIZE, only allocate
         * as many a1pa items as would fill the rest of the page, instead
         * of the full pages_in_unit count.
         */
        if (alloc_total > PAGE_SIZE) {
                num_a1pa = (PAGE_SIZE - sizeof_stripe_pages_2d) / sizeof__a1pa;
                alloc_size = sizeof_stripe_pages_2d + sizeof__a1pa * num_a1pa;
        } else {
                num_a1pa = pages_in_unit;
                alloc_size = alloc_total;
        }

        *psp2d = sp2d = kzalloc(alloc_size, GFP_KERNEL);
        if (unlikely(!sp2d)) {
                ORE_DBGMSG("!! Failed to alloc sp2d size=%d\n", alloc_size);
                return -ENOMEM;
        }
        /* From here Just call _sp2d_free */

        /* Find start of a1pa area. */
        __a1pa = (char *)sp2d + sizeof_stripe_pages_2d;
        /* Find end of the _allocated_ a1pa area. */
        __a1pa_end = __a1pa + alloc_size;

        /* Allocate additionally needed a1pa items in PAGE_SIZE chunks. */
        for (i = 0; i < pages_in_unit; ++i) {
                struct __1_page_stripe *stripe = &sp2d->_1p_stripes[i];

                if (unlikely(__a1pa >= __a1pa_end)) {
                        num_a1pa = min_t(unsigned, PAGE_SIZE / sizeof__a1pa,
                                                        pages_in_unit - i);
                        alloc_size = sizeof__a1pa * num_a1pa;

                        __a1pa = kzalloc(alloc_size, GFP_KERNEL);
                        if (unlikely(!__a1pa)) {
                                ORE_DBGMSG("!! Failed to _alloc_1p_arrays=%d\n",
                                           num_a1pa);
                                return -ENOMEM;
                        }
                        __a1pa_end = __a1pa + alloc_size;
                        /* First *pages is marked for kfree of the buffer */
                        stripe->alloc = true;
                }

                /*
                 * Attach all _lp_stripes pointers to the allocation for
                 * it which was either part of the original PAGE_SIZE
                 * allocation or the subsequent allocation in this loop.
                 */
                stripe->pages = (void *)__a1pa;
                stripe->scribble = stripe->pages + group_width;
                stripe->page_is_read = (char *)stripe->scribble + group_width;
                __a1pa += sizeof__a1pa;
        }

        sp2d->parity = parity;
        sp2d->data_devs = data_devs;
        sp2d->pages_in_unit = pages_in_unit;
        return 0;
}

static void _sp2d_reset(struct __stripe_pages_2d *sp2d,
                        const struct _ore_r4w_op *r4w, void *priv)
{
        unsigned data_devs = sp2d->data_devs;
        unsigned group_width = data_devs + sp2d->parity;
        int p, c;

        if (!sp2d->needed)
                return;

        for (c = data_devs - 1; c >= 0; --c)
                for (p = sp2d->pages_in_unit - 1; p >= 0; --p) {
                        struct __1_page_stripe *_1ps = &sp2d->_1p_stripes[p];

                        if (_1ps->page_is_read[c]) {
                                struct page *page = _1ps->pages[c];

                                r4w->put_page(priv, page);
                                _1ps->page_is_read[c] = false;
                        }
                }

        for (p = 0; p < sp2d->pages_in_unit; p++) {
                struct __1_page_stripe *_1ps = &sp2d->_1p_stripes[p];

                memset(_1ps->pages, 0, group_width * sizeof(*_1ps->pages));
                _1ps->write_count = 0;
                _1ps->tx = NULL;
        }

        sp2d->needed = false;
}

static void _sp2d_free(struct __stripe_pages_2d *sp2d)
{
        unsigned i;

        if (!sp2d)
                return;

        for (i = 0; i < sp2d->pages_in_unit; ++i) {
                if (sp2d->_1p_stripes[i].alloc)
                        kfree(sp2d->_1p_stripes[i].pages);
        }

        kfree(sp2d);
}

static unsigned _sp2d_min_pg(struct __stripe_pages_2d *sp2d)
{
        unsigned p;

        for (p = 0; p < sp2d->pages_in_unit; p++) {
                struct __1_page_stripe *_1ps = &sp2d->_1p_stripes[p];

                if (_1ps->write_count)
                        return p;
        }

        return ~0;
}

static unsigned _sp2d_max_pg(struct __stripe_pages_2d *sp2d)
{
        int p;

        for (p = sp2d->pages_in_unit - 1; p >= 0; --p) {
                struct __1_page_stripe *_1ps = &sp2d->_1p_stripes[p];

                if (_1ps->write_count)
                        return p;
        }

        return ~0;
}

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, tx_flags,
                        NULL, NULL, NULL, (addr_conv_t *)_1ps->scribble);

