xref: /linux/crypto/acompress.c (revision 184e56e77c06a7eef68a021e9d4b11a11a8ab096)
1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3  * Asynchronous Compression operations
4  *
5  * Copyright (c) 2016, Intel Corporation
6  * Authors: Weigang Li <weigang.li@intel.com>
7  *          Giovanni Cabiddu <giovanni.cabiddu@intel.com>
8  */
9 
10 #include <crypto/internal/acompress.h>
11 #include <crypto/scatterwalk.h>
12 #include <linux/cryptouser.h>
13 #include <linux/cpumask.h>
14 #include <linux/errno.h>
15 #include <linux/kernel.h>
16 #include <linux/module.h>
17 #include <linux/page-flags.h>
18 #include <linux/percpu.h>
19 #include <linux/scatterlist.h>
20 #include <linux/sched.h>
21 #include <linux/seq_file.h>
22 #include <linux/slab.h>
23 #include <linux/smp.h>
24 #include <linux/spinlock.h>
25 #include <linux/string.h>
26 #include <linux/workqueue.h>
27 #include <net/netlink.h>
28 
29 #include "compress.h"
30 
31 struct crypto_scomp;
32 
33 enum {
34 	ACOMP_WALK_SLEEP = 1 << 0,
35 	ACOMP_WALK_SRC_LINEAR = 1 << 1,
36 	ACOMP_WALK_SRC_FOLIO = 1 << 2,
37 	ACOMP_WALK_DST_LINEAR = 1 << 3,
38 	ACOMP_WALK_DST_FOLIO = 1 << 4,
39 };
40 
41 static const struct crypto_type crypto_acomp_type;
42 
43 static void acomp_reqchain_done(void *data, int err);
44 
45 static inline struct acomp_alg *__crypto_acomp_alg(struct crypto_alg *alg)
46 {
47 	return container_of(alg, struct acomp_alg, calg.base);
48 }
49 
50 static inline struct acomp_alg *crypto_acomp_alg(struct crypto_acomp *tfm)
51 {
52 	return __crypto_acomp_alg(crypto_acomp_tfm(tfm)->__crt_alg);
53 }
54 
55 static int __maybe_unused crypto_acomp_report(
56 	struct sk_buff *skb, struct crypto_alg *alg)
57 {
58 	struct crypto_report_acomp racomp;
59 
60 	memset(&racomp, 0, sizeof(racomp));
61 
62 	strscpy(racomp.type, "acomp", sizeof(racomp.type));
63 
64 	return nla_put(skb, CRYPTOCFGA_REPORT_ACOMP, sizeof(racomp), &racomp);
65 }
66 
67 static void crypto_acomp_show(struct seq_file *m, struct crypto_alg *alg)
68 	__maybe_unused;
69 
70 static void crypto_acomp_show(struct seq_file *m, struct crypto_alg *alg)
71 {
72 	seq_puts(m, "type         : acomp\n");
73 }
74 
75 static void crypto_acomp_exit_tfm(struct crypto_tfm *tfm)
76 {
77 	struct crypto_acomp *acomp = __crypto_acomp_tfm(tfm);
78 	struct acomp_alg *alg = crypto_acomp_alg(acomp);
79 
80 	if (alg->exit)
81 		alg->exit(acomp);
82 
83 	if (acomp_is_async(acomp))
84 		crypto_free_acomp(acomp->fb);
85 }
86 
87 static int crypto_acomp_init_tfm(struct crypto_tfm *tfm)
88 {
89 	struct crypto_acomp *acomp = __crypto_acomp_tfm(tfm);
90 	struct acomp_alg *alg = crypto_acomp_alg(acomp);
91 	struct crypto_acomp *fb = NULL;
92 	int err;
93 
94 	acomp->fb = acomp;
95 
96 	if (tfm->__crt_alg->cra_type != &crypto_acomp_type)
97 		return crypto_init_scomp_ops_async(tfm);
98 
99 	if (acomp_is_async(acomp)) {
100 		fb = crypto_alloc_acomp(crypto_acomp_alg_name(acomp), 0,
101 					CRYPTO_ALG_ASYNC);
102 		if (IS_ERR(fb))
103 			return PTR_ERR(fb);
104 
105 		err = -EINVAL;
106 		if (crypto_acomp_reqsize(fb) > MAX_SYNC_COMP_REQSIZE)
107 			goto out_free_fb;
108 
