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-integrity.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 #include "blk-cgroup.h"
27
28 #define POOL_SIZE 64
29 #define ISA_POOL_SIZE 16
30
31 static struct bio_set bounce_bio_set, bounce_bio_split;
32 static mempool_t page_pool;
33
34 static void init_bounce_bioset(void)
35 {
36 static bool bounce_bs_setup;
37 int ret;
38
39 if (bounce_bs_setup)
40 return;
41
42 ret = bioset_init(&bounce_bio_set, BIO_POOL_SIZE, 0, BIOSET_NEED_BVECS);
43 BUG_ON(ret);
44 if (bioset_integrity_create(&bounce_bio_set, BIO_POOL_SIZE))
45 BUG_ON(1);
46
47 ret = bioset_init(&bounce_bio_split, BIO_POOL_SIZE, 0, 0);
48 BUG_ON(ret);
49 bounce_bs_setup = true;
50 }
51
52 static __init int init_emergency_pool(void)
53 {
54 int ret;
55
56 #ifndef CONFIG_MEMORY_HOTPLUG
57 if (max_pfn <= max_low_pfn)
58 return 0;
59 #endif
60
61 ret = mempool_init_page_pool(&page_pool, POOL_SIZE, 0);
62 BUG_ON(ret);
63 pr_info("pool size: %d pages\n", POOL_SIZE);
64
65 init_bounce_bioset();
66 return 0;
67 }
68
69 __initcall(init_emergency_pool);
70
71 /*
72 * Simple bounce buffer support for highmem pages. Depending on the
73 * queue gfp mask set, *to may or may not be a highmem page. kmap it
74 * always, it will do the Right Thing
75 */
76 static void copy_to_high_bio_irq(struct bio *to, struct bio *from)
77 {
78 struct bio_vec tovec, fromvec;
79 struct bvec_iter iter;
80 /*
81 * The bio of @from is created by bounce, so we can iterate
82 * its bvec from start to end, but the @from->bi_iter can't be
83 * trusted because it might be changed by splitting.
84 */
85 struct bvec_iter from_iter = BVEC_ITER_ALL_INIT;
86
87 bio_for_each_segment(tovec, to, iter) {
88 fromvec = bio_iter_iovec(from, from_iter);
89 if (tovec.bv_page != fromvec.bv_page) {
90 /*
91 * fromvec->bv_offset and fromvec->bv_len might have
92 * been modified by the block layer, so use the original
93 * copy, bounce_copy_vec already uses tovec->bv_len
94 */
95 memcpy_to_bvec(&tovec, page_address(fromvec.bv_page) +
96 tovec.bv_offset);
97 }
98 bio_advance_iter(from, &from_iter, tovec.bv_len);
99 }
100 }
101
102 static void bounce_end_io(struct bio *bio)
103 {
104 struct bio *bio_orig = bio->bi_private;
105 struct bio_vec *bvec, orig_vec;
106 struct bvec_iter orig_iter = bio_orig->bi_iter;
107 struct bvec_iter_all iter_all;
108
109 /*
110 * free up bounce indirect pages used
111 */
112 bio_for_each_segment_all(bvec, bio, iter_all) {
113 orig_vec = bio_iter_iovec(bio_orig, orig_iter);
114 if (bvec->bv_page != orig_vec.bv_page) {
115 dec_zone_page_state(bvec->bv_page, NR_BOUNCE);
116 mempool_free(bvec->bv_page, &page_pool);
117 }
118 bio_advance_iter(bio_orig, &orig_iter, orig_vec.bv_len);
119 }
120
121 bio_orig->bi_status = bio->bi_status;
122 bio_endio(bio_orig);
123 bio_put(bio);
124 }
125
126 static void bounce_end_io_write(struct bio *bio)
127 {
128 bounce_end_io(bio);
129 }
130
131 static void bounce_end_io_read(struct bio *bio)
132 {
133 struct bio *bio_orig = bio->bi_private;
134
135 if (!bio->bi_status)
136 copy_to_high_bio_irq(bio_orig, bio);
137
138 bounce_end_io(bio);
139 }
140
141 static struct bio *bounce_clone_bio(struct bio *bio_src)
142 {
143 struct bvec_iter iter;
144 struct bio_vec bv;
145 struct bio *bio;
146
147 /*
148 * Pre immutable biovecs, __bio_clone() used to just do a memcpy from
149 * bio_src->bi_io_vec to bio->bi_io_vec.
150 *
151 * We can't do that anymore, because:
152 *
153 * - The point of cloning the biovec is to produce a bio with a biovec
154 * the caller can modify: bi_idx and bi_bvec_done should be 0.
