/*
 * Functions related to generic helpers functions
 */
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/bio.h>
#include <linux/blkdev.h>
#include <linux/scatterlist.h>

#include "blk.h"

static void blkdev_discard_end_io(struct bio *bio, int err)
{
        if (err) {
                if (err == -EOPNOTSUPP)
                        set_bit(BIO_EOPNOTSUPP, &bio->bi_flags);
                clear_bit(BIO_UPTODATE, &bio->bi_flags);
        }

        if (bio->bi_private)
                complete(bio->bi_private);
        __free_page(bio_page(bio));

        bio_put(bio);
}

/**
 * blkdev_issue_discard - queue a discard
 * @bdev:       blockdev to issue discard for
 * @sector:     start sector
 * @nr_sects:   number of sectors to discard
 * @gfp_mask:   memory allocation flags (for bio_alloc)
 * @flags:      BLKDEV_IFL_* flags to control behaviour
 *
 * Description:
 *    Issue a discard request for the sectors in question.
 */
int blkdev_issue_discard(struct block_device *bdev, sector_t sector,
                sector_t nr_sects, gfp_t gfp_mask, unsigned long flags)
{
        DECLARE_COMPLETION_ONSTACK(wait);
        struct request_queue *q = bdev_get_queue(bdev);
        int type = flags & BLKDEV_IFL_BARRIER ?
                DISCARD_BARRIER : DISCARD_NOBARRIER;
        struct bio *bio;
        struct page *page;
        int ret = 0;

        if (!q)
                return -ENXIO;

        if (!blk_queue_discard(q))
                return -EOPNOTSUPP;

        while (nr_sects && !ret) {
                unsigned int sector_size = q->limits.logical_block_size;
                unsigned int max_discard_sectors =
                        min(q->limits.max_discard_sectors, UINT_MAX >> 9);

                bio = bio_alloc(gfp_mask, 1);
                if (!bio)
                        goto out;
                bio->bi_sector = sector;
                bio->bi_end_io = blkdev_discard_end_io;
                bio->bi_bdev = bdev;
                if (flags & BLKDEV_IFL_WAIT)
                        bio->bi_private = &wait;

                /*
                 * Add a zeroed one-sector payload as that's what
                 * our current implementations need.  If we'll ever need
                 * more the interface will need revisiting.
                 */
                page = alloc_page(gfp_mask | __GFP_ZERO);
                if (!page)
                        goto out_free_bio;
                if (bio_add_pc_page(q, bio, page, sector_size, 0) < sector_size)
                        goto out_free_page;

                /*
                 * And override the bio size - the way discard works we
                 * touch many more blocks on disk than the actual payload
                 * length.
                 */
                if (nr_sects > max_discard_sectors) {
                        bio->bi_size = max_discard_sectors << 9;
                        nr_sects -= max_discard_sectors;
                        sector += max_discard_sectors;
                } else {
                        bio->bi_size = nr_sects << 9;
                        nr_sects = 0;
                }

                bio_get(bio);
                submit_bio(type, bio);

                if (flags & BLKDEV_IFL_WAIT)
                        wait_for_completion(&wait);

                if (bio_flagged(bio, BIO_EOPNOTSUPP))
                        ret = -EOPNOTSUPP;
                else if (!bio_flagged(bio, BIO_UPTODATE))
                        ret = -EIO;
                bio_put(bio);
        }
        return ret;
out_free_page:
        __free_page(page);
out_free_bio:
        bio_put(bio);
out:
        return -ENOMEM;
}
EXPORT_SYMBOL(blkdev_issue_discard);

struct bio_batch
{
        atomic_t                done;
        unsigned long           flags;
        struct completion       *wait;
        bio_end_io_t            *end_io;
};

static void bio_batch_end_io(struct bio *bio, int err)
{
        struct bio_batch *bb = bio->bi_private;

        if (err) {
                if (err == -EOPNOTSUPP)
                        set_bit(BIO_EOPNOTSUPP, &bb->flags);
                else
                        clear_bit(BIO_UPTODATE, &bb->flags);
        }
        if (bb) {
                if (bb->end_io)
                        bb->end_io(bio, err);
                atomic_inc(&bb->done);
                complete(bb->wait);
        }
        bio_put(bio);
}

/**
 * blkdev_issue_zeroout generate number of zero filed write bios
 * @bdev:       blockdev to issue
 * @sector:     start sector
 * @nr_sects:   number of sectors to write
 * @gfp_mask:   memory allocation flags (for bio_alloc)
 * @flags:      BLKDEV_IFL_* flags to control behaviour
 *
 * Description:
 *  Generate and issue number of bios with zerofiled pages.
 *  Send barrier at the beginning and at the end if requested. This guarantie
 *  correct request ordering. Empty barrier allow us to avoid post queue flush.
 */

int blkdev_issue_zeroout(struct block_device *bdev, sector_t sector,
                        sector_t nr_sects, gfp_t gfp_mask, unsigned long flags)
{
        int ret = 0;
        struct bio *bio;
        struct bio_batch bb;
        unsigned int sz, issued = 0;
        DECLARE_COMPLETION_ONSTACK(wait);

        atomic_set(&bb.done, 0);
        bb.flags = 1 << BIO_UPTODATE;
        bb.wait = &wait;
        bb.end_io = NULL;

        if (flags & BLKDEV_IFL_BARRIER) {
                /* issue async barrier before the data */
                ret = blkdev_issue_flush(bdev, gfp_mask, NULL, 0);
                if (ret)
                        return ret;
        }
submit:
        while (nr_sects != 0) {
                bio = bio_alloc(gfp_mask,
                                min(nr_sects, (sector_t)BIO_MAX_PAGES));
                if (!bio)
                        break;

                bio->bi_sector = sector;
                bio->bi_bdev   = bdev;
                bio->bi_end_io = bio_batch_end_io;
                if (flags & BLKDEV_IFL_WAIT)
                        bio->bi_private = &bb;

                while (nr_sects != 0) {
                        sz = min((sector_t) PAGE_SIZE >> 9 , nr_sects);
                        if (sz == 0)
                                /* bio has maximum size possible */
                                break;
                        ret = bio_add_page(bio, ZERO_PAGE(0), sz << 9, 0);
                        nr_sects -= ret >> 9;
                        sector += ret >> 9;
                        if (ret < (sz << 9))
                                break;
                }
                issued++;
                submit_bio(WRITE, bio);
        }
        /*
         * When all data bios are in flight. Send final barrier if requeted.
         */
        if (nr_sects == 0 && flags & BLKDEV_IFL_BARRIER)
                ret = blkdev_issue_flush(bdev, gfp_mask, NULL,
                                        flags & BLKDEV_IFL_WAIT);


        if (flags & BLKDEV_IFL_WAIT)
                /* Wait for bios in-flight */
                while ( issued != atomic_read(&bb.done))
                        wait_for_completion(&wait);

        if (!test_bit(BIO_UPTODATE, &bb.flags))
                /* One of bios in the batch was completed with error.*/
                ret = -EIO;

        if (ret)
                goto out;

        if (test_bit(BIO_EOPNOTSUPP, &bb.flags)) {
                ret = -EOPNOTSUPP;
                goto out;
        }
        if (nr_sects != 0)
                goto submit;
out:
        return ret;
}
EXPORT_SYMBOL(blkdev_issue_zeroout);