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, bio_orig->bi_size, err);
 144         bio_put(bio);
 145 }
 146
 147 static int bounce_end_io_write(struct bio *bio, unsigned int bytes_done, int err)
 148 {
 149         if (bio->bi_size)
 150                 return 1;
 151
 152         bounce_end_io(bio, page_pool, err);
 153         return 0;
 154 }
 155
 156 static int bounce_end_io_write_isa(struct bio *bio, unsigned int bytes_done, int err)
 157 {
 158         if (bio->bi_size)
 159                 return 1;
 160
 161         bounce_end_io(bio, isa_page_pool, err);
 162         return 0;
 163 }
 164
 165 static void __bounce_end_io_read(struct bio *bio, mempool_t *pool, int err)
 166 {
 167         struct bio *bio_orig = bio->bi_private;
 168
 169         if (test_bit(BIO_UPTODATE, &bio->bi_flags))
 170                 copy_to_high_bio_irq(bio_orig, bio);
 171
 172         bounce_end_io(bio, pool, err);
 173 }
 174
 175 static int bounce_end_io_read(struct bio *bio, unsigned int bytes_done, int err)
 176 {
 177         if (bio->bi_size)
 178                 return 1;
 179
 180         __bounce_end_io_read(bio, page_pool, err);
 181         return 0;
 182 }
 183
 184 static int bounce_end_io_read_isa(struct bio *bio, unsigned int bytes_done, int err)
 185 {
 186         if (bio->bi_size)
 187                 return 1;
 188
 189         __bounce_end_io_read(bio, isa_page_pool, err);
 190         return 0;
 191 }
 192
 193 static void __blk_queue_bounce(struct request_queue *q, struct bio **bio_orig,
 194                                mempool_t *pool)
 195 {
 196         struct page *page;
 197         struct bio *bio = NULL;
 198         int i, rw = bio_data_dir(*bio_orig);
 199         struct bio_vec *to, *from;
 200
 201         bio_for_each_segment(from, *bio_orig, i) {
 202                 page = from->bv_page;
 203
 204                 /*
 205                  * is destination page below bounce pfn?
 206                  */
 207                 if (page_to_pfn(page) <= q->bounce_pfn)
 208                         continue;
 209
 210                 /*
 211                  * irk, bounce it
 212                  */
 213                 if (!bio)
 214                         bio = bio_alloc(GFP_NOIO, (*bio_orig)->bi_vcnt);
 215
 216                 to = bio->bi_io_vec + i;
 217
 218                 to->bv_page = mempool_alloc(pool, q->bounce_gfp);
 219                 to->bv_len = from->bv_len;
 220                 to->bv_offset = from->bv_offset;
 221                 inc_zone_page_state(to->bv_page, NR_BOUNCE);
 222
 223                 if (rw == WRITE) {
 224                         char *vto, *vfrom;
 225
 226                         flush_dcache_page(from->bv_page);
 227                         vto = page_address(to->bv_page) + to->bv_offset;
 228                         vfrom = kmap(from->bv_page) + from->bv_offset;
 229                         memcpy(vto, vfrom, to->bv_len);
 230                         kunmap(from->bv_page);
 231                 }
 232         }
 233
 234         /*
 235          * no pages bounced
 236          */
 237         if (!bio)
 238                 return;
 239
 240         blk_add_trace_bio(q, *bio_orig, BLK_TA_BOUNCE);
 241
 242         /*
 243          * at least one page was bounced, fill in possible non-highmem
 244          * pages
 245          */
 246         __bio_for_each_segment(from, *bio_orig, i, 0) {
 247                 to = bio_iovec_idx(bio, i);
 248                 if (!to->bv_page) {
 249                         to->bv_page = from->bv_page;
 250                         to->bv_len = from->bv_len;
 251                         to->bv_offset = from->bv_offset;
 252                 }
 253         }
 254
 255         bio->bi_bdev = (*bio_orig)->bi_bdev;
 256         bio->bi_flags |= (1 << BIO_BOUNCED);
 257         bio->bi_sector = (*bio_orig)->bi_sector;
 258         bio->bi_rw = (*bio_orig)->bi_rw;
 259
 260         bio->bi_vcnt = (*bio_orig)->bi_vcnt;
 261         bio->bi_idx = (*bio_orig)->bi_idx;
 262         bio->bi_size = (*bio_orig)->bi_size;
 263
 264         if (pool == page_pool) {
 265                 bio->bi_end_io = bounce_end_io_write;
 266                 if (rw == READ)
 267                         bio->bi_end_io = bounce_end_io_read;
 268         } else {
 269                 bio->bi_end_io = bounce_end_io_write_isa;
 270                 if (rw == READ)
 271                         bio->bi_end_io = bounce_end_io_read_isa;
 272         }
 273
 274         bio->bi_private = *bio_orig;
 275         *bio_orig = bio;
 276 }
 277
 278 void blk_queue_bounce(struct request_queue *q, struct bio **bio_orig)
 279 {
 280         mempool_t *pool;
 281
 282         /*
 283          * for non-isa bounce case, just check if the bounce pfn is equal
 284          * to or bigger than the highest pfn in the system -- in that case,
 285          * don't waste time iterating over bio segments
 286          */
 287         if (!(q->bounce_gfp & GFP_DMA)) {
 288                 if (q->bounce_pfn >= blk_max_pfn)
 289                         return;
 290                 pool = page_pool;
 291         } else {
 292                 BUG_ON(!isa_page_pool);
 293                 pool = isa_page_pool;
 294         }
 295
 296         /*
 297          * slow path
 298          */
 299         __blk_queue_bounce(q, bio_orig, pool);
 300 }
 301
 302 EXPORT_SYMBOL(blk_queue_bounce);