// SPDX-License-Identifier: GPL-2.0
/*
 * 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 sector_t bio_discard_limit(struct block_device *bdev, sector_t sector)
{
        unsigned int discard_granularity = bdev_discard_granularity(bdev);
        sector_t granularity_aligned_sector;

        if (bdev_is_partition(bdev))
                sector += bdev->bd_start_sect;

        granularity_aligned_sector =
                round_up(sector, discard_granularity >> SECTOR_SHIFT);

        /*
         * Make sure subsequent bios start aligned to the discard granularity if
         * it needs to be split.
         */
        if (granularity_aligned_sector != sector)
                return granularity_aligned_sector - sector;

        /*
         * Align the bio size to the discard granularity to make splitting the bio
         * at discard granularity boundaries easier in the driver if needed.
         */
        return round_down(UINT_MAX, discard_granularity) >> SECTOR_SHIFT;
}

int __blkdev_issue_discard(struct block_device *bdev, sector_t sector,
                sector_t nr_sects, gfp_t gfp_mask, struct bio **biop)
{
        struct bio *bio = *biop;
        sector_t bs_mask;

        if (bdev_read_only(bdev))
                return -EPERM;
        if (!bdev_max_discard_sectors(bdev))
                return -EOPNOTSUPP;

        /* In case the discard granularity isn't set by buggy device driver */
        if (WARN_ON_ONCE(!bdev_discard_granularity(bdev))) {
                pr_err_ratelimited("%pg: Error: discard_granularity is 0.\n",
                                   bdev);
                return -EOPNOTSUPP;
        }

        bs_mask = (bdev_logical_block_size(bdev) >> 9) - 1;
        if ((sector | nr_sects) & bs_mask)
                return -EINVAL;

        if (!nr_sects)
                return -EINVAL;

        while (nr_sects) {
                sector_t req_sects =
                        min(nr_sects, bio_discard_limit(bdev, sector));

                bio = blk_next_bio(bio, bdev, 0, REQ_OP_DISCARD, gfp_mask);
                bio->bi_iter.bi_sector = sector;
                bio->bi_iter.bi_size = req_sects << 9;
                sector += req_sects;
                nr_sects -= req_sects;

                /*
                 * We can loop for a long time in here, if someone does
                 * full device discards (like mkfs). Be nice and allow
                 * us to schedule out to avoid softlocking if preempt
                 * is disabled.
                 */
                cond_resched();
        }

        *biop = bio;
        return 0;
}
EXPORT_SYMBOL(__blkdev_issue_discard);

/**
 * 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)
 *
 * 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)
{
        struct bio *bio = NULL;
        struct blk_plug plug;
        int ret;

        blk_start_plug(&plug);
        ret = __blkdev_issue_discard(bdev, sector, nr_sects, gfp_mask, &bio);
        if (!ret && bio) {
                ret = submit_bio_wait(bio);
                if (ret == -EOPNOTSUPP)
                        ret = 0;
                bio_put(bio);
        }
        blk_finish_plug(&plug);

        return ret;
}
EXPORT_SYMBOL(blkdev_issue_discard);

static int __blkdev_issue_write_zeroes(struct block_device *bdev,
                sector_t sector, sector_t nr_sects, gfp_t gfp_mask,
                struct bio **biop, unsigned flags)
{
        struct bio *bio = *biop;
        unsigned int max_write_zeroes_sectors;

        if (bdev_read_only(bdev))
                return -EPERM;

        /* Ensure that max_write_zeroes_sectors doesn't overflow bi_size */
        max_write_zeroes_sectors = bdev_write_zeroes_sectors(bdev);

        if (max_write_zeroes_sectors == 0)
                return -EOPNOTSUPP;

        while (nr_sects) {
                bio = blk_next_bio(bio, bdev, 0, REQ_OP_WRITE_ZEROES, gfp_mask);
                bio->bi_iter.bi_sector = sector;
                if (flags & BLKDEV_ZERO_NOUNMAP)
                        bio->bi_opf |= REQ_NOUNMAP;

                if (nr_sects > max_write_zeroes_sectors) {
                        bio->bi_iter.bi_size = max_write_zeroes_sectors << 9;
                        nr_sects -= max_write_zeroes_sectors;
                        sector += max_write_zeroes_sectors;
                } else {
                        bio->bi_iter.bi_size = nr_sects << 9;
                        nr_sects = 0;
                }
                cond_resched();
        }

        *biop = bio;
        return 0;
}

/*
 * Convert a number of 512B sectors to a number of pages.
 * The result is limited to a number of pages that can fit into a BIO.
 * Also make sure that the result is always at least 1 (page) for the cases
 * where nr_sects is lower than the number of sectors in a page.
 */
static unsigned int __blkdev_sectors_to_bio_pages(sector_t nr_sects)
{
        sector_t pages = DIV_ROUND_UP_SECTOR_T(nr_sects, PAGE_SIZE / 512);

        return min(pages, (sector_t)BIO_MAX_VECS);
}

static int __blkdev_issue_zero_pages(struct block_device *bdev,
                sector_t sector, sector_t nr_sects, gfp_t gfp_mask,
                struct bio **biop)
{
        struct bio *bio = *biop;
        int bi_size = 0;
        unsigned int sz;

        if (bdev_read_only(bdev))
                return -EPERM;

        while (nr_sects != 0) {
                bio = blk_next_bio(bio, bdev, __blkdev_sectors_to_bio_pages(nr_sects),
                                   REQ_OP_WRITE, gfp_mask);
                bio->bi_iter.bi_sector = sector;

                while (nr_sects != 0) {
                        sz = min((sector_t) PAGE_SIZE, nr_sects << 9);
                        bi_size = bio_add_page(bio, ZERO_PAGE(0), sz, 0);
                        nr_sects -= bi_size >> 9;
                        sector += bi_size >> 9;
                        if (bi_size < sz)
                                break;
                }
                cond_resched();
        }

