async_xor.c

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/*
 * xor offload engine api
 *
 * Copyright © 2006, Intel Corporation.
 *
 *      Dan Williams <[email protected]>
 *
 *      with architecture considerations by:
 *      Neil Brown <[email protected]>
 *      Jeff Garzik <[email protected]>
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms and conditions of the GNU General Public License,
 * version 2, as published by the Free Software Foundation.
 *
 * This program is distributed in the hope 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.,
 * 51 Franklin St - Fifth Floor, Boston, MA 02110-1301 USA.
 *
 */
#include <linux/kernel.h>
#include <linux/interrupt.h>
#include <linux/module.h>
#include <linux/mm.h>
#include <linux/dma-mapping.h>
#include <linux/raid/xor.h>
#include <linux/async_tx.h>

/* do_async_xor - dma map the pages and perform the xor with an engine */
static __async_inline struct dma_async_tx_descriptor *
do_async_xor(struct dma_chan *chan, struct page *dest, struct page **src_list,
         unsigned int offset, int src_cnt, size_t len, dma_addr_t *dma_src,
         struct async_submit_ctl *submit)
{
    struct dma_device *dma = chan->device;
    struct dma_async_tx_descriptor *tx = NULL;
    int src_off = 0;
    int i;
    dma_async_tx_callback cb_fn_orig = submit->cb_fn;
    void *cb_param_orig = submit->cb_param;
    enum async_tx_flags flags_orig = submit->flags;
    enum dma_ctrl_flags dma_flags;
    int xor_src_cnt = 0;
    dma_addr_t dma_dest;

    /* map the dest bidrectional in case it is re-used as a source */
    dma_dest = dma_map_page(dma->dev, dest, offset, len, DMA_BIDIRECTIONAL);
    for (i = 0; i < src_cnt; i++) {
        /* only map the dest once */
        if (!src_list[i])
            continue;
        if (unlikely(src_list[i] == dest)) {
            dma_src[xor_src_cnt++] = dma_dest;
            continue;
        }
        dma_src[xor_src_cnt++] = dma_map_page(dma->dev, src_list[i], offset,
                              len, DMA_TO_DEVICE);
    }
    src_cnt = xor_src_cnt;

    while (src_cnt) {
        submit->flags = flags_orig;
        dma_flags = 0;
        xor_src_cnt = min(src_cnt, (int)dma->max_xor);
        /* if we are submitting additional xors, leave the chain open,
         * clear the callback parameters, and leave the destination
         * buffer mapped
         */
        if (src_cnt > xor_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 {
            submit->cb_fn = cb_fn_orig;
            submit->cb_param = cb_param_orig;
        }
        if (submit->cb_fn)
            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
         */
        tx = dma->device_prep_dma_xor(chan, dma_dest, &dma_src[src_off],
                          xor_src_cnt, len, dma_flags);

        if (unlikely(!tx))
            async_tx_quiesce(&submit->depend_tx);

        /* spin wait for the preceding transactions to complete */
        while (unlikely(!tx)) {
            dma_async_issue_pending(chan);
            tx = dma->device_prep_dma_xor(chan, dma_dest,
                              &dma_src[src_off],
                              xor_src_cnt, len,
                              dma_flags);
        }

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

        if (src_cnt > xor_src_cnt) {
            /* drop completed sources */
            src_cnt -= xor_src_cnt;
            src_off += xor_src_cnt;

            /* use the intermediate result a source */
            dma_src[--src_off] = dma_dest;
            src_cnt++;
        } else
            break;
    }

    return tx;
}

static void
do_sync_xor(struct page *dest, struct page **src_list, unsigned int offset,
        int src_cnt, size_t len, struct async_submit_ctl *submit)
{
    int i;
    int xor_src_cnt = 0;
    int src_off = 0;
    void *dest_buf;
    void **srcs;

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

    /* convert to buffer pointers */
    for (i = 0; i < src_cnt; i++)
        if (src_list[i])
            srcs[xor_src_cnt++] = page_address(src_list[i]) + offset;
    src_cnt = xor_src_cnt;
    /* set destination address */
    dest_buf = page_address(dest) + offset;

    if (submit->flags & ASYNC_TX_XOR_ZERO_DST)
        memset(dest_buf, 0, len);

    while (src_cnt > 0) {
        /* process up to 'MAX_XOR_BLOCKS' sources */
        xor_src_cnt = min(src_cnt, MAX_XOR_BLOCKS);
        xor_blocks(xor_src_cnt, len, dest_buf, &srcs[src_off]);

