root/mm/bounce.c

DEFINITIONS

1. init_emergency_pool
2. bounce_copy_vec
3. mempool_alloc_pages_isa
4. init_emergency_isa_pool
5. copy_to_high_bio_irq
6. bounce_end_io
7. bounce_end_io_write
8. bounce_end_io_write_isa
9. __bounce_end_io_read
10. bounce_end_io_read
11. bounce_end_io_read_isa
12. __blk_queue_bounce
13. blk_queue_bounce

/* bounce buffer handling for block devices
 *
 * - Split from highmem.c
 */

#include <linux/mm.h>
#include <linux/module.h>
#include <linux/swap.h>
#include <linux/bio.h>
#include <linux/pagemap.h>
#include <linux/mempool.h>
#include <linux/blkdev.h>
#include <linux/init.h>
#include <linux/hash.h>
#include <linux/highmem.h>
#include <linux/blktrace_api.h>
#include <asm/tlbflush.h>

#define POOL_SIZE       64
#define ISA_POOL_SIZE   16

static mempool_t *page_pool, *isa_page_pool;

#ifdef CONFIG_HIGHMEM
static __init int init_emergency_pool(void)
{
        struct sysinfo i;
        si_meminfo(&i);
        si_swapinfo(&i);

        if (!i.totalhigh)
                return 0;

        page_pool = mempool_create_page_pool(POOL_SIZE, 0);
        BUG_ON(!page_pool);
        printk("highmem bounce pool size: %d pages\n", POOL_SIZE);

        return 0;
}

__initcall(init_emergency_pool);

/*
 * highmem version, map in to vec
 */
static void bounce_copy_vec(struct bio_vec *to, unsigned char *vfrom)
{
        unsigned long flags;
        unsigned char *vto;

        local_irq_save(flags);
        vto = kmap_atomic(to->bv_page, KM_BOUNCE_READ);
        memcpy(vto + to->bv_offset, vfrom, to->bv_len);
        kunmap_atomic(vto, KM_BOUNCE_READ);
        local_irq_restore(flags);
}

#else /* CONFIG_HIGHMEM */

#define bounce_copy_vec(to, vfrom)      \
        memcpy(page_address((to)->bv_page) + (to)->bv_offset, vfrom, (to)->bv_len)

#endif /* CONFIG_HIGHMEM */

/*
 * allocate pages in the DMA region for the ISA pool
 */
static void *mempool_alloc_pages_isa(gfp_t gfp_mask, void *data)
{
        return mempool_alloc_pages(gfp_mask | GFP_DMA, data);
}

/*
 * gets called "every" time someone init's a queue with BLK_BOUNCE_ISA
 * as the max address, so check if the pool has already been created.
 */
int init_emergency_isa_pool(void)
{
        if (isa_page_pool)
                return 0;

        isa_page_pool = mempool_create(ISA_POOL_SIZE, mempool_alloc_pages_isa,
                                       mempool_free_pages, (void *) 0);
        BUG_ON(!isa_page_pool);

        printk("isa bounce pool size: %d pages\n", ISA_POOL_SIZE);
        return 0;
}

/*
 * Simple bounce buffer support for highmem pages. Depending on the
 * queue gfp mask set, *to may or may not be a highmem page. kmap it
 * always, it will do the Right Thing
 */
static void copy_to_high_bio_irq(struct bio *to, struct bio *from)
{
        unsigned char *vfrom;
        struct bio_vec *tovec, *fromvec;
        int i;

        __bio_for_each_segment(tovec, to, i, 0) {
                fromvec = from->bi_io_vec + i;

                /*
                 * not bounced
                 */
                if (tovec->bv_page == fromvec->bv_page)
                        continue;

                /*
                 * fromvec->bv_offset and fromvec->bv_len might have been
                 * modified by the block layer, so use the original copy,
                 * bounce_copy_vec already uses tovec->bv_len
                 */
                vfrom = page_address(fromvec->bv_page) + tovec->bv_offset;

                flush_dcache_page(tovec->bv_page);
                bounce_copy_vec(tovec, vfrom);
        }
}

static void bounce_end_io(struct bio *bio, mempool_t *pool, int err)
{
        struct bio *bio_orig = bio->bi_private;
        struct bio_vec *bvec, *org_vec;
        int i;

        if (test_bit(BIO_EOPNOTSUPP, &bio->bi_flags))
                set_bit(BIO_EOPNOTSUPP, &bio_orig->bi_flags);

