xref: /openbmc/linux/block/bounce.c (revision 51d798cd)
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 #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 
init_bounce_bioset(void)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 
init_emergency_pool(void)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  */
copy_to_high_bio_irq(struct bio * to,struct bio * from)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 
bounce_end_io(struct bio * bio)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 
bounce_end_io_write(struct bio * bio)126 static void bounce_end_io_write(struct bio *bio)
127 {
128 	bounce_end_io(bio);
129 }
130 
bounce_end_io_read(struct bio * bio)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 
bounce_clone_bio(struct bio * bio_src)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_iter.bi_sector	= bio_src->bi_iter.bi_sector;
173 	bio->bi_iter.bi_size	= bio_src->bi_iter.bi_size;
174 
175 	switch (bio_op(bio)) {
176 	case REQ_OP_DISCARD:
177 	case REQ_OP_SECURE_ERASE:
178 	case REQ_OP_WRITE_ZEROES:
179 		break;
180 	default:
181 		bio_for_each_segment(bv, bio_src, iter)
182 			bio->bi_io_vec[bio->bi_vcnt++] = bv;
183 		break;
184 	}
185 
186 	if (bio_crypt_clone(bio, bio_src, GFP_NOIO) < 0)
187 		goto err_put;
188 
189 	if (bio_integrity(bio_src) &&
190 	    bio_integrity_clone(bio, bio_src, GFP_NOIO) < 0)
191 		goto err_put;
192 
193 	bio_clone_blkg_association(bio, bio_src);
194 
195 	return bio;
196 
197 err_put:
198 	bio_put(bio);
199 	return NULL;
200 }
201 
__blk_queue_bounce(struct bio * bio_orig,struct request_queue * q)202 struct bio *__blk_queue_bounce(struct bio *bio_orig, struct request_queue *q)
203 {
204 	struct bio *bio;
205 	int rw = bio_data_dir(bio_orig);
206 	struct bio_vec *to, from;
207 	struct bvec_iter iter;
208 	unsigned i = 0, bytes = 0;
209 	bool bounce = false;
210 	int sectors;
211 
212 	bio_for_each_segment(from, bio_orig, iter) {
213 		if (i++ < BIO_MAX_VECS)
214 			bytes += from.bv_len;
215 		if (PageHighMem(from.bv_page))
216 			bounce = true;
217 	}
218 	if (!bounce)
219 		return bio_orig;
220 
221 	/*
222 	 * Individual bvecs might not be logical block aligned. Round down
223 	 * the split size so that each bio is properly block size aligned,
224 	 * even if we do not use the full hardware limits.
225 	 */
226 	sectors = ALIGN_DOWN(bytes, queue_logical_block_size(q)) >>
227 			SECTOR_SHIFT;
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 	return bio;
268 }
269