109 		acomp->fb = fb;
110 	}
111 
112 	acomp->compress = alg->compress;
113 	acomp->decompress = alg->decompress;
114 	acomp->reqsize = alg->reqsize;
115 
116 	acomp->base.exit = crypto_acomp_exit_tfm;
117 
118 	if (!alg->init)
119 		return 0;
120 
121 	err = alg->init(acomp);
122 	if (err)
123 		goto out_free_fb;
124 
125 	return 0;
126 
127 out_free_fb:
128 	crypto_free_acomp(fb);
129 	return err;
130 }
131 
132 static unsigned int crypto_acomp_extsize(struct crypto_alg *alg)
133 {
134 	int extsize = crypto_alg_extsize(alg);
135 
136 	if (alg->cra_type != &crypto_acomp_type)
137 		extsize += sizeof(struct crypto_scomp *);
138 
139 	return extsize;
140 }
141 
142 static const struct crypto_type crypto_acomp_type = {
143 	.extsize = crypto_acomp_extsize,
144 	.init_tfm = crypto_acomp_init_tfm,
145 #ifdef CONFIG_PROC_FS
146 	.show = crypto_acomp_show,
147 #endif
148 #if IS_ENABLED(CONFIG_CRYPTO_USER)
149 	.report = crypto_acomp_report,
150 #endif
151 	.maskclear = ~CRYPTO_ALG_TYPE_MASK,
152 	.maskset = CRYPTO_ALG_TYPE_ACOMPRESS_MASK,
153 	.type = CRYPTO_ALG_TYPE_ACOMPRESS,
154 	.tfmsize = offsetof(struct crypto_acomp, base),
155 };
156 
157 struct crypto_acomp *crypto_alloc_acomp(const char *alg_name, u32 type,
158 					u32 mask)
159 {
160 	return crypto_alloc_tfm(alg_name, &crypto_acomp_type, type, mask);
161 }
162 EXPORT_SYMBOL_GPL(crypto_alloc_acomp);
163 
164 struct crypto_acomp *crypto_alloc_acomp_node(const char *alg_name, u32 type,
165 					u32 mask, int node)
166 {
167 	return crypto_alloc_tfm_node(alg_name, &crypto_acomp_type, type, mask,
168 				node);
169 }
170 EXPORT_SYMBOL_GPL(crypto_alloc_acomp_node);
171 
172 static void acomp_save_req(struct acomp_req *req, crypto_completion_t cplt)
173 {
174 	struct acomp_req_chain *state = &req->chain;
175 
176 	state->compl = req->base.complete;
177 	state->data = req->base.data;
178 	req->base.complete = cplt;
179 	req->base.data = state;
180 	state->req0 = req;
181 }
182 
183 static void acomp_restore_req(struct acomp_req *req)
184 {
185 	struct acomp_req_chain *state = req->base.data;
186 
187 	req->base.complete = state->compl;
188 	req->base.data = state->data;
189 }
190 
191 static void acomp_reqchain_virt(struct acomp_req_chain *state, int err)
192 {
193 	struct acomp_req *req = state->cur;
194 	unsigned int slen = req->slen;
195 	unsigned int dlen = req->dlen;
196 
197 	req->base.err = err;
198 	state = &req->chain;
199 
200 	if (state->flags & CRYPTO_ACOMP_REQ_SRC_VIRT)
201 		acomp_request_set_src_dma(req, state->src, slen);
202 	else if (state->flags & CRYPTO_ACOMP_REQ_SRC_FOLIO)
203 		acomp_request_set_src_folio(req, state->sfolio, state->soff, slen);
204 	if (state->flags & CRYPTO_ACOMP_REQ_DST_VIRT)
205 		acomp_request_set_dst_dma(req, state->dst, dlen);
206 	else if (state->flags & CRYPTO_ACOMP_REQ_DST_FOLIO)
207 		acomp_request_set_dst_folio(req, state->dfolio, state->doff, dlen);
208 }
209 
210 static void acomp_virt_to_sg(struct acomp_req *req)
211 {
212 	struct acomp_req_chain *state = &req->chain;
213 
214 	state->flags = req->base.flags & (CRYPTO_ACOMP_REQ_SRC_VIRT |
215 					  CRYPTO_ACOMP_REQ_DST_VIRT |
