async_pq.c

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/*
 * Copyright(c) 2007 Yuri Tikhonov <[email protected]>
 * Copyright(c) 2009 Intel Corporation
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by the Free
 * Software Foundation; either version 2 of the License, or (at your option)
 * any later version.
 *
 * This program is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
 * more details.
 *
 * You should have received a copy of the GNU General Public License along with
 * this program; if not, write to the Free Software Foundation, Inc., 59
 * Temple Place - Suite 330, Boston, MA  02111-1307, USA.
 *
 * The full GNU General Public License is included in this distribution in the
 * file called COPYING.
 */
#include <linux/kernel.h>
#include <linux/interrupt.h>
#include <linux/module.h>
#include <linux/dma-mapping.h>
#include <linux/raid/pq.h>
#include <linux/async_tx.h>
#include <linux/gfp.h>

static struct page *pq_scribble_page;

/* the struct page *blocks[] parameter passed to async_gen_syndrome()
 * and async_syndrome_val() contains the 'P' destination address at
 * blocks[disks-2] and the 'Q' destination address at blocks[disks-1]
 *
 * note: these are macros as they are used as lvalues
 */
#define P(b, d) (b[d-2])
#define Q(b, d) (b[d-1])

static __async_inline struct dma_async_tx_descriptor *
do_async_gen_syndrome(struct dma_chan *chan, struct page **blocks,
              const unsigned char *scfs, unsigned int offset, int disks,
              size_t len, dma_addr_t *dma_src,
              struct async_submit_ctl *submit)
{
    struct dma_async_tx_descriptor *tx = NULL;
    struct dma_device *dma = chan->device;
    enum dma_ctrl_flags dma_flags = 0;
    enum async_tx_flags flags_orig = submit->flags;
    dma_async_tx_callback cb_fn_orig = submit->cb_fn;
    dma_async_tx_callback cb_param_orig = submit->cb_param;
    int src_cnt = disks - 2;
    unsigned char coefs[src_cnt];
    unsigned short pq_src_cnt;
    dma_addr_t dma_dest[2];
    int src_off = 0;
    int idx;
    int i;

    /* DMAs use destinations as sources, so use BIDIRECTIONAL mapping */
    if (P(blocks, disks))
        dma_dest[0] = dma_map_page(dma->dev, P(blocks, disks), offset,
                       len, DMA_BIDIRECTIONAL);
    else
        dma_flags |= DMA_PREP_PQ_DISABLE_P;
    if (Q(blocks, disks))
        dma_dest[1] = dma_map_page(dma->dev, Q(blocks, disks), offset,
                       len, DMA_BIDIRECTIONAL);
    else
        dma_flags |= DMA_PREP_PQ_DISABLE_Q;

    /* convert source addresses being careful to collapse 'empty'
     * sources and update the coefficients accordingly
     */
    for (i = 0, idx = 0; i < src_cnt; i++) {
        if (blocks[i] == NULL)
            continue;
        dma_src[idx] = dma_map_page(dma->dev, blocks[i], offset, len,
                        DMA_TO_DEVICE);
        coefs[idx] = scfs[i];
        idx++;
    }
    src_cnt = idx;

    while (src_cnt > 0) {
        submit->flags = flags_orig;
        pq_src_cnt = min(src_cnt, dma_maxpq(dma, dma_flags));
        /* if we are submitting additional pqs, leave the chain open,
         * clear the callback parameters, and leave the destination
         * buffers mapped
         */
        if (src_cnt > pq_src_cnt) {
            submit->flags &= ~ASYNC_TX_ACK;
            submit->flags |= ASYNC_TX_FENCE;
            dma_flags |= DMA_COMPL_SKIP_DEST_UNMAP;
            submit->cb_fn = NULL;
            submit->cb_param = NULL;
        } else {
            dma_flags &= ~DMA_COMPL_SKIP_DEST_UNMAP;
            submit->cb_fn = cb_fn_orig;
            submit->cb_param = cb_param_orig;
            if (cb_fn_orig)
                dma_flags |= DMA_PREP_INTERRUPT;
        }
        if (submit->flags & ASYNC_TX_FENCE)
            dma_flags |= DMA_PREP_FENCE;

