1// SPDX-License-Identifier: GPL-2.0
  2/*
  3 * Functions related to mapping data to requests
  4 */
  5#include <linux/kernel.h>
  6#include <linux/sched/task_stack.h>
  7#include <linux/module.h>
  8#include <linux/bio.h>
  9#include <linux/blkdev.h>
 10#include <linux/uio.h>
 11
 12#include "blk.h"
 13
 14struct bio_map_data {
 15	bool is_our_pages : 1;
 16	bool is_null_mapped : 1;
 17	struct iov_iter iter;
 18	struct iovec iov[];
 19};
 20
 21static struct bio_map_data *bio_alloc_map_data(struct iov_iter *data,
 22					       gfp_t gfp_mask)
 23{
 24	struct bio_map_data *bmd;
 25
 26	if (data->nr_segs > UIO_MAXIOV)
 27		return NULL;
 28
 29	bmd = kmalloc(struct_size(bmd, iov, data->nr_segs), gfp_mask);
 30	if (!bmd)
 31		return NULL;
 32	memcpy(bmd->iov, data->iov, sizeof(struct iovec) * data->nr_segs);
 33	bmd->iter = *data;
 34	bmd->iter.iov = bmd->iov;
 35	return bmd;
 36}
 37
 38/**
 39 * bio_copy_from_iter - copy all pages from iov_iter to bio
 40 * @bio: The &struct bio which describes the I/O as destination
 41 * @iter: iov_iter as source
 42 *
 43 * Copy all pages from iov_iter to bio.
 44 * Returns 0 on success, or error on failure.
 45 */
 46static int bio_copy_from_iter(struct bio *bio, struct iov_iter *iter)
 47{
 48	struct bio_vec *bvec;
 49	struct bvec_iter_all iter_all;
 50
 51	bio_for_each_segment_all(bvec, bio, iter_all) {
 52		ssize_t ret;
 53
 54		ret = copy_page_from_iter(bvec->bv_page,
 55					  bvec->bv_offset,
 56					  bvec->bv_len,
 57					  iter);
 58
 59		if (!iov_iter_count(iter))
 60			break;
 61
 62		if (ret < bvec->bv_len)
 63			return -EFAULT;
 64	}
 65
 66	return 0;
 67}
 68
 69/**
 70 * bio_copy_to_iter - copy all pages from bio to iov_iter
 71 * @bio: The &struct bio which describes the I/O as source
 72 * @iter: iov_iter as destination
 73 *
 74 * Copy all pages from bio to iov_iter.
 75 * Returns 0 on success, or error on failure.
 76 */
 77static int bio_copy_to_iter(struct bio *bio, struct iov_iter iter)
 78{
 79	struct bio_vec *bvec;
 80	struct bvec_iter_all iter_all;
 81
 82	bio_for_each_segment_all(bvec, bio, iter_all) {
 83		ssize_t ret;
 84
 85		ret = copy_page_to_iter(bvec->bv_page,
 86					bvec->bv_offset,
 87					bvec->bv_len,
 88					&iter);
 89
 90		if (!iov_iter_count(&iter))
 91			break;
 92
 93		if (ret < bvec->bv_len)
 94			return -EFAULT;
 95	}
 96
 97	return 0;
 98}
 99
100/**
101 *	bio_uncopy_user	-	finish previously mapped bio
102 *	@bio: bio being terminated
103 *
104 *	Free pages allocated from bio_copy_user_iov() and write back data
105 *	to user space in case of a read.
106 */
107static int bio_uncopy_user(struct bio *bio)
108{
109	struct bio_map_data *bmd = bio->bi_private;
110	int ret = 0;
111
112	if (!bmd->is_null_mapped) {
113		/*
114		 * if we're in a workqueue, the request is orphaned, so
115		 * don't copy into a random user address space, just free
116		 * and return -EINTR so user space doesn't expect any data.
117		 */
118		if (!current->mm)
119			ret = -EINTR;
120		else if (bio_data_dir(bio) == READ)
121			ret = bio_copy_to_iter(bio, bmd->iter);
122		if (bmd->is_our_pages)
123			bio_free_pages(bio);
124	}
125	kfree(bmd);
126	return ret;
127}
128
129static int bio_copy_user_iov(struct request *rq, struct rq_map_data *map_data,
130		struct iov_iter *iter, gfp_t gfp_mask)
131{
132	struct bio_map_data *bmd;
133	struct page *page;
134	struct bio *bio;
135	int i = 0, ret;
136	int nr_pages;
137	unsigned int len = iter->count;
138	unsigned int offset = map_data ? offset_in_page(map_data->offset) : 0;
139
140	bmd = bio_alloc_map_data(iter, gfp_mask);
141	if (!bmd)
142		return -ENOMEM;
143
144	/*
145	 * We need to do a deep copy of the iov_iter including the iovecs.
146	 * The caller provided iov might point to an on-stack or otherwise
147	 * shortlived one.
148	 */
149	bmd->is_our_pages = !map_data;
150	bmd->is_null_mapped = (map_data && map_data->null_mapped);
151
152	nr_pages = bio_max_segs(DIV_ROUND_UP(offset + len, PAGE_SIZE));
153
154	ret = -ENOMEM;
155	bio = bio_kmalloc(nr_pages, gfp_mask);
156	if (!bio)
157		goto out_bmd;
158	bio_init(bio, NULL, bio->bi_inline_vecs, nr_pages, req_op(rq));
159
160	if (map_data) {
161		nr_pages = 1U << map_data->page_order;
162		i = map_data->offset / PAGE_SIZE;
163	}
164	while (len) {
165		unsigned int bytes = PAGE_SIZE;
166
167		bytes -= offset;
168
169		if (bytes > len)
170			bytes = len;
171
172		if (map_data) {
173			if (i == map_data->nr_entries * nr_pages) {
174				ret = -ENOMEM;
175				goto cleanup;
176			}
177
178			page = map_data->pages[i / nr_pages];
179			page += (i % nr_pages);
180
181			i++;
182		} else {
183			page = alloc_page(GFP_NOIO | gfp_mask);
184			if (!page) {
185				ret = -ENOMEM;
186				goto cleanup;
 
