1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3  * Asynchronous RAID-6 recovery calculations ASYNC_TX API.
4  * Copyright(c) 2009 Intel Corporation
5  *
6  * based on raid6recov.c:
7  *   Copyright 2002 H. Peter Anvin
8  */
9 #include <linux/kernel.h>
10 #include <linux/interrupt.h>
11 #include <linux/module.h>
12 #include <linux/dma-mapping.h>
13 #include <linux/raid/pq.h>
14 #include <linux/async_tx.h>
15 #include <linux/dmaengine.h>
16 
17 static struct dma_async_tx_descriptor *
async_sum_product(struct page * dest,unsigned int d_off,struct page ** srcs,unsigned int * src_offs,unsigned char * coef,size_t len,struct async_submit_ctl * submit)18 async_sum_product(struct page *dest, unsigned int d_off,
19 		struct page **srcs, unsigned int *src_offs, unsigned char *coef,
20 		size_t len, struct async_submit_ctl *submit)
21 {
22 	struct dma_chan *chan = async_tx_find_channel(submit, DMA_PQ,
23 						      &dest, 1, srcs, 2, len);
24 	struct dma_device *dma = chan ? chan->device : NULL;
25 	struct dmaengine_unmap_data *unmap = NULL;
26 	const u8 *amul, *bmul;
27 	u8 ax, bx;
28 	u8 *a, *b, *c;
29 
30 	if (dma)
31 		unmap = dmaengine_get_unmap_data(dma->dev, 3, GFP_NOWAIT);
32 
33 	if (unmap) {
34 		struct device *dev = dma->dev;
35 		dma_addr_t pq[2];
36 		struct dma_async_tx_descriptor *tx;
37 		enum dma_ctrl_flags dma_flags = DMA_PREP_PQ_DISABLE_P;
38 
39 		if (submit->flags & ASYNC_TX_FENCE)
40 			dma_flags |= DMA_PREP_FENCE;
41 		unmap->addr[0] = dma_map_page(dev, srcs[0], src_offs[0],
42 						len, DMA_TO_DEVICE);
43 		unmap->addr[1] = dma_map_page(dev, srcs[1], src_offs[1],
44 						len, DMA_TO_DEVICE);
45 		unmap->to_cnt = 2;
46 
47 		unmap->addr[2] = dma_map_page(dev, dest, d_off,
48 						len, DMA_BIDIRECTIONAL);
49 		unmap->bidi_cnt = 1;
50 		/* engine only looks at Q, but expects it to follow P */
51 		pq[1] = unmap->addr[2];
52 
53 		unmap->len = len;
54 		tx = dma->device_prep_dma_pq(chan, pq, unmap->addr, 2, coef,
55 					     len, dma_flags);
56 		if (tx) {
57 			dma_set_unmap(tx, unmap);
58 			async_tx_submit(chan, tx, submit);
59 			dmaengine_unmap_put(unmap);
60 			return tx;
61 		}
62 
63 		/* could not get a descriptor, unmap and fall through to
64 		 * the synchronous path
65 		 */
66 		dmaengine_unmap_put(unmap);
67 	}
68 
69 	/* run the operation synchronously */
70 	async_tx_quiesce(&submit->depend_tx);
71 	amul = raid6_gfmul[coef[0]];
72 	bmul = raid6_gfmul[coef[1]];
73 	a = page_address(srcs[0]) + src_offs[0];
74 	b = page_address(srcs[1]) + src_offs[1];
75 	c = page_address(dest) + d_off;
76 
77 	while (len--) {
78 		ax    = amul[*a++];
79 		bx    = bmul[*b++];
80 		*c++ = ax ^ bx;
81 	}
82 
83 	return NULL;
84 }
85 
86 static struct dma_async_tx_descriptor *
async_mult(struct page * dest,unsigned int d_off,struct page * src,unsigned int s_off,u8 coef,size_t len,struct async_submit_ctl * submit)87 async_mult(struct page *dest, unsigned int d_off, struct page *src,
88 		unsigned int s_off, u8 coef, size_t len,
89 		struct async_submit_ctl *submit)
90 {
91 	struct dma_chan *chan = async_tx_find_channel(submit, DMA_PQ,
92 						      &dest, 1, &src, 1, len);
93 	struct dma_device *dma = chan ? chan->device : NULL;
94 	struct dmaengine_unmap_data *unmap = NULL;
95 	const u8 *qmul; /* Q multiplier table */
96 	u8 *d, *s;
97 
98 	if (dma)
99 		unmap = dmaengine_get_unmap_data(dma->dev, 3, GFP_NOWAIT);
100 
101 	if (unmap) {
102 		dma_addr_t dma_dest[2];
103 		struct device *dev = dma->dev;