        /* Since we have clobbered the src_list we are committed
         * to doing this asynchronously.  Drivers force forward
         * progress in case they can not provide a descriptor
         */
        for (;;) {
            tx = dma->device_prep_dma_pq(chan, dma_dest,
                             &dma_src[src_off],
                             pq_src_cnt,
                             &coefs[src_off], len,
                             dma_flags);
            if (likely(tx))
                break;
            async_tx_quiesce(&submit->depend_tx);
            dma_async_issue_pending(chan);
        }

        async_tx_submit(chan, tx, submit);
        submit->depend_tx = tx;

        /* drop completed sources */
        src_cnt -= pq_src_cnt;
        src_off += pq_src_cnt;

        dma_flags |= DMA_PREP_CONTINUE;
    }

    return tx;
}

static void
do_sync_gen_syndrome(struct page **blocks, unsigned int offset, int disks,
             size_t len, struct async_submit_ctl *submit)
{
    void **srcs;
    int i;

    if (submit->scribble)
        srcs = submit->scribble;
    else
        srcs = (void **) blocks;

    for (i = 0; i < disks; i++) {
        if (blocks[i] == NULL) {
            BUG_ON(i > disks - 3); /* P or Q can't be zero */
            srcs[i] = (void*)raid6_empty_zero_page;
        } else
            srcs[i] = page_address(blocks[i]) + offset;
    }
    raid6_call.gen_syndrome(disks, len, srcs);
    async_tx_sync_epilog(submit);
}

struct dma_async_tx_descriptor *
async_gen_syndrome(struct page **blocks, unsigned int offset, int disks,
           size_t len, struct async_submit_ctl *submit)
{
    int src_cnt = disks - 2;
    struct dma_chan *chan = async_tx_find_channel(submit, DMA_PQ,
                              &P(blocks, disks), 2,
                              blocks, src_cnt, len);
    struct dma_device *device = chan ? chan->device : NULL;
    dma_addr_t *dma_src = NULL;

    BUG_ON(disks > 255 || !(P(blocks, disks) || Q(blocks, disks)));

    if (submit->scribble)
        dma_src = submit->scribble;
    else if (sizeof(dma_addr_t) <= sizeof(struct page *))
        dma_src = (dma_addr_t *) blocks;

    if (dma_src && device &&
        (src_cnt <= dma_maxpq(device, 0) ||
         dma_maxpq(device, DMA_PREP_CONTINUE) > 0) &&
        is_dma_pq_aligned(device, offset, 0, len)) {
        /* run the p+q asynchronously */
        pr_debug("%s: (async) disks: %d len: %zu\n",
             __func__, disks, len);
        return do_async_gen_syndrome(chan, blocks, raid6_gfexp, offset,
                         disks, len, dma_src, submit);
    }

    /* run the pq synchronously */
    pr_debug("%s: (sync) disks: %d len: %zu\n", __func__, disks, len);

    /* wait for any prerequisite operations */
    async_tx_quiesce(&submit->depend_tx);

    if (!P(blocks, disks)) {
        P(blocks, disks) = pq_scribble_page;
        BUG_ON(len + offset > PAGE_SIZE);
    }
    if (!Q(blocks, disks)) {
        Q(blocks, disks) = pq_scribble_page;
        BUG_ON(len + offset > PAGE_SIZE);
    }
    do_sync_gen_syndrome(blocks, offset, disks, len, submit);

    return NULL;
}
EXPORT_SYMBOL_GPL(async_gen_syndrome);

static inline struct dma_chan *
pq_val_chan(struct async_submit_ctl *submit, struct page **blocks, int disks, size_t len)
{
    #ifdef CONFIG_ASYNC_TX_DISABLE_PQ_VAL_DMA
    return NULL;
    #endif
    return async_tx_find_channel(submit, DMA_PQ_VAL, NULL, 0,  blocks,
                     disks, len);
}

struct dma_async_tx_descriptor *
async_syndrome_val(struct page **blocks, unsigned int offset, int disks,
           size_t len, enum sum_check_flags *pqres, struct page *spare,
           struct async_submit_ctl *submit)
{
    struct dma_chan *chan = pq_val_chan(submit, blocks, disks, len);
    struct dma_device *device = chan ? chan->device : NULL;
    struct dma_async_tx_descriptor *tx;
    unsigned char coefs[disks-2];
    enum dma_ctrl_flags dma_flags = submit->cb_fn ? DMA_PREP_INTERRUPT : 0;
    dma_addr_t *dma_src = NULL;
    int src_cnt = 0;

