// 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"

struct bio *blk_next_bio(struct bio *bio, unsigned int nr_pages, gfp_t gfp)
{
        struct bio *new = bio_alloc(gfp, nr_pages);

        if (bio) {
                bio_chain(bio, new);
                submit_bio(bio);
        }

        return new;
}

int __blkdev_issue_discard(struct block_device *bdev, sector_t sector,
                sector_t nr_sects, gfp_t gfp_mask, int flags,
                struct bio **biop)
{
        struct request_queue *q = bdev_get_queue(bdev);
        struct bio *bio = *biop;
        unsigned int op;
        sector_t bs_mask, part_offset = 0;

        if (!q)
                return -ENXIO;

        if (bdev_read_only(bdev))
                return -EPERM;

        if (flags & BLKDEV_DISCARD_SECURE) {
                if (!blk_queue_secure_erase(q))
                        return -EOPNOTSUPP;
                op = REQ_OP_SECURE_ERASE;
        } else {
                if (!blk_queue_discard(q))
                        return -EOPNOTSUPP;
                op = REQ_OP_DISCARD;
        }

        /* In case the discard granularity isn't set by buggy device driver */
        if (WARN_ON_ONCE(!q->limits.discard_granularity)) {
                char dev_name[BDEVNAME_SIZE];

                bdevname(bdev, dev_name);
                pr_err_ratelimited("%s: Error: discard_granularity is 0.\n", dev_name);
                return -EOPNOTSUPP;
        }

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

        if (!nr_sects)
                return -EINVAL;

        /* In case the discard request is in a partition */
        if (bdev_is_partition(bdev))
                part_offset = bdev->bd_start_sect;

        while (nr_sects) {
                sector_t granularity_aligned_lba, req_sects;
                sector_t sector_mapped = sector + part_offset;

                granularity_aligned_lba = round_up(sector_mapped,
                                q->limits.discard_granularity >> SECTOR_SHIFT);

                /*
                 * Check whether the discard bio starts at a discard_granularity
                 * aligned LBA,
                 * - If no: set (granularity_aligned_lba - sector_mapped) to
                 *   bi_size of the first split bio, then the second bio will
                 *   start at a discard_granularity aligned LBA on the device.
                 * - If yes: use bio_aligned_discard_max_sectors() as the max
                 *   possible bi_size of the first split bio. Then when this bio
                 *   is split in device drive, the split ones are very probably
                 *   to be aligned to discard_granularity of the device's queue.
                 */
                if (granularity_aligned_lba == sector_mapped)
                        req_sects = min_t(sector_t, nr_sects,
                                          bio_aligned_discard_max_sectors(q));
                else
                        req_sects = min_t(sector_t, nr_sects,
                                          granularity_aligned_lba - sector_mapped);

                WARN_ON_ONCE((req_sects << 9) > UINT_MAX);

                bio = blk_next_bio(bio, 0, gfp_mask);
                bio->bi_iter.bi_sector = sector;
                bio_set_dev(bio, bdev);
                bio_set_op_attrs(bio, op, 0);

                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)
 * @flags:      BLKDEV_DISCARD_* 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)
{
        struct bio *bio = NULL;
        struct blk_plug plug;
        int ret;

        blk_start_plug(&plug);
        ret = __blkdev_issue_discard(bdev, sector, nr_sects, gfp_mask, flags,
                        &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);

/**
 * __blkdev_issue_write_same - generate number of bios with same page
 * @bdev:       target blockdev
 * @sector:     start sector
 * @nr_sects:   number of sectors to write
 * @gfp_mask:   memory allocation flags (for bio_alloc)
 * @page:       page containing data to write
 * @biop:       pointer to anchor bio
 *
 * Description:
 *  Generate and issue number of bios(REQ_OP_WRITE_SAME) with same page.
 */
static int __blkdev_issue_write_same(struct block_device *bdev, sector_t sector,
                sector_t nr_sects, gfp_t gfp_mask, struct page *page,
                struct bio **biop)
{
        struct request_queue *q = bdev_get_queue(bdev);
        unsigned int max_write_same_sectors;
        struct bio *bio = *biop;
        sector_t bs_mask;

        if (!q)
                return -ENXIO;

        if (bdev_read_only(bdev))
                return -EPERM;

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

        if (!bdev_write_same(bdev))
                return -EOPNOTSUPP;

        /* Ensure that max_write_same_sectors doesn't overflow bi_size */
        max_write_same_sectors = bio_allowed_max_sectors(q);

        while (nr_sects) {
                bio = blk_next_bio(bio, 1, gfp_mask);
                bio->bi_iter.bi_sector = sector;
                bio_set_dev(bio, bdev);
                bio->bi_vcnt = 1;
                bio->bi_io_vec->bv_page = page;
                bio->bi_io_vec->bv_offset = 0;
                bio->bi_io_vec->bv_len = bdev_logical_block_size(bdev);
                bio_set_op_attrs(bio, REQ_OP_WRITE_SAME, 0);

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

        *biop = bio;
        return 0;
}

/**
 * blkdev_issue_write_same - queue a write same operation
 * @bdev:       target blockdev
 * @sector:     start sector
 * @nr_sects:   number of sectors to write
 * @gfp_mask:   memory allocation flags (for bio_alloc)
 * @page:       page containing data
 *
 * Description:
 *    Issue a write same request for the sectors in question.
 */
int blkdev_issue_write_same(struct block_device *bdev, sector_t sector,
                                sector_t nr_sects, gfp_t gfp_mask,
                                struct page *page)
{
        struct bio *bio = NULL;
        struct blk_plug plug;
        int ret;

        blk_start_plug(&plug);
        ret = __blkdev_issue_write_same(bdev, sector, nr_sects, gfp_mask, page,
                        &bio);
        if (ret == 0 && bio) {
                ret = submit_bio_wait(bio);
                bio_put(bio);
        }
        blk_finish_plug(&plug);
        return ret;
}
EXPORT_SYMBOL(blkdev_issue_write_same);

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;
        struct request_queue *q = bdev_get_queue(bdev);

        if (!q)
                return -ENXIO;

        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, 0, gfp_mask);
                bio->bi_iter.bi_sector = sector;
                bio_set_dev(bio, bdev);
                bio->bi_opf = REQ_OP_WRITE_ZEROES;
                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 request_queue *q = bdev_get_queue(bdev);
        struct bio *bio = *biop;
        int bi_size = 0;
        unsigned int sz;

        if (!q)
                return -ENXIO;

        if (bdev_read_only(bdev))
                return -EPERM;

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

                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);