187			}
 
188		}
189
190		if (bio_add_pc_page(rq->q, bio, page, bytes, offset) < bytes) {
191			if (!map_data)
192				__free_page(page);
193			break;
194		}
195
196		len -= bytes;
197		offset = 0;
198	}
199
200	if (map_data)
201		map_data->offset += bio->bi_iter.bi_size;
202
203	/*
204	 * success
205	 */
206	if ((iov_iter_rw(iter) == WRITE &&
207	     (!map_data || !map_data->null_mapped)) ||
208	    (map_data && map_data->from_user)) {
209		ret = bio_copy_from_iter(bio, iter);
210		if (ret)
211			goto cleanup;
212	} else {
213		if (bmd->is_our_pages)
214			zero_fill_bio(bio);
215		iov_iter_advance(iter, bio->bi_iter.bi_size);
216	}
217
218	bio->bi_private = bmd;
219
220	ret = blk_rq_append_bio(rq, bio);
221	if (ret)
222		goto cleanup;
223	return 0;
224cleanup:
225	if (!map_data)
226		bio_free_pages(bio);
227	bio_uninit(bio);
228	kfree(bio);
229out_bmd:
230	kfree(bmd);
231	return ret;
232}
233
234static void blk_mq_map_bio_put(struct bio *bio)
235{
236	if (bio->bi_opf & REQ_ALLOC_CACHE) {
237		bio_put(bio);
238	} else {
239		bio_uninit(bio);
240		kfree(bio);
241	}
242}
243
244static struct bio *blk_rq_map_bio_alloc(struct request *rq,
245		unsigned int nr_vecs, gfp_t gfp_mask)
246{
247	struct bio *bio;
248
249	if (rq->cmd_flags & REQ_POLLED) {
250		blk_opf_t opf = rq->cmd_flags | REQ_ALLOC_CACHE;
251
252		bio = bio_alloc_bioset(NULL, nr_vecs, opf, gfp_mask,
253					&fs_bio_set);
254		if (!bio)
255			return NULL;
256	} else {
257		bio = bio_kmalloc(nr_vecs, gfp_mask);
258		if (!bio)
259			return NULL;
260		bio_init(bio, NULL, bio->bi_inline_vecs, nr_vecs, req_op(rq));
261	}
262	return bio;
263}
 
