crypto/async_tx/async_raid6_recov.c

0001 // SPDX-License-Identifier: GPL-2.0-or-later
0002 /*
0003  * Asynchronous RAID-6 recovery calculations ASYNC_TX API.
0004  * Copyright(c) 2009 Intel Corporation
0005  *
0006  * based on raid6recov.c:
0007  *   Copyright 2002 H. Peter Anvin
0008  */
0009 #include <linux/kernel.h>
0010 #include <linux/interrupt.h>
0011 #include <linux/module.h>
0012 #include <linux/dma-mapping.h>
0013 #include <linux/raid/pq.h>
0014 #include <linux/async_tx.h>
0015 #include <linux/dmaengine.h>
0016
0017 static struct dma_async_tx_descriptor *
0018 async_sum_product(struct page *dest, unsigned int d_off,
0019         struct page **srcs, unsigned int *src_offs, unsigned char *coef,
0020         size_t len, struct async_submit_ctl *submit)
0021 {
0022     struct dma_chan *chan = async_tx_find_channel(submit, DMA_PQ,
0023                               &dest, 1, srcs, 2, len);
0024     struct dma_device *dma = chan ? chan->device : NULL;
0025     struct dmaengine_unmap_data *unmap = NULL;
0026     const u8 *amul, *bmul;
0027     u8 ax, bx;
0028     u8 *a, *b, *c;
0029
0030     if (dma)
0031         unmap = dmaengine_get_unmap_data(dma->dev, 3, GFP_NOWAIT);
0032
0033     if (unmap) {
0034         struct device *dev = dma->dev;
0035         dma_addr_t pq[2];
0036         struct dma_async_tx_descriptor *tx;
0037         enum dma_ctrl_flags dma_flags = DMA_PREP_PQ_DISABLE_P;
0038
0039         if (submit->flags & ASYNC_TX_FENCE)
0040             dma_flags |= DMA_PREP_FENCE;
0041         unmap->addr[0] = dma_map_page(dev, srcs[0], src_offs[0],
0042                         len, DMA_TO_DEVICE);
0043         unmap->addr[1] = dma_map_page(dev, srcs[1], src_offs[1],
0044                         len, DMA_TO_DEVICE);
0045         unmap->to_cnt = 2;
0046
0047         unmap->addr[2] = dma_map_page(dev, dest, d_off,
0048                         len, DMA_BIDIRECTIONAL);
0049         unmap->bidi_cnt = 1;
0050         /* engine only looks at Q, but expects it to follow P */
0051         pq[1] = unmap->addr[2];
0052
0053         unmap->len = len;
0054         tx = dma->device_prep_dma_pq(chan, pq, unmap->addr, 2, coef,
0055                          len, dma_flags);
0056         if (tx) {
0057             dma_set_unmap(tx, unmap);
0058             async_tx_submit(chan, tx, submit);
0059             dmaengine_unmap_put(unmap);
0060             return tx;
0061         }
0062
0063         /* could not get a descriptor, unmap and fall through to
0064          * the synchronous path
0065          */
0066         dmaengine_unmap_put(unmap);
0067     }
0068
0069     /* run the operation synchronously */
0070     async_tx_quiesce(&submit->depend_tx);
0071     amul = raid6_gfmul[coef[0]];
0072     bmul = raid6_gfmul[coef[1]];
0073     a = page_address(srcs[0]) + src_offs[0];
0074     b = page_address(srcs[1]) + src_offs[1];
0075     c = page_address(dest) + d_off;
0076
0077     while (len--) {
0078         ax    = amul[*a++];
0079         bx    = bmul[*b++];
0080         *c++ = ax ^ bx;
0081     }
0082
0083     return NULL;
0084 }
0085
0086 static struct dma_async_tx_descriptor *
0087 async_mult(struct page *dest, unsigned int d_off, struct page *src,
0088         unsigned int s_off, u8 coef, size_t len,
0089         struct async_submit_ctl *submit)
0090 {
0091     struct dma_chan *chan = async_tx_find_channel(submit, DMA_PQ,
0092                               &dest, 1, &src, 1, len);
0093     struct dma_device *dma = chan ? chan->device : NULL;
0094     struct dmaengine_unmap_data *unmap = NULL;
0095     const u8 *qmul; /* Q multiplier table */
0096     u8 *d, *s;
0097
0098     if (dma)
0099         unmap = dmaengine_get_unmap_data(dma->dev, 3, GFP_NOWAIT);
0100
0101     if (unmap) {