216 					  CRYPTO_ACOMP_REQ_SRC_FOLIO |
217 					  CRYPTO_ACOMP_REQ_DST_FOLIO);
218 
219 	if (acomp_request_src_isvirt(req)) {
220 		unsigned int slen = req->slen;
221 		const u8 *svirt = req->svirt;
222 
223 		state->src = svirt;
224 		sg_init_one(&state->ssg, svirt, slen);
225 		acomp_request_set_src_sg(req, &state->ssg, slen);
226 	} else if (acomp_request_src_isfolio(req)) {
227 		struct folio *folio = req->sfolio;
228 		unsigned int slen = req->slen;
229 		size_t off = req->soff;
230 
231 		state->sfolio = folio;
232 		state->soff = off;
233 		sg_init_table(&state->ssg, 1);
234 		sg_set_page(&state->ssg, folio_page(folio, off / PAGE_SIZE),
235 			    slen, off % PAGE_SIZE);
236 		acomp_request_set_src_sg(req, &state->ssg, slen);
237 	}
238 
239 	if (acomp_request_dst_isvirt(req)) {
240 		unsigned int dlen = req->dlen;
241 		u8 *dvirt = req->dvirt;
242 
243 		state->dst = dvirt;
244 		sg_init_one(&state->dsg, dvirt, dlen);
245 		acomp_request_set_dst_sg(req, &state->dsg, dlen);
246 	} else if (acomp_request_dst_isfolio(req)) {
247 		struct folio *folio = req->dfolio;
248 		unsigned int dlen = req->dlen;
249 		size_t off = req->doff;
250 
251 		state->dfolio = folio;
252 		state->doff = off;
253 		sg_init_table(&state->dsg, 1);
254 		sg_set_page(&state->dsg, folio_page(folio, off / PAGE_SIZE),
255 			    dlen, off % PAGE_SIZE);
256 		acomp_request_set_src_sg(req, &state->dsg, dlen);
257 	}
258 }
259 
260 static int acomp_do_nondma(struct acomp_req_chain *state,
261 			   struct acomp_req *req)
262 {
263 	u32 keep = CRYPTO_ACOMP_REQ_SRC_VIRT |
264 		   CRYPTO_ACOMP_REQ_SRC_NONDMA |
265 		   CRYPTO_ACOMP_REQ_DST_VIRT |
266 		   CRYPTO_ACOMP_REQ_DST_NONDMA;
267 	ACOMP_REQUEST_ON_STACK(fbreq, crypto_acomp_reqtfm(req));
268 	int err;
269 
270 	acomp_request_set_callback(fbreq, req->base.flags, NULL, NULL);
271 	fbreq->base.flags &= ~keep;
272 	fbreq->base.flags |= req->base.flags & keep;
273 	fbreq->src = req->src;
274 	fbreq->dst = req->dst;
275 	fbreq->slen = req->slen;
276 	fbreq->dlen = req->dlen;
277 
278 	if (state->op == crypto_acomp_reqtfm(req)->compress)
279 		err = crypto_acomp_compress(fbreq);
280 	else
281 		err = crypto_acomp_decompress(fbreq);
282 
283 	req->dlen = fbreq->dlen;
284 	return err;
285 }
286 
287 static int acomp_do_one_req(struct acomp_req_chain *state,
288 			    struct acomp_req *req)
289 {
290 	state->cur = req;
291 
292 	if (acomp_request_isnondma(req))
293 		return acomp_do_nondma(state, req);
294 
295 	acomp_virt_to_sg(req);
296 	return state->op(req);
297 }
298 
299 static int acomp_reqchain_finish(struct acomp_req *req0, int err, u32 mask)
300 {
301 	struct acomp_req_chain *state = req0->base.data;
302 	struct acomp_req *req = state->cur;
303 	struct acomp_req *n;
304 
305 	acomp_reqchain_virt(state, err);
306 
307 	if (req != req0)
308 		list_add_tail(&req->base.list, &req0->base.list);
309 
310 	list_for_each_entry_safe(req, n, &state->head, base.list) {
311 		list_del_init(&req->base.list);
312 
313 		req->base.flags &= mask;
314 		req->base.complete = acomp_reqchain_done;
315 		req->base.data = state;
316 