264
265static int bio_map_user_iov(struct request *rq, struct iov_iter *iter,
266		gfp_t gfp_mask)
267{
268	unsigned int max_sectors = queue_max_hw_sectors(rq->q);
269	unsigned int nr_vecs = iov_iter_npages(iter, BIO_MAX_VECS);
270	unsigned int gup_flags = 0;
271	struct bio *bio;
272	int ret;
273	int j;
274
275	if (!iov_iter_count(iter))
276		return -EINVAL;
277
278	bio = blk_rq_map_bio_alloc(rq, nr_vecs, gfp_mask);
279	if (bio == NULL)
280		return -ENOMEM;
281
282	if (blk_queue_pci_p2pdma(rq->q))
283		gup_flags |= FOLL_PCI_P2PDMA;
284
285	while (iov_iter_count(iter)) {
286		struct page **pages, *stack_pages[UIO_FASTIOV];
287		ssize_t bytes;
288		size_t offs;
289		int npages;
290
291		if (nr_vecs <= ARRAY_SIZE(stack_pages)) {
292			pages = stack_pages;
293			bytes = iov_iter_get_pages(iter, pages, LONG_MAX,
294						   nr_vecs, &offs, gup_flags);
295		} else {
296			bytes = iov_iter_get_pages_alloc(iter, &pages,
297						LONG_MAX, &offs, gup_flags);
298		}
299		if (unlikely(bytes <= 0)) {
300			ret = bytes ? bytes : -EFAULT;
301			goto out_unmap;
302		}
303
304		npages = DIV_ROUND_UP(offs + bytes, PAGE_SIZE);
305
306		if (unlikely(offs & queue_dma_alignment(rq->q)))
307			j = 0;
308		else {
309			for (j = 0; j < npages; j++) {
310				struct page *page = pages[j];
311				unsigned int n = PAGE_SIZE - offs;
312				bool same_page = false;
313
314				if (n > bytes)
315					n = bytes;
316
317				if (!bio_add_hw_page(rq->q, bio, page, n, offs,
318						     max_sectors, &same_page)) {
319					if (same_page)
320						put_page(page);
321					break;
322				}
323
324				bytes -= n;
325				offs = 0;
326			}
327		}
328		/*
329		 * release the pages we didn't map into the bio, if any
330		 */
331		while (j < npages)
332			put_page(pages[j++]);
333		if (pages != stack_pages)
334			kvfree(pages);
335		/* couldn't stuff something into bio? */
336		if (bytes) {
337			iov_iter_revert(iter, bytes);
338			break;
339		}
340	}
341
342	ret = blk_rq_append_bio(rq, bio);
343	if (ret)
344		goto out_unmap;
345	return 0;
346
347 out_unmap:
348	bio_release_pages(bio, false);
349	blk_mq_map_bio_put(bio);
350	return ret;
351}
352
353static void bio_invalidate_vmalloc_pages(struct bio *bio)
 
