linux/mm/bounce.c
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   1/* bounce buffer handling for block devices
   2 *
   3 * - Split from highmem.c
   4 */
   5
   6#include <linux/mm.h>
   7#include <linux/export.h>
   8#include <linux/swap.h>
   9#include <linux/gfp.h>
  10#include <linux/bio.h>
  11#include <linux/pagemap.h>
  12#include <linux/mempool.h>
  13#include <linux/blkdev.h>
  14#include <linux/init.h>
  15#include <linux/hash.h>
  16#include <linux/highmem.h>
  17#include <linux/bootmem.h>
  18#include <asm/tlbflush.h>
  19
  20#include <trace/events/block.h>
  21
  22#define POOL_SIZE       64
  23#define ISA_POOL_SIZE   16
  24
  25static mempool_t *page_pool, *isa_page_pool;
  26
  27#if defined(CONFIG_HIGHMEM) || defined(CONFIG_NEED_BOUNCE_POOL)
  28static __init int init_emergency_pool(void)
  29{
  30#if defined(CONFIG_HIGHMEM) && !defined(CONFIG_MEMORY_HOTPLUG)
  31        if (max_pfn <= max_low_pfn)
  32                return 0;
  33#endif
  34
  35        page_pool = mempool_create_page_pool(POOL_SIZE, 0);
  36        BUG_ON(!page_pool);
  37        printk("bounce pool size: %d pages\n", POOL_SIZE);
  38
  39        return 0;
  40}
  41
  42__initcall(init_emergency_pool);
  43#endif
  44
  45#ifdef CONFIG_HIGHMEM
  46/*
  47 * highmem version, map in to vec
  48 */
  49static void bounce_copy_vec(struct bio_vec *to, unsigned char *vfrom)
  50{
  51        unsigned long flags;
  52        unsigned char *vto;
  53
  54        local_irq_save(flags);
  55        vto = kmap_atomic(to->bv_page);
  56        memcpy(vto + to->bv_offset, vfrom, to->bv_len);
  57        kunmap_atomic(vto);
  58        local_irq_restore(flags);
  59}
  60
  61#else /* CONFIG_HIGHMEM */
  62
  63#define bounce_copy_vec(to, vfrom)      \
  64        memcpy(page_address((to)->bv_page) + (to)->bv_offset, vfrom, (to)->bv_len)
  65
  66#endif /* CONFIG_HIGHMEM */
  67
  68/*
  69 * allocate pages in the DMA region for the ISA pool
  70 */
  71static void *mempool_alloc_pages_isa(gfp_t gfp_mask, void *data)
  72{
  73        return mempool_alloc_pages(gfp_mask | GFP_DMA, data);
  74}
  75
  76/*
  77 * gets called "every" time someone init's a queue with BLK_BOUNCE_ISA
  78 * as the max address, so check if the pool has already been created.
  79 */
  80int init_emergency_isa_pool(void)
  81{
  82        if (isa_page_pool)
  83                return 0;
  84
  85        isa_page_pool = mempool_create(ISA_POOL_SIZE, mempool_alloc_pages_isa,
  86                                       mempool_free_pages, (void *) 0);
  87        BUG_ON(!isa_page_pool);
  88
  89        printk("isa bounce pool size: %d pages\n", ISA_POOL_SIZE);
  90        return 0;
  91}
  92
  93/*
  94 * Simple bounce buffer support for highmem pages. Depending on the
  95 * queue gfp mask set, *to may or may not be a highmem page. kmap it
  96 * always, it will do the Right Thing
  97 */
  98static void copy_to_high_bio_irq(struct bio *to, struct bio *from)
  99{
 100        unsigned char *vfrom;
 101        struct bio_vec *tovec, *fromvec;
 102        int i;
 103
 104        __bio_for_each_segment(tovec, to, i, 0) {
 105                fromvec = from->bi_io_vec + i;
 106
 107                /*
 108                 * not bounced
 109                 */
 110                if (tovec->bv_page == fromvec->bv_page)
 111                        continue;
 112
 113                /*
 114                 * fromvec->bv_offset and fromvec->bv_len might have been
 115                 * modified by the block layer, so use the original copy,
 116                 * bounce_copy_vec already uses tovec->bv_len
 117                 */
