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