317 		err = acomp_do_one_req(state, req);
318 
319 		if (err == -EINPROGRESS) {
320 			if (!list_empty(&state->head))
321 				err = -EBUSY;
322 			goto out;
323 		}
324 
325 		if (err == -EBUSY)
326 			goto out;
327 
328 		acomp_reqchain_virt(state, err);
329 		list_add_tail(&req->base.list, &req0->base.list);
330 	}
331 
332 	acomp_restore_req(req0);
333 
334 out:
335 	return err;
336 }
337 
338 static void acomp_reqchain_done(void *data, int err)
339 {
340 	struct acomp_req_chain *state = data;
341 	crypto_completion_t compl = state->compl;
342 
343 	data = state->data;
344 
345 	if (err == -EINPROGRESS) {
346 		if (!list_empty(&state->head))
347 			return;
348 		goto notify;
349 	}
350 
351 	err = acomp_reqchain_finish(state->req0, err,
352 				    CRYPTO_TFM_REQ_MAY_BACKLOG);
353 	if (err == -EBUSY)
354 		return;
355 
356 notify:
357 	compl(data, err);
358 }
359 
360 static int acomp_do_req_chain(struct acomp_req *req,
361 			      int (*op)(struct acomp_req *req))
362 {
363 	struct crypto_acomp *tfm = crypto_acomp_reqtfm(req);
364 	struct acomp_req_chain *state;
365 	int err;
366 
367 	if (crypto_acomp_req_chain(tfm) ||
368 	    (!acomp_request_chained(req) && acomp_request_issg(req)))
369 		return op(req);
370 
371 	acomp_save_req(req, acomp_reqchain_done);
372 	state = req->base.data;
373 
374 	state->op = op;
375 	state->src = NULL;
376 	INIT_LIST_HEAD(&state->head);
377 	list_splice_init(&req->base.list, &state->head);
378 
379 	err = acomp_do_one_req(state, req);
380 	if (err == -EBUSY || err == -EINPROGRESS)
381 		return -EBUSY;
382 
383 	return acomp_reqchain_finish(req, err, ~0);
384 }
385 
386 int crypto_acomp_compress(struct acomp_req *req)
387 {
388 	return acomp_do_req_chain(req, crypto_acomp_reqtfm(req)->compress);
389 }
390 EXPORT_SYMBOL_GPL(crypto_acomp_compress);
391 
392 int crypto_acomp_decompress(struct acomp_req *req)
393 {
394 	return acomp_do_req_chain(req, crypto_acomp_reqtfm(req)->decompress);
395 }
396 EXPORT_SYMBOL_GPL(crypto_acomp_decompress);
397 
398 void comp_prepare_alg(struct comp_alg_common *alg)
399 {
400 	struct crypto_alg *base = &alg->base;
401 
402 	base->cra_flags &= ~CRYPTO_ALG_TYPE_MASK;
403 }
404 
405 int crypto_register_acomp(struct acomp_alg *alg)
406 {
407 	struct crypto_alg *base = &alg->calg.base;
408 
409 	comp_prepare_alg(&alg->calg);
410 
411 	base->cra_type = &crypto_acomp_type;
412 	base->cra_flags |= CRYPTO_ALG_TYPE_ACOMPRESS;
413 
414 	return crypto_register_alg(base);
415 }
416 EXPORT_SYMBOL_GPL(crypto_register_acomp);
417 
418 void crypto_unregister_acomp(struct acomp_alg *alg)
419 {
420 	crypto_unregister_alg(&alg->base);
421 }
422 EXPORT_SYMBOL_GPL(crypto_unregister_acomp);
423 
424 int crypto_register_acomps(struct acomp_alg *algs, int count)
425 {
426 	int i, ret;
427 
428 	for (i = 0; i < count; i++) {
429 		ret = crypto_register_acomp(&algs[i]);
430 		if (ret)
431 			goto err;
432 	}
433 
434 	return 0;
435 
436 err:
437 	for (--i; i >= 0; --i)
438 		crypto_unregister_acomp(&algs[i]);
439 
440 	return ret;
441 }
442 EXPORT_SYMBOL_GPL(crypto_register_acomps);
443 
