block/bounce.c

   1 /* bounce buffer handling for block devices
   2  *
   3  * - Split from highmem.c
   4  */
   5
   6 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
   7
   8 #include <linux/mm.h>
   9 #include <linux/export.h>
  10 #include <linux/swap.h>
  11 #include <linux/gfp.h>
  12 #include <linux/bio.h>
  13 #include <linux/pagemap.h>
  14 #include <linux/mempool.h>
  15 #include <linux/blkdev.h>
  16 #include <linux/backing-dev.h>
  17 #include <linux/init.h>
  18 #include <linux/hash.h>
  19 #include <linux/highmem.h>
  20 #include <linux/bootmem.h>
  21 #include <linux/printk.h>
  22 #include <asm/tlbflush.h>
  23
  24 #include <trace/events/block.h>
  25
  26 #define POOL_SIZE       64
  27 #define ISA_POOL_SIZE   16
  28
  29 static mempool_t *page_pool, *isa_page_pool;
  30
  31 #if defined(CONFIG_HIGHMEM) || defined(CONFIG_NEED_BOUNCE_POOL)
  32 static __init int init_emergency_pool(void)
  33 {
  34 #if defined(CONFIG_HIGHMEM) && !defined(CONFIG_MEMORY_HOTPLUG)
  35         if (max_pfn <= max_low_pfn)
  36                 return 0;
  37 #endif
  38
  39         page_pool = mempool_create_page_pool(POOL_SIZE, 0);
  40         BUG_ON(!page_pool);
  41         pr_info("pool size: %d pages\n", POOL_SIZE);
  42
  43         return 0;
  44 }
  45
  46 __initcall(init_emergency_pool);
  47 #endif
  48
  49 #ifdef CONFIG_HIGHMEM
  50 /*
  51  * highmem version, map in to vec
  52  */
  53 static void bounce_copy_vec(struct bio_vec *to, unsigned char *vfrom)
  54 {
  55         unsigned long flags;
  56         unsigned char *vto;
  57
  58         local_irq_save(flags);
  59         vto = kmap_atomic(to->bv_page);
  60         memcpy(vto + to->bv_offset, vfrom, to->bv_len);
  61         kunmap_atomic(vto);
  62         local_irq_restore(flags);
  63 }
  64
  65 #else /* CONFIG_HIGHMEM */
  66
  67 #define bounce_copy_vec(to, vfrom)      \
  68         memcpy(page_address((to)->bv_page) + (to)->bv_offset, vfrom, (to)->bv_len)
  69
  70 #endif /* CONFIG_HIGHMEM */
  71
  72 /*
  73  * allocate pages in the DMA region for the ISA pool
  74  */
  75 static void *mempool_alloc_pages_isa(gfp_t gfp_mask, void *data)
  76 {
  77         return mempool_alloc_pages(gfp_mask | GFP_DMA, data);
  78 }
  79
  80 /*
  81  * gets called "every" time someone init's a queue with BLK_BOUNCE_ISA
  82  * as the max address, so check if the pool has already been created.
  83  */
  84 int init_emergency_isa_pool(void)
  85 {
  86         if (isa_page_pool)
  87                 return 0;
  88
  89         isa_page_pool = mempool_create(ISA_POOL_SIZE, mempool_alloc_pages_isa,
  90                                        mempool_free_pages, (void *) 0);
  91         BUG_ON(!isa_page_pool);
  92
  93         pr_info("isa pool size: %d pages\n", ISA_POOL_SIZE);
  94         return 0;
  95 }
  96
  97 /*
  98  * Simple bounce buffer support for highmem pages. Depending on the
  99  * queue gfp mask set, *to may or may not be a highmem page. kmap it
 100  * always, it will do the Right Thing
 101  */
 102 static void copy_to_high_bio_irq(struct bio *to, struct bio *from)
 103 {
 104         unsigned char *vfrom;
 105         struct bio_vec tovec, *fromvec = from->bi_io_vec;
 106         struct bvec_iter iter;
 107
 108         bio_for_each_segment(tovec, to, iter) {
 109                 if (tovec.bv_page != fromvec->bv_page) {
 110                         /*
 111                          * fromvec->bv_offset and fromvec->bv_len might have
 112                          * been modified by the block layer, so use the original
 113                          * copy, bounce_copy_vec already uses tovec->bv_len
 114                          */
 115                         vfrom = page_address(fromvec->bv_page) +
 116                                 tovec.bv_offset;
 117
 118                         bounce_copy_vec(&tovec, vfrom);
 119                         flush_dcache_page(tovec.bv_page);
 120                 }
 121
 122                 fromvec++;
 123         }
 124 }
 125
 126 static void bounce_end_io(struct bio *bio, mempool_t *pool)
 127 {
 128         struct bio *bio_orig = bio->bi_private;
 129         struct bio_vec *bvec, *org_vec;
 130         int i;
 131
 132         /*
 133          * free up bounce indirect pages used
 134          */
 135         bio_for_each_segment_all(bvec, bio, i) {
 136                 org_vec = bio_orig->bi_io_vec + i;
 137                 if (bvec->bv_page == org_vec->bv_page)
 138                         continue;
 139
 140                 dec_zone_page_state(bvec->bv_page, NR_BOUNCE);
 141                 mempool_free(bvec->bv_page, pool);
 142         }
 143
 144         bio_orig->bi_error = bio->bi_error;
