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) {
 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_all(bvec, bio, i) {
 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         if (bio_data_dir(bio) != WRITE)
 185                 return 0;
 186
 187         if (!bdi_cap_stable_pages_required(&q->backing_dev_info))
 188                 return 0;
 189
 190         return test_bit(BIO_SNAP_STABLE, &bio->bi_flags);
 191 }
 192 #else
 193 static int must_snapshot_stable_pages(struct request_queue *q, struct bio *bio)
 194 {
 195         return 0;
 196 }
 197 #endif /* CONFIG_NEED_BOUNCE_POOL */
 198
 199 static void __blk_queue_bounce(struct request_queue *q, struct bio **bio_orig,
 200                                mempool_t *pool, int force)
 201 {
 202         struct bio *bio;
 203         int rw = bio_data_dir(*bio_orig);
 204         struct bio_vec *to, *from;
 205         unsigned i;
 206
 207         bio_for_each_segment(from, *bio_orig, i)
 208                 if (page_to_pfn(from->bv_page) > queue_bounce_pfn(q))
 209                         goto bounce;
 210
 211         return;
 212 bounce:
 213         bio = bio_clone_bioset(*bio_orig, GFP_NOIO, fs_bio_set);
 214
 215         bio_for_each_segment_all(to, bio, i) {
 216                 struct page *page = to->bv_page;
 217
 218                 if (page_to_pfn(page) <= queue_bounce_pfn(q) && !force)
 219                         continue;
 220
 221                 inc_zone_page_state(to->bv_page, NR_BOUNCE);
 222                 to->bv_page = mempool_alloc(pool, q->bounce_gfp);
 223
 224                 if (rw == WRITE) {
 225                         char *vto, *vfrom;
 226
 227                         flush_dcache_page(page);
 228
 229                         vto = page_address(to->bv_page) + to->bv_offset;
 230                         vfrom = kmap_atomic(page) + to->bv_offset;
 231                         memcpy(vto, vfrom, to->bv_len);
 232                         kunmap_atomic(vfrom);
 233                 }
 234         }
 235
 236         trace_block_bio_bounce(q, *bio_orig);
 237
 238         bio->bi_flags |= (1 << BIO_BOUNCED);
 239
 240         if (pool == page_pool) {
 241                 bio->bi_end_io = bounce_end_io_write;
 242                 if (rw == READ)
 243                         bio->bi_end_io = bounce_end_io_read;
 244         } else {
 245                 bio->bi_end_io = bounce_end_io_write_isa;
 246                 if (rw == READ)
 247                         bio->bi_end_io = bounce_end_io_read_isa;
 248         }
 249
 250         bio->bi_private = *bio_orig;
 251         *bio_orig = bio;
 252 }
 253
 254 void blk_queue_bounce(struct request_queue *q, struct bio **bio_orig)
 255 {
 256         int must_bounce;
 257         mempool_t *pool;
 258
 259         /*
 260          * Data-less bio, nothing to bounce
 261          */
 262         if (!bio_has_data(*bio_orig))
 263                 return;
 264
 265         must_bounce = must_snapshot_stable_pages(q, *bio_orig);
 266
 267         /*
 268          * for non-isa bounce case, just check if the bounce pfn is equal
 269          * to or bigger than the highest pfn in the system -- in that case,
 270          * don't waste time iterating over bio segments
 271          */
 272         if (!(q->bounce_gfp & GFP_DMA)) {
 273                 if (queue_bounce_pfn(q) >= blk_max_pfn && !must_bounce)
 274                         return;
 275                 pool = page_pool;
 276         } else {
 277                 BUG_ON(!isa_page_pool);
 278                 pool = isa_page_pool;
 279         }
 280
 281         /*
 282          * slow path
 283          */
 284         __blk_queue_bounce(q, bio_orig, pool, must_bounce);
 285 }
 286
 287 EXPORT_SYMBOL(blk_queue_bounce);