0102         dma_addr_t dma_dest[2];
0103         struct device *dev = dma->dev;
0104         struct dma_async_tx_descriptor *tx;
0105         enum dma_ctrl_flags dma_flags = DMA_PREP_PQ_DISABLE_P;
0106
0107         if (submit->flags & ASYNC_TX_FENCE)
0108             dma_flags |= DMA_PREP_FENCE;
0109         unmap->addr[0] = dma_map_page(dev, src, s_off,
0110                         len, DMA_TO_DEVICE);
0111         unmap->to_cnt++;
0112         unmap->addr[1] = dma_map_page(dev, dest, d_off,
0113                         len, DMA_BIDIRECTIONAL);
0114         dma_dest[1] = unmap->addr[1];
0115         unmap->bidi_cnt++;
0116         unmap->len = len;
0117
0118         /* this looks funny, but the engine looks for Q at
0119          * dma_dest[1] and ignores dma_dest[0] as a dest
0120          * due to DMA_PREP_PQ_DISABLE_P
0121          */
0122         tx = dma->device_prep_dma_pq(chan, dma_dest, unmap->addr,
0123                          1, &coef, len, dma_flags);
0124
0125         if (tx) {
0126             dma_set_unmap(tx, unmap);
0127             dmaengine_unmap_put(unmap);
0128             async_tx_submit(chan, tx, submit);
0129             return tx;
0130         }
0131
0132         /* could not get a descriptor, unmap and fall through to
0133          * the synchronous path
0134          */
0135         dmaengine_unmap_put(unmap);
0136     }
0137
0138     /* no channel available, or failed to allocate a descriptor, so
0139      * perform the operation synchronously
0140      */
0141     async_tx_quiesce(&submit->depend_tx);
0142     qmul  = raid6_gfmul[coef];
0143     d = page_address(dest) + d_off;
0144     s = page_address(src) + s_off;
0145
0146     while (len--)
0147         *d++ = qmul[*s++];
0148
0149     return NULL;
0150 }
0151
0152 static struct dma_async_tx_descriptor *
0153 __2data_recov_4(int disks, size_t bytes, int faila, int failb,
0154         struct page **blocks, unsigned int *offs,
0155         struct async_submit_ctl *submit)
0156 {
0157     struct dma_async_tx_descriptor *tx = NULL;
0158     struct page *p, *q, *a, *b;
0159     unsigned int p_off, q_off, a_off, b_off;
0160     struct page *srcs[2];
0161     unsigned int src_offs[2];
0162     unsigned char coef[2];
0163     enum async_tx_flags flags = submit->flags;
0164     dma_async_tx_callback cb_fn = submit->cb_fn;
0165     void *cb_param = submit->cb_param;
0166     void *scribble = submit->scribble;
0167
0168     p = blocks[disks-2];
0169     p_off = offs[disks-2];
0170     q = blocks[disks-1];
0171     q_off = offs[disks-1];
0172
0173     a = blocks[faila];
0174     a_off = offs[faila];
0175     b = blocks[failb];
0176     b_off = offs[failb];
0177
0178     /* in the 4 disk case P + Pxy == P and Q + Qxy == Q */
0179     /* Dx = A*(P+Pxy) + B*(Q+Qxy) */
0180     srcs[0] = p;
0181     src_offs[0] = p_off;
0182     srcs[1] = q;
0183     src_offs[1] = q_off;
0184     coef[0] = raid6_gfexi[failb-faila];
0185     coef[1] = raid6_gfinv[raid6_gfexp[faila]^raid6_gfexp[failb]];
0186     init_async_submit(submit, ASYNC_TX_FENCE, tx, NULL, NULL, scribble);
0187     tx = async_sum_product(b, b_off, srcs, src_offs, coef, bytes, submit);
0188
0189     /* Dy = P+Pxy+Dx */
0190     srcs[0] = p;
0191     src_offs[0] = p_off;
0192     srcs[1] = b;
0193     src_offs[1] = b_off;
0194     init_async_submit(submit, flags | ASYNC_TX_XOR_ZERO_DST, tx, cb_fn,
0195               cb_param, scribble);
0196     tx = async_xor_offs(a, a_off, srcs, src_offs, 2, bytes, submit);
0197
0198     return tx;
0199
0200 }
0201
0202 static struct dma_async_tx_descriptor *
0203 __2data_recov_5(int disks, size_t bytes, int faila, int failb,
0204         struct page **blocks, unsigned int *offs,
0205         struct async_submit_ctl *submit)
