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