// SPDX-License-Identifier: GPL-2.0+
/*
 * NILFS segment usage file.
 *
 * Copyright (C) 2006-2008 Nippon Telegraph and Telephone Corporation.
 *
 * Written by Koji Sato.
 * Revised by Ryusuke Konishi.
 */

#include <linux/kernel.h>
#include <linux/fs.h>
#include <linux/string.h>
#include <linux/buffer_head.h>
#include <linux/errno.h>
#include "mdt.h"
#include "sufile.h"

#include <trace/events/nilfs2.h>

/**
 * struct nilfs_sufile_info - on-memory private data of sufile
 * @mi: on-memory private data of metadata file
 * @ncleansegs: number of clean segments
 * @allocmin: lower limit of allocatable segment range
 * @allocmax: upper limit of allocatable segment range
 */
struct nilfs_sufile_info {
        struct nilfs_mdt_info mi;
        unsigned long ncleansegs;/* number of clean segments */
        __u64 allocmin;         /* lower limit of allocatable segment range */
        __u64 allocmax;         /* upper limit of allocatable segment range */
};

static inline struct nilfs_sufile_info *NILFS_SUI(struct inode *sufile)
{
        return (struct nilfs_sufile_info *)NILFS_MDT(sufile);
}

static inline unsigned long
nilfs_sufile_segment_usages_per_block(const struct inode *sufile)
{
        return NILFS_MDT(sufile)->mi_entries_per_block;
}

static unsigned long
nilfs_sufile_get_blkoff(const struct inode *sufile, __u64 segnum)
{
        __u64 t = segnum + NILFS_MDT(sufile)->mi_first_entry_offset;

        t = div64_ul(t, nilfs_sufile_segment_usages_per_block(sufile));
        return (unsigned long)t;
}

static unsigned long
nilfs_sufile_get_offset(const struct inode *sufile, __u64 segnum)
{
        __u64 t = segnum + NILFS_MDT(sufile)->mi_first_entry_offset;

        return do_div(t, nilfs_sufile_segment_usages_per_block(sufile));
}

static unsigned long
nilfs_sufile_segment_usages_in_block(const struct inode *sufile, __u64 curr,
                                     __u64 max)
{
        return min_t(unsigned long,
                     nilfs_sufile_segment_usages_per_block(sufile) -
                     nilfs_sufile_get_offset(sufile, curr),
                     max - curr + 1);
}

/**
 * nilfs_sufile_segment_usage_offset - calculate the byte offset of a segment
 *                                     usage entry in the folio containing it
 * @sufile: segment usage file inode
 * @segnum: number of segment usage
 * @bh:     buffer head of block containing segment usage indexed by @segnum
 *
 * Return: Byte offset in the folio of the segment usage entry.
 */
static size_t nilfs_sufile_segment_usage_offset(const struct inode *sufile,
                                                __u64 segnum,
                                                struct buffer_head *bh)
{
        return offset_in_folio(bh->b_folio, bh->b_data) +
                nilfs_sufile_get_offset(sufile, segnum) *
                NILFS_MDT(sufile)->mi_entry_size;
}

static int nilfs_sufile_get_header_block(struct inode *sufile,
                                         struct buffer_head **bhp)
{
        int err = nilfs_mdt_get_block(sufile, 0, 0, NULL, bhp);

        if (unlikely(err == -ENOENT)) {
                nilfs_error(sufile->i_sb,
                            "missing header block in segment usage metadata");
                err = -EIO;
        }
        return err;
}

static inline int
nilfs_sufile_get_segment_usage_block(struct inode *sufile, __u64 segnum,
                                     int create, struct buffer_head **bhp)
{
        return nilfs_mdt_get_block(sufile,
                                   nilfs_sufile_get_blkoff(sufile, segnum),
                                   create, NULL, bhp);
}

static int nilfs_sufile_delete_segment_usage_block(struct inode *sufile,
                                                   __u64 segnum)
{
        return nilfs_mdt_delete_block(sufile,
                                      nilfs_sufile_get_blkoff(sufile, segnum));
}

static void nilfs_sufile_mod_counter(struct buffer_head *header_bh,
                                     u64 ncleanadd, u64 ndirtyadd)
{
        struct nilfs_sufile_header *header;

        header = kmap_local_folio(header_bh->b_folio, 0);
        le64_add_cpu(&header->sh_ncleansegs, ncleanadd);
        le64_add_cpu(&header->sh_ndirtysegs, ndirtyadd);
        kunmap_local(header);

        mark_buffer_dirty(header_bh);
}

/**
 * nilfs_sufile_get_ncleansegs - return the number of clean segments
 * @sufile: inode of segment usage file
 *
 * Return: Number of clean segments.
 */
unsigned long nilfs_sufile_get_ncleansegs(struct inode *sufile)
{
        return NILFS_SUI(sufile)->ncleansegs;
}

/**
 * nilfs_sufile_updatev - modify multiple segment usages at a time
 * @sufile: inode of segment usage file
 * @segnumv: array of segment numbers
 * @nsegs: size of @segnumv array
 * @create: creation flag
 * @ndone: place to store number of modified segments on @segnumv
 * @dofunc: primitive operation for the update
 *
 * Description: nilfs_sufile_updatev() repeatedly calls @dofunc
 * against the given array of segments.  The @dofunc is called with
 * buffers of a header block and the sufile block in which the target
 * segment usage entry is contained.  If @ndone is given, the number
 * of successfully modified segments from the head is stored in the
 * place @ndone points to.
 *
 * Return: 0 on success, or one of the following negative error codes on
 * failure:
 * * %-EINVAL   - Invalid segment usage number
 * * %-EIO      - I/O error (including metadata corruption).
 * * %-ENOENT   - Given segment usage is in hole block (may be returned if
 *                @create is zero)
 * * %-ENOMEM   - Insufficient memory available.
 */
int nilfs_sufile_updatev(struct inode *sufile, __u64 *segnumv, size_t nsegs,
                         int create, size_t *ndone,
                         void (*dofunc)(struct inode *, __u64,
                                        struct buffer_head *,
                                        struct buffer_head *))
{
        struct buffer_head *header_bh, *bh;
        unsigned long blkoff, prev_blkoff;
        __u64 *seg;
        size_t nerr = 0, n = 0;
        int ret = 0;

        if (unlikely(nsegs == 0))
                goto out;

        down_write(&NILFS_MDT(sufile)->mi_sem);
        for (seg = segnumv; seg < segnumv + nsegs; seg++) {
                if (unlikely(*seg >= nilfs_sufile_get_nsegments(sufile))) {
                        nilfs_warn(sufile->i_sb,
                                   "%s: invalid segment number: %llu",
                                   __func__, (unsigned long long)*seg);
                        nerr++;
                }
        }
        if (nerr > 0) {
                ret = -EINVAL;
                goto out_sem;
        }

        ret = nilfs_sufile_get_header_block(sufile, &header_bh);
        if (ret < 0)
                goto out_sem;

        seg = segnumv;
        blkoff = nilfs_sufile_get_blkoff(sufile, *seg);
        ret = nilfs_mdt_get_block(sufile, blkoff, create, NULL, &bh);
        if (ret < 0)
                goto out_header;

        for (;;) {
                dofunc(sufile, *seg, header_bh, bh);

                if (++seg >= segnumv + nsegs)
                        break;
                prev_blkoff = blkoff;
                blkoff = nilfs_sufile_get_blkoff(sufile, *seg);
                if (blkoff == prev_blkoff)
                        continue;

                /* get different block */
                brelse(bh);
                ret = nilfs_mdt_get_block(sufile, blkoff, create, NULL, &bh);
                if (unlikely(ret < 0))
                        goto out_header;
        }
        brelse(bh);

 out_header:
        n = seg - segnumv;
        brelse(header_bh);
 out_sem:
        up_write(&NILFS_MDT(sufile)->mi_sem);
 out:
        if (ndone)
                *ndone = n;
        return ret;
}

int nilfs_sufile_update(struct inode *sufile, __u64 segnum, int create,
                        void (*dofunc)(struct inode *, __u64,
                                       struct buffer_head *,
                                       struct buffer_head *))
{
        struct buffer_head *header_bh, *bh;
        int ret;

        if (unlikely(segnum >= nilfs_sufile_get_nsegments(sufile))) {
                nilfs_warn(sufile->i_sb, "%s: invalid segment number: %llu",
                           __func__, (unsigned long long)segnum);
                return -EINVAL;
        }
        down_write(&NILFS_MDT(sufile)->mi_sem);

        ret = nilfs_sufile_get_header_block(sufile, &header_bh);
        if (ret < 0)
                goto out_sem;

        ret = nilfs_sufile_get_segment_usage_block(sufile, segnum, create, &bh);
        if (!ret) {
                dofunc(sufile, segnum, header_bh, bh);
                brelse(bh);
        }
        brelse(header_bh);

 out_sem:
        up_write(&NILFS_MDT(sufile)->mi_sem);
        return ret;
}

/**
 * nilfs_sufile_set_alloc_range - limit range of segment to be allocated
 * @sufile: inode of segment usage file
 * @start: minimum segment number of allocatable region (inclusive)
 * @end: maximum segment number of allocatable region (inclusive)
 *
 * Return: 0 on success, or %-ERANGE if segment range is invalid.
 */
int nilfs_sufile_set_alloc_range(struct inode *sufile, __u64 start, __u64 end)
{
        struct nilfs_sufile_info *sui = NILFS_SUI(sufile);
        __u64 nsegs;
        int ret = -ERANGE;

        down_write(&NILFS_MDT(sufile)->mi_sem);
        nsegs = nilfs_sufile_get_nsegments(sufile);

        if (start <= end && end < nsegs) {
                sui->allocmin = start;
                sui->allocmax = end;
                ret = 0;
        }
        up_write(&NILFS_MDT(sufile)->mi_sem);
        return ret;
}

/**
 * nilfs_sufile_alloc - allocate a segment
 * @sufile: inode of segment usage file
 * @segnump: pointer to segment number
 *
 * Description: nilfs_sufile_alloc() allocates a clean segment, and stores
 * its segment number in the place pointed to by @segnump.
 *
 * Return: 0 on success, or one of the following negative error codes on
 * failure:
 * * %-EIO      - I/O error (including metadata corruption).
 * * %-ENOMEM   - Insufficient memory available.
 * * %-ENOSPC   - No clean segment left.
 */
int nilfs_sufile_alloc(struct inode *sufile, __u64 *segnump)
{
        struct buffer_head *header_bh, *su_bh;
        struct nilfs_sufile_header *header;
        struct nilfs_segment_usage *su;
        struct nilfs_sufile_info *sui = NILFS_SUI(sufile);
        size_t susz = NILFS_MDT(sufile)->mi_entry_size;
        __u64 segnum, maxsegnum, last_alloc;
        size_t offset;
        void *kaddr;
        unsigned long nsegments, nsus, cnt;
        int ret, j;

        down_write(&NILFS_MDT(sufile)->mi_sem);

        ret = nilfs_sufile_get_header_block(sufile, &header_bh);
        if (ret < 0)
                goto out_sem;
        header = kmap_local_folio(header_bh->b_folio, 0);
        last_alloc = le64_to_cpu(header->sh_last_alloc);
        kunmap_local(header);

        nsegments = nilfs_sufile_get_nsegments(sufile);
        maxsegnum = sui->allocmax;
        segnum = last_alloc + 1;
        if (segnum < sui->allocmin || segnum > sui->allocmax)
                segnum = sui->allocmin;

        for (cnt = 0; cnt < nsegments; cnt += nsus) {
                if (segnum > maxsegnum) {
                        if (cnt < sui->allocmax - sui->allocmin + 1) {
                                /*
                                 * wrap around in the limited region.
                                 * if allocation started from
                                 * sui->allocmin, this never happens.
                                 */
                                segnum = sui->allocmin;
                                maxsegnum = last_alloc;
                        } else if (segnum > sui->allocmin &&
                                   sui->allocmax + 1 < nsegments) {
                                segnum = sui->allocmax + 1;
                                maxsegnum = nsegments - 1;
                        } else if (sui->allocmin > 0)  {
                                segnum = 0;
                                maxsegnum = sui->allocmin - 1;
                        } else {
                                break; /* never happens */
                        }
                }
                trace_nilfs2_segment_usage_check(sufile, segnum, cnt);
                ret = nilfs_sufile_get_segment_usage_block(sufile, segnum, 1,
                                                           &su_bh);
                if (ret < 0)
                        goto out_header;

                offset = nilfs_sufile_segment_usage_offset(sufile, segnum,
                                                           su_bh);
                su = kaddr = kmap_local_folio(su_bh->b_folio, offset);

                nsus = nilfs_sufile_segment_usages_in_block(
                        sufile, segnum, maxsegnum);
                for (j = 0; j < nsus; j++, su = (void *)su + susz, segnum++) {
                        if (!nilfs_segment_usage_clean(su))
                                continue;
                        /* found a clean segment */
                        nilfs_segment_usage_set_dirty(su);
                        kunmap_local(kaddr);

                        header = kmap_local_folio(header_bh->b_folio, 0);
                        le64_add_cpu(&header->sh_ncleansegs, -1);
                        le64_add_cpu(&header->sh_ndirtysegs, 1);
                        header->sh_last_alloc = cpu_to_le64(segnum);
                        kunmap_local(header);

                        sui->ncleansegs--;
                        mark_buffer_dirty(header_bh);
                        mark_buffer_dirty(su_bh);
                        nilfs_mdt_mark_dirty(sufile);
                        brelse(su_bh);
                        *segnump = segnum;

                        trace_nilfs2_segment_usage_allocated(sufile, segnum);

                        goto out_header;
                }

                kunmap_local(kaddr);
                brelse(su_bh);
        }

        /* no segments left */
        ret = -ENOSPC;

 out_header:
        brelse(header_bh);

 out_sem:
        up_write(&NILFS_MDT(sufile)->mi_sem);
        return ret;
}

void nilfs_sufile_do_cancel_free(struct inode *sufile, __u64 segnum,
                                 struct buffer_head *header_bh,
                                 struct buffer_head *su_bh)
{
        struct nilfs_segment_usage *su;
        size_t offset;

        offset = nilfs_sufile_segment_usage_offset(sufile, segnum, su_bh);
        su = kmap_local_folio(su_bh->b_folio, offset);
        if (unlikely(!nilfs_segment_usage_clean(su))) {
                nilfs_warn(sufile->i_sb, "%s: segment %llu must be clean",
                           __func__, (unsigned long long)segnum);
                kunmap_local(su);
                return;
        }
        nilfs_segment_usage_set_dirty(su);
        kunmap_local(su);

        nilfs_sufile_mod_counter(header_bh, -1, 1);
        NILFS_SUI(sufile)->ncleansegs--;

        mark_buffer_dirty(su_bh);
        nilfs_mdt_mark_dirty(sufile);
}

void nilfs_sufile_do_scrap(struct inode *sufile, __u64 segnum,
                           struct buffer_head *header_bh,
                           struct buffer_head *su_bh)
{
        struct nilfs_segment_usage *su;
        size_t offset;
        int clean, dirty;

        offset = nilfs_sufile_segment_usage_offset(sufile, segnum, su_bh);
        su = kmap_local_folio(su_bh->b_folio, offset);
        if (su->su_flags == cpu_to_le32(BIT(NILFS_SEGMENT_USAGE_DIRTY)) &&
            su->su_nblocks == cpu_to_le32(0)) {
                kunmap_local(su);
                return;
        }
        clean = nilfs_segment_usage_clean(su);
        dirty = nilfs_segment_usage_dirty(su);

        /* make the segment garbage */
        su->su_lastmod = cpu_to_le64(0);
        su->su_nblocks = cpu_to_le32(0);
        su->su_flags = cpu_to_le32(BIT(NILFS_SEGMENT_USAGE_DIRTY));
        kunmap_local(su);

        nilfs_sufile_mod_counter(header_bh, clean ? (u64)-1 : 0, dirty ? 0 : 1);
        NILFS_SUI(sufile)->ncleansegs -= clean;

        mark_buffer_dirty(su_bh);
        nilfs_mdt_mark_dirty(sufile);
}

void nilfs_sufile_do_free(struct inode *sufile, __u64 segnum,
                          struct buffer_head *header_bh,
                          struct buffer_head *su_bh)
{
        struct nilfs_segment_usage *su;
        size_t offset;
        int sudirty;

        offset = nilfs_sufile_segment_usage_offset(sufile, segnum, su_bh);
        su = kmap_local_folio(su_bh->b_folio, offset);
        if (nilfs_segment_usage_clean(su)) {
                nilfs_warn(sufile->i_sb, "%s: segment %llu is already clean",
                           __func__, (unsigned long long)segnum);
                kunmap_local(su);
                return;
        }
        if (unlikely(nilfs_segment_usage_error(su)))
                nilfs_warn(sufile->i_sb, "free segment %llu marked in error",
                           (unsigned long long)segnum);

        sudirty = nilfs_segment_usage_dirty(su);
        if (unlikely(!sudirty))
                nilfs_warn(sufile->i_sb, "free unallocated segment %llu",
                           (unsigned long long)segnum);

        nilfs_segment_usage_set_clean(su);
        kunmap_local(su);
        mark_buffer_dirty(su_bh);

        nilfs_sufile_mod_counter(header_bh, 1, sudirty ? (u64)-1 : 0);
        NILFS_SUI(sufile)->ncleansegs++;

        nilfs_mdt_mark_dirty(sufile);

        trace_nilfs2_segment_usage_freed(sufile, segnum);
}

/**
 * nilfs_sufile_mark_dirty - mark the buffer having a segment usage dirty
 * @sufile: inode of segment usage file
 * @segnum: segment number
 *
 * Return: 0 on success, or a negative error code on failure.
 */
int nilfs_sufile_mark_dirty(struct inode *sufile, __u64 segnum)
{
        struct buffer_head *bh;
        size_t offset;
        struct nilfs_segment_usage *su;
        int ret;

        down_write(&NILFS_MDT(sufile)->mi_sem);
        ret = nilfs_sufile_get_segment_usage_block(sufile, segnum, 0, &bh);
        if (unlikely(ret)) {
                if (ret == -ENOENT) {
                        nilfs_error(sufile->i_sb,
                                    "segment usage for segment %llu is unreadable due to a hole block",
                                    (unsigned long long)segnum);
                        ret = -EIO;
                }
                goto out_sem;
        }

        offset = nilfs_sufile_segment_usage_offset(sufile, segnum, bh);
        su = kmap_local_folio(bh->b_folio, offset);
        if (unlikely(nilfs_segment_usage_error(su))) {
                struct the_nilfs *nilfs = sufile->i_sb->s_fs_info;

                kunmap_local(su);
                brelse(bh);
                if (nilfs_segment_is_active(nilfs, segnum)) {
                        nilfs_error(sufile->i_sb,
                                    "active segment %llu is erroneous",
                                    (unsigned long long)segnum);
                } else {
                        /*
                         * Segments marked erroneous are never allocated by
                         * nilfs_sufile_alloc(); only active segments, ie,
                         * the segments indexed by ns_segnum or ns_nextnum,
                         * can be erroneous here.
                         */
                        WARN_ON_ONCE(1);
                }
                ret = -EIO;
        } else {
                nilfs_segment_usage_set_dirty(su);
                kunmap_local(su);
                mark_buffer_dirty(bh);
                nilfs_mdt_mark_dirty(sufile);
                brelse(bh);
        }
out_sem:
        up_write(&NILFS_MDT(sufile)->mi_sem);
        return ret;
}

/**
 * nilfs_sufile_set_segment_usage - set usage of a segment
 * @sufile: inode of segment usage file
 * @segnum: segment number
 * @nblocks: number of live blocks in the segment
 * @modtime: modification time (option)
 *
 * Return: 0 on success, or a negative error code on failure.
 */
int nilfs_sufile_set_segment_usage(struct inode *sufile, __u64 segnum,
                                   unsigned long nblocks, time64_t modtime)
{
        struct buffer_head *bh;
        struct nilfs_segment_usage *su;
        size_t offset;
        int ret;

        down_write(&NILFS_MDT(sufile)->mi_sem);
        ret = nilfs_sufile_get_segment_usage_block(sufile, segnum, 0, &bh);
        if (ret < 0)
                goto out_sem;

        offset = nilfs_sufile_segment_usage_offset(sufile, segnum, bh);
        su = kmap_local_folio(bh->b_folio, offset);
        if (modtime) {
                /*
                 * Check segusage error and set su_lastmod only when updating
                 * this entry with a valid timestamp, not for cancellation.
                 */
                WARN_ON_ONCE(nilfs_segment_usage_error(su));
                su->su_lastmod = cpu_to_le64(modtime);
        }
        su->su_nblocks = cpu_to_le32(nblocks);
        kunmap_local(su);

        mark_buffer_dirty(bh);
        nilfs_mdt_mark_dirty(sufile);
        brelse(bh);

 out_sem:
        up_write(&NILFS_MDT(sufile)->mi_sem);
        return ret;
}

/**
 * nilfs_sufile_get_stat - get segment usage statistics
 * @sufile: inode of segment usage file
 * @sustat: pointer to a structure of segment usage statistics
 *
 * Description: nilfs_sufile_get_stat() retrieves segment usage statistics
 * and stores them in the location pointed to by @sustat.
 *
 * Return: 0 on success, or one of the following negative error codes on
 * failure:
 * * %-EIO      - I/O error (including metadata corruption).
 * * %-ENOMEM   - Insufficient memory available.
 */
int nilfs_sufile_get_stat(struct inode *sufile, struct nilfs_sustat *sustat)
{
        struct buffer_head *header_bh;
        struct nilfs_sufile_header *header;
        struct the_nilfs *nilfs = sufile->i_sb->s_fs_info;
        int ret;

        down_read(&NILFS_MDT(sufile)->mi_sem);

        ret = nilfs_sufile_get_header_block(sufile, &header_bh);
        if (ret < 0)
                goto out_sem;

        header = kmap_local_folio(header_bh->b_folio, 0);
        sustat->ss_nsegs = nilfs_sufile_get_nsegments(sufile);
        sustat->ss_ncleansegs = le64_to_cpu(header->sh_ncleansegs);
        sustat->ss_ndirtysegs = le64_to_cpu(header->sh_ndirtysegs);
        sustat->ss_ctime = nilfs->ns_ctime;
        sustat->ss_nongc_ctime = nilfs->ns_nongc_ctime;
        spin_lock(&nilfs->ns_last_segment_lock);
        sustat->ss_prot_seq = nilfs->ns_prot_seq;
        spin_unlock(&nilfs->ns_last_segment_lock);
        kunmap_local(header);
        brelse(header_bh);

 out_sem:
        up_read(&NILFS_MDT(sufile)->mi_sem);
        return ret;
}

void nilfs_sufile_do_set_error(struct inode *sufile, __u64 segnum,
                               struct buffer_head *header_bh,
                               struct buffer_head *su_bh)
{
        struct nilfs_segment_usage *su;
        size_t offset;
        int suclean;

        offset = nilfs_sufile_segment_usage_offset(sufile, segnum, su_bh);
        su = kmap_local_folio(su_bh->b_folio, offset);
        if (nilfs_segment_usage_error(su)) {
                kunmap_local(su);
                return;
        }
        suclean = nilfs_segment_usage_clean(su);
        nilfs_segment_usage_set_error(su);
        kunmap_local(su);

        if (suclean) {
                nilfs_sufile_mod_counter(header_bh, -1, 0);
                NILFS_SUI(sufile)->ncleansegs--;
        }
        mark_buffer_dirty(su_bh);
        nilfs_mdt_mark_dirty(sufile);
}

/**
 * nilfs_sufile_truncate_range - truncate range of segment array
 * @sufile: inode of segment usage file
 * @start: start segment number (inclusive)
 * @end: end segment number (inclusive)
 *
 * Return: 0 on success, or one of the following negative error codes on
 * failure:
 * * %-EBUSY    - Dirty or active segments are present in the range.
 * * %-EINVAL   - Invalid number of segments specified.
 * * %-EIO      - I/O error (including metadata corruption).
 * * %-ENOMEM   - Insufficient memory available.
 */
static int nilfs_sufile_truncate_range(struct inode *sufile,
                                       __u64 start, __u64 end)
{
        struct the_nilfs *nilfs = sufile->i_sb->s_fs_info;
        struct buffer_head *header_bh;
        struct buffer_head *su_bh;
        struct nilfs_segment_usage *su, *su2;
        size_t susz = NILFS_MDT(sufile)->mi_entry_size;
        unsigned long segusages_per_block;
        unsigned long nsegs, ncleaned;
        __u64 segnum;
        size_t offset;
        ssize_t n, nc;
        int ret;
        int j;

        nsegs = nilfs_sufile_get_nsegments(sufile);

        ret = -EINVAL;
        if (start > end || start >= nsegs)
                goto out;

        ret = nilfs_sufile_get_header_block(sufile, &header_bh);
        if (ret < 0)
                goto out;

        segusages_per_block = nilfs_sufile_segment_usages_per_block(sufile);
        ncleaned = 0;

        for (segnum = start; segnum <= end; segnum += n) {
                n = min_t(unsigned long,
                          segusages_per_block -
                                  nilfs_sufile_get_offset(sufile, segnum),
                          end - segnum + 1);
                ret = nilfs_sufile_get_segment_usage_block(sufile, segnum, 0,
                                                           &su_bh);
                if (ret < 0) {
                        if (ret != -ENOENT)
                                goto out_header;
                        /* hole */
                        continue;
                }
                offset = nilfs_sufile_segment_usage_offset(sufile, segnum,
                                                           su_bh);
                su = kmap_local_folio(su_bh->b_folio, offset);
                su2 = su;
                for (j = 0; j < n; j++, su = (void *)su + susz) {
                        if ((le32_to_cpu(su->su_flags) &
                             ~BIT(NILFS_SEGMENT_USAGE_ERROR)) ||
                            