104 		struct dma_async_tx_descriptor *tx;
105 		enum dma_ctrl_flags dma_flags = DMA_PREP_PQ_DISABLE_P;
106 
107 		if (submit->flags & ASYNC_TX_FENCE)
108 			dma_flags |= DMA_PREP_FENCE;
109 		unmap->addr[0] = dma_map_page(dev, src, s_off,
110 						len, DMA_TO_DEVICE);
111 		unmap->to_cnt++;
112 		unmap->addr[1] = dma_map_page(dev, dest, d_off,
113 						len, DMA_BIDIRECTIONAL);
114 		dma_dest[1] = unmap->addr[1];
115 		unmap->bidi_cnt++;
116 		unmap->len = len;
117 
118 		/* this looks funny, but the engine looks for Q at
119 		 * dma_dest[1] and ignores dma_dest[0] as a dest
120 		 * due to DMA_PREP_PQ_DISABLE_P
121 		 */
122 		tx = dma->device_prep_dma_pq(chan, dma_dest, unmap->addr,
123 					     1, &coef, len, dma_flags);
124 
125 		if (tx) {
126 			dma_set_unmap(tx, unmap);
127 			dmaengine_unmap_put(unmap);
128 			async_tx_submit(chan, tx, submit);
129 			return tx;
130 		}
131 
132 		/* could not get a descriptor, unmap and fall through to
133 		 * the synchronous path
134 		 */
135 		dmaengine_unmap_put(unmap);
136 	}
137 
138 	/* no channel available, or failed to allocate a descriptor, so
139 	 * perform the operation synchronously
140 	 */
141 	async_tx_quiesce(&submit->depend_tx);
142 	qmul  = raid6_gfmul[coef];
143 	d = page_address(dest) + d_off;
144 	s = page_address(src) + s_off;
145 
146 	while (len--)
147 		*d++ = qmul[*s++];
148 
149 	return NULL;
150 }
151 
152 static struct dma_async_tx_descriptor *
__2data_recov_4(int disks,size_t bytes,int faila,int failb,struct page ** blocks,unsigned int * offs,struct async_submit_ctl * submit)153 __2data_recov_4(int disks, size_t bytes, int faila, int failb,
154 		struct page **blocks, unsigned int *offs,
155 		struct async_submit_ctl *submit)
156 {
157 	struct dma_async_tx_descriptor *tx = NULL;
158 	struct page *p, *q, *a, *b;
159 	unsigned int p_off, q_off, a_off, b_off;
160 	struct page *srcs[2];
161 	unsigned int src_offs[2];
162 	unsigned char coef[2];
163 	enum async_tx_flags flags = submit->flags;
164 	dma_async_tx_callback cb_fn = submit->cb_fn;
165 	void *cb_param = submit->cb_param;
166 	void *scribble = submit->scribble;
167 
168 	p = blocks[disks-2];
169 	p_off = offs[disks-2];
170 	q = blocks[disks-1];
171 	q_off = offs[disks-1];
172 
173 	a = blocks[faila];
174 	a_off = offs[faila];
175 	b = blocks[failb];
176 	b_off = offs[failb];
177 
178 	/* in the 4 disk case P + Pxy == P and Q + Qxy == Q */
179 	/* Dx = A*(P+Pxy) + B*(Q+Qxy) */
180 	srcs[0] = p;
181 	src_offs[0] = p_off;
182 	srcs[1] = q;
183 	src_offs[1] = q_off;
184 	coef[0] = raid6_gfexi[failb-faila];
185 	coef[1] = raid6_gfinv[raid6_gfexp[faila]^raid6_gfexp[failb]];
186 	init_async_submit(submit, ASYNC_TX_FENCE, tx, NULL, NULL, scribble);
187 	tx = async_sum_product(b, b_off, srcs, src_offs, coef, bytes, submit);
188 
189 	/* Dy = P+Pxy+Dx */
190 	srcs[0] = p;
191 	src_offs[0] = p_off;
192 	srcs[1] = b;
193 	src_offs[1] = b_off;
194 	init_async_submit(submit, flags | ASYNC_TX_XOR_ZERO_DST, tx, cb_fn,
195 			  cb_param, scribble);
196 	tx = async_xor_offs(a, a_off, srcs, src_offs, 2, bytes, submit);
197 
198 	return tx;
199 
200 }
201 
202 static struct dma_async_tx_descriptor *
__2data_recov_5(int disks,size_t bytes,int faila,int failb,struct page ** blocks,unsigned int * offs,struct async_submit_ctl * submit)203 __2data_recov_5(int disks, size_t bytes, int faila, int failb,
204 		struct page **blocks, unsigned int *offs,
205 		struct async_submit_ctl *submit)
206 {
207 	struct dma_async_tx_descriptor *tx = NULL;