                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++) {
                struct __1_page_stripe *_1ps = &sp2d->_1p_stripes[p];
                /* NOTE: We wait for HW synchronously (I don't have such HW
                 * to test with.) Is parallelism needed with today's multi
                 * cores?
                 */
                async_tx_issue_pending(_1ps->tx);
        }
}

void _ore_add_stripe_page(struct __stripe_pages_2d *sp2d,
                       struct ore_striping_info *si, struct page *page)
{
        struct __1_page_stripe *_1ps;

        sp2d->needed = true;

        _1ps = &sp2d->_1p_stripes[si->cur_pg];
        _1ps->pages[si->cur_comp] = page;
        ++_1ps->write_count;

        si->cur_pg = (si->cur_pg + 1) % sp2d->pages_in_unit;
        /* si->cur_comp is advanced outside at main loop */
}

void _ore_add_sg_seg(struct ore_per_dev_state *per_dev, unsigned cur_len,
                     bool not_last)
{
        struct osd_sg_entry *sge;

        ORE_DBGMSG("dev=%d cur_len=0x%x not_last=%d cur_sg=%d "
                     "offset=0x%llx length=0x%x last_sgs_total=0x%x\n",
                     per_dev->dev, cur_len, not_last, per_dev->cur_sg,
                     _LLU(per_dev->offset), per_dev->length,
                     per_dev->last_sgs_total);

        if (!per_dev->cur_sg) {
                sge = per_dev->sglist;

                /* First time we prepare two entries */
                if (per_dev->length) {
                        ++per_dev->cur_sg;
                        sge->offset = per_dev->offset;
                        sge->len = per_dev->length;
                } else {
                        /* Here the parity is the first unit of this object.
                         * This happens every time we reach a parity device on
                         * the same stripe as the per_dev->offset. We need to
                         * just skip this unit.
                         */
                        per_dev->offset += cur_len;
                        return;
                }
        } else {
                /* finalize the last one */
                sge = &per_dev->sglist[per_dev->cur_sg - 1];
                sge->len = per_dev->length - per_dev->last_sgs_total;
        }

        if (not_last) {
                /* Partly prepare the next one */
                struct osd_sg_entry *next_sge = sge + 1;

                ++per_dev->cur_sg;
                next_sge->offset = sge->offset + sge->len + cur_len;
                /* Save cur len so we know how mutch was added next time */
                per_dev->last_sgs_total = per_dev->length;
                next_sge->len = 0;
        } else if (!sge->len) {
                /* Optimize for when the last unit is a parity */
                --per_dev->cur_sg;
        }
}

static int _alloc_read_4_write(struct ore_io_state *ios)
{
        struct ore_layout *layout = ios->layout;
        int ret;
        /* We want to only read those pages not in cache so worst case
         * is a stripe populated with every other page
         */
        unsigned sgs_per_dev = ios->sp2d->pages_in_unit + 2;

        ret = _ore_get_io_state(layout, ios->oc,
                                layout->group_width * layout->mirrors_p1,
                                sgs_per_dev, 0, &ios->ios_read_4_write);
        return ret;
}

/* @si contains info of the to-be-inserted page. Update of @si should be
 * maintained by caller. Specificaly si->dev, si->obj_offset, ...
 */
static int _add_to_r4w(struct ore_io_state *ios, struct ore_striping_info *si,
                       struct page *page, unsigned pg_len)
{
        struct request_queue *q;
        struct ore_per_dev_state *per_dev;
        struct ore_io_state *read_ios;
        unsigned first_dev = si->dev - (si->dev %
                          (ios->layout->group_width * ios->layout->mirrors_p1));
        unsigned comp = si->dev - first_dev;
        unsigned added_len;

        if (!ios->ios_read_4_write) {
                int ret = _alloc_read_4_write(ios);

                if (unlikely(ret))
                        return ret;
        }

        read_ios = ios->ios_read_4_write;
        read_ios->numdevs = ios->layout->group_width * ios->layout->mirrors_p1;

