/* SPDX-License-Identifier: GPL-2.0 */
/*
 * bvec iterator
 *
 * Copyright (C) 2001 Ming Lei <ming.lei@canonical.com>
 */
#ifndef __LINUX_BVEC_H
#define __LINUX_BVEC_H

#include <linux/highmem.h>
#include <linux/bug.h>
#include <linux/errno.h>
#include <linux/limits.h>
#include <linux/minmax.h>
#include <linux/mm.h>
#include <linux/types.h>

struct page;

/**
 * struct bio_vec - a contiguous range of physical memory addresses
 * @bv_page:   First page associated with the address range.
 * @bv_len:    Number of bytes in the address range.
 * @bv_offset: Start of the address range relative to the start of @bv_page.
 *
 * The following holds for a bvec if n * PAGE_SIZE < bv_offset + bv_len:
 *
 *   nth_page(@bv_page, n) == @bv_page + n
 *
 * This holds because page_is_mergeable() checks the above property.
 */
struct bio_vec {
        struct page     *bv_page;
        unsigned int    bv_len;
        unsigned int    bv_offset;
};

struct bvec_iter {
        sector_t                bi_sector;      /* device address in 512 byte
                                                   sectors */
        unsigned int            bi_size;        /* residual I/O count */

        unsigned int            bi_idx;         /* current index into bvl_vec */

        unsigned int            bi_bvec_done;   /* number of bytes completed in
                                                   current bvec */
};

struct bvec_iter_all {
        struct bio_vec  bv;
        int             idx;
        unsigned        done;
};

/*
 * various member access, note that bio_data should of course not be used
 * on highmem page vectors
 */
#define __bvec_iter_bvec(bvec, iter)    (&(bvec)[(iter).bi_idx])

/* multi-page (mp_bvec) helpers */
#define mp_bvec_iter_page(bvec, iter)                           \
        (__bvec_iter_bvec((bvec), (iter))->bv_page)

#define mp_bvec_iter_len(bvec, iter)                            \
        min((iter).bi_size,                                     \
            __bvec_iter_bvec((bvec), (iter))->bv_len - (iter).bi_bvec_done)

#define mp_bvec_iter_offset(bvec, iter)                         \
        (__bvec_iter_bvec((bvec), (iter))->bv_offset + (iter).bi_bvec_done)

#define mp_bvec_iter_page_idx(bvec, iter)                       \
        (mp_bvec_iter_offset((bvec), (iter)) / PAGE_SIZE)

#define mp_bvec_iter_bvec(bvec, iter)                           \
((struct bio_vec) {                                             \
        .bv_page        = mp_bvec_iter_page((bvec), (iter)),    \
        .bv_len         = mp_bvec_iter_len((bvec), (iter)),     \
        .bv_offset      = mp_bvec_iter_offset((bvec), (iter)),  \
})

/* For building single-page bvec in flight */
 #define bvec_iter_offset(bvec, iter)                           \
        (mp_bvec_iter_offset((bvec), (iter)) % PAGE_SIZE)

#define bvec_iter_len(bvec, iter)                               \
        min_t(unsigned, mp_bvec_iter_len((bvec), (iter)),               \
              PAGE_SIZE - bvec_iter_offset((bvec), (iter)))

#define bvec_iter_page(bvec, iter)                              \
        (mp_bvec_iter_page((bvec), (iter)) +                    \
         mp_bvec_iter_page_idx((bvec), (iter)))

#define bvec_iter_bvec(bvec, iter)                              \
((struct bio_vec) {                                             \
        .bv_page        = bvec_iter_page((bvec), (iter)),       \
        .bv_len         = bvec_iter_len((bvec), (iter)),        \
        .bv_offset      = bvec_iter_offset((bvec), (iter)),     \
})

static inline bool bvec_iter_advance(const struct bio_vec *bv,
                struct bvec_iter *iter, unsigned bytes)
{
        unsigned int idx = iter->bi_idx;

        if (WARN_ONCE(bytes > iter->bi_size,
                     "Attempted to advance past end of bvec iter\n")) {
                iter->bi_size = 0;
                return false;
        }

        iter->bi_size -= bytes;
        bytes += iter->bi_bvec_done;