208 	struct page *p, *q, *g, *dp, *dq;
209 	unsigned int p_off, q_off, g_off, dp_off, dq_off;
210 	struct page *srcs[2];
211 	unsigned int src_offs[2];
212 	unsigned char coef[2];
213 	enum async_tx_flags flags = submit->flags;
214 	dma_async_tx_callback cb_fn = submit->cb_fn;
215 	void *cb_param = submit->cb_param;
216 	void *scribble = submit->scribble;
217 	int good_srcs, good, i;
218 
219 	good_srcs = 0;
220 	good = -1;
221 	for (i = 0; i < disks-2; i++) {
222 		if (blocks[i] == NULL)
223 			continue;
224 		if (i == faila || i == failb)
225 			continue;
226 		good = i;
227 		good_srcs++;
228 	}
229 	BUG_ON(good_srcs > 1);
230 
231 	p = blocks[disks-2];
232 	p_off = offs[disks-2];
233 	q = blocks[disks-1];
234 	q_off = offs[disks-1];
235 	g = blocks[good];
236 	g_off = offs[good];
237 
238 	/* Compute syndrome with zero for the missing data pages
239 	 * Use the dead data pages as temporary storage for delta p and
240 	 * delta q
241 	 */
242 	dp = blocks[faila];
243 	dp_off = offs[faila];
244 	dq = blocks[failb];
245 	dq_off = offs[failb];
246 
247 	init_async_submit(submit, ASYNC_TX_FENCE, tx, NULL, NULL, scribble);
248 	tx = async_memcpy(dp, g, dp_off, g_off, bytes, submit);
249 	init_async_submit(submit, ASYNC_TX_FENCE, tx, NULL, NULL, scribble);
250 	tx = async_mult(dq, dq_off, g, g_off,
251 			raid6_gfexp[good], bytes, submit);
252 
253 	/* compute P + Pxy */
254 	srcs[0] = dp;
255 	src_offs[0] = dp_off;
256 	srcs[1] = p;
257 	src_offs[1] = p_off;
258 	init_async_submit(submit, ASYNC_TX_FENCE|ASYNC_TX_XOR_DROP_DST, tx,
259 			  NULL, NULL, scribble);
260 	tx = async_xor_offs(dp, dp_off, srcs, src_offs, 2, bytes, submit);
261 
262 	/* compute Q + Qxy */
263 	srcs[0] = dq;
264 	src_offs[0] = dq_off;
265 	srcs[1] = q;
266 	src_offs[1] = q_off;
267 	init_async_submit(submit, ASYNC_TX_FENCE|ASYNC_TX_XOR_DROP_DST, tx,
268 			  NULL, NULL, scribble);
269 	tx = async_xor_offs(dq, dq_off, srcs, src_offs, 2, bytes, submit);
270 
271 	/* Dx = A*(P+Pxy) + B*(Q+Qxy) */
272 	srcs[0] = dp;
273 	src_offs[0] = dp_off;
274 	srcs[1] = dq;
275 	src_offs[1] = dq_off;
276 	coef[0] = raid6_gfexi[failb-faila];
277 	coef[1] = raid6_gfinv[raid6_gfexp[faila]^raid6_gfexp[failb]];
278 	init_async_submit(submit, ASYNC_TX_FENCE, tx, NULL, NULL, scribble);
279 	tx = async_sum_product(dq, dq_off, srcs, src_offs, coef, bytes, submit);
280 
281 	/* Dy = P+Pxy+Dx */
282 	srcs[0] = dp;
283 	src_offs[0] = dp_off;
284 	srcs[1] = dq;
285 	src_offs[1] = dq_off;
286 	init_async_submit(submit, flags | ASYNC_TX_XOR_DROP_DST, tx, cb_fn,
287 			  cb_param, scribble);
288 	tx = async_xor_offs(dp, dp_off, srcs, src_offs, 2, bytes, submit);
289 
290 	return tx;
291 }
292 
293 static struct dma_async_tx_descriptor *
__2data_recov_n(int disks,size_t bytes,int faila,int failb,struct page ** blocks,unsigned int * offs,struct async_submit_ctl * submit)294 __2data_recov_n(int disks, size_t bytes, int faila, int failb,
295 	      struct page **blocks, unsigned int *offs,
296 		  struct async_submit_ctl *submit)
297 {
298 	struct dma_async_tx_descriptor *tx = NULL;
299 	struct page *p, *q, *dp, *dq;
300 	unsigned int p_off, q_off, dp_off, dq_off;
301 	struct page *srcs[2];
302 	unsigned int src_offs[2];
303 	unsigned char coef[2];
304 	enum async_tx_flags flags = submit->flags;
305 	dma_async_tx_callback cb_fn = submit->cb_fn;
306 	void *cb_param = submit->cb_param;
307 	void *scribble = submit->scribble;
308 
309 	p = blocks[disks-2];
310 	p_off = offs[disks-2];