        per_dev = &read_ios->per_dev[comp];
        if (!per_dev->length) {
                per_dev->bio = bio_kmalloc(GFP_KERNEL,
                                           ios->sp2d->pages_in_unit);
                if (unlikely(!per_dev->bio)) {
                        ORE_DBGMSG("Failed to allocate BIO size=%u\n",
                                     ios->sp2d->pages_in_unit);
                        return -ENOMEM;
                }
                per_dev->offset = si->obj_offset;
                per_dev->dev = si->dev;
        } else if (si->obj_offset != (per_dev->offset + per_dev->length)) {
                u64 gap = si->obj_offset - (per_dev->offset + per_dev->length);

                _ore_add_sg_seg(per_dev, gap, true);
        }
        q = osd_request_queue(ore_comp_dev(read_ios->oc, per_dev->dev));
        added_len = bio_add_pc_page(q, per_dev->bio, page, pg_len,
                                    si->obj_offset % PAGE_SIZE);
        if (unlikely(added_len != pg_len)) {
                ORE_DBGMSG("Failed to bio_add_pc_page bi_vcnt=%d\n",
                              per_dev->bio->bi_vcnt);
                return -ENOMEM;
        }

        per_dev->length += pg_len;
        return 0;
}

/* read the beginning of an unaligned first page */
static int _add_to_r4w_first_page(struct ore_io_state *ios, struct page *page)
{
        struct ore_striping_info si;
        unsigned pg_len;

        ore_calc_stripe_info(ios->layout, ios->offset, 0, &si);

        pg_len = si.obj_offset % PAGE_SIZE;
        si.obj_offset -= pg_len;

        ORE_DBGMSG("offset=0x%llx len=0x%x index=0x%lx dev=%x\n",
                   _LLU(si.obj_offset), pg_len, page->index, si.dev);

        return _add_to_r4w(ios, &si, page, pg_len);
}

/* read the end of an incomplete last page */
static int _add_to_r4w_last_page(struct ore_io_state *ios, u64 *offset)
{
        struct ore_striping_info si;
        struct page *page;
        unsigned pg_len, p, c;

        ore_calc_stripe_info(ios->layout, *offset, 0, &si);

        p = si.cur_pg;
        c = si.cur_comp;
        page = ios->sp2d->_1p_stripes[p].pages[c];

        pg_len = PAGE_SIZE - (si.unit_off % PAGE_SIZE);
        *offset += pg_len;

        ORE_DBGMSG("p=%d, c=%d next-offset=0x%llx len=0x%x dev=%x par_dev=%d\n",
                   p, c, _LLU(*offset), pg_len, si.dev, si.par_dev);

        BUG_ON(!page);

        return _add_to_r4w(ios, &si, page, pg_len);
}

static void _mark_read4write_pages_uptodate(struct ore_io_state *ios, int ret)
{
        struct bio_vec *bv;
        unsigned i, d;

        /* loop on all devices all pages */
        for (d = 0; d < ios->numdevs; d++) {
                struct bio *bio = ios->per_dev[d].bio;

                if (!bio)
                        continue;

                bio_for_each_segment_all(bv, bio, i) {
                        struct page *page = bv->bv_page;

                        SetPageUptodate(page);
                        if (PageError(page))
                                ClearPageError(page);
                }
        }
}

/* read_4_write is hacked to read the start of the first stripe and/or
 * the end of the last stripe. If needed, with an sg-gap at each device/page.
 * It is assumed to be called after the to_be_written pages of the first stripe
 * are populating ios->sp2d[][]
 *
 * NOTE: We call ios->r4w->lock_fn for all pages needed for parity calculations
 * These pages are held at sp2d[p].pages[c] but with
 * sp2d[p].page_is_read[c] = true. At _sp2d_reset these pages are
 * ios->r4w->lock_fn(). The ios->r4w->lock_fn might signal that the page is
 * @uptodate=true, so we don't need to read it, only unlock, after IO.
 *
 * TODO: The read_4_write should calc a need_to_read_pages_count, if bigger then
 * to-be-written count, we should consider the xor-in-place mode.
 * need_to_read_pages_count is the actual number of pages not present in cache.
 * maybe "devs_in_group - ios->sp2d[p].write_count" is a good enough
 * approximation? In this mode the read pages are put in the empty places of
 * ios->sp2d[p][*], xor is calculated the same way. These pages are
 * allocated/freed and don't go through cache
 */
static int _read_4_write_first_stripe(struct ore_io_state *ios)
{
        struct ore_striping_info read_si;
        struct __stripe_pages_2d *sp2d = ios->sp2d;
        u64 offset = ios->si.first_stripe_start;
        unsigned c, p, min_p = sp2d->pages_in_unit, max_p = -1;

        if (offset == ios->offset) /* Go to start collect $200 */
                goto read_last_stripe;

        min_p = _sp2d_min_pg(sp2d);
        max_p = _sp2d_max_pg(sp2d);