0206 {
0207     struct dma_async_tx_descriptor *tx = NULL;
0208     struct page *p, *q, *g, *dp, *dq;
0209     unsigned int p_off, q_off, g_off, dp_off, dq_off;
0210     struct page *srcs[2];
0211     unsigned int src_offs[2];
0212     unsigned char coef[2];
0213     enum async_tx_flags flags = submit->flags;
0214     dma_async_tx_callback cb_fn = submit->cb_fn;
0215     void *cb_param = submit->cb_param;
0216     void *scribble = submit->scribble;
0217     int good_srcs, good, i;
0218
0219     good_srcs = 0;
0220     good = -1;
0221     for (i = 0; i < disks-2; i++) {
0222         if (blocks[i] == NULL)
0223             continue;
0224         if (i == faila || i == failb)
0225             continue;
0226         good = i;
0227         good_srcs++;
0228     }
0229     BUG_ON(good_srcs > 1);
0230
0231     p = blocks[disks-2];
0232     p_off = offs[disks-2];
0233     q = blocks[disks-1];
0234     q_off = offs[disks-1];
0235     g = blocks[good];
0236     g_off = offs[good];
0237
0238     /* Compute syndrome with zero for the missing data pages
0239      * Use the dead data pages as temporary storage for delta p and
0240      * delta q
0241      */
0242     dp = blocks[faila];
0243     dp_off = offs[faila];
0244     dq = blocks[failb];
0245     dq_off = offs[failb];
0246
0247     init_async_submit(submit, ASYNC_TX_FENCE, tx, NULL, NULL, scribble);
0248     tx = async_memcpy(dp, g, dp_off, g_off, bytes, submit);
0249     init_async_submit(submit, ASYNC_TX_FENCE, tx, NULL, NULL, scribble);
0250     tx = async_mult(dq, dq_off, g, g_off,
0251             raid6_gfexp[good], bytes, submit);
0252
0253     /* compute P + Pxy */
0254     srcs[0] = dp;
0255     src_offs[0] = dp_off;
0256     srcs[1] = p;
0257     src_offs[1] = p_off;
0258     init_async_submit(submit, ASYNC_TX_FENCE|ASYNC_TX_XOR_DROP_DST, tx,
0259               NULL, NULL, scribble);
0260     tx = async_xor_offs(dp, dp_off, srcs, src_offs, 2, bytes, submit);
0261
0262     /* compute Q + Qxy */
0263     srcs[0] = dq;
0264     src_offs[0] = dq_off;
0265     srcs[1] = q;
0266     src_offs[1] = q_off;
0267     init_async_submit(submit, ASYNC_TX_FENCE|ASYNC_TX_XOR_DROP_DST, tx,
0268               NULL, NULL, scribble);
0269     tx = async_xor_offs(dq, dq_off, srcs, src_offs, 2, bytes, submit);
0270
0271     /* Dx = A*(P+Pxy) + B*(Q+Qxy) */
0272     srcs[0] = dp;
0273     src_offs[0] = dp_off;
0274     srcs[1] = dq;
0275     src_offs[1] = dq_off;
0276     coef[0] = raid6_gfexi[failb-faila];
0277     coef[1] = raid6_gfinv[raid6_gfexp[faila]^raid6_gfexp[failb]];
0278     init_async_submit(submit, ASYNC_TX_FENCE, tx, NULL, NULL, scribble);
0279     tx = async_sum_product(dq, dq_off, srcs, src_offs, coef, bytes, submit);
0280
0281     /* Dy = P+Pxy+Dx */
0282     srcs[0] = dp;
0283     src_offs[0] = dp_off;
0284     srcs[1] = dq;
0285     src_offs[1] = dq_off;
0286     init_async_submit(submit, flags | ASYNC_TX_XOR_DROP_DST, tx, cb_fn,
0287               cb_param, scribble);
0288     tx = async_xor_offs(dp, dp_off, srcs, src_offs, 2, bytes, submit);
0289
0290     return tx;
0291 }
0292
0293 static struct dma_async_tx_descriptor *
0294 __2data_recov_n(int disks, size_t bytes, int faila, int failb,
0295           struct page **blocks, unsigned int *offs,
0296           struct async_submit_ctl *submit)
0297 {
0298     struct dma_async_tx_descriptor *tx = NULL;
0299     struct page *p, *q, *dp, *dq;
0300     unsigned int p_off, q_off, dp_off, dq_off;
0301     struct page *srcs[2];
0302     unsigned int src_offs[2];
0303     unsigned char coef[2];
0304     enum async_tx_flags flags = submit->flags;
0305     dma_async_tx_callback cb_fn = submit->cb_fn;
0306     void *cb_param = submit->cb_param;
0307     void *scribble = submit->scribble;