444 void crypto_unregister_acomps(struct acomp_alg *algs, int count)
445 {
446 	int i;
447 
448 	for (i = count - 1; i >= 0; --i)
449 		crypto_unregister_acomp(&algs[i]);
450 }
451 EXPORT_SYMBOL_GPL(crypto_unregister_acomps);
452 
453 static void acomp_stream_workfn(struct work_struct *work)
454 {
455 	struct crypto_acomp_streams *s =
456 		container_of(work, struct crypto_acomp_streams, stream_work);
457 	struct crypto_acomp_stream __percpu *streams = s->streams;
458 	int cpu;
459 
460 	for_each_cpu(cpu, &s->stream_want) {
461 		struct crypto_acomp_stream *ps;
462 		void *ctx;
463 
464 		ps = per_cpu_ptr(streams, cpu);
465 		if (ps->ctx)
466 			continue;
467 
468 		ctx = s->alloc_ctx();
469 		if (IS_ERR(ctx))
470 			break;
471 
472 		spin_lock_bh(&ps->lock);
473 		ps->ctx = ctx;
474 		spin_unlock_bh(&ps->lock);
475 
476 		cpumask_clear_cpu(cpu, &s->stream_want);
477 	}
478 }
479 
480 void crypto_acomp_free_streams(struct crypto_acomp_streams *s)
481 {
482 	struct crypto_acomp_stream __percpu *streams = s->streams;
483 	void (*free_ctx)(void *);
484 	int i;
485 
486 	cancel_work_sync(&s->stream_work);
487 	free_ctx = s->free_ctx;
488 
489 	for_each_possible_cpu(i) {
490 		struct crypto_acomp_stream *ps = per_cpu_ptr(streams, i);
491 
492 		if (!ps->ctx)
493 			continue;
494 
495 		free_ctx(ps->ctx);
496 	}
497 
498 	free_percpu(streams);
499 }
500 EXPORT_SYMBOL_GPL(crypto_acomp_free_streams);
501 
502 int crypto_acomp_alloc_streams(struct crypto_acomp_streams *s)
503 {
504 	struct crypto_acomp_stream __percpu *streams;
505 	struct crypto_acomp_stream *ps;
506 	unsigned int i;
507 	void *ctx;
508 
509 	if (s->streams)
510 		return 0;
511 
512 	streams = alloc_percpu(struct crypto_acomp_stream);
513 	if (!streams)
514 		return -ENOMEM;
515 
516 	ctx = s->alloc_ctx();
517 	if (IS_ERR(ctx)) {
518 		free_percpu(streams);
519 		return PTR_ERR(ctx);
520 	}
521 
522 	i = cpumask_first(cpu_possible_mask);
523 	ps = per_cpu_ptr(streams, i);
524 	ps->ctx = ctx;
525 
526 	for_each_possible_cpu(i) {
527 		ps = per_cpu_ptr(streams, i);
528 		spin_lock_init(&ps->lock);
529 	}
530 
531 	s->streams = streams;
532 
533 	INIT_WORK(&s->stream_work, acomp_stream_workfn);
534 	return 0;
535 }
536 EXPORT_SYMBOL_GPL(crypto_acomp_alloc_streams);
537 
538 struct crypto_acomp_stream *crypto_acomp_lock_stream_bh(
539 	struct crypto_acomp_streams *s) __acquires(stream)
540 {
541 	struct crypto_acomp_stream __percpu *streams = s->streams;
542 	int cpu = raw_smp_processor_id();
543 	struct crypto_acomp_stream *ps;
544 
545 	ps = per_cpu_ptr(streams, cpu);
546 	spin_lock_bh(&ps->lock);
547 	if (likely(ps->ctx))
548 		return ps;
549 	spin_unlock(&ps->lock);
550 
551 	cpumask_set_cpu(cpu, &s->stream_want);
552 	schedule_work(&s->stream_work);
553 
554 	ps = per_cpu_ptr(streams, cpumask_first(cpu_possible_mask));
555 	spin_lock(&ps->lock);
556 	return ps;
557 }
558 EXPORT_SYMBOL_GPL(crypto_acomp_lock_stream_bh);
559 
560 void acomp_walk_done_src(struct acomp_walk *walk, int used)
561 {
562 	walk->slen -= used;
563 	if ((walk->flags & ACOMP_WALK_SRC_LINEAR))
564 		scatterwalk_advance(&walk->in, used);
565 	else
