// 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(BIO_MAX_SIZE, discard_granularity) >> SECTOR_SHIFT;
}

struct bio *blk_alloc_discard_bio(struct block_device *bdev,
                sector_t *sector, sector_t *nr_sects, gfp_t gfp_mask)
{
        sector_t bio_sects = min(*nr_sects, bio_discard_limit(bdev, *sector));
        struct bio *bio;

        if (!bio_sects)
                return NULL;

        bio = bio_alloc(bdev, 0, REQ_OP_DISCARD, gfp_mask);
        if (!bio)
                return NULL;
        bio->bi_iter.bi_sector = *sector;
        bio->bi_iter.bi_size = bio_sects << SECTOR_SHIFT;
        *sector += bio_sects;
        *nr_sects -= bio_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();
        return bio;
}

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

        while ((bio = blk_alloc_discard_bio(bdev, &sector, &nr_sects,
                        gfp_mask)))
                *biop = bio_chain_and_submit(*biop, bio);
}
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 = 0;

        blk_start_plug(&plug);
        __blkdev_issue_discard(bdev, sector, nr_sects, gfp_mask, &bio);
        if (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 sector_t bio_write_zeroes_limit(struct block_device *bdev)
{
        sector_t bs_mask = (bdev_logical_block_size(bdev) >> 9) - 1;

        return min(bdev_write_zeroes_sectors(bdev), BIO_MAX_SECTORS & ~bs_mask);
}

/*
 * There is no reliable way for the SCSI subsystem to determine whether a
 * device supports a WRITE SAME operation without actually performing a write
 * to media. As a result, write_zeroes is enabled by default and will be
 * disabled if a zeroing operation subsequently fails. This means that this
 * queue limit is likely to change at runtime.
 */
static void __blkdev_issue_write_zeroes(struct block_device *bdev,
                sector_t sector, sector_t nr_sects, gfp_t gfp_mask,
                struct bio **biop, unsigned flags, sector_t limit)
{

        while (nr_sects) {
                unsigned int len = min(nr_sects, limit);
                struct bio *bio;

                if ((flags & BLKDEV_ZERO_KILLABLE) &&
                    fatal_signal_pending(current))
                        break;

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

                bio->bi_iter.bi_size = len << SECTOR_SHIFT;
                *biop = bio_chain_and_submit(*biop, bio);

                nr_sects -= len;
                sector += len;
                cond_resched();
        }
}

static int blkdev_issue_write_zeroes(struct block_device *bdev, sector_t sector,
                sector_t nr_sects, gfp_t gfp, unsigned flags)
{
        sector_t limit = bio_write_zeroes_limit(bdev);
        struct bio *bio = NULL;
        struct blk_plug plug;
        int ret = 0;

        blk_start_plug(&plug);
        __blkdev_issue_write_zeroes(bdev, sector, nr_sects, gfp, &bio,
                        flags, limit);
        if (bio) {
                if ((flags & BLKDEV_ZERO_KILLABLE) &&
                    fatal_signal_pending(current)) {
                        bio_await_chain(bio);
                        blk_finish_plug(&plug);
                        return -EINTR;
                }
                ret = submit_bio_wait(bio);
                bio_put(bio);
        }
        blk_finish_plug(&plug);

        /*
         * For some devices there is no non-destructive way to verify whether
         * WRITE ZEROES is actually supported.  These will clear the capability
         * on an I/O error, in which case we'll turn any error into
         * "not supported" here.
         */
        if (ret && !bdev_write_zeroes_sectors(bdev))
                return -EOPNOTSUPP;
        return ret;
}

/*
 * 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 void __blkdev_issue_zero_pages(struct block_device *bdev,
                sector_t sector, sector_t nr_sects, gfp_t gfp_mask,
                struct bio **biop, unsigned int flags)
{
        struct folio *zero_folio = largest_zero_folio();

        while (nr_sects) {
                unsigned int nr_vecs = __blkdev_sectors_to_bio_pages(nr_sects);
                struct bio *bio;

                if ((flags & BLKDEV_ZERO_KILLABLE) &&
                    fatal_signal_pending(current))
                        break;

                bio = bio_alloc(bdev, nr_vecs, REQ_OP_WRITE, gfp_mask);
                bio->bi_iter.bi_sector = sector;

                do {
                        unsigned int len;

                        len = min_t(sector_t, folio_size(zero_folio),
                                    nr_sects << SECTOR_SHIFT);
                        if (!bio_add_folio(bio, zero_folio, len, 0))
                                break;
                        nr_sects -= len >> SECTOR_SHIFT;
                        sector += len >> SECTOR_SHIFT;
                } while (nr_sects);

                *biop = bio_chain_and_submit(*biop, bio);
                cond_resched();
        }
}

static int blkdev_issue_zero_pages(struct block_device *bdev, sector_t sector,
                sector_t nr_sects, gfp_t gfp, unsigned flags)
{
        struct bio *bio = NULL;
        struct blk_plug plug;
        int ret = 0;

        if (flags & BLKDEV_ZERO_NOFALLBACK)
                return -EOPNOTSUPP;

        blk_start_plug(&plug);
        __blkdev_issue_zero_pages(bdev, sector, nr_sects, gfp, &bio, flags);
        if (bio) {
                if ((flags & BLKDEV_ZERO_KILLABLE) &&
                    fatal_signal_pending(current)) {
                        bio_await_chain(bio);
                        blk_finish_plug(&plug);
                        return -EINTR;
                }
                ret = submit_bio_wait(bio);
                bio_put(bio);
        }
        blk_finish_plug(&plug);

        return ret;
}

/**
 * __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)
{
        sector_t limit = bio_write_zeroes_limit(bdev);

        if (bdev_read_only(bdev))
                return -EPERM;

        if (limit) {
                __blkdev_issue_write_zeroes(bdev, sector, nr_sects,
                                gfp_mask, biop, flags, limit);
        } else {
                if (flags & BLKDEV_ZERO_NOFALLBACK)
                        return -EOPNOTSUPP;
                __blkdev_issue_zero_pages(bdev, sector, nr_sects, gfp_mask,
                                biop, flags);
        }
        return 0;
}
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;

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

        if (bdev_write_zeroes_sectors(bdev)) {
                ret = blkdev_issue_write_zeroes(bdev, sector, nr_sects,
                                gfp_mask, flags);
                if (ret != -EOPNOTSUPP)
                        return ret;
        }

        return blkdev_issue_zero_pages(bdev, sector, nr_sects, gfp_mask, flags);
}
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 > BIO_MAX_SECTORS)
                max_sectors = BIO_MAX_SECTORS;
        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);
        while (nr_sects) {
                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;
                cond_resched();
        }
        if (bio) {
                ret = submit_bio_wait(bio);
                bio_put(bio);
        }
        blk_finish_plug(&plug);

        return ret;
}
EXPORT_SYMBOL(blkdev_issue_secure_erase);