0308
0309     p = blocks[disks-2];
0310     p_off = offs[disks-2];
0311     q = blocks[disks-1];
0312     q_off = offs[disks-1];
0313
0314     /* Compute syndrome with zero for the missing data pages
0315      * Use the dead data pages as temporary storage for
0316      * delta p and delta q
0317      */
0318     dp = blocks[faila];
0319     dp_off = offs[faila];
0320     blocks[faila] = NULL;
0321     blocks[disks-2] = dp;
0322     offs[disks-2] = dp_off;
0323     dq = blocks[failb];
0324     dq_off = offs[failb];
0325     blocks[failb] = NULL;
0326     blocks[disks-1] = dq;
0327     offs[disks-1] = dq_off;
0328
0329     init_async_submit(submit, ASYNC_TX_FENCE, tx, NULL, NULL, scribble);
0330     tx = async_gen_syndrome(blocks, offs, disks, bytes, submit);
0331
0332     /* Restore pointer table */
0333     blocks[faila]   = dp;
0334     offs[faila] = dp_off;
0335     blocks[failb]   = dq;
0336     offs[failb] = dq_off;
0337     blocks[disks-2] = p;
0338     offs[disks-2] = p_off;
0339     blocks[disks-1] = q;
0340     offs[disks-1] = q_off;
0341
0342     /* compute P + Pxy */
0343     srcs[0] = dp;
0344     src_offs[0] = dp_off;
0345     srcs[1] = p;
0346     src_offs[1] = p_off;
0347     init_async_submit(submit, ASYNC_TX_FENCE|ASYNC_TX_XOR_DROP_DST, tx,
0348               NULL, NULL, scribble);
0349     tx = async_xor_offs(dp, dp_off, srcs, src_offs, 2, bytes, submit);
0350
0351     /* compute Q + Qxy */
0352     srcs[0] = dq;
0353     src_offs[0] = dq_off;
0354     srcs[1] = q;
0355     src_offs[1] = q_off;
0356     init_async_submit(submit, ASYNC_TX_FENCE|ASYNC_TX_XOR_DROP_DST, tx,
0357               NULL, NULL, scribble);
0358     tx = async_xor_offs(dq, dq_off, srcs, src_offs, 2, bytes, submit);
0359
0360     /* Dx = A*(P+Pxy) + B*(Q+Qxy) */
0361     srcs[0] = dp;
0362     src_offs[0] = dp_off;
0363     srcs[1] = dq;
0364     src_offs[1] = dq_off;
0365     coef[0] = raid6_gfexi[failb-faila];
0366     coef[1] = raid6_gfinv[raid6_gfexp[faila]^raid6_gfexp[failb]];
0367     init_async_submit(submit, ASYNC_TX_FENCE, tx, NULL, NULL, scribble);
0368     tx = async_sum_product(dq, dq_off, srcs, src_offs, coef, bytes, submit);
0369
0370     /* Dy = P+Pxy+Dx */
0371     srcs[0] = dp;
0372     src_offs[0] = dp_off;
0373     srcs[1] = dq;
0374     src_offs[1] = dq_off;
0375     init_async_submit(submit, flags | ASYNC_TX_XOR_DROP_DST, tx, cb_fn,
0376               cb_param, scribble);
0377     tx = async_xor_offs(dp, dp_off, srcs, src_offs, 2, bytes, submit);
0378
0379     return tx;
0380 }
0381
0382 /**
0383  * async_raid6_2data_recov - asynchronously calculate two missing data blocks
0384  * @disks: number of disks in the RAID-6 array
0385  * @bytes: block size
0386  * @faila: first failed drive index
0387  * @failb: second failed drive index
0388  * @blocks: array of source pointers where the last two entries are p and q
0389  * @offs: array of offset for pages in blocks
0390  * @submit: submission/completion modifiers
0391  */
0392 struct dma_async_tx_descriptor *
0393 async_raid6_2data_recov(int disks, size_t bytes, int faila, int failb,
0394             struct page **blocks, unsigned int *offs,
0395             struct async_submit_ctl *submit)
0396 {
0397     void *scribble = submit->scribble;
0398     int non_zero_srcs, i;
0399
0400     BUG_ON(faila == failb);
0401     if (failb < faila)
0402         swap(faila, failb);
0403
0404     pr_debug("%s: disks: %d len: %zu\n", __func__, disks, bytes);
0405
0406     /* if a dma resource is not available or a scribble buffer is not
0407      * available punt to the synchronous path.  In the 'dma not
0408      * available' case be sure to use the scribble buffer to
0409      * preserve the content of 'blocks' as the caller intended.
