aboutsummaryrefslogtreecommitdiff
path: root/block/bounce.c
blob: d6a5219f29dd53b5fa7aa379d69a71aa5a087ebc (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
// SPDX-License-Identifier: GPL-2.0
/* bounce buffer handling for block devices
 *
 * - Split from highmem.c
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/mm.h>
#include <linux/export.h>
#include <linux/swap.h>
#include <linux/gfp.h>
#include <linux/bio.h>
#include <linux/pagemap.h>
#include <linux/mempool.h>
#include <linux/blkdev.h>
#include <linux/backing-dev.h>
#include <linux/init.h>
#include <linux/hash.h>
#include <linux/highmem.h>
#include <linux/printk.h>
#include <asm/tlbflush.h>

#include <trace/events/block.h>
#include "blk.h"
#include "blk-cgroup.h"

#define POOL_SIZE	64
#define ISA_POOL_SIZE	16

static struct bio_set bounce_bio_set, bounce_bio_split;
static mempool_t page_pool;

static void init_bounce_bioset(void)
{
	static bool bounce_bs_setup;
	int ret;

	if (bounce_bs_setup)
		return;

	ret = bioset_init(&bounce_bio_set, BIO_POOL_SIZE, 0, BIOSET_NEED_BVECS);
	BUG_ON(ret);
	if (bioset_integrity_create(&bounce_bio_set, BIO_POOL_SIZE))
		BUG_ON(1);

	ret = bioset_init(&bounce_bio_split, BIO_POOL_SIZE, 0, 0);
	BUG_ON(ret);
	bounce_bs_setup = true;
}

static __init int init_emergency_pool(void)
{
	int ret;

#ifndef CONFIG_MEMORY_HOTPLUG
	if (max_pfn <= max_low_pfn)
		return 0;
#endif

	ret = mempool_init_page_pool(&page_pool, POOL_SIZE, 0);
	BUG_ON(ret);
	pr_info("pool size: %d pages\n", POOL_SIZE);

	init_bounce_bioset();
	return 0;
}

__initcall(init_emergency_pool);

/*
 * Simple bounce buffer support for highmem pages. Depending on the
 * queue gfp mask set, *to may or may not be a highmem page. kmap it
 * always, it will do the Right Thing
 */
static void copy_to_high_bio_irq(struct bio *to, struct bio *from)
{
	struct bio_vec tovec, fromvec;
	struct bvec_iter iter;
	/*
	 * The bio of @from is created by bounce, so we can iterate
	 * its bvec from start to end, but the @from->bi_iter can't be
	 * trusted because it might be changed by splitting.
	 */
	struct bvec_iter from_iter = BVEC_ITER_ALL_INIT;

	bio_for_each_segment(tovec, to, iter) {
		fromvec = bio_iter_iovec(from, from_iter);
		if (tovec.bv_page != fromvec.bv_page) {
			/*
			 * fromvec->bv_offset and fromvec->bv_len might have
			 * been modified by the block layer, so use the original
			 * copy, bounce_copy_vec already uses tovec->bv_len
			 */
			memcpy_to_bvec(&tovec, page_address(fromvec.bv_page) +
				       tovec.bv_offset);
		}
		bio_advance_iter(from, &from_iter, tovec.bv_len);
	}
}

static void bounce_end_io(struct bio *bio)
{
	struct bio *bio_orig = bio->bi_private;
	struct bio_vec *bvec, orig_vec;
	struct bvec_iter orig_iter = bio_orig->bi_iter;
	struct bvec_iter_all iter_all;

	/*
	 * free up bounce indirect pages used
	 */
	bio_for_each_segment_all(bvec, bio, iter_all) {
		orig_vec = bio_iter_iovec(bio_orig, orig_iter);
		if (bvec->bv_page != orig_vec.bv_page) {
			dec_zone_page_state(bvec->bv_page, NR_BOUNCE);
			mempool_free(bvec->bv_page, &page_pool);
		}
		bio_advance_iter(bio_orig, &orig_iter, orig_vec.bv_len);
	}

	bio_orig->bi_status = bio->bi_status;
	bio_endio(bio_orig);
	bio_put(bio);
}

static void bounce_end_io_write(struct bio *bio)
{
	bounce_end_io(bio);
}

static void bounce_end_io_read(struct bio *bio)
{
	struct bio *bio_orig = bio->bi_private;

	if (!bio->bi_status)
		copy_to_high_bio_irq(bio_orig, bio);

	bounce_end_io(bio);
}

static struct bio *bounce_clone_bio(struct bio *bio_src)
{
	struct bvec_iter iter;
	struct bio_vec bv;
	struct bio *bio;