        while (bytes && bytes >= bv[idx].bv_len) {
                bytes -= bv[idx].bv_len;
                idx++;
        }

        iter->bi_idx = idx;
        iter->bi_bvec_done = bytes;
        return true;
}

/*
 * A simpler version of bvec_iter_advance(), @bytes should not span
 * across multiple bvec entries, i.e. bytes <= bv[i->bi_idx].bv_len
 */
static inline void bvec_iter_advance_single(const struct bio_vec *bv,
                                struct bvec_iter *iter, unsigned int bytes)
{
        unsigned int done = iter->bi_bvec_done + bytes;

        if (done == bv[iter->bi_idx].bv_len) {
                done = 0;
                iter->bi_idx++;
        }
        iter->bi_bvec_done = done;
        iter->bi_size -= bytes;
}

#define for_each_bvec(bvl, bio_vec, iter, start)                        \
        for (iter = (start);                                            \
             (iter).bi_size &&                                          \
                ((bvl = bvec_iter_bvec((bio_vec), (iter))), 1); \
             bvec_iter_advance_single((bio_vec), &(iter), (bvl).bv_len))

/* for iterating one bio from start to end */
#define BVEC_ITER_ALL_INIT (struct bvec_iter)                           \
{                                                                       \
        .bi_sector      = 0,                                            \
        .bi_size        = UINT_MAX,                                     \
        .bi_idx         = 0,                                            \
        .bi_bvec_done   = 0,                                            \
}

static inline struct bio_vec *bvec_init_iter_all(struct bvec_iter_all *iter_all)
{
        iter_all->done = 0;
        iter_all->idx = 0;

        return &iter_all->bv;
}

static inline void bvec_advance(const struct bio_vec *bvec,
                                struct bvec_iter_all *iter_all)
{
        struct bio_vec *bv = &iter_all->bv;

        if (iter_all->done) {
                bv->bv_page++;
                bv->bv_offset = 0;
        } else {
                bv->bv_page = bvec->bv_page + (bvec->bv_offset >> PAGE_SHIFT);
                bv->bv_offset = bvec->bv_offset & ~PAGE_MASK;
        }
        bv->bv_len = min_t(unsigned int, PAGE_SIZE - bv->bv_offset,
                           bvec->bv_len - iter_all->done);
        iter_all->done += bv->bv_len;

        if (iter_all->done == bvec->bv_len) {
                iter_all->idx++;
                iter_all->done = 0;
        }
}

/**
 * bvec_kmap_local - map a bvec into the kernel virtual address space
 * @bvec: bvec to map
 *
 * Must be called on single-page bvecs only.  Call kunmap_local on the returned
 * address to unmap.
 */
static inline void *bvec_kmap_local(struct bio_vec *bvec)
{
        return kmap_local_page(bvec->bv_page) + bvec->bv_offset;
}

/**
 * memcpy_from_bvec - copy data from a bvec
 * @bvec: bvec to copy from
 *
 * Must be called on single-page bvecs only.
 */
static inline void memcpy_from_bvec(char *to, struct bio_vec *bvec)
{
        memcpy_from_page(to, bvec->bv_page, bvec->bv_offset, bvec->bv_len);
}

/**
 * memcpy_to_bvec - copy data to a bvec
 * @bvec: bvec to copy to
 *
 * Must be called on single-page bvecs only.
 */
static inline void memcpy_to_bvec(struct bio_vec *bvec, const char *from)
{
        memcpy_to_page(bvec->bv_page, bvec->bv_offset, from, bvec->bv_len);
}

/**
 * memzero_bvec - zero all data in a bvec
 * @bvec: bvec to zero
 *
 * Must be called on single-page bvecs only.
 */
static inline void memzero_bvec(struct bio_vec *bvec)
{
        memzero_page(bvec->bv_page, bvec->bv_offset, bvec->bv_len);
}

/**
 * bvec_virt - return the virtual address for a bvec
 * @bvec: bvec to return the virtual address for
 *
 * Note: the caller must ensure that @bvec->bv_page is not a highmem page.
 */
static inline void *bvec_virt(struct bio_vec *bvec)
{
        WARN_ON_ONCE(PageHighMem(bvec->bv_page));
        return page_address(bvec->bv_page) + bvec->bv_offset;
}

#endif /* __LINUX_BVEC_H */