566 		scatterwalk_done_src(&walk->in, used);
567 
568 	if ((walk->flags & ACOMP_WALK_SLEEP))
569 		cond_resched();
570 }
571 EXPORT_SYMBOL_GPL(acomp_walk_done_src);
572 
573 void acomp_walk_done_dst(struct acomp_walk *walk, int used)
574 {
575 	walk->dlen -= used;
576 	if ((walk->flags & ACOMP_WALK_DST_LINEAR))
577 		scatterwalk_advance(&walk->out, used);
578 	else
579 		scatterwalk_done_dst(&walk->out, used);
580 
581 	if ((walk->flags & ACOMP_WALK_SLEEP))
582 		cond_resched();
583 }
584 EXPORT_SYMBOL_GPL(acomp_walk_done_dst);
585 
586 int acomp_walk_next_src(struct acomp_walk *walk)
587 {
588 	unsigned int slen = walk->slen;
589 	unsigned int max = UINT_MAX;
590 
591 	if (!preempt_model_preemptible() && (walk->flags & ACOMP_WALK_SLEEP))
592 		max = PAGE_SIZE;
593 	if ((walk->flags & ACOMP_WALK_SRC_LINEAR)) {
594 		walk->in.__addr = (void *)(((u8 *)walk->in.sg) +
595 					   walk->in.offset);
596 		return min(slen, max);
597 	}
598 
599 	return slen ? scatterwalk_next(&walk->in, slen) : 0;
600 }
601 EXPORT_SYMBOL_GPL(acomp_walk_next_src);
602 
603 int acomp_walk_next_dst(struct acomp_walk *walk)
604 {
605 	unsigned int dlen = walk->dlen;
606 	unsigned int max = UINT_MAX;
607 
608 	if (!preempt_model_preemptible() && (walk->flags & ACOMP_WALK_SLEEP))
609 		max = PAGE_SIZE;
610 	if ((walk->flags & ACOMP_WALK_DST_LINEAR)) {
611 		walk->out.__addr = (void *)(((u8 *)walk->out.sg) +
612 					    walk->out.offset);
613 		return min(dlen, max);
614 	}
615 
616 	return dlen ? scatterwalk_next(&walk->out, dlen) : 0;
617 }
618 EXPORT_SYMBOL_GPL(acomp_walk_next_dst);
619 
620 int acomp_walk_virt(struct acomp_walk *__restrict walk,
621 		    struct acomp_req *__restrict req)
622 {
623 	struct scatterlist *src = req->src;
624 	struct scatterlist *dst = req->dst;
625 
626 	walk->slen = req->slen;
627 	walk->dlen = req->dlen;
628 
629 	if (!walk->slen || !walk->dlen)
630 		return -EINVAL;
631 
632 	walk->flags = 0;
633 	if ((req->base.flags & CRYPTO_TFM_REQ_MAY_SLEEP))
634 		walk->flags |= ACOMP_WALK_SLEEP;
635 	if ((req->base.flags & CRYPTO_ACOMP_REQ_SRC_VIRT))
636 		walk->flags |= ACOMP_WALK_SRC_LINEAR;
637 	else if ((req->base.flags & CRYPTO_ACOMP_REQ_SRC_FOLIO)) {
638 		src = &req->chain.ssg;
639 		sg_init_table(src, 1);
640 		sg_set_folio(src, req->sfolio, walk->slen, req->soff);
641 	}
642 	if ((req->base.flags & CRYPTO_ACOMP_REQ_DST_VIRT))
643 		walk->flags |= ACOMP_WALK_DST_LINEAR;
644 	else if ((req->base.flags & CRYPTO_ACOMP_REQ_DST_FOLIO)) {
645 		dst = &req->chain.dsg;
646 		sg_init_table(dst, 1);
647 		sg_set_folio(dst, req->dfolio, walk->dlen, req->doff);
648 	}
649 
650 	if ((walk->flags & ACOMP_WALK_SRC_LINEAR)) {
651 		walk->in.sg = (void *)req->svirt;
652 		walk->in.offset = 0;
653 	} else
654 		scatterwalk_start(&walk->in, src);
655 	if ((walk->flags & ACOMP_WALK_DST_LINEAR)) {
656 		walk->out.sg = (void *)req->dvirt;
657 		walk->out.offset = 0;
658 	} else
659 		scatterwalk_start(&walk->out, dst);
660 
661 	return 0;
662 }
663 EXPORT_SYMBOL_GPL(acomp_walk_virt);
664 
665 MODULE_LICENSE("GPL");
666 MODULE_DESCRIPTION("Asynchronous compression type");
667