    BUG_ON(disks < 4);

    if (submit->scribble)
        dma_src = submit->scribble;
    else if (sizeof(dma_addr_t) <= sizeof(struct page *))
        dma_src = (dma_addr_t *) blocks;

    if (dma_src && device && disks <= dma_maxpq(device, 0) &&
        is_dma_pq_aligned(device, offset, 0, len)) {
        struct device *dev = device->dev;
        dma_addr_t *pq = &dma_src[disks-2];
        int i;

        pr_debug("%s: (async) disks: %d len: %zu\n",
             __func__, disks, len);
        if (!P(blocks, disks))
            dma_flags |= DMA_PREP_PQ_DISABLE_P;
        else
            pq[0] = dma_map_page(dev, P(blocks, disks),
                         offset, len,
                         DMA_TO_DEVICE);
        if (!Q(blocks, disks))
            dma_flags |= DMA_PREP_PQ_DISABLE_Q;
        else
            pq[1] = dma_map_page(dev, Q(blocks, disks),
                         offset, len,
                         DMA_TO_DEVICE);

        if (submit->flags & ASYNC_TX_FENCE)
            dma_flags |= DMA_PREP_FENCE;
        for (i = 0; i < disks-2; i++)
            if (likely(blocks[i])) {
                dma_src[src_cnt] = dma_map_page(dev, blocks[i],
                                offset, len,
                                DMA_TO_DEVICE);
                coefs[src_cnt] = raid6_gfexp[i];
                src_cnt++;
            }

        for (;;) {
            tx = device->device_prep_dma_pq_val(chan, pq, dma_src,
                                src_cnt,
                                coefs,
                                len, pqres,
                                dma_flags);
            if (likely(tx))
                break;
            async_tx_quiesce(&submit->depend_tx);
            dma_async_issue_pending(chan);
        }
        async_tx_submit(chan, tx, submit);

        return tx;
    } else {
        struct page *p_src = P(blocks, disks);
        struct page *q_src = Q(blocks, disks);
        enum async_tx_flags flags_orig = submit->flags;
        dma_async_tx_callback cb_fn_orig = submit->cb_fn;
        void *scribble = submit->scribble;
        void *cb_param_orig = submit->cb_param;
        void *p, *q, *s;

        pr_debug("%s: (sync) disks: %d len: %zu\n",
             __func__, disks, len);

        /* caller must provide a temporary result buffer and
         * allow the input parameters to be preserved
         */
        BUG_ON(!spare || !scribble);

        /* wait for any prerequisite operations */
        async_tx_quiesce(&submit->depend_tx);

        /* recompute p and/or q into the temporary buffer and then
         * check to see the result matches the current value
         */
        tx = NULL;
        *pqres = 0;
        if (p_src) {
            init_async_submit(submit, ASYNC_TX_XOR_ZERO_DST, NULL,
                      NULL, NULL, scribble);
            tx = async_xor(spare, blocks, offset, disks-2, len, submit);
            async_tx_quiesce(&tx);
            p = page_address(p_src) + offset;
            s = page_address(spare) + offset;
            *pqres |= !!memcmp(p, s, len) << SUM_CHECK_P;
        }

        if (q_src) {
            P(blocks, disks) = NULL;
            Q(blocks, disks) = spare;
            init_async_submit(submit, 0, NULL, NULL, NULL, scribble);
            tx = async_gen_syndrome(blocks, offset, disks, len, submit);
            async_tx_quiesce(&tx);
            q = page_address(q_src) + offset;
            s = page_address(spare) + offset;
            *pqres |= !!memcmp(q, s, len) << SUM_CHECK_Q;
        }

        /* restore P, Q and submit */
        P(blocks, disks) = p_src;
        Q(blocks, disks) = q_src;

        submit->cb_fn = cb_fn_orig;
        submit->cb_param = cb_param_orig;
        submit->flags = flags_orig;
        async_tx_sync_epilog(submit);

        return NULL;
    }
}
EXPORT_SYMBOL_GPL(async_syndrome_val);

static int __init async_pq_init(void)
{
    pq_scribble_page = alloc_page(GFP_KERNEL);

    if (pq_scribble_page)
        return 0;

    pr_err("%s: failed to allocate required spare page\n", __func__);

    return -ENOMEM;
}

static void __exit async_pq_exit(void)
{
    put_page(pq_scribble_page);
}

module_init(async_pq_init);
module_exit(async_pq_exit);

MODULE_DESCRIPTION("asynchronous raid6 syndrome generation/validation");
MODULE_LICENSE("GPL");