 118                vfrom = page_address(fromvec->bv_page) + tovec->bv_offset;
 119
 120                bounce_copy_vec(tovec, vfrom);
 121                flush_dcache_page(tovec->bv_page);
 122        }
 123}
 124
 125static void bounce_end_io(struct bio *bio, mempool_t *pool, int err)
 126{
 127        struct bio *bio_orig = bio->bi_private;
 128        struct bio_vec *bvec, *org_vec;
 129        int i;
 130
 131        if (test_bit(BIO_EOPNOTSUPP, &bio->bi_flags))
 132                set_bit(BIO_EOPNOTSUPP, &bio_orig->bi_flags);
 133
 134        /*
 135         * free up bounce indirect pages used
 136         */
 137        __bio_for_each_segment(bvec, bio, i, 0) {
 138                org_vec = bio_orig->bi_io_vec + i;
 139                if (bvec->bv_page == org_vec->bv_page)
 140                        continue;
 141
 142                dec_zone_page_state(bvec->bv_page, NR_BOUNCE);
 143                mempool_free(bvec->bv_page, pool);
 144        }
 145
 146        bio_endio(bio_orig, err);
 147        bio_put(bio);
 148}
 149
 150static void bounce_end_io_write(struct bio *bio, int err)
 151{
 152        bounce_end_io(bio, page_pool, err);
 153}
 154
 155static void bounce_end_io_write_isa(struct bio *bio, int err)
 156{
 157
 158        bounce_end_io(bio, isa_page_pool, err);
 159}
 160
 161static void __bounce_end_io_read(struct bio *bio, mempool_t *pool, int err)
 162{
 163        struct bio *bio_orig = bio->bi_private;
 164
 165        if (test_bit(BIO_UPTODATE, &bio->bi_flags))
 166                copy_to_high_bio_irq(bio_orig, bio);
 167
 168        bounce_end_io(bio, pool, err);
 169}
 170
 171static void bounce_end_io_read(struct bio *bio, int err)
 172{
 173        __bounce_end_io_read(bio, page_pool, err);
 174}
 175
 176static void bounce_end_io_read_isa(struct bio *bio, int err)
 177{
 178        __bounce_end_io_read(bio, isa_page_pool, err);
 179}
 180
 181#ifdef CONFIG_NEED_BOUNCE_POOL
 182static int must_snapshot_stable_pages(struct request_queue *q, struct bio *bio)
 183{
 184        struct page *page;
 185        struct backing_dev_info *bdi;
 186        struct address_space *mapping;
 187        struct bio_vec *from;
 188        int i;
 189
 190        if (bio_data_dir(bio) != WRITE)
 191                return 0;
 192
 193        if (!bdi_cap_stable_pages_required(&q->backing_dev_info))
 194                return 0;
 195
 196        /*
 197         * Based on the first page that has a valid mapping, decide whether or
 198         * not we have to employ bounce buffering to guarantee stable pages.
 199         */
 200        bio_for_each_segment(from, bio, i) {
 201                page = from->bv_page;
 202                mapping = page_mapping(page);
 203                if (!mapping)
 204                        continue;
 205                bdi = mapping->backing_dev_info;
 206                return mapping->host->i_sb->s_flags & MS_SNAP_STABLE;
 207        }
 208
 209        return 0;
 210}
 211#else
 212static int must_snapshot_stable_pages(struct request_queue *q, struct bio *bio)
 213{
 214        return 0;
 215}
 216#endif /* CONFIG_NEED_BOUNCE_POOL */
 217
 218static void __blk_queue_bounce(struct request_queue *q, struct bio **bio_orig,
 219                               mempool_t *pool, int force)
 220{
 221        struct page *page;
 222        struct bio *bio = NULL;
 223        int i, rw = bio_data_dir(*bio_orig);
 224        struct bio_vec *to, *from;
 225
 226        bio_for_each_segment(from, *bio_orig, i) {
 227                page = from->bv_page;
 228
 229                /*
 230                 * is destination page below bounce pfn?