311 	q = blocks[disks-1];
312 	q_off = offs[disks-1];
313 
314 	/* Compute syndrome with zero for the missing data pages
315 	 * Use the dead data pages as temporary storage for
316 	 * delta p and delta q
317 	 */
318 	dp = blocks[faila];
319 	dp_off = offs[faila];
320 	blocks[faila] = NULL;
321 	blocks[disks-2] = dp;
322 	offs[disks-2] = dp_off;
323 	dq = blocks[failb];
324 	dq_off = offs[failb];
325 	blocks[failb] = NULL;
326 	blocks[disks-1] = dq;
327 	offs[disks-1] = dq_off;
328 
329 	init_async_submit(submit, ASYNC_TX_FENCE, tx, NULL, NULL, scribble);
330 	tx = async_gen_syndrome(blocks, offs, disks, bytes, submit);
331 
332 	/* Restore pointer table */
333 	blocks[faila]   = dp;
334 	offs[faila] = dp_off;
335 	blocks[failb]   = dq;
336 	offs[failb] = dq_off;
337 	blocks[disks-2] = p;
338 	offs[disks-2] = p_off;
339 	blocks[disks-1] = q;
340 	offs[disks-1] = q_off;
341 
342 	/* compute P + Pxy */
343 	srcs[0] = dp;
344 	src_offs[0] = dp_off;
345 	srcs[1] = p;
346 	src_offs[1] = p_off;
347 	init_async_submit(submit, ASYNC_TX_FENCE|ASYNC_TX_XOR_DROP_DST, tx,
348 			  NULL, NULL, scribble);
349 	tx = async_xor_offs(dp, dp_off, srcs, src_offs, 2, bytes, submit);
350 
351 	/* compute Q + Qxy */
352 	srcs[0] = dq;
353 	src_offs[0] = dq_off;
354 	srcs[1] = q;
355 	src_offs[1] = q_off;
356 	init_async_submit(submit, ASYNC_TX_FENCE|ASYNC_TX_XOR_DROP_DST, tx,
357 			  NULL, NULL, scribble);
358 	tx = async_xor_offs(dq, dq_off, srcs, src_offs, 2, bytes, submit);
359 
360 	/* Dx = A*(P+Pxy) + B*(Q+Qxy) */
361 	srcs[0] = dp;
362 	src_offs[0] = dp_off;
363 	srcs[1] = dq;
364 	src_offs[1] = dq_off;
365 	coef[0] = raid6_gfexi[failb-faila];
366 	coef[1] = raid6_gfinv[raid6_gfexp[faila]^raid6_gfexp[failb]];
367 	init_async_submit(submit, ASYNC_TX_FENCE, tx, NULL, NULL, scribble);
368 	tx = async_sum_product(dq, dq_off, srcs, src_offs, coef, bytes, submit);
369 
370 	/* Dy = P+Pxy+Dx */
371 	srcs[0] = dp;
372 	src_offs[0] = dp_off;
373 	srcs[1] = dq;
374 	src_offs[1] = dq_off;
375 	init_async_submit(submit, flags | ASYNC_TX_XOR_DROP_DST, tx, cb_fn,
376 			  cb_param, scribble);
377 	tx = async_xor_offs(dp, dp_off, srcs, src_offs, 2, bytes, submit);
378 
379 	return tx;
380 }
381 
382 /**
383  * async_raid6_2data_recov - asynchronously calculate two missing data blocks
384  * @disks: number of disks in the RAID-6 array
385  * @bytes: block size
386  * @faila: first failed drive index
387  * @failb: second failed drive index
388  * @blocks: array of source pointers where the last two entries are p and q
389  * @offs: array of offset for pages in blocks
390  * @submit: submission/completion modifiers
391  */
392 struct dma_async_tx_descriptor *
async_raid6_2data_recov(int disks,size_t bytes,int faila,int failb,struct page ** blocks,unsigned int * offs,struct async_submit_ctl * submit)393 async_raid6_2data_recov(int disks, size_t bytes, int faila, int failb,
394 			struct page **blocks, unsigned int *offs,
395 			struct async_submit_ctl *submit)
396 {
397 	void *scribble = submit->scribble;
398 	int non_zero_srcs, i;
399 
400 	BUG_ON(faila == failb);
401 	if (failb < faila)
402 		swap(faila, failb);
403 
404 	pr_debug("%s: disks: %d len: %zu\n", __func__, disks, bytes);
405 
406 	/* if a dma resource is not available or a scribble buffer is not
407 	 * available punt to the synchronous path.  In the 'dma not
408 	 * available' case be sure to use the scribble buffer to
409 	 * preserve the content of 'blocks' as the caller intended.