        ORE_DBGMSG("stripe_start=0x%llx ios->offset=0x%llx min_p=%d max_p=%d\n",
                   offset, ios->offset, min_p, max_p);

        for (c = 0; ; c++) {
                ore_calc_stripe_info(ios->layout, offset, 0, &read_si);
                read_si.obj_offset += min_p * PAGE_SIZE;
                offset += min_p * PAGE_SIZE;
                for (p = min_p; p <= max_p; p++) {
                        struct __1_page_stripe *_1ps = &sp2d->_1p_stripes[p];
                        struct page **pp = &_1ps->pages[c];
                        bool uptodate;

                        if (*pp) {
                                if (ios->offset % PAGE_SIZE)
                                        /* Read the remainder of the page */
                                        _add_to_r4w_first_page(ios, *pp);
                                /* to-be-written pages start here */
                                goto read_last_stripe;
                        }

                        *pp = ios->r4w->get_page(ios->private, offset,
                                                 &uptodate);
                        if (unlikely(!*pp))
                                return -ENOMEM;

                        if (!uptodate)
                                _add_to_r4w(ios, &read_si, *pp, PAGE_SIZE);

                        /* Mark read-pages to be cache_released */
                        _1ps->page_is_read[c] = true;
                        read_si.obj_offset += PAGE_SIZE;
                        offset += PAGE_SIZE;
                }
                offset += (sp2d->pages_in_unit - p) * PAGE_SIZE;
        }

read_last_stripe:
        return 0;
}

static int _read_4_write_last_stripe(struct ore_io_state *ios)
{
        struct ore_striping_info read_si;
        struct __stripe_pages_2d *sp2d = ios->sp2d;
        u64 offset;
        u64 last_stripe_end;
        unsigned bytes_in_stripe = ios->si.bytes_in_stripe;
        unsigned c, p, min_p = sp2d->pages_in_unit, max_p = -1;

        offset = ios->offset + ios->length;
        if (offset % PAGE_SIZE)
                _add_to_r4w_last_page(ios, &offset);
                /* offset will be aligned to next page */

        last_stripe_end = div_u64(offset + bytes_in_stripe - 1, bytes_in_stripe)
                                 * bytes_in_stripe;
        if (offset == last_stripe_end) /* Optimize for the aligned case */
                goto read_it;

        ore_calc_stripe_info(ios->layout, offset, 0, &read_si);
        p = read_si.cur_pg;
        c = read_si.cur_comp;

        if (min_p == sp2d->pages_in_unit) {
                /* Didn't do it yet */
                min_p = _sp2d_min_pg(sp2d);
                max_p = _sp2d_max_pg(sp2d);
        }

        ORE_DBGMSG("offset=0x%llx stripe_end=0x%llx min_p=%d max_p=%d\n",
                   offset, last_stripe_end, min_p, max_p);

        while (offset < last_stripe_end) {
                struct __1_page_stripe *_1ps = &sp2d->_1p_stripes[p];

                if ((min_p <= p) && (p <= max_p)) {
                        struct page *page;
                        bool uptodate;

                        BUG_ON(_1ps->pages[c]);
                        page = ios->r4w->get_page(ios->private, offset,
                                                  &uptodate);
                        if (unlikely(!page))
                                return -ENOMEM;

                        _1ps->pages[c] = page;
                        /* Mark read-pages to be cache_released */
                        _1ps->page_is_read[c] = true;
                        if (!uptodate)
                                _add_to_r4w(ios, &read_si, page, PAGE_SIZE);
                }

                offset += PAGE_SIZE;
                if (p == (sp2d->pages_in_unit - 1)) {
                        ++c;
                        p = 0;
                        ore_calc_stripe_info(ios->layout, offset, 0, &read_si);
                } else {
                        read_si.obj_offset += PAGE_SIZE;
                        ++p;
                }
        }

read_it:
        return 0;
}

static int _read_4_write_execute(struct ore_io_state *ios)
{
        struct ore_io_state *ios_read;
        unsigned i;
        int ret;

        ios_read = ios->ios_read_4_write;
        if (!ios_read)
                return 0;

