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 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