410 	 */
411 	if (!async_dma_find_channel(DMA_PQ) || !scribble) {
412 		void **ptrs = scribble ? scribble : (void **) blocks;
413 
414 		async_tx_quiesce(&submit->depend_tx);
415 		for (i = 0; i < disks; i++)
416 			if (blocks[i] == NULL)
417 				ptrs[i] = (void *) raid6_empty_zero_page;
418 			else
419 				ptrs[i] = page_address(blocks[i]) + offs[i];
420 
421 		raid6_2data_recov(disks, bytes, faila, failb, ptrs);
422 
423 		async_tx_sync_epilog(submit);
424 
425 		return NULL;
426 	}
427 
428 	non_zero_srcs = 0;
429 	for (i = 0; i < disks-2 && non_zero_srcs < 4; i++)
430 		if (blocks[i])
431 			non_zero_srcs++;
432 	switch (non_zero_srcs) {
433 	case 0:
434 	case 1:
435 		/* There must be at least 2 sources - the failed devices. */
436 		BUG();
437 
438 	case 2:
439 		/* dma devices do not uniformly understand a zero source pq
440 		 * operation (in contrast to the synchronous case), so
441 		 * explicitly handle the special case of a 4 disk array with
442 		 * both data disks missing.
443 		 */
444 		return __2data_recov_4(disks, bytes, faila, failb,
445 				blocks, offs, submit);
446 	case 3:
447 		/* dma devices do not uniformly understand a single
448 		 * source pq operation (in contrast to the synchronous
449 		 * case), so explicitly handle the special case of a 5 disk
450 		 * array with 2 of 3 data disks missing.
451 		 */
452 		return __2data_recov_5(disks, bytes, faila, failb,
453 				blocks, offs, submit);
454 	default:
455 		return __2data_recov_n(disks, bytes, faila, failb,
456 				blocks, offs, submit);
457 	}
458 }
459 EXPORT_SYMBOL_GPL(async_raid6_2data_recov);
460 
461 /**
462  * async_raid6_datap_recov - asynchronously calculate a data and the 'p' block
463  * @disks: number of disks in the RAID-6 array
464  * @bytes: block size
465  * @faila: failed drive index
466  * @blocks: array of source pointers where the last two entries are p and q
467  * @offs: array of offset for pages in blocks
468  * @submit: submission/completion modifiers
469  */
470 struct dma_async_tx_descriptor *
async_raid6_datap_recov(int disks,size_t bytes,int faila,struct page ** blocks,unsigned int * offs,struct async_submit_ctl * submit)471 async_raid6_datap_recov(int disks, size_t bytes, int faila,
472 			struct page **blocks, unsigned int *offs,
473 			struct async_submit_ctl *submit)
474 {
475 	struct dma_async_tx_descriptor *tx = NULL;
476 	struct page *p, *q, *dq;
477 	unsigned int p_off, q_off, dq_off;
478 	u8 coef;
479 	enum async_tx_flags flags = submit->flags;
480 	dma_async_tx_callback cb_fn = submit->cb_fn;
481 	void *cb_param = submit->cb_param;
482 	void *scribble = submit->scribble;
483 	int good_srcs, good, i;
484 	struct page *srcs[2];
485 	unsigned int src_offs[2];
486 
487 	pr_debug("%s: disks: %d len: %zu\n", __func__, disks, bytes);
488 
489 	/* if a dma resource is not available or a scribble buffer is not
490 	 * available punt to the synchronous path.  In the 'dma not
491 	 * available' case be sure to use the scribble buffer to
492 	 * preserve the content of 'blocks' as the caller intended.
