/*
 * 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"

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

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

        if (err && (err != -EOPNOTSUPP))
                clear_bit(BIO_UPTODATE, &bb->flags);
        if (atomic_dec_and_test(&bb->done))
                complete(bb->wait);
        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 = REQ_WRITE | REQ_DISCARD;
        unsigned int max_discard_sectors;
        unsigned int granularity, alignment, mask;
        struct bio_batch bb;
        struct bio *bio;
        int ret = 0;

        if (!q)
                return -ENXIO;

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

        /* Zero-sector (unknown) and one-sector granularities are the same.  */
        granularity = max(q->limits.discard_granularity >> 9, 1U);
        mask = granularity - 1;
        alignment = (bdev_discard_alignment(bdev) >> 9) & mask;

        /*
         * Ensure that max_discard_sectors is of the proper
         * granularity, so that requests stay aligned after a split.
         */
        max_discard_sectors = min(q->limits.max_discard_sectors, UINT_MAX >> 9);
        max_discard_sectors = round_down(max_discard_sectors, granularity);
        if (unlikely(!max_discard_sectors)) {
                /* Avoid infinite loop below. Being cautious never hurts. */
                return -EOPNOTSUPP;
        }

        if (flags & BLKDEV_DISCARD_SECURE) {
                if (!blk_queue_secdiscard(q))
                        return -EOPNOTSUPP;
                type |= REQ_SECURE;
        }

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

        while (nr_sects) {
                unsigned int req_sects;
                sector_t end_sect;

                bio = bio_alloc(gfp_mask, 1);
                if (!bio) {
                        ret = -ENOMEM;
                        break;
                }

                req_sects = min_t(sector_t, nr_sects, max_discard_sectors);

                /*
                 * If splitting a request, and the next starting sector would be
                 * misaligned, stop the discard at the previous aligned sector.
                 */
                end_sect = sector + req_sects;
                if (req_sects < nr_sects && (end_sect & mask) != alignment) {
                        end_sect =
                                round_down(end_sect - alignment, granularity)
                                + alignment;
                        req_sects = end_sect - sector;
                }

                bio->bi_sector = sector;
                bio->bi_end_io = bio_batch_end_io;
                bio->bi_bdev = bdev;
                bio->bi_private = &bb;

                bio->bi_size = req_sects << 9;
                nr_sects -= req_sects;
                sector = end_sect;

                atomic_inc(&bb.done);
                submit_bio(type, bio);
        }

        /* Wait for bios in-flight */
        if (!atomic_dec_and_test(&bb.done))
                wait_for_completion(&wait);

        if (!test_bit(BIO_UPTODATE, &bb.flags))
                ret = -EIO;

        return ret;
}
EXPORT_SYMBOL(blkdev_issue_discard);

/**
 * 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)
 *
 * Description:
 *  Generate and issue number of bios with zerofiled pages.
 */

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

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

        ret = 0;
        while (nr_sects != 0) {
                bio = bio_alloc(gfp_mask,
                                min(nr_sects, (sector_t)BIO_MAX_PAGES));
                if (!bio) {
                        ret = -ENOMEM;
                        break;
                }

                bio->bi_sector = sector;
                bio->bi_bdev   = bdev;
                bio->bi_end_io = bio_batch_end_io;
                bio->bi_private = &bb;

                while (nr_sects != 0) {
                        sz = min((sector_t) PAGE_SIZE >> 9 , nr_sects);
                        ret = bio_add_page(bio, ZERO_PAGE(0), sz << 9, 0);
                        nr_sects -= ret >> 9;
                        sector += ret >> 9;
                        if (ret < (sz << 9))
                                break;
                }
                ret = 0;
                atomic_inc(&bb.done);
                submit_bio(WRITE, bio);
        }

        /* Wait for bios in-flight */
        if (!atomic_dec_and_test(&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;

        return ret;
}
EXPORT_SYMBOL(blkdev_issue_zeroout);