1 // SPDX-License-Identifier: GPL-2.0
2 /* bounce buffer handling for block devices
3 *
4 * - Split from highmem.c
5 */
6
7 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
8
9 #include <linux/mm.h>
10 #include <linux/export.h>
11 #include <linux/swap.h>
12 #include <linux/gfp.h>
13 #include <linux/bio.h>
14 #include <linux/pagemap.h>
15 #include <linux/mempool.h>
16 #include <linux/blkdev.h>
17 #include <linux/backing-dev.h>
18 #include <linux/init.h>
19 #include <linux/hash.h>
20 #include <linux/highmem.h>
21 #include <linux/printk.h>
22 #include <asm/tlbflush.h>
23
24 #include <trace/events/block.h>
25 #include "blk.h"
26
27 #define POOL_SIZE 64
28 #define ISA_POOL_SIZE 16
29
30 static struct bio_set bounce_bio_set, bounce_bio_split;
31 static mempool_t page_pool;
32
init_bounce_bioset(void)33 static void init_bounce_bioset(void)
34 {
35 static bool bounce_bs_setup;
36 int ret;
37
38 if (bounce_bs_setup)
39 return;
40
41 ret = bioset_init(&bounce_bio_set, BIO_POOL_SIZE, 0, BIOSET_NEED_BVECS);
42 BUG_ON(ret);
43 if (bioset_integrity_create(&bounce_bio_set, BIO_POOL_SIZE))
44 BUG_ON(1);
45
46 ret = bioset_init(&bounce_bio_split, BIO_POOL_SIZE, 0, 0);
47 BUG_ON(ret);
48 bounce_bs_setup = true;
49 }
50
init_emergency_pool(void)51 static __init int init_emergency_pool(void)
52 {
53 int ret;
54
55 #ifndef CONFIG_MEMORY_HOTPLUG
56 if (max_pfn <= max_low_pfn)
57 return 0;
58 #endif
59
60 ret = mempool_init_page_pool(&page_pool, POOL_SIZE, 0);
61 BUG_ON(ret);
62 pr_info("pool size: %d pages\n", POOL_SIZE);
63
64 init_bounce_bioset();
65 return 0;
66 }
67
68 __initcall(init_emergency_pool);
69
70 /*
71 * Simple bounce buffer support for highmem pages. Depending on the
72 * queue gfp mask set, *to may or may not be a highmem page. kmap it
73 * always, it will do the Right Thing
74 */
copy_to_high_bio_irq(struct bio * to,struct bio * from)75 static void copy_to_high_bio_irq(struct bio *to, struct bio *from)
76 {
77 struct bio_vec tovec, fromvec;
78 struct bvec_iter iter;
79 /*
80 * The bio of @from is created by bounce, so we can iterate
81 * its bvec from start to end, but the @from->bi_iter can't be
82 * trusted because it might be changed by splitting.
83 */
84 struct bvec_iter from_iter = BVEC_ITER_ALL_INIT;
85
86 bio_for_each_segment(tovec, to, iter) {
87 fromvec = bio_iter_iovec(from, from_iter);
88 if (tovec.bv_page != fromvec.bv_page) {
89 /*
90 * fromvec->bv_offset and fromvec->bv_len might have
91 * been modified by the block layer, so use the original
92 * copy, bounce_copy_vec already uses tovec->bv_len
93 */
94 memcpy_to_bvec(&tovec, page_address(fromvec.bv_page) +
95 tovec.bv_offset);
96 }
97 bio_advance_iter(from, &from_iter, tovec.bv_len);
98 }
99 }
100
bounce_end_io(struct bio * bio)101 static void bounce_end_io(struct bio *bio)
102 {
103 struct bio *bio_orig = bio->bi_private;
104 struct bio_vec *bvec, orig_vec;
105 struct bvec_iter orig_iter = bio_orig->bi_iter;
106 struct bvec_iter_all iter_all;
107
108 /*
109 * free up bounce indirect pages used
110 */
111 bio_for_each_segment_all(bvec, bio, iter_all) {
112 orig_vec = bio_iter_iovec(bio_orig, orig_iter);
113 if (bvec->bv_page != orig_vec.bv_page) {
114 dec_zone_page_state(bvec->bv_page, NR_BOUNCE);
115 mempool_free(bvec->bv_page, &page_pool);
116 }
117 bio_advance_iter(bio_orig, &orig_iter, orig_vec.bv_len);
118 }
119
120 bio_orig->bi_status = bio->bi_status;
121 bio_endio(bio_orig);
122 bio_put(bio);
123 }
124
bounce_end_io_write(struct bio * bio)125 static void bounce_end_io_write(struct bio *bio)
126 {
127 bounce_end_io(bio);
128 }
129
bounce_end_io_read(struct bio * bio)130 static void bounce_end_io_read(struct bio *bio)
131 {
132 struct bio *bio_orig = bio->bi_private;
133
134 if (!bio->bi_status)
135 copy_to_high_bio_irq(bio_orig, bio);
136
137 bounce_end_io(bio);
138 }
139
bounce_clone_bio(struct bio * bio_src)140 static struct bio *bounce_clone_bio(struct bio *bio_src)
141 {
142 struct bvec_iter iter;
143 struct bio_vec bv;
144 struct bio *bio;
145
146 /*
147 * Pre immutable biovecs, __bio_clone() used to just do a memcpy from
148 * bio_src->bi_io_vec to bio->bi_io_vec.