        /* FIXME: Ugly to signal _sbi_read_mirror that we have bio(s). Change
         * to check for per_dev->bio
         */
        ios_read->pages = ios->pages;

        /* Now read these devices */
        for (i = 0; i < ios_read->numdevs; i += ios_read->layout->mirrors_p1) {
                ret = _ore_read_mirror(ios_read, i);
                if (unlikely(ret))
                        return ret;
        }

        ret = ore_io_execute(ios_read); /* Synchronus execution */
        if (unlikely(ret)) {
                ORE_DBGMSG("!! ore_io_execute => %d\n", ret);
                return ret;
        }

        _mark_read4write_pages_uptodate(ios_read, ret);
        ore_put_io_state(ios_read);
        ios->ios_read_4_write = NULL; /* Might need a reuse at last stripe */
        return 0;
}

/* In writes @cur_len means length left. .i.e cur_len==0 is the last parity U */
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, bool do_xor)
{
        if (ios->reading) {
                if (per_dev->cur_sg >= ios->sgs_per_dev) {
                        ORE_DBGMSG("cur_sg(%d) >= sgs_per_dev(%d)\n" ,
                                per_dev->cur_sg, ios->sgs_per_dev);
                        return -ENOMEM;
                }
                _ore_add_sg_seg(per_dev, cur_len, true);
        } else {
                struct __stripe_pages_2d *sp2d = ios->sp2d;
                struct page **pages = ios->parity_pages + ios->cur_par_page;
                unsigned num_pages;
                unsigned array_start = 0;
                unsigned i;
                int ret;

                si->cur_pg = _sp2d_min_pg(sp2d);
                num_pages  = _sp2d_max_pg(sp2d) + 1 - si->cur_pg;

                if (!per_dev->length) {
                        per_dev->offset += si->cur_pg * PAGE_SIZE;
                        /* If first stripe, Read in all read4write pages
                         * (if needed) before we calculate the first parity.
                         */
                        if (do_xor)
                                _read_4_write_first_stripe(ios);
                }
                if (!cur_len && do_xor)
                        /* If last stripe r4w pages of last stripe */
                        _read_4_write_last_stripe(ios);
                _read_4_write_execute(ios);

                for (i = 0; i < num_pages; i++) {
                        pages[i] = _raid_page_alloc();
                        if (unlikely(!pages[i]))
                                return -ENOMEM;

                        ++(ios->cur_par_page);
                }

                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,
                                           per_dev, num_pages * PAGE_SIZE);
                if (unlikely(ret))
                        return ret;

                if (do_xor) {
                        _gen_xor_unit(sp2d);
                        _sp2d_reset(sp2d, ios->r4w, ios->private);
                }
        }
        return 0;
}

int _ore_post_alloc_raid_stuff(struct ore_io_state *ios)
{
        if (ios->parity_pages) {
                struct ore_layout *layout = ios->layout;
                unsigned pages_in_unit = layout->stripe_unit / PAGE_SIZE;

                if (_sp2d_alloc(pages_in_unit, layout->group_width,
                                layout->parity, &ios->sp2d)) {
                        return -ENOMEM;
                }
        }
        return 0;
}

void _ore_free_raid_stuff(struct ore_io_state *ios)
{
        if (ios->sp2d) { /* writing and raid */
                unsigned i;

                for (i = 0; i < ios->cur_par_page; i++) {
                        struct page *page = ios->parity_pages[i];

                        if (page)
                                _raid_page_free(page);
                }
                if (ios->extra_part_alloc)
                        kfree(ios->parity_pages);
                /* If IO returned an error pages might need unlocking */
                _sp2d_reset(ios->sp2d, ios->r4w, ios->private);
                _sp2d_free(ios->sp2d);
        } else {
                /* Will only be set if raid reading && sglist is big */
                if (ios->extra_part_alloc)
                        kfree(ios->per_dev[0].sglist);
        }
        if (ios->ios_read_4_write)
                ore_put_io_state(ios->ios_read_4_write);
}