mm/bounce.c

   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
  25 static mempool_t *page_pool, *isa_page_pool;
  26
  27 #if defined(CONFIG_HIGHMEM) || defined(CONFIG_NEED_BOUNCE_POOL)
  28 static __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  */
  49 static 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  */
  71 static 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  */
  80 int 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  */
  98 static 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
 125 static 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
 150 static void bounce_end_io_write(struct bio *bio, int err)
 151 {
 152         bounce_end_io(bio, page_pool, err);
 153 }
 154
 155 static void bounce_end_io_write_isa(struct bio *bio, int err)
 156 {
 157
 158         bounce_end_io(bio, isa_page_pool, err);
 159 }
 160
 161 static 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
 171 static void bounce_end_io_read(struct bio *bio, int err)
 172 {
 173         __bounce_end_io_read(bio, page_pool, err);
 174 }
 175
 176 static 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
 182 static 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
 212 static int must_snapshot_stable_pages(struct request_queue *q, struct bio *bio)
 213 {
 214         return 0;
 215 }
 216 #endif /* CONFIG_NEED_BOUNCE_POOL */
 217
 218 static 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
 308 void 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
 341 EXPORT_SYMBOL(blk_queue_bounce);