block/bounce.c

   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 }