        /*
         * free up bounce indirect pages used
         */
        __bio_for_each_segment(bvec, bio, i, 0) {
                org_vec = bio_orig->bi_io_vec + i;
                if (bvec->bv_page == org_vec->bv_page)
                        continue;

                dec_zone_page_state(bvec->bv_page, NR_BOUNCE);
                mempool_free(bvec->bv_page, pool);
        }

        bio_endio(bio_orig, err);
        bio_put(bio);
}

static void bounce_end_io_write(struct bio *bio, int err)
{
        bounce_end_io(bio, page_pool, err);
}

static void bounce_end_io_write_isa(struct bio *bio, int err)
{

        bounce_end_io(bio, isa_page_pool, err);
}

static void __bounce_end_io_read(struct bio *bio, mempool_t *pool, int err)
{
        struct bio *bio_orig = bio->bi_private;

        if (test_bit(BIO_UPTODATE, &bio->bi_flags))
                copy_to_high_bio_irq(bio_orig, bio);

        bounce_end_io(bio, pool, err);
}

static void bounce_end_io_read(struct bio *bio, int err)
{
        __bounce_end_io_read(bio, page_pool, err);
}

static void bounce_end_io_read_isa(struct bio *bio, int err)
{
        __bounce_end_io_read(bio, isa_page_pool, err);
}

static void __blk_queue_bounce(struct request_queue *q, struct bio **bio_orig,
                               mempool_t *pool)
{
        struct page *page;
        struct bio *bio = NULL;
        int i, rw = bio_data_dir(*bio_orig);
        struct bio_vec *to, *from;

        bio_for_each_segment(from, *bio_orig, i) {
                page = from->bv_page;

                /*
                 * is destination page below bounce pfn?
                 */
                if (page_to_pfn(page) <= q->bounce_pfn)
                        continue;

                /*
                 * irk, bounce it
                 */
                if (!bio)
                        bio = bio_alloc(GFP_NOIO, (*bio_orig)->bi_vcnt);

                to = bio->bi_io_vec + i;

                to->bv_page = mempool_alloc(pool, q->bounce_gfp);
                to->bv_len = from->bv_len;
                to->bv_offset = from->bv_offset;
                inc_zone_page_state(to->bv_page, NR_BOUNCE);

                if (rw == WRITE) {
                        char *vto, *vfrom;

                        flush_dcache_page(from->bv_page);
                        vto = page_address(to->bv_page) + to->bv_offset;
                        vfrom = kmap(from->bv_page) + from->bv_offset;
                        memcpy(vto, vfrom, to->bv_len);
                        kunmap(from->bv_page);
                }
        }

        /*
         * no pages bounced
         */
        if (!bio)
                return;

        blk_add_trace_bio(q, *bio_orig, BLK_TA_BOUNCE);

        /*
         * at least one page was bounced, fill in possible non-highmem
         * pages
         */
        __bio_for_each_segment(from, *bio_orig, i, 0) {
                to = bio_iovec_idx(bio, i);
                if (!to->bv_page) {
                        to->bv_page = from->bv_page;
                        to->bv_len = from->bv_len;
                        to->bv_offset = from->bv_offset;
                }
        }

        bio->bi_bdev = (*bio_orig)->bi_bdev;
        bio->bi_flags |= (1 << BIO_BOUNCED);
        bio->bi_sector = (*bio_orig)->bi_sector;
        bio->bi_rw = (*bio_orig)->bi_rw;

        bio->bi_vcnt = (*bio_orig)->bi_vcnt;
        bio->bi_idx = (*bio_orig)->bi_idx;
        bio->bi_size = (*bio_orig)->bi_size;

        if (pool == page_pool) {
                bio->bi_end_io = bounce_end_io_write;
                if (rw == READ)
                        bio->bi_end_io = bounce_end_io_read;
        } else {
                bio->bi_end_io = bounce_end_io_write_isa;
                if (rw == READ)
                        bio->bi_end_io = bounce_end_io_read_isa;
        }

        bio->bi_private = *bio_orig;
        *bio_orig = bio;
}

void blk_queue_bounce(struct request_queue *q, struct bio **bio_orig)
{
        mempool_t *pool;

        /*
         * Data-less bio, nothing to bounce
         */
        if (!bio_has_data(*bio_orig))
                return;

        /*
         * for non-isa bounce case, just check if the bounce pfn is equal
         * to or bigger than the highest pfn in the system -- in that case,
         * don't waste time iterating over bio segments
         */
        if (!(q->bounce_gfp & GFP_DMA)) {
                if (q->bounce_pfn >= blk_max_pfn)
                        return;
                pool = page_pool;
        } else {
                BUG_ON(!isa_page_pool);
                pool = isa_page_pool;
        }

        /*
         * slow path
         */
        __blk_queue_bounce(q, bio_orig, pool);
}

EXPORT_SYMBOL(blk_queue_bounce);