 
354{
355#ifdef ARCH_IMPLEMENTS_FLUSH_KERNEL_VMAP_RANGE
356	if (bio->bi_private && !op_is_write(bio_op(bio))) {
357		unsigned long i, len = 0;
358
359		for (i = 0; i < bio->bi_vcnt; i++)
360			len += bio->bi_io_vec[i].bv_len;
361		invalidate_kernel_vmap_range(bio->bi_private, len);
362	}
363#endif
364}
365
366static void bio_map_kern_endio(struct bio *bio)
367{
368	bio_invalidate_vmalloc_pages(bio);
369	bio_uninit(bio);
370	kfree(bio);
371}
372
373/**
374 *	bio_map_kern	-	map kernel address into bio
375 *	@q: the struct request_queue for the bio
376 *	@data: pointer to buffer to map
377 *	@len: length in bytes
378 *	@gfp_mask: allocation flags for bio allocation
379 *
380 *	Map the kernel address into a bio suitable for io to a block
381 *	device. Returns an error pointer in case of error.
382 */
383static struct bio *bio_map_kern(struct request_queue *q, void *data,
384		unsigned int len, gfp_t gfp_mask)
385{
386	unsigned long kaddr = (unsigned long)data;
387	unsigned long end = (kaddr + len + PAGE_SIZE - 1) >> PAGE_SHIFT;
388	unsigned long start = kaddr >> PAGE_SHIFT;
389	const int nr_pages = end - start;
390	bool is_vmalloc = is_vmalloc_addr(data);
391	struct page *page;
392	int offset, i;
393	struct bio *bio;
394
395	bio = bio_kmalloc(nr_pages, gfp_mask);
396	if (!bio)
397		return ERR_PTR(-ENOMEM);
398	bio_init(bio, NULL, bio->bi_inline_vecs, nr_pages, 0);
399
400	if (is_vmalloc) {
401		flush_kernel_vmap_range(data, len);
402		bio->bi_private = data;
403	}
404
405	offset = offset_in_page(kaddr);
406	for (i = 0; i < nr_pages; i++) {
407		unsigned int bytes = PAGE_SIZE - offset;
408
409		if (len <= 0)
410			break;
411
412		if (bytes > len)
413			bytes = len;
414
415		if (!is_vmalloc)
416			page = virt_to_page(data);
417		else
418			page = vmalloc_to_page(data);
419		if (bio_add_pc_page(q, bio, page, bytes,
420				    offset) < bytes) {
421			/* we don't support partial mappings */
422			bio_uninit(bio);
423			kfree(bio);
424			return ERR_PTR(-EINVAL);
425		}
426
427		data += bytes;
428		len -= bytes;
429		offset = 0;
430	}
431
432	bio->bi_end_io = bio_map_kern_endio;
433	return bio;
434}
435
436static void bio_copy_kern_endio(struct bio *bio)
437{
438	bio_free_pages(bio);
439	bio_uninit(bio);
440	kfree(bio);
441}
442
443static void bio_copy_kern_endio_read(struct bio *bio)
444{
445	char *p = bio->bi_private;
446	struct bio_vec *bvec;
447	struct bvec_iter_all iter_all;
448
449	bio_for_each_segment_all(bvec, bio, iter_all) {
450		memcpy_from_bvec(p, bvec);
451		p += bvec->bv_len;
452	}
453
454	bio_copy_kern_endio(bio);
455}
456
457/**
458 *	bio_copy_kern	-	copy kernel address into bio
459 *	@q: the struct request_queue for the bio
460 *	@data: pointer to buffer to copy
461 *	@len: length in bytes
462 *	@gfp_mask: allocation flags for bio and page allocation
463 *	@reading: data direction is READ
464 *
465 *	copy the kernel address into a bio suitable for io to a block
466 *	device. Returns an error pointer in case of error.
467 */
468static struct bio *bio_copy_kern(struct request_queue *q, void *data,
469		unsigned int len, gfp_t gfp_mask, int reading)
470{
471	unsigned long kaddr = (unsigned long)data;
472	unsigned long end = (kaddr + len + PAGE_SIZE - 1) >> PAGE_SHIFT;
473	unsigned long start = kaddr >> PAGE_SHIFT;
474	struct bio *bio;
475	void *p = data;
476	int nr_pages = 0;
477
478	/*
479	 * Overflow, abort
 