0410      */
0411     if (!async_dma_find_channel(DMA_PQ) || !scribble) {
0412         void **ptrs = scribble ? scribble : (void **) blocks;
0413
0414         async_tx_quiesce(&submit->depend_tx);
0415         for (i = 0; i < disks; i++)
0416             if (blocks[i] == NULL)
0417                 ptrs[i] = (void *) raid6_empty_zero_page;
0418             else
0419                 ptrs[i] = page_address(blocks[i]) + offs[i];
0420
0421         raid6_2data_recov(disks, bytes, faila, failb, ptrs);
0422
0423         async_tx_sync_epilog(submit);
0424
0425         return NULL;
0426     }
0427
0428     non_zero_srcs = 0;
0429     for (i = 0; i < disks-2 && non_zero_srcs < 4; i++)
0430         if (blocks[i])
0431             non_zero_srcs++;
0432     switch (non_zero_srcs) {
0433     case 0:
0434     case 1:
0435         /* There must be at least 2 sources - the failed devices. */
0436         BUG();
0437
0438     case 2:
0439         /* dma devices do not uniformly understand a zero source pq
0440          * operation (in contrast to the synchronous case), so
0441          * explicitly handle the special case of a 4 disk array with
0442          * both data disks missing.
0443          */
0444         return __2data_recov_4(disks, bytes, faila, failb,
0445                 blocks, offs, submit);
0446     case 3:
0447         /* dma devices do not uniformly understand a single
0448          * source pq operation (in contrast to the synchronous
0449          * case), so explicitly handle the special case of a 5 disk
0450          * array with 2 of 3 data disks missing.
0451          */
0452         return __2data_recov_5(disks, bytes, faila, failb,
0453                 blocks, offs, submit);
0454     default:
0455         return __2data_recov_n(disks, bytes, faila, failb,
0456                 blocks, offs, submit);
0457     }
0458 }
0459 EXPORT_SYMBOL_GPL(async_raid6_2data_recov);
0460
0461 /**
0462  * async_raid6_datap_recov - asynchronously calculate a data and the 'p' block
0463  * @disks: number of disks in the RAID-6 array
0464  * @bytes: block size
0465  * @faila: failed drive index
0466  * @blocks: array of source pointers where the last two entries are p and q
0467  * @offs: array of offset for pages in blocks
0468  * @submit: submission/completion modifiers
0469  */
0470 struct dma_async_tx_descriptor *
0471 async_raid6_datap_recov(int disks, size_t bytes, int faila,
0472             struct page **blocks, unsigned int *offs,
0473             struct async_submit_ctl *submit)
0474 {
0475     struct dma_async_tx_descriptor *tx = NULL;
0476     struct page *p, *q, *dq;
0477     unsigned int p_off, q_off, dq_off;
0478     u8 coef;
0479     enum async_tx_flags flags = submit->flags;
0480     dma_async_tx_callback cb_fn = submit->cb_fn;
0481     void *cb_param = submit->cb_param;
0482     void *scribble = submit->scribble;
0483     int good_srcs, good, i;
0484     struct page *srcs[2];
0485     unsigned int src_offs[2];
0486
0487     pr_debug("%s: disks: %d len: %zu\n", __func__, disks, bytes);
0488
0489     /* if a dma resource is not available or a scribble buffer is not
0490      * available punt to the synchronous path.  In the 'dma not
0491      * available' case be sure to use the scribble buffer to
0492      * preserve the content of 'blocks' as the caller intended.
