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/init.h>
  17 #include <linux/hash.h>
  18 #include <linux/highmem.h>
  19 #include <linux/bootmem.h>
  20 #include <linux/printk.h>
  21 #include <asm/tlbflush.h>
  22
  23 #include <trace/events/block.h>
  24
  25 #define POOL_SIZE       64
  26 #define ISA_POOL_SIZE   16
  27
  28 static mempool_t *page_pool, *isa_page_pool;
  29
  30 #if defined(CONFIG_HIGHMEM) || defined(CONFIG_NEED_BOUNCE_POOL)
  31 static __init int init_emergency_pool(void)
  32 {
  33 #if defined(CONFIG_HIGHMEM) && !defined(CONFIG_MEMORY_HOTPLUG)
  34         if (max_pfn <= max_low_pfn)
  35                 return 0;
  36 #endif
  37
  38         page_pool = mempool_create_page_pool(POOL_SIZE, 0);
  39         BUG_ON(!page_pool);
  40         pr_info("pool size: %d pages\n", POOL_SIZE);
  41
  42         return 0;
  43 }
  44
  45 __initcall(init_emergency_pool);
  46 #endif
  47
  48 #ifdef CONFIG_HIGHMEM
  49 /*
  50  * highmem version, map in to vec
  51  */
  52 static void bounce_copy_vec(struct bio_vec *to, unsigned char *vfrom)
  53 {
  54         unsigned long flags;
  55         unsigned char *vto;
  56
  57         local_irq_save(flags);
  58         vto = kmap_atomic(to->bv_page);
  59         memcpy(vto + to->bv_offset, vfrom, to->bv_len);
  60         kunmap_atomic(vto);
  61         local_irq_restore(flags);
  62 }
  63
  64 #else /* CONFIG_HIGHMEM */
  65
  66 #define bounce_copy_vec(to, vfrom)      \
  67         memcpy(page_address((to)->bv_page) + (to)->bv_offset, vfrom, (to)->bv_len)
  68
  69 #endif /* CONFIG_HIGHMEM */
  70
  71 /*
  72  * allocate pages in the DMA region for the ISA pool
  73  */
  74 static void *mempool_alloc_pages_isa(gfp_t gfp_mask, void *data)
  75 {
  76         return mempool_alloc_pages(gfp_mask | GFP_DMA, data);
  77 }
  78
  79 /*
  80  * gets called "every" time someone init's a queue with BLK_BOUNCE_ISA
  81  * as the max address, so check if the pool has already been created.
  82  */
  83 int init_emergency_isa_pool(void)
  84 {
  85         if (isa_page_pool)
  86                 return 0;
  87
  88         isa_page_pool = mempool_create(ISA_POOL_SIZE, mempool_alloc_pages_isa,
  89                                        mempool_free_pages, (void *) 0);
  90         BUG_ON(!isa_page_pool);
  91
  92         pr_info("isa pool size: %d pages\n", ISA_POOL_SIZE);
  93         return 0;
  94 }
  95
  96 /*
  97  * Simple bounce buffer support for highmem pages. Depending on the
  98  * queue gfp mask set, *to may or may not be a highmem page. kmap it
  99  * always, it will do the Right Thing
 100  */
 101 static void copy_to_high_bio_irq(struct bio *to, struct bio *from)
 102 {
 103         unsigned char *vfrom;
 104         struct bio_vec tovec, *fromvec = from->bi_io_vec;
 105         struct bvec_iter iter;
 106
 107         bio_for_each_segment(tovec, to, iter) {
 108                 if (tovec.bv_page != fromvec->bv_page) {
 109                         /*
 110                          * fromvec->bv_offset and fromvec->bv_len might have
 111                          * been modified by the block layer, so use the original
 112                          * copy, bounce_copy_vec already uses tovec->bv_len
 113                          */
 114                         vfrom = page_address(fromvec->bv_page) +
 115                                 tovec.bv_offset;
 116
 117                         bounce_copy_vec(&tovec, vfrom);
 118                         flush_dcache_page(tovec.bv_page);
 119                 }
 120
 121                 fromvec++;
 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         /*
 132          * free up bounce indirect pages used
 133          */
 134         bio_for_each_segment_all(bvec, bio, i) {
 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 #ifdef CONFIG_NEED_BOUNCE_POOL
 179 static int must_snapshot_stable_pages(struct request_queue *q, struct bio *bio)
 180 {
 181         if (bio_data_dir(bio) != WRITE)
 182                 return 0;
 183
 184         if (!bdi_cap_stable_pages_required(&q->backing_dev_info))
 185                 return 0;
 186
 187         return test_bit(BIO_SNAP_STABLE, &bio->bi_flags);
 188 }
 189 #else
 190 static int must_snapshot_stable_pages(struct request_queue *q, struct bio *bio)
 191 {
 192         return 0;
 193 }
 194 #endif /* CONFIG_NEED_BOUNCE_POOL */
 195
 196 static void __blk_queue_bounce(struct request_queue *q, struct bio **bio_orig,
 197                                mempool_t *pool, int force)
 198 {
 199         struct bio *bio;
 200         int rw = bio_data_dir(*bio_orig);
 201         struct bio_vec *to, from;
 202         struct bvec_iter iter;
 203         unsigned i;
 204
 205         if (force)
 206                 goto bounce;
 207         bio_for_each_segment(from, *bio_orig, iter)
 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);