summaryrefslogtreecommitdiffstats
path: root/fs/netfs/iterator.c
blob: 8a4c866874297c18bdf63ebcf878d8e5b313b586 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
// SPDX-License-Identifier: GPL-2.0-or-later
/* Iterator helpers.
 *
 * Copyright (C) 2022 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells (dhowells@redhat.com)
 */

#include <linux/export.h>
#include <linux/slab.h>
#include <linux/mm.h>
#include <linux/uio.h>
#include <linux/scatterlist.h>
#include <linux/netfs.h>
#include "internal.h"

/**
 * netfs_extract_user_iter - Extract the pages from a user iterator into a bvec
 * @orig: The original iterator
 * @orig_len: The amount of iterator to copy
 * @new: The iterator to be set up
 * @extraction_flags: Flags to qualify the request
 *
 * Extract the page fragments from the given amount of the source iterator and
 * build up a second iterator that refers to all of those bits.  This allows
 * the original iterator to disposed of.
 *
 * @extraction_flags can have ITER_ALLOW_P2PDMA set to request peer-to-peer DMA be
 * allowed on the pages extracted.
 *
 * On success, the number of elements in the bvec is returned, the original
 * iterator will have been advanced by the amount extracted.
 *
 * The iov_iter_extract_mode() function should be used to query how cleanup
 * should be performed.
 */
ssize_t netfs_extract_user_iter(struct iov_iter *orig, size_t orig_len,
				struct iov_iter *new,
				iov_iter_extraction_t extraction_flags)
{
	struct bio_vec *bv = NULL;
	struct page **pages;
	unsigned int cur_npages;
	unsigned int max_pages;
	unsigned int npages = 0;
	unsigned int i;
	ssize_t ret;
	size_t count = orig_len, offset, len;
	size_t bv_size, pg_size;

	if (WARN_ON_ONCE(!iter_is_ubuf(orig) && !iter_is_iovec(orig)))
		return -EIO;

	max_pages = iov_iter_npages(orig, INT_MAX);
	bv_size = array_size(max_pages, sizeof(*bv));
	bv = kvmalloc(bv_size, GFP_KERNEL);
	if (!bv)
		return -ENOMEM;

	/* Put the page list at the end of the bvec list storage.  bvec
	 * elements are larger than page pointers, so as long as we work
	 * 0->last, we should be fine.
	 */
	pg_size = array_size(max_pages, sizeof(*pages));
	pages = (void *)bv + bv_size - pg_size;

	while (count && npages < max_pages) {
		ret = iov_iter_extract_pages(orig, &pages, count,
					     max_pages - npages, extraction_flags,
					     &offset);
		if (ret < 0) {
			pr_err("Couldn't get user pages (rc=%zd)\n", ret);
			break;
		}

		if (ret > count) {
			pr_err("get_pages rc=%zd more than %zu\n", ret, count);
			break;
		}

		count -= ret;
		ret += offset;
		cur_npages = DIV_ROUND_UP(ret, PAGE_SIZE);

		if (npages + cur_npages > max_pages) {
			pr_err("Out of bvec array capacity (%u vs %u)\n",
			       npages + cur_npages, max_pages);
			break;
		}

		for (i = 0; i < cur_npages; i++) {
			len = ret > PAGE_SIZE ? PAGE_SIZE : ret;
			bvec_set_page(bv + npages + i, *pages++, len - offset, offset);
			ret -= len;
			offset = 0;
		}

		npages += cur_npages;
	}

	iov_iter_bvec(new, orig->data_source, bv, npages, orig_len - count);
	return npages;
}
EXPORT_SYMBOL_GPL(netfs_extract_user_iter);

/*
 * Extract and pin a list of up to sg_max pages from UBUF- or IOVEC-class
 * iterators, and add them to the scatterlist.
 */
static ssize_t netfs_extract_user_to_sg(struct iov_iter *iter,
					ssize_t maxsize,
					struct sg_table *sgtable,
					unsigned int sg_max,
					iov_iter_extraction_t extraction_flags)
{
	struct scatterlist *sg = sgtable->sgl + sgtable->nents;
	struct page **pages;
	unsigned int npages;
	ssize_t ret = 0, res;
	size_t len, off;