 145         bio_endio(bio_orig);
 146         bio_put(bio);
 147 }
 148
 149 static void bounce_end_io_write(struct bio *bio)
 150 {
 151         bounce_end_io(bio, page_pool);
 152 }
 153
 154 static void bounce_end_io_write_isa(struct bio *bio)
 155 {
 156
 157         bounce_end_io(bio, isa_page_pool);
 158 }
 159
 160 static void __bounce_end_io_read(struct bio *bio, mempool_t *pool)
 161 {
 162         struct bio *bio_orig = bio->bi_private;
 163
 164         if (!bio->bi_error)
 165                 copy_to_high_bio_irq(bio_orig, bio);
 166
 167         bounce_end_io(bio, pool);
 168 }
 169
 170 static void bounce_end_io_read(struct bio *bio)
 171 {
 172         __bounce_end_io_read(bio, page_pool);
 173 }
 174
 175 static void bounce_end_io_read_isa(struct bio *bio)
 176 {
 177         __bounce_end_io_read(bio, isa_page_pool);
 178 }
 179
 180 #ifdef CONFIG_NEED_BOUNCE_POOL
 181 static int must_snapshot_stable_pages(struct request_queue *q, struct bio *bio)
 182 {
 183         if (bio_data_dir(bio) != WRITE)
 184                 return 0;
 185
 186         if (!bdi_cap_stable_pages_required(&q->backing_dev_info))
 187                 return 0;
 188
 189         return test_bit(BIO_SNAP_STABLE, &bio->bi_flags);
 190 }
 191 #else
 192 static int must_snapshot_stable_pages(struct request_queue *q, struct bio *bio)
 193 {
 194         return 0;
 195 }
 196 #endif /* CONFIG_NEED_BOUNCE_POOL */
 197
 198 static void __blk_queue_bounce(struct request_queue *q, struct bio **bio_orig,
 199                                mempool_t *pool, int force)
 200 {
 201         struct bio *bio;
 202         int rw = bio_data_dir(*bio_orig);
 203         struct bio_vec *to, from;
 204         struct bvec_iter iter;
 205         unsigned i;
 206
 207         if (force)
 208                 goto bounce;
 209         bio_for_each_segment(from, *bio_orig, iter)
 210                 if (page_to_pfn(from.bv_page) > queue_bounce_pfn(q))
 211                         goto bounce;
 212
 213         return;
 214 bounce:
 215         bio = bio_clone_bioset(*bio_orig, GFP_NOIO, fs_bio_set);
 216
 217         bio_for_each_segment_all(to, bio, i) {
 218                 struct page *page = to->bv_page;
 219
 220                 if (page_to_pfn(page) <= queue_bounce_pfn(q) && !force)
 221                         continue;
 222
 223                 to->bv_page = mempool_alloc(pool, q->bounce_gfp);
 224                 inc_zone_page_state(to->bv_page, NR_BOUNCE);
 225
 226                 if (rw == WRITE) {
 227                         char *vto, *vfrom;
 228
 229                         flush_dcache_page(page);
 230
 231                         vto = page_address(to->bv_page) + to->bv_offset;
 232                         vfrom = kmap_atomic(page) + to->bv_offset;
 233                         memcpy(vto, vfrom, to->bv_len);
 234                         kunmap_atomic(vfrom);
 235                 }
 236         }
 237
 238         trace_block_bio_bounce(q, *bio_orig);
 239
 240         bio->bi_flags |= (1 << BIO_BOUNCED);
 241
 242         if (pool == page_pool) {
 243                 bio->bi_end_io = bounce_end_io_write;
 244                 if (rw == READ)
 245                         bio->bi_end_io = bounce_end_io_read;
 246         } else {
 247                 bio->bi_end_io = bounce_end_io_write_isa;
 248                 if (rw == READ)
 249                         bio->bi_end_io = bounce_end_io_read_isa;
 250         }
 251
 252         bio->bi_private = *bio_orig;
 253         *bio_orig = bio;
 254 }
 255
 256 void blk_queue_bounce(struct request_queue *q, struct bio **bio_orig)
 257 {
 258         int must_bounce;
 259         mempool_t *pool;
 260
 261         /*
 262          * Data-less bio, nothing to bounce
 263          */
 264         if (!bio_has_data(*bio_orig))
 265                 return;
 266
 267         must_bounce = must_snapshot_stable_pages(q, *bio_orig);
 268
 269         /*
 270          * for non-isa bounce case, just check if the bounce pfn is equal
 271          * to or bigger than the highest pfn in the system -- in that case,
 272          * don't waste time iterating over bio segments
 273          */
 274         if (!(q->bounce_gfp & GFP_DMA)) {
 275                 if (queue_bounce_pfn(q) >= blk_max_pfn && !must_bounce)
 276                         return;
 277                 pool = page_pool;
 278         } else {
 279                 BUG_ON(!isa_page_pool);
 280                 pool = isa_page_pool;
 281         }
 282
 283         /*
 284          * slow path
 285          */
 286         __blk_queue_bounce(q, bio_orig, pool, must_bounce);
 287 }
 288
 289 EXPORT_SYMBOL(blk_queue_bounce);