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 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 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 */ 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 } 100 101 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 } 124 125 static void bounce_end_io_write(struct bio *bio) 126 { 127 bounce_end_io(bio); 128 } 129 130 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 } 139 140 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 } 208 209 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