        /* drop completed sources */
        src_cnt -= xor_src_cnt;
        src_off += xor_src_cnt;
    }

    async_tx_sync_epilog(submit);
}

struct dma_async_tx_descriptor *
async_xor(struct page *dest, struct page **src_list, unsigned int offset,
      int src_cnt, size_t len, struct async_submit_ctl *submit)
{
    struct dma_chan *chan = async_tx_find_channel(submit, DMA_XOR,
                              &dest, 1, src_list,
                              src_cnt, len);
    dma_addr_t *dma_src = NULL;

    BUG_ON(src_cnt <= 1);

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

    if (dma_src && chan && is_dma_xor_aligned(chan->device, offset, 0, len)) {
        /* run the xor asynchronously */
        pr_debug("%s (async): len: %zu\n", __func__, len);

        return do_async_xor(chan, dest, src_list, offset, src_cnt, len,
                    dma_src, submit);
    } else {
        /* run the xor synchronously */
        pr_debug("%s (sync): len: %zu\n", __func__, len);
        WARN_ONCE(chan, "%s: no space for dma address conversion\n",
              __func__);

        /* in the sync case the dest is an implied source
         * (assumes the dest is the first source)
         */
        if (submit->flags & ASYNC_TX_XOR_DROP_DST) {
            src_cnt--;
            src_list++;
        }

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

        do_sync_xor(dest, src_list, offset, src_cnt, len, submit);

        return NULL;
    }
}
EXPORT_SYMBOL_GPL(async_xor);

static int page_is_zero(struct page *p, unsigned int offset, size_t len)
{
    char *a = page_address(p) + offset;
    return ((*(u32 *) a) == 0 &&
        memcmp(a, a + 4, len - 4) == 0);
}

static inline struct dma_chan *
xor_val_chan(struct async_submit_ctl *submit, struct page *dest,
         struct page **src_list, int src_cnt, size_t len)
{
    #ifdef CONFIG_ASYNC_TX_DISABLE_XOR_VAL_DMA
    return NULL;
    #endif
    return async_tx_find_channel(submit, DMA_XOR_VAL, &dest, 1, src_list,
                     src_cnt, len);
}

struct dma_async_tx_descriptor *
async_xor_val(struct page *dest, struct page **src_list, unsigned int offset,
          int src_cnt, size_t len, enum sum_check_flags *result,
          struct async_submit_ctl *submit)
{
    struct dma_chan *chan = xor_val_chan(submit, dest, src_list, src_cnt, len);
    struct dma_device *device = chan ? chan->device : NULL;
    struct dma_async_tx_descriptor *tx = NULL;
    dma_addr_t *dma_src = NULL;

    BUG_ON(src_cnt <= 1);

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

    if (dma_src && device && src_cnt <= device->max_xor &&
        is_dma_xor_aligned(device, offset, 0, len)) {
        unsigned long dma_prep_flags = 0;
        int i;

        pr_debug("%s: (async) len: %zu\n", __func__, len);

        if (submit->cb_fn)
            dma_prep_flags |= DMA_PREP_INTERRUPT;
        if (submit->flags & ASYNC_TX_FENCE)
            dma_prep_flags |= DMA_PREP_FENCE;
        for (i = 0; i < src_cnt; i++)
            dma_src[i] = dma_map_page(device->dev, src_list[i],
                          offset, len, DMA_TO_DEVICE);

        tx = device->device_prep_dma_xor_val(chan, dma_src, src_cnt,
                             len, result,
                             dma_prep_flags);
        if (unlikely(!tx)) {
            async_tx_quiesce(&submit->depend_tx);

            while (!tx) {
                dma_async_issue_pending(chan);
                tx = device->device_prep_dma_xor_val(chan,
                    dma_src, src_cnt, len, result,
                    dma_prep_flags);
            }
        }

        async_tx_submit(chan, tx, submit);
    } else {
        enum async_tx_flags flags_orig = submit->flags;

        pr_debug("%s: (sync) len: %zu\n", __func__, len);
        WARN_ONCE(device && src_cnt <= device->max_xor,
              "%s: no space for dma address conversion\n",
              __func__);

        submit->flags |= ASYNC_TX_XOR_DROP_DST;
        submit->flags &= ~ASYNC_TX_ACK;

        tx = async_xor(dest, src_list, offset, src_cnt, len, submit);

        async_tx_quiesce(&tx);

        *result = !page_is_zero(dest, offset, len) << SUM_CHECK_P;

        async_tx_sync_epilog(submit);
        submit->flags = flags_orig;
    }

    return tx;
}
EXPORT_SYMBOL_GPL(async_xor_val);

MODULE_AUTHOR("Intel Corporation");
MODULE_DESCRIPTION("asynchronous xor/xor-zero-sum api");
MODULE_LICENSE("GPL");