493 	 */
494 	if (!async_dma_find_channel(DMA_PQ) || !scribble) {
495 		void **ptrs = scribble ? scribble : (void **) blocks;
496 
497 		async_tx_quiesce(&submit->depend_tx);
498 		for (i = 0; i < disks; i++)
499 			if (blocks[i] == NULL)
500 				ptrs[i] = (void*)raid6_empty_zero_page;
501 			else
502 				ptrs[i] = page_address(blocks[i]) + offs[i];
503 
504 		raid6_datap_recov(disks, bytes, faila, ptrs);
505 
506 		async_tx_sync_epilog(submit);
507 
508 		return NULL;
509 	}
510 
511 	good_srcs = 0;
512 	good = -1;
513 	for (i = 0; i < disks-2; i++) {
514 		if (i == faila)
515 			continue;
516 		if (blocks[i]) {
517 			good = i;
518 			good_srcs++;
519 			if (good_srcs > 1)
520 				break;
521 		}
522 	}
523 	BUG_ON(good_srcs == 0);
524 
525 	p = blocks[disks-2];
526 	p_off = offs[disks-2];
527 	q = blocks[disks-1];
528 	q_off = offs[disks-1];
529 
530 	/* Compute syndrome with zero for the missing data page
531 	 * Use the dead data page as temporary storage for delta q
532 	 */
533 	dq = blocks[faila];
534 	dq_off = offs[faila];
535 	blocks[faila] = NULL;
536 	blocks[disks-1] = dq;
537 	offs[disks-1] = dq_off;
538 
539 	/* in the 4-disk case we only need to perform a single source
540 	 * multiplication with the one good data block.
541 	 */
542 	if (good_srcs == 1) {
543 		struct page *g = blocks[good];
544 		unsigned int g_off = offs[good];
545 
546 		init_async_submit(submit, ASYNC_TX_FENCE, tx, NULL, NULL,
547 				  scribble);
548 		tx = async_memcpy(p, g, p_off, g_off, bytes, submit);
549 
550 		init_async_submit(submit, ASYNC_TX_FENCE, tx, NULL, NULL,
551 				  scribble);
552 		tx = async_mult(dq, dq_off, g, g_off,
553 				raid6_gfexp[good], bytes, submit);
554 	} else {
555 		init_async_submit(submit, ASYNC_TX_FENCE, tx, NULL, NULL,
556 				  scribble);
557 		tx = async_gen_syndrome(blocks, offs, disks, bytes, submit);
558 	}
559 
560 	/* Restore pointer table */
561 	blocks[faila]   = dq;
562 	offs[faila] = dq_off;
563 	blocks[disks-1] = q;
564 	offs[disks-1] = q_off;
565 
566 	/* calculate g^{-faila} */
567 	coef = raid6_gfinv[raid6_gfexp[faila]];
568 
569 	srcs[0] = dq;
570 	src_offs[0] = dq_off;
571 	srcs[1] = q;
572 	src_offs[1] = q_off;
573 	init_async_submit(submit, ASYNC_TX_FENCE|ASYNC_TX_XOR_DROP_DST, tx,
574 			  NULL, NULL, scribble);
575 	tx = async_xor_offs(dq, dq_off, srcs, src_offs, 2, bytes, submit);
576 
577 	init_async_submit(submit, ASYNC_TX_FENCE, tx, NULL, NULL, scribble);
578 	tx = async_mult(dq, dq_off, dq, dq_off, coef, bytes, submit);
579 
580 	srcs[0] = p;
581 	src_offs[0] = p_off;
582 	srcs[1] = dq;
583 	src_offs[1] = dq_off;
584 	init_async_submit(submit, flags | ASYNC_TX_XOR_DROP_DST, tx, cb_fn,
585 			  cb_param, scribble);
586 	tx = async_xor_offs(p, p_off, srcs, src_offs, 2, bytes, submit);
587 
588 	return tx;
589 }
590 EXPORT_SYMBOL_GPL(async_raid6_datap_recov);
591 
592 MODULE_AUTHOR("Dan Williams <dan.j.williams@intel.com>");
593 MODULE_DESCRIPTION("asynchronous RAID-6 recovery api");
594 MODULE_LICENSE("GPL");
595