        *biop = bio;
        return 0;
}

/**
 * __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)
 * @biop:       pointer to anchor bio
 * @flags:      controls detailed behavior
 *
 * Description:
 *  Zero-fill a block range, either using hardware offload or by explicitly
 *  writing zeroes to the device.
 *
 *  If a device is using logical block provisioning, the underlying space will
 *  not be released if %flags contains BLKDEV_ZERO_NOUNMAP.
 *
 *  If %flags contains BLKDEV_ZERO_NOFALLBACK, the function will return
 *  -EOPNOTSUPP if no explicit hardware offload for zeroing is provided.
 */
int __blkdev_issue_zeroout(struct block_device *bdev, sector_t sector,
                sector_t nr_sects, gfp_t gfp_mask, struct bio **biop,
                unsigned flags)
{
        int ret;
        sector_t bs_mask;

        bs_mask = (bdev_logical_block_size(bdev) >> 9) - 1;
        if ((sector | nr_sects) & bs_mask)
                return -EINVAL;

        ret = __blkdev_issue_write_zeroes(bdev, sector, nr_sects, gfp_mask,
                        biop, flags);
        if (ret != -EOPNOTSUPP || (flags & BLKDEV_ZERO_NOFALLBACK))
                return ret;

        return __blkdev_issue_zero_pages(bdev, sector, nr_sects, gfp_mask,
                                         biop);
}
EXPORT_SYMBOL(__blkdev_issue_zeroout);

/**
 * blkdev_issue_zeroout - zero-fill a block range
 * @bdev:       blockdev to write
 * @sector:     start sector
 * @nr_sects:   number of sectors to write
 * @gfp_mask:   memory allocation flags (for bio_alloc)
 * @flags:      controls detailed behavior
 *
 * Description:
 *  Zero-fill a block range, either using hardware offload or by explicitly
 *  writing zeroes to the device.  See __blkdev_issue_zeroout() for the
 *  valid values for %flags.
 */
int blkdev_issue_zeroout(struct block_device *bdev, sector_t sector,
                sector_t nr_sects, gfp_t gfp_mask, unsigned flags)
{
        int ret = 0;
        sector_t bs_mask;
        struct bio *bio;
        struct blk_plug plug;
        bool try_write_zeroes = !!bdev_write_zeroes_sectors(bdev);

        bs_mask = (bdev_logical_block_size(bdev) >> 9) - 1;
        if ((sector | nr_sects) & bs_mask)
                return -EINVAL;

retry:
        bio = NULL;
        blk_start_plug(&plug);
        if (try_write_zeroes) {
                ret = __blkdev_issue_write_zeroes(bdev, sector, nr_sects,
                                                  gfp_mask, &bio, flags);
        } else if (!(flags & BLKDEV_ZERO_NOFALLBACK)) {
                ret = __blkdev_issue_zero_pages(bdev, sector, nr_sects,
                                                gfp_mask, &bio);
        } else {
                /* No zeroing offload support */
                ret = -EOPNOTSUPP;
        }
        if (ret == 0 && bio) {
                ret = submit_bio_wait(bio);
                bio_put(bio);
        }
        blk_finish_plug(&plug);
        if (ret && try_write_zeroes) {
                if (!(flags & BLKDEV_ZERO_NOFALLBACK)) {
                        try_write_zeroes = false;
                        goto retry;
                }
                if (!bdev_write_zeroes_sectors(bdev)) {
                        /*
                         * Zeroing offload support was indicated, but the
                         * device reported ILLEGAL REQUEST (for some devices
                         * there is no non-destructive way to verify whether
                         * WRITE ZEROES is actually supported).
                         */
                        ret = -EOPNOTSUPP;
                }
        }

        return ret;
}
EXPORT_SYMBOL(blkdev_issue_zeroout);

int blkdev_issue_secure_erase(struct block_device *bdev, sector_t sector,
                sector_t nr_sects, gfp_t gfp)
{
        sector_t bs_mask = (bdev_logical_block_size(bdev) >> 9) - 1;
        unsigned int max_sectors = bdev_max_secure_erase_sectors(bdev);
        struct bio *bio = NULL;
        struct blk_plug plug;
        int ret = 0;

        /* make sure that "len << SECTOR_SHIFT" doesn't overflow */
        if (max_sectors > UINT_MAX >> SECTOR_SHIFT)
                max_sectors = UINT_MAX >> SECTOR_SHIFT;
        max_sectors &= ~bs_mask;

        if (max_sectors == 0)
                return -EOPNOTSUPP;
        if ((sector | nr_sects) & bs_mask)
                return -EINVAL;
        if (bdev_read_only(bdev))
                return -EPERM;

        blk_start_plug(&plug);
        for (;;) {
                unsigned int len = min_t(sector_t, nr_sects, max_sectors);

                bio = blk_next_bio(bio, bdev, 0, REQ_OP_SECURE_ERASE, gfp);
                bio->bi_iter.bi_sector = sector;
                bio->bi_iter.bi_size = len << SECTOR_SHIFT;

                sector += len;
                nr_sects -= len;
                if (!nr_sects) {
                        ret = submit_bio_wait(bio);
                        bio_put(bio);
                        break;
                }
                cond_resched();
        }
        blk_finish_plug(&plug);

        return ret;
}
EXPORT_SYMBOL(blkdev_issue_secure_erase);