The Design and Implementation of the FreeBSD Operating System, Second Edition
Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)


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FreeBSD/Linux Kernel Cross Reference
sys/mm/bounce.c

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    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, 0) {
  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(bvec, bio, i, 0) {
  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 static void __blk_queue_bounce(struct request_queue *q, struct bio **bio_orig,
  182                                mempool_t *pool)
  183 {
  184         struct page *page;
  185         struct bio *bio = NULL;
  186         int i, rw = bio_data_dir(*bio_orig);
  187         struct bio_vec *to, *from;
  188 
  189         bio_for_each_segment(from, *bio_orig, i) {
  190                 page = from->bv_page;
  191 
  192                 /*
  193                  * is destination page below bounce pfn?
  194                  */
  195                 if (page_to_pfn(page) <= queue_bounce_pfn(q))
  196                         continue;
  197 
  198                 /*
  199                  * irk, bounce it
  200                  */
  201                 if (!bio) {
  202                         unsigned int cnt = (*bio_orig)->bi_vcnt;
  203 
  204                         bio = bio_alloc(GFP_NOIO, cnt);
  205                         memset(bio->bi_io_vec, 0, cnt * sizeof(struct bio_vec));
  206                 }
  207                         
  208 
  209                 to = bio->bi_io_vec + i;
  210 
  211                 to->bv_page = mempool_alloc(pool, q->bounce_gfp);
  212                 to->bv_len = from->bv_len;
  213                 to->bv_offset = from->bv_offset;
  214                 inc_zone_page_state(to->bv_page, NR_BOUNCE);
  215 
  216                 if (rw == WRITE) {
  217                         char *vto, *vfrom;
  218 
  219                         flush_dcache_page(from->bv_page);
  220                         vto = page_address(to->bv_page) + to->bv_offset;
  221                         vfrom = kmap(from->bv_page) + from->bv_offset;
  222                         memcpy(vto, vfrom, to->bv_len);
  223                         kunmap(from->bv_page);
  224                 }
  225         }
  226 
  227         /*
  228          * no pages bounced
  229          */
  230         if (!bio)
  231                 return;
  232 
  233         trace_block_bio_bounce(q, *bio_orig);
  234 
  235         /*
  236          * at least one page was bounced, fill in possible non-highmem
  237          * pages
  238          */
  239         __bio_for_each_segment(from, *bio_orig, i, 0) {
  240                 to = bio_iovec_idx(bio, i);
  241                 if (!to->bv_page) {
  242                         to->bv_page = from->bv_page;
  243                         to->bv_len = from->bv_len;
  244                         to->bv_offset = from->bv_offset;
  245                 }
  246         }
  247 
  248         bio->bi_bdev = (*bio_orig)->bi_bdev;
  249         bio->bi_flags |= (1 << BIO_BOUNCED);
  250         bio->bi_sector = (*bio_orig)->bi_sector;
  251         bio->bi_rw = (*bio_orig)->bi_rw;
  252 
  253         bio->bi_vcnt = (*bio_orig)->bi_vcnt;
  254         bio->bi_idx = (*bio_orig)->bi_idx;
  255         bio->bi_size = (*bio_orig)->bi_size;
  256 
  257         if (pool == page_pool) {
  258                 bio->bi_end_io = bounce_end_io_write;
  259                 if (rw == READ)
  260                         bio->bi_end_io = bounce_end_io_read;
  261         } else {
  262                 bio->bi_end_io = bounce_end_io_write_isa;
  263                 if (rw == READ)
  264                         bio->bi_end_io = bounce_end_io_read_isa;
  265         }
  266 
  267         bio->bi_private = *bio_orig;
  268         *bio_orig = bio;
  269 }
  270 
  271 void blk_queue_bounce(struct request_queue *q, struct bio **bio_orig)
  272 {
  273         mempool_t *pool;
  274 
  275         /*
  276          * Data-less bio, nothing to bounce
  277          */
  278         if (!bio_has_data(*bio_orig))
  279                 return;
  280 
  281         /*
  282          * for non-isa bounce case, just check if the bounce pfn is equal
  283          * to or bigger than the highest pfn in the system -- in that case,
  284          * don't waste time iterating over bio segments
  285          */
  286         if (!(q->bounce_gfp & GFP_DMA)) {
  287                 if (queue_bounce_pfn(q) >= blk_max_pfn)
  288                         return;
  289                 pool = page_pool;
  290         } else {
  291                 BUG_ON(!isa_page_pool);
  292                 pool = isa_page_pool;
  293         }
  294 
  295         /*
  296          * slow path
  297          */
  298         __blk_queue_bounce(q, bio_orig, pool);
  299 }
  300 
  301 EXPORT_SYMBOL(blk_queue_bounce);

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