	/* We decant the page list into the tail of the scatterlist */
	pages = (void *)sgtable->sgl + array_size(sg_max, sizeof(struct scatterlist));
	pages -= sg_max;

	do {
		res = iov_iter_extract_pages(iter, &pages, maxsize, sg_max,
					     extraction_flags, &off);
		if (res < 0)
			goto failed;

		len = res;
		maxsize -= len;
		ret += len;
		npages = DIV_ROUND_UP(off + len, PAGE_SIZE);
		sg_max -= npages;

		for (; npages > 0; npages--) {
			struct page *page = *pages;
			size_t seg = min_t(size_t, PAGE_SIZE - off, len);

			*pages++ = NULL;
			sg_set_page(sg, page, seg, off);
			sgtable->nents++;
			sg++;
			len -= seg;
			off = 0;
		}
	} while (maxsize > 0 && sg_max > 0);

	return ret;

failed:
	while (sgtable->nents > sgtable->orig_nents)
		put_page(sg_page(&sgtable->sgl[--sgtable->nents]));
	return res;
}

/*
 * Extract up to sg_max pages from a BVEC-type iterator and add them to the
 * scatterlist.  The pages are not pinned.
 */
static ssize_t netfs_extract_bvec_to_sg(struct iov_iter *iter,
					ssize_t maxsize,
					struct sg_table *sgtable,
					unsigned int sg_max,
					iov_iter_extraction_t extraction_flags)
{
	const struct bio_vec *bv = iter->bvec;
	struct scatterlist *sg = sgtable->sgl + sgtable->nents;
	unsigned long start = iter->iov_offset;
	unsigned int i;
	ssize_t ret = 0;

	for (i = 0; i < iter->nr_segs; i++) {
		size_t off, len;

		len = bv[i].bv_len;
		if (start >= len) {
			start -= len;
			continue;
		}

		len = min_t(size_t, maxsize, len - start);
		off = bv[i].bv_offset + start;

		sg_set_page(sg, bv[i].bv_page, len, off);
		sgtable->nents++;
		sg++;
		sg_max--;

		ret += len;
		maxsize -= len;
		if (maxsize <= 0 || sg_max == 0)
			break;
		start = 0;
	}

	if (ret > 0)
		iov_iter_advance(iter, ret);
	return ret;
}

/*
 * Extract up to sg_max pages from a KVEC-type iterator and add them to the
 * scatterlist.  This can deal with vmalloc'd buffers as well as kmalloc'd or
 * static buffers.  The pages are not pinned.
 */
static ssize_t netfs_extract_kvec_to_sg(struct iov_iter *iter,
					ssize_t maxsize,
					struct sg_table *sgtable,
					unsigned int sg_max,
					iov_iter_extraction_t extraction_flags)
{
	const struct kvec *kv = iter->kvec;
	struct scatterlist *sg = sgtable->sgl + sgtable->nents;
	unsigned long start = iter->iov_offset;
	unsigned int i;
	ssize_t ret = 0;

	for (i = 0; i < iter->nr_segs; i++) {
		struct page *page;
		unsigned long kaddr;
		size_t off, len, seg;

		len = kv[i].iov_len;
		if (start >= len) {
			start -= len;
			continue;
		}

		kaddr = (unsigned long)kv[i].iov_base + start;
		off = kaddr & ~PAGE_MASK;
		len = min_t(size_t, maxsize, len - start);
		kaddr &= PAGE_MASK;

		maxsize -= len;
		ret += len;
		do {
			seg = min_t(size_t, len, PAGE_SIZE - off);
			if (is_vmalloc_or_module_addr((void *)kaddr))
				page = vmalloc_to_page((void *)kaddr);
			else
				page = virt_to_page(kaddr);

			sg_set_page(sg, page, len, off);
			sgtable->nents++;
			sg++;
			sg_max--;

			len -= seg;
			kaddr += PAGE_SIZE;
			off = 0;
		} while (len > 0 && sg_max > 0);