480	 */
481	if (end < start)
482		return ERR_PTR(-EINVAL);
483
484	nr_pages = end - start;
485	bio = bio_kmalloc(nr_pages, gfp_mask);
486	if (!bio)
487		return ERR_PTR(-ENOMEM);
488	bio_init(bio, NULL, bio->bi_inline_vecs, nr_pages, 0);
489
490	while (len) {
491		struct page *page;
492		unsigned int bytes = PAGE_SIZE;
493
494		if (bytes > len)
495			bytes = len;
496
497		page = alloc_page(GFP_NOIO | __GFP_ZERO | gfp_mask);
498		if (!page)
499			goto cleanup;
500
501		if (!reading)
502			memcpy(page_address(page), p, bytes);
503
504		if (bio_add_pc_page(q, bio, page, bytes, 0) < bytes)
505			break;
506
507		len -= bytes;
508		p += bytes;
509	}
510
511	if (reading) {
512		bio->bi_end_io = bio_copy_kern_endio_read;
513		bio->bi_private = data;
514	} else {
515		bio->bi_end_io = bio_copy_kern_endio;
516	}
517
518	return bio;
519
520cleanup:
521	bio_free_pages(bio);
522	bio_uninit(bio);
523	kfree(bio);
524	return ERR_PTR(-ENOMEM);
525}
526
527/*
528 * Append a bio to a passthrough request.  Only works if the bio can be merged
529 * into the request based on the driver constraints.
530 */
531int blk_rq_append_bio(struct request *rq, struct bio *bio)
532{
533	struct bvec_iter iter;
534	struct bio_vec bv;
535	unsigned int nr_segs = 0;
536
537	bio_for_each_bvec(bv, bio, iter)
538		nr_segs++;
539
540	if (!rq->bio) {
541		blk_rq_bio_prep(rq, bio, nr_segs);
542	} else {
543		if (!ll_back_merge_fn(rq, bio, nr_segs))
544			return -EINVAL;
545		rq->biotail->bi_next = bio;
546		rq->biotail = bio;
547		rq->__data_len += (bio)->bi_iter.bi_size;
548		bio_crypt_free_ctx(bio);
549	}
 
550
551	return 0;
552}
553EXPORT_SYMBOL(blk_rq_append_bio);
554
555/* Prepare bio for passthrough IO given ITER_BVEC iter */
556static int blk_rq_map_user_bvec(struct request *rq, const struct iov_iter *iter)
557{
558	struct request_queue *q = rq->q;
559	size_t nr_iter = iov_iter_count(iter);
560	size_t nr_segs = iter->nr_segs;
561	struct bio_vec *bvecs, *bvprvp = NULL;
562	const struct queue_limits *lim = &q->limits;
563	unsigned int nsegs = 0, bytes = 0;
564	struct bio *bio;
565	size_t i;
566
567	if (!nr_iter || (nr_iter >> SECTOR_SHIFT) > queue_max_hw_sectors(q))
568		return -EINVAL;
569	if (nr_segs > queue_max_segments(q))
570		return -EINVAL;
571
572	/* no iovecs to alloc, as we already have a BVEC iterator */
573	bio = blk_rq_map_bio_alloc(rq, 0, GFP_KERNEL);
574	if (bio == NULL)
575		return -ENOMEM;
576
577	bio_iov_bvec_set(bio, (struct iov_iter *)iter);
578	blk_rq_bio_prep(rq, bio, nr_segs);
579
580	/* loop to perform a bunch of sanity checks */
581	bvecs = (struct bio_vec *)iter->bvec;
582	for (i = 0; i < nr_segs; i++) {
583		struct bio_vec *bv = &bvecs[i];
584
585		/*
586		 * If the queue doesn't support SG gaps and adding this
587		 * offset would create a gap, fallback to copy.
588		 */
589		if (bvprvp && bvec_gap_to_prev(lim, bvprvp, bv->bv_offset)) {
590			blk_mq_map_bio_put(bio);
591			return -EREMOTEIO;
592		}
593		/* check full condition */
594		if (nsegs >= nr_segs || bytes > UINT_MAX - bv->bv_len)
595			goto put_bio;
596		if (bytes + bv->bv_len > nr_iter)
597			goto put_bio;
598		if (bv->bv_offset + bv->bv_len > PAGE_SIZE)
599			goto put_bio;
600
601		nsegs++;
602		bytes += bv->bv_len;
603		bvprvp = bv;
604	}
605	return 0;
606put_bio:
607	blk_mq_map_bio_put(bio);
608	return -EINVAL;
609}
610
611/**
612 * blk_rq_map_user_iov - map user data to a request, for passthrough requests
613 * @q:		request queue where request should be inserted
614 * @rq:		request to map data to
615 * @map_data:   pointer to the rq_map_data holding pages (if necessary)
616 * @iter:	iovec iterator
617 * @gfp_mask:	memory allocation flags
618 *
619 * Description:
620 *    Data will be mapped directly for zero copy I/O, if possible. Otherwise
621 *    a kernel bounce buffer is used.
622 *
623 *    A matching blk_rq_unmap_user() must be issued at the end of I/O, while
624 *    still in process context.
 