 231                 */
 232                if (page_to_pfn(page) <= queue_bounce_pfn(q) && !force)
 233                        continue;
 234
 235                /*
 236                 * irk, bounce it
 237                 */
 238                if (!bio) {
 239                        unsigned int cnt = (*bio_orig)->bi_vcnt;
 240
 241                        bio = bio_alloc(GFP_NOIO, cnt);
 242                        memset(bio->bi_io_vec, 0, cnt * sizeof(struct bio_vec));
 243                }
 244                        
 245
 246                to = bio->bi_io_vec + i;
 247
 248                to->bv_page = mempool_alloc(pool, q->bounce_gfp);
 249                to->bv_len = from->bv_len;
 250                to->bv_offset = from->bv_offset;
 251                inc_zone_page_state(to->bv_page, NR_BOUNCE);
 252
 253                if (rw == WRITE) {
 254                        char *vto, *vfrom;
 255
 256                        flush_dcache_page(from->bv_page);
 257                        vto = page_address(to->bv_page) + to->bv_offset;
 258                        vfrom = kmap(from->bv_page) + from->bv_offset;
 259                        memcpy(vto, vfrom, to->bv_len);
 260                        kunmap(from->bv_page);
 261                }
 262        }
 263
 264        /*
 265         * no pages bounced
 266         */
 267        if (!bio)
 268                return;
 269
 270        trace_block_bio_bounce(q, *bio_orig);
 271
 272        /*
 273         * at least one page was bounced, fill in possible non-highmem
 274         * pages
 275         */
 276        __bio_for_each_segment(from, *bio_orig, i, 0) {
 277                to = bio_iovec_idx(bio, i);
 278                if (!to->bv_page) {
 279                        to->bv_page = from->bv_page;
 280                        to->bv_len = from->bv_len;
 281                        to->bv_offset = from->bv_offset;
 282                }
 283        }
 284
 285        bio->bi_bdev = (*bio_orig)->bi_bdev;
 286        bio->bi_flags |= (1 << BIO_BOUNCED);
 287        bio->bi_sector = (*bio_orig)->bi_sector;
 288        bio->bi_rw = (*bio_orig)->bi_rw;
 289
 290        bio->bi_vcnt = (*bio_orig)->bi_vcnt;
 291        bio->bi_idx = (*bio_orig)->bi_idx;
 292        bio->bi_size = (*bio_orig)->bi_size;
 293
 294        if (pool == page_pool) {
 295                bio->bi_end_io = bounce_end_io_write;
 296                if (rw == READ)
 297                        bio->bi_end_io = bounce_end_io_read;
 298        } else {
 299                bio->bi_end_io = bounce_end_io_write_isa;
 300                if (rw == READ)
 301                        bio->bi_end_io = bounce_end_io_read_isa;
 302        }
 303
 304        bio->bi_private = *bio_orig;
 305        *bio_orig = bio;
 306}
 307
 308void blk_queue_bounce(struct request_queue *q, struct bio **bio_orig)
 309{
 310        int must_bounce;
 311        mempool_t *pool;
 312
 313        /*
 314         * Data-less bio, nothing to bounce
 315         */
 316        if (!bio_has_data(*bio_orig))
 317                return;
 318
 319        must_bounce = must_snapshot_stable_pages(q, *bio_orig);
 320
 321        /*
 322         * for non-isa bounce case, just check if the bounce pfn is equal
 323         * to or bigger than the highest pfn in the system -- in that case,
 324         * don't waste time iterating over bio segments
 325         */
 326        if (!(q->bounce_gfp & GFP_DMA)) {
 327                if (queue_bounce_pfn(q) >= blk_max_pfn && !must_bounce)
 328                        return;
 329                pool = page_pool;
 330        } else {
 331                BUG_ON(!isa_page_pool);
 332                pool = isa_page_pool;
 333        }
 334
 335        /*
 336         * slow path
 337         */
 338        __blk_queue_bounce(q, bio_orig, pool, must_bounce);
 339}
 340
 341EXPORT_SYMBOL(blk_queue_bounce);
 342
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