149 *
150 * We can't do that anymore, because:
151 *
152 * - The point of cloning the biovec is to produce a bio with a biovec
153 * the caller can modify: bi_idx and bi_bvec_done should be 0.
154 *
155 * - The original bio could've had more than BIO_MAX_VECS biovecs; if
156 * we tried to clone the whole thing bio_alloc_bioset() would fail.
157 * But the clone should succeed as long as the number of biovecs we
158 * actually need to allocate is fewer than BIO_MAX_VECS.
159 *
160 * - Lastly, bi_vcnt should not be looked at or relied upon by code
161 * that does not own the bio - reason being drivers don't use it for
162 * iterating over the biovec anymore, so expecting it to be kept up
163 * to date (i.e. for clones that share the parent biovec) is just
164 * asking for trouble and would force extra work on
165 * __bio_clone_fast() anyways.
166 */
167 bio = bio_alloc_bioset(GFP_NOIO, bio_segments(bio_src),
168 &bounce_bio_set);
169 bio->bi_bdev = bio_src->bi_bdev;
170 if (bio_flagged(bio_src, BIO_REMAPPED))
171 bio_set_flag(bio, BIO_REMAPPED);
172 bio->bi_opf = bio_src->bi_opf;
173 bio->bi_ioprio = bio_src->bi_ioprio;
174 bio->bi_write_hint = bio_src->bi_write_hint;
175 bio->bi_iter.bi_sector = bio_src->bi_iter.bi_sector;
176 bio->bi_iter.bi_size = bio_src->bi_iter.bi_size;
177
178 switch (bio_op(bio)) {
179 case REQ_OP_DISCARD:
180 case REQ_OP_SECURE_ERASE:
181 case REQ_OP_WRITE_ZEROES:
182 break;
183 case REQ_OP_WRITE_SAME:
184 bio->bi_io_vec[bio->bi_vcnt++] = bio_src->bi_io_vec[0];
185 break;
186 default:
187 bio_for_each_segment(bv, bio_src, iter)
188 bio->bi_io_vec[bio->bi_vcnt++] = bv;
189 break;
190 }
191
192 if (bio_crypt_clone(bio, bio_src, GFP_NOIO) < 0)
193 goto err_put;
194
195 if (bio_integrity(bio_src) &&
196 bio_integrity_clone(bio, bio_src, GFP_NOIO) < 0)
197 goto err_put;
198
199 bio_clone_blkg_association(bio, bio_src);
200 blkcg_bio_issue_init(bio);
201
202 return bio;
203
204 err_put:
205 bio_put(bio);
206 return NULL;
207 }
208
__blk_queue_bounce(struct request_queue * q,struct bio ** bio_orig)209 void __blk_queue_bounce(struct request_queue *q, struct bio **bio_orig)
210 {
211 struct bio *bio;
212 int rw = bio_data_dir(*bio_orig);
213 struct bio_vec *to, from;
214 struct bvec_iter iter;
215 unsigned i = 0;
216 bool bounce = false;
217 int sectors = 0;
218
219 bio_for_each_segment(from, *bio_orig, iter) {
220 if (i++ < BIO_MAX_VECS)
221 sectors += from.bv_len >> 9;
222 if (PageHighMem(from.bv_page))
223 bounce = true;
224 }
225 if (!bounce)
226 return;
227
228 if (sectors < bio_sectors(*bio_orig)) {
229 bio = bio_split(*bio_orig, sectors, GFP_NOIO, &bounce_bio_split);
230 bio_chain(bio, *bio_orig);
231 submit_bio_noacct(*bio_orig);
232 *bio_orig = bio;
233 }
234 bio = bounce_clone_bio(*bio_orig);
235
236 /*
237 * Bvec table can't be updated by bio_for_each_segment_all(),
238 * so retrieve bvec from the table directly. This way is safe
239 * because the 'bio' is single-page bvec.
240 */
241 for (i = 0, to = bio->bi_io_vec; i < bio->bi_vcnt; to++, i++) {
242 struct page *bounce_page;
243
244 if (!PageHighMem(to->bv_page))
245 continue;
246
247 bounce_page = mempool_alloc(&page_pool, GFP_NOIO);
248 inc_zone_page_state(bounce_page, NR_BOUNCE);
249
250 if (rw == WRITE) {
251 flush_dcache_page(to->bv_page);
252 memcpy_from_bvec(page_address(bounce_page), to);
253 }
254 to->bv_page = bounce_page;
255 }
256
257 trace_block_bio_bounce(*bio_orig);
258
259 bio->bi_flags |= (1 << BIO_BOUNCED);
260
261 if (rw == READ)
262 bio->bi_end_io = bounce_end_io_read;
263 else
264 bio->bi_end_io = bounce_end_io_write;
265
266 bio->bi_private = *bio_orig;
267 *bio_orig = bio;
268 }
269