 
 
 
 
 
625 */
626int blk_rq_map_user_iov(struct request_queue *q, struct request *rq,
627			struct rq_map_data *map_data,
628			const struct iov_iter *iter, gfp_t gfp_mask)
629{
630	bool copy = false, map_bvec = false;
631	unsigned long align = q->dma_pad_mask | queue_dma_alignment(q);
632	struct bio *bio = NULL;
633	struct iov_iter i;
634	int ret = -EINVAL;
635
 
 
 
636	if (map_data)
637		copy = true;
638	else if (blk_queue_may_bounce(q))
639		copy = true;
640	else if (iov_iter_alignment(iter) & align)
641		copy = true;
642	else if (iov_iter_is_bvec(iter))
643		map_bvec = true;
644	else if (!iter_is_iovec(iter))
645		copy = true;
646	else if (queue_virt_boundary(q))
647		copy = queue_virt_boundary(q) & iov_iter_gap_alignment(iter);
648
649	if (map_bvec) {
650		ret = blk_rq_map_user_bvec(rq, iter);
651		if (!ret)
652			return 0;
653		if (ret != -EREMOTEIO)
654			goto fail;
655		/* fall back to copying the data on limits mismatches */
656		copy = true;
657	}
658
659	i = *iter;
660	do {
661		if (copy)
662			ret = bio_copy_user_iov(rq, map_data, &i, gfp_mask);
663		else
664			ret = bio_map_user_iov(rq, &i, gfp_mask);
665		if (ret)
666			goto unmap_rq;
667		if (!bio)
668			bio = rq->bio;
669	} while (iov_iter_count(&i));
670
 
 
671	return 0;
672
673unmap_rq:
674	blk_rq_unmap_user(bio);
675fail:
676	rq->bio = NULL;
677	return ret;
678}
679EXPORT_SYMBOL(blk_rq_map_user_iov);
680
681int blk_rq_map_user(struct request_queue *q, struct request *rq,
682		    struct rq_map_data *map_data, void __user *ubuf,
683		    unsigned long len, gfp_t gfp_mask)
684{
685	struct iovec iov;
686	struct iov_iter i;
687	int ret = import_single_range(rq_data_dir(rq), ubuf, len, &iov, &i);
688
689	if (unlikely(ret < 0))
690		return ret;
691
692	return blk_rq_map_user_iov(q, rq, map_data, &i, gfp_mask);
693}
694EXPORT_SYMBOL(blk_rq_map_user);
695
696int blk_rq_map_user_io(struct request *req, struct rq_map_data *map_data,
697		void __user *ubuf, unsigned long buf_len, gfp_t gfp_mask,
698		bool vec, int iov_count, bool check_iter_count, int rw)
699{
700	int ret = 0;
701
702	if (vec) {
703		struct iovec fast_iov[UIO_FASTIOV];
704		struct iovec *iov = fast_iov;
705		struct iov_iter iter;
706
707		ret = import_iovec(rw, ubuf, iov_count ? iov_count : buf_len,
708				UIO_FASTIOV, &iov, &iter);
709		if (ret < 0)
710			return ret;
711
712		if (iov_count) {
713			/* SG_IO howto says that the shorter of the two wins */
714			iov_iter_truncate(&iter, buf_len);
715			if (check_iter_count && !iov_iter_count(&iter)) {
716				kfree(iov);
717				return -EINVAL;
718			}
719		}
720
721		ret = blk_rq_map_user_iov(req->q, req, map_data, &iter,
722				gfp_mask);
723		kfree(iov);
724	} else if (buf_len) {
725		ret = blk_rq_map_user(req->q, req, map_data, ubuf, buf_len,
726				gfp_mask);
727	}
728	return ret;
729}
730EXPORT_SYMBOL(blk_rq_map_user_io);
731
732/**
733 * blk_rq_unmap_user - unmap a request with user data
734 * @bio:	       start of bio list
735 *
736 * Description:
737 *    Unmap a rq previously mapped by blk_rq_map_user(). The caller must
738 *    supply the original rq->bio from the blk_rq_map_user() return, since
739 *    the I/O completion may have changed rq->bio.
740 */
741int blk_rq_unmap_user(struct bio *bio)
742{
743	struct bio *next_bio;
744	int ret = 0, ret2;
745
746	while (bio) {
747		if (bio->bi_private) {
748			ret2 = bio_uncopy_user(bio);
749			if (ret2 && !ret)
750				ret = ret2;
751		} else {
752			bio_release_pages(bio, bio_data_dir(bio) == READ);
753		}
754
755		next_bio = bio;
756		bio = bio->bi_next;
757		blk_mq_map_bio_put(next_bio);
758	}
759
760	return ret;
761}
762EXPORT_SYMBOL(blk_rq_unmap_user);
763
764/**
765 * blk_rq_map_kern - map kernel data to a request, for passthrough requests
766 * @q:		request queue where request should be inserted
767 * @rq:		request to fill
768 * @kbuf:	the kernel buffer
769 * @len:	length of user data
770 * @gfp_mask:	memory allocation flags
771 *
772 * Description:
773 *    Data will be mapped directly if possible. Otherwise a bounce
774 *    buffer is used. Can be called multiple times to append multiple
775 *    buffers.
776 */
777int blk_rq_map_kern(struct request_queue *q, struct request *rq, void *kbuf,
778		    unsigned int len, gfp_t gfp_mask)
779{
780	int reading = rq_data_dir(rq) == READ;
781	unsigned long addr = (unsigned long) kbuf;
782	struct bio *bio;
 
783	int ret;
784
785	if (len > (queue_max_hw_sectors(q) << 9))
786		return -EINVAL;
787	if (!len || !kbuf)
788		return -EINVAL;
789
790	if (!blk_rq_aligned(q, addr, len) || object_is_on_stack(kbuf) ||
791	    blk_queue_may_bounce(q))
792		bio = bio_copy_kern(q, kbuf, len, gfp_mask, reading);
793	else
794		bio = bio_map_kern(q, kbuf, len, gfp_mask);
795
796	if (IS_ERR(bio))
797		return PTR_ERR(bio);
798
799	bio->bi_opf &= ~REQ_OP_MASK;
800	bio->bi_opf |= req_op(rq);
801
802	ret = blk_rq_append_bio(rq, bio);
 
 
 
 
803	if (unlikely(ret)) {
804		bio_uninit(bio);
805		kfree(bio);
 
806	}
807	return ret;
 
808}
809EXPORT_SYMBOL(blk_rq_map_kern);