	/*
	 * Pre immutable biovecs, __bio_clone() used to just do a memcpy from
	 * bio_src->bi_io_vec to bio->bi_io_vec.
	 *
	 * We can't do that anymore, because:
	 *
	 *  - The point of cloning the biovec is to produce a bio with a biovec
	 *    the caller can modify: bi_idx and bi_bvec_done should be 0.
	 *
	 *  - The original bio could've had more than BIO_MAX_VECS biovecs; if
	 *    we tried to clone the whole thing bio_alloc_bioset() would fail.
	 *    But the clone should succeed as long as the number of biovecs we
	 *    actually need to allocate is fewer than BIO_MAX_VECS.
	 *
	 *  - Lastly, bi_vcnt should not be looked at or relied upon by code
	 *    that does not own the bio - reason being drivers don't use it for
	 *    iterating over the biovec anymore, so expecting it to be kept up
	 *    to date (i.e. for clones that share the parent biovec) is just
	 *    asking for trouble and would force extra work.
	 */
	bio = bio_alloc_bioset(bio_src->bi_bdev, bio_segments(bio_src),
			       bio_src->bi_opf, GFP_NOIO, &bounce_bio_set);
	if (bio_flagged(bio_src, BIO_REMAPPED))
		bio_set_flag(bio, BIO_REMAPPED);
	bio->bi_ioprio		= bio_src->bi_ioprio;
	bio->bi_write_hint	= bio_src->bi_write_hint;
	bio->bi_iter.bi_sector	= bio_src->bi_iter.bi_sector;
	bio->bi_iter.bi_size	= bio_src->bi_iter.bi_size;

	switch (bio_op(bio)) {
	case REQ_OP_DISCARD:
	case REQ_OP_SECURE_ERASE:
	case REQ_OP_WRITE_ZEROES:
		break;
	default:
		bio_for_each_segment(bv, bio_src, iter)
			bio->bi_io_vec[bio->bi_vcnt++] = bv;
		break;
	}

	if (bio_crypt_clone(bio, bio_src, GFP_NOIO) < 0)
		goto err_put;

	if (bio_integrity(bio_src) &&
	    bio_integrity_clone(bio, bio_src, GFP_NOIO) < 0)
		goto err_put;

	bio_clone_blkg_association(bio, bio_src);

	return bio;

err_put:
	bio_put(bio);
	return NULL;
}

struct bio *__blk_queue_bounce(struct bio *bio_orig, struct request_queue *q)
{
	struct bio *bio;
	int rw = bio_data_dir(bio_orig);
	struct bio_vec *to, from;
	struct bvec_iter iter;
	unsigned i = 0, bytes = 0;
	bool bounce = false;
	int sectors;

	bio_for_each_segment(from, bio_orig, iter) {
		if (i++ < BIO_MAX_VECS)
			bytes += from.bv_len;
		if (PageHighMem(from.bv_page))
			bounce = true;
	}
	if (!bounce)
		return bio_orig;

	/*
	 * Individual bvecs might not be logical block aligned. Round down
	 * the split size so that each bio is properly block size aligned,
	 * even if we do not use the full hardware limits.
	 */
	sectors = ALIGN_DOWN(bytes, queue_logical_block_size(q)) >>
			SECTOR_SHIFT;
	if (sectors < bio_sectors(bio_orig)) {
		bio = bio_split(bio_orig, sectors, GFP_NOIO, &bounce_bio_split);
		bio_chain(bio, bio_orig);
		submit_bio_noacct(bio_orig);
		bio_orig = bio;
	}
	bio = bounce_clone_bio(bio_orig);

	/*
	 * Bvec table can't be updated by bio_for_each_segment_all(),
	 * so retrieve bvec from the table directly. This way is safe
	 * because the 'bio' is single-page bvec.
	 */
	for (i = 0, to = bio->bi_io_vec; i < bio->bi_vcnt; to++, i++) {
		struct page *bounce_page;

		if (!PageHighMem(to->bv_page))
			continue;

		bounce_page = mempool_alloc(&page_pool, GFP_NOIO);
		inc_zone_page_state(bounce_page, NR_BOUNCE);

		if (rw == WRITE) {
			flush_dcache_page(to->bv_page);
			memcpy_from_bvec(page_address(bounce_page), to);
		}
		to->bv_page = bounce_page;
	}

	trace_block_bio_bounce(bio_orig);

	bio->bi_flags |= (1 << BIO_BOUNCED);

	if (rw == READ)
		bio->bi_end_io = bounce_end_io_read;
	else
		bio->bi_end_io = bounce_end_io_write;

	bio->bi_private = bio_orig;
	return bio;
}