bounce.c

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

#include <linux/mm.h>
#include <linux/export.h>
#include <linux/swap.h>
#include <linux/gfp.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/bootmem.h>
#include <asm/tlbflush.h>

#include <trace/events/block.h>

#define POOL_SIZE   64
#define ISA_POOL_SIZE   16

static mempool_t *page_pool, *isa_page_pool;

#if defined(CONFIG_HIGHMEM) || defined(CONFIG_NEED_BOUNCE_POOL)
static __init int init_emergency_pool(void)
{
#if defined(CONFIG_HIGHMEM) && !defined(CONFIG_MEMORY_HOTPLUG)
    if (max_pfn <= max_low_pfn)
        return 0;
#endif

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

    return 0;
}

__initcall(init_emergency_pool);
#endif

#ifdef CONFIG_HIGHMEM
/*
 * 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);
    memcpy(vto + to->bv_offset, vfrom, to->bv_len);
    kunmap_atomic(vto);
    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;

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

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) <= queue_bounce_pfn(q))
            continue;

        /*
         * irk, bounce it
         */
        if (!bio) {
            unsigned int cnt = (*bio_orig)->bi_vcnt;

            bio = bio_alloc(GFP_NOIO, cnt);
            memset(bio->bi_io_vec, 0, cnt * sizeof(struct bio_vec));
        }
            

        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;

    trace_block_bio_bounce(q, *bio_orig);

    /*
     * 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 (queue_bounce_pfn(q) >= 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);