155 *
156 * - The original bio could've had more than BIO_MAX_VECS biovecs; if
157 * we tried to clone the whole thing bio_alloc_bioset() would fail.
158 * But the clone should succeed as long as the number of biovecs we
159 * actually need to allocate is fewer than BIO_MAX_VECS.
160 *
161 * - Lastly, bi_vcnt should not be looked at or relied upon by code
162 * that does not own the bio - reason being drivers don't use it for
163 * iterating over the biovec anymore, so expecting it to be kept up
164 * to date (i.e. for clones that share the parent biovec) is just
165 * asking for trouble and would force extra work.
166 */
167 bio = bio_alloc_bioset(bio_src->bi_bdev, bio_segments(bio_src),
168 bio_src->bi_opf, GFP_NOIO, &bounce_bio_set);
169 if (bio_flagged(bio_src, BIO_REMAPPED))
170 bio_set_flag(bio, BIO_REMAPPED);
171 bio->bi_ioprio = bio_src->bi_ioprio;
172 bio->bi_write_hint = bio_src->bi_write_hint;
173 bio->bi_iter.bi_sector = bio_src->bi_iter.bi_sector;
174 bio->bi_iter.bi_size = bio_src->bi_iter.bi_size;
175
176 switch (bio_op(bio)) {
177 case REQ_OP_DISCARD:
178 case REQ_OP_SECURE_ERASE:
179 case REQ_OP_WRITE_ZEROES:
180 break;
181 default:
182 bio_for_each_segment(bv, bio_src, iter)
183 bio->bi_io_vec[bio->bi_vcnt++] = bv;
184 break;
185 }
186
187 if (bio_crypt_clone(bio, bio_src, GFP_NOIO) < 0)
188 goto err_put;
189
190 if (bio_integrity(bio_src) &&
191 bio_integrity_clone(bio, bio_src, GFP_NOIO) < 0)
192 goto err_put;
193
194 bio_clone_blkg_association(bio, bio_src);
195
196 return bio;
197
198 err_put:
199 bio_put(bio);
200 return NULL;
201 }
202
203 struct bio *__blk_queue_bounce(struct bio *bio_orig, struct request_queue *q)
204 {
205 struct bio *bio;
206 int rw = bio_data_dir(bio_orig);
207 struct bio_vec *to, from;
208 struct bvec_iter iter;
209 unsigned i = 0, bytes = 0;
210 bool bounce = false;
211 int sectors;
212
213 bio_for_each_segment(from, bio_orig, iter) {
214 if (i++ < BIO_MAX_VECS)
215 bytes += from.bv_len;
216 if (PageHighMem(from.bv_page))
217 bounce = true;
218 }
219 if (!bounce)
220 return bio_orig;
221
222 /*
223 * Individual bvecs might not be logical block aligned. Round down
224 * the split size so that each bio is properly block size aligned,
225 * even if we do not use the full hardware limits.
226 */
227 sectors = ALIGN_DOWN(bytes, queue_logical_block_size(q)) >>
228 SECTOR_SHIFT;
229 if (sectors < bio_sectors(bio_orig)) {
230 bio = bio_split(bio_orig, sectors, GFP_NOIO, &bounce_bio_split);
231 bio_chain(bio, bio_orig);
232 submit_bio_noacct(bio_orig);
233 bio_orig = bio;
234 }
235 bio = bounce_clone_bio(bio_orig);
236
237 /*
238 * Bvec table can't be updated by bio_for_each_segment_all(),
239 * so retrieve bvec from the table directly. This way is safe
240 * because the 'bio' is single-page bvec.
241 */
242 for (i = 0, to = bio->bi_io_vec; i < bio->bi_vcnt; to++, i++) {
243 struct page *bounce_page;
244
245 if (!PageHighMem(to->bv_page))
246 continue;
247
248 bounce_page = mempool_alloc(&page_pool, GFP_NOIO);
249 inc_zone_page_state(bounce_page, NR_BOUNCE);
250
251 if (rw == WRITE) {
252 flush_dcache_page(to->bv_page);
253 memcpy_from_bvec(page_address(bounce_page), to);
254 }
255 to->bv_page = bounce_page;
256 }
257
258 trace_block_bio_bounce(bio_orig);
259
260 bio->bi_flags |= (1 << BIO_BOUNCED);
261
262 if (rw == READ)
263 bio->bi_end_io = bounce_end_io_read;
264 else
265 bio->bi_end_io = bounce_end_io_write;
266
267 bio->bi_private = bio_orig;
268 return bio;
269 }
270
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