0493      */
0494     if (!async_dma_find_channel(DMA_PQ) || !scribble) {
0495         void **ptrs = scribble ? scribble : (void **) blocks;
0496
0497         async_tx_quiesce(&submit->depend_tx);
0498         for (i = 0; i < disks; i++)
0499             if (blocks[i] == NULL)
0500                 ptrs[i] = (void*)raid6_empty_zero_page;
0501             else
0502                 ptrs[i] = page_address(blocks[i]) + offs[i];
0503
0504         raid6_datap_recov(disks, bytes, faila, ptrs);
0505
0506         async_tx_sync_epilog(submit);
0507
0508         return NULL;
0509     }
0510
0511     good_srcs = 0;
0512     good = -1;
0513     for (i = 0; i < disks-2; i++) {
0514         if (i == faila)
0515             continue;
0516         if (blocks[i]) {
0517             good = i;
0518             good_srcs++;
0519             if (good_srcs > 1)
0520                 break;
0521         }
0522     }
0523     BUG_ON(good_srcs == 0);
0524
0525     p = blocks[disks-2];
0526     p_off = offs[disks-2];
0527     q = blocks[disks-1];
0528     q_off = offs[disks-1];
0529
0530     /* Compute syndrome with zero for the missing data page
0531      * Use the dead data page as temporary storage for delta q
0532      */
0533     dq = blocks[faila];
0534     dq_off = offs[faila];
0535     blocks[faila] = NULL;
0536     blocks[disks-1] = dq;
0537     offs[disks-1] = dq_off;
0538
0539     /* in the 4-disk case we only need to perform a single source
0540      * multiplication with the one good data block.
0541      */
0542     if (good_srcs == 1) {
0543         struct page *g = blocks[good];
0544         unsigned int g_off = offs[good];
0545
0546         init_async_submit(submit, ASYNC_TX_FENCE, tx, NULL, NULL,
0547                   scribble);
0548         tx = async_memcpy(p, g, p_off, g_off, bytes, submit);
0549
0550         init_async_submit(submit, ASYNC_TX_FENCE, tx, NULL, NULL,
0551                   scribble);
0552         tx = async_mult(dq, dq_off, g, g_off,
0553                 raid6_gfexp[good], bytes, submit);
0554     } else {
0555         init_async_submit(submit, ASYNC_TX_FENCE, tx, NULL, NULL,
0556                   scribble);
0557         tx = async_gen_syndrome(blocks, offs, disks, bytes, submit);
0558     }
0559
0560     /* Restore pointer table */
0561     blocks[faila]   = dq;
0562     offs[faila] = dq_off;
0563     blocks[disks-1] = q;
0564     offs[disks-1] = q_off;
0565
0566     /* calculate g^{-faila} */
0567     coef = raid6_gfinv[raid6_gfexp[faila]];
0568
0569     srcs[0] = dq;
0570     src_offs[0] = dq_off;
0571     srcs[1] = q;
0572     src_offs[1] = q_off;
0573     init_async_submit(submit, ASYNC_TX_FENCE|ASYNC_TX_XOR_DROP_DST, tx,
0574               NULL, NULL, scribble);
0575     tx = async_xor_offs(dq, dq_off, srcs, src_offs, 2, bytes, submit);
0576
0577     init_async_submit(submit, ASYNC_TX_FENCE, tx, NULL, NULL, scribble);
0578     tx = async_mult(dq, dq_off, dq, dq_off, coef, bytes, submit);
0579
0580     srcs[0] = p;
0581     src_offs[0] = p_off;
0582     srcs[1] = dq;
0583     src_offs[1] = dq_off;
0584     init_async_submit(submit, flags | ASYNC_TX_XOR_DROP_DST, tx, cb_fn,
0585               cb_param, scribble);
0586     tx = async_xor_offs(p, p_off, srcs, src_offs, 2, bytes, submit);
0587
0588     return tx;
0589 }
0590 EXPORT_SYMBOL_GPL(async_raid6_datap_recov);
0591
0592 MODULE_AUTHOR("Dan Williams <dan.j.williams@intel.com>");
0593 MODULE_DESCRIPTION("asynchronous RAID-6 recovery api");
0594 MODULE_LICENSE("GPL");