// SPDX-License-Identifier: GPL-2.0
/*
 * random utility code, for bcache but in theory not specific to bcache
 *
 * Copyright 2010, 2011 Kent Overstreet <kent.overstreet@gmail.com>
 * Copyright 2012 Google, Inc.
 */

#include <linux/bio.h>
#include <linux/blkdev.h>
#include <linux/ctype.h>
#include <linux/debugfs.h>
#include <linux/module.h>
#include <linux/seq_file.h>
#include <linux/types.h>
#include <linux/sched/clock.h>

#include "util.h"

#define simple_strtoint(c, end, base)   simple_strtol(c, end, base)
#define simple_strtouint(c, end, base)  simple_strtoul(c, end, base)

#define STRTO_H(name, type)                                     \
int bch_ ## name ## _h(const char *cp, type *res)               \
{                                                               \
        int u = 0;                                              \
        char *e;                                                \
        type i = simple_ ## name(cp, &e, 10);                   \
                                                                \
        switch (tolower(*e)) {                                  \
        default:                                                \
                return -EINVAL;                                 \
        case 'y':                                               \
        case 'z':                                               \
                u++;                                            \
                fallthrough;                                    \
        case 'e':                                               \
                u++;                                            \
                fallthrough;                                    \
        case 'p':                                               \
                u++;                                            \
                fallthrough;                                    \
        case 't':                                               \
                u++;                                            \
                fallthrough;                                    \
        case 'g':                                               \
                u++;                                            \
                fallthrough;                                    \
        case 'm':                                               \
                u++;                                            \
                fallthrough;                                    \
        case 'k':                                               \
                u++;                                            \
                if (e++ == cp)                                  \
                        return -EINVAL;                         \
                fallthrough;                                    \
        case '\n':                                              \
        case '\0':                                              \
                if (*e == '\n')                                 \
                        e++;                                    \
        }                                                       \
                                                                \
        if (*e)                                                 \
                return -EINVAL;                                 \
                                                                \
        while (u--) {                                           \
                if ((type) ~0 > 0 &&                            \
                    (type) ~0 / 1024 <= i)                      \
                        return -EINVAL;                         \
                if ((i > 0 && ANYSINT_MAX(type) / 1024 < i) ||  \
                    (i < 0 && -ANYSINT_MAX(type) / 1024 > i))   \
                        return -EINVAL;                         \
                i *= 1024;                                      \
        }                                                       \
                                                                \
        *res = i;                                               \
        return 0;                                               \
}                                                               \

STRTO_H(strtoint, int)
STRTO_H(strtouint, unsigned int)
STRTO_H(strtoll, long long)
STRTO_H(strtoull, unsigned long long)

/**
 * bch_hprint - formats @v to human readable string for sysfs.
 * @buf: the (at least 8 byte) buffer to format the result into.
 * @v: signed 64 bit integer
 *
 * Returns the number of bytes used by format.
 */
ssize_t bch_hprint(char *buf, int64_t v)
{
        static const char units[] = "?kMGTPEZY";
        int u = 0, t;

        uint64_t q;

        if (v < 0)
                q = -v;
        else
                q = v;

        /* For as long as the number is more than 3 digits, but at least
         * once, shift right / divide by 1024.  Keep the remainder for
         * a digit after the decimal point.
         */
        do {
                u++;

                t = q & ~(~0 << 10);
                q >>= 10;
        } while (q >= 1000);

        if (v < 0)
                /* '-', up to 3 digits, '.', 1 digit, 1 character, null;
                 * yields 8 bytes.
                 */
                return sprintf(buf, "-%llu.%i%c", q, t * 10 / 1024, units[u]);
        else
                return sprintf(buf, "%llu.%i%c", q, t * 10 / 1024, units[u]);
}

bool bch_is_zero(const char *p, size_t n)
{
        size_t i;

        for (i = 0; i < n; i++)
                if (p[i])
                        return false;
        return true;
}

int bch_parse_uuid(const char *s, char *uuid)
{
        size_t i, j, x;

        memset(uuid, 0, 16);

        for (i = 0, j = 0;
             i < strspn(s, "-0123456789:ABCDEFabcdef") && j < 32;
             i++) {
                x = s[i] | 32;

                switch (x) {
                case '0'...'9':
                        x -= '0';
                        break;
                case 'a'...'f':
                        x -= 'a' - 10;
                        break;
                default:
                        continue;
                }