		if (maxsize <= 0 || sg_max == 0)
			break;
		start = 0;
	}

	if (ret > 0)
		iov_iter_advance(iter, ret);
	return ret;
}

/*
 * Extract up to sg_max folios from an XARRAY-type iterator and add them to
 * the scatterlist.  The pages are not pinned.
 */
static ssize_t netfs_extract_xarray_to_sg(struct iov_iter *iter,
					  ssize_t maxsize,
					  struct sg_table *sgtable,
					  unsigned int sg_max,
					  iov_iter_extraction_t extraction_flags)
{
	struct scatterlist *sg = sgtable->sgl + sgtable->nents;
	struct xarray *xa = iter->xarray;
	struct folio *folio;
	loff_t start = iter->xarray_start + iter->iov_offset;
	pgoff_t index = start / PAGE_SIZE;
	ssize_t ret = 0;
	size_t offset, len;
	XA_STATE(xas, xa, index);

	rcu_read_lock();

	xas_for_each(&xas, folio, ULONG_MAX) {
		if (xas_retry(&xas, folio))
			continue;
		if (WARN_ON(xa_is_value(folio)))
			break;
		if (WARN_ON(folio_test_hugetlb(folio)))
			break;

		offset = offset_in_folio(folio, start);
		len = min_t(size_t, maxsize, folio_size(folio) - offset);

		sg_set_page(sg, folio_page(folio, 0), len, offset);
		sgtable->nents++;
		sg++;
		sg_max--;

		maxsize -= len;
		ret += len;
		if (maxsize <= 0 || sg_max == 0)
			break;
	}

	rcu_read_unlock();
	if (ret > 0)
		iov_iter_advance(iter, ret);
	return ret;
}

/**
 * netfs_extract_iter_to_sg - Extract pages from an iterator and add ot an sglist
 * @iter: The iterator to extract from
 * @maxsize: The amount of iterator to copy
 * @sgtable: The scatterlist table to fill in
 * @sg_max: Maximum number of elements in @sgtable that may be filled
 * @extraction_flags: Flags to qualify the request
 *
 * Extract the page fragments from the given amount of the source iterator and
 * add them to a scatterlist that refers to all of those bits, to a maximum
 * addition of @sg_max elements.
 *
 * The pages referred to by UBUF- and IOVEC-type iterators are extracted and
 * pinned; BVEC-, KVEC- and XARRAY-type are extracted but aren't pinned; PIPE-
 * and DISCARD-type are not supported.
 *
 * No end mark is placed on the scatterlist; that's left to the caller.
 *
 * @extraction_flags can have ITER_ALLOW_P2PDMA set to request peer-to-peer DMA
 * be allowed on the pages extracted.
 *
 * If successul, @sgtable->nents is updated to include the number of elements
 * added and the number of bytes added is returned.  @sgtable->orig_nents is
 * left unaltered.
 *
 * The iov_iter_extract_mode() function should be used to query how cleanup
 * should be performed.
 */
ssize_t netfs_extract_iter_to_sg(struct iov_iter *iter, size_t maxsize,
				 struct sg_table *sgtable, unsigned int sg_max,
				 iov_iter_extraction_t extraction_flags)
{
	if (maxsize == 0)
		return 0;

	switch (iov_iter_type(iter)) {
	case ITER_UBUF:
	case ITER_IOVEC:
		return netfs_extract_user_to_sg(iter, maxsize, sgtable, sg_max,
						extraction_flags);
	case ITER_BVEC:
		return netfs_extract_bvec_to_sg(iter, maxsize, sgtable, sg_max,
						extraction_flags);
	case ITER_KVEC:
		return netfs_extract_kvec_to_sg(iter, maxsize, sgtable, sg_max,
						extraction_flags);
	case ITER_XARRAY:
		return netfs_extract_xarray_to_sg(iter, maxsize, sgtable, sg_max,
						  extraction_flags);
	default:
		pr_err("%s(%u) unsupported\n", __func__, iov_iter_type(iter));
		WARN_ON_ONCE(1);
		return -EIO;
	}
}
EXPORT_SYMBOL_GPL(netfs_extract_iter_to_sg);