                if (!(j & 1))
                        x <<= 4;
                uuid[j++ >> 1] |= x;
        }
        return i;
}

void bch_time_stats_update(struct time_stats *stats, uint64_t start_time)
{
        uint64_t now, duration, last;

        spin_lock(&stats->lock);

        now             = local_clock();
        duration        = time_after64(now, start_time)
                ? now - start_time : 0;
        last            = time_after64(now, stats->last)
                ? now - stats->last : 0;

        stats->max_duration = max(stats->max_duration, duration);

        if (stats->last) {
                ewma_add(stats->average_duration, duration, 8, 8);

                if (stats->average_frequency)
                        ewma_add(stats->average_frequency, last, 8, 8);
                else
                        stats->average_frequency  = last << 8;
        } else {
                stats->average_duration  = duration << 8;
        }

        stats->last = now ?: 1;

        spin_unlock(&stats->lock);
}

/**
 * bch_next_delay() - update ratelimiting statistics and calculate next delay
 * @d: the struct bch_ratelimit to update
 * @done: the amount of work done, in arbitrary units
 *
 * Increment @d by the amount of work done, and return how long to delay in
 * jiffies until the next time to do some work.
 */
uint64_t bch_next_delay(struct bch_ratelimit *d, uint64_t done)
{
        uint64_t now = local_clock();

        d->next += div_u64(done * NSEC_PER_SEC, atomic_long_read(&d->rate));

        /* Bound the time.  Don't let us fall further than 2 seconds behind
         * (this prevents unnecessary backlog that would make it impossible
         * to catch up).  If we're ahead of the desired writeback rate,
         * don't let us sleep more than 2.5 seconds (so we can notice/respond
         * if the control system tells us to speed up!).
         */
        if (time_before64(now + NSEC_PER_SEC * 5LLU / 2LLU, d->next))
                d->next = now + NSEC_PER_SEC * 5LLU / 2LLU;

        if (time_after64(now - NSEC_PER_SEC * 2, d->next))
                d->next = now - NSEC_PER_SEC * 2;

        return time_after64(d->next, now)
                ? div_u64(d->next - now, NSEC_PER_SEC / HZ)
                : 0;
}

/*
 * Generally it isn't good to access .bi_io_vec and .bi_vcnt directly,
 * the preferred way is bio_add_page, but in this case, bch_bio_map()
 * supposes that the bvec table is empty, so it is safe to access
 * .bi_vcnt & .bi_io_vec in this way even after multipage bvec is
 * supported.
 */
void bch_bio_map(struct bio *bio, void *base)
{
        size_t size = bio->bi_iter.bi_size;
        struct bio_vec *bv = bio->bi_io_vec;

        BUG_ON(!bio->bi_iter.bi_size);
        BUG_ON(bio->bi_vcnt);

        bv->bv_offset = base ? offset_in_page(base) : 0;
        goto start;

        for (; size; bio->bi_vcnt++, bv++) {
                bv->bv_offset   = 0;
start:          bv->bv_len      = min_t(size_t, PAGE_SIZE - bv->bv_offset,
                                        size);
                if (base) {
                        bv->bv_page = is_vmalloc_addr(base)
                                ? vmalloc_to_page(base)
                                : virt_to_page(base);

                        base += bv->bv_len;
                }

                size -= bv->bv_len;
        }
}

/**
 * bch_bio_alloc_pages - allocates a single page for each bvec in a bio
 * @bio: bio to allocate pages for
 * @gfp_mask: flags for allocation
 *
 * Allocates pages up to @bio->bi_vcnt.
 *
 * Returns 0 on success, -ENOMEM on failure. On failure, any allocated pages are
 * freed.
 */
int bch_bio_alloc_pages(struct bio *bio, gfp_t gfp_mask)
{
        int i;
        struct bio_vec *bv;

        /*
         * This is called on freshly new bio, so it is safe to access the
         * bvec table directly.
         */
        for (i = 0, bv = bio->bi_io_vec; i < bio->bi_vcnt; bv++, i++) {
                bv->bv_page = alloc_page(gfp_mask);
                if (!bv->bv_page) {
                        while (--bv >= bio->bi_io_vec)
                                __free_page(bv->bv_page);
                        return -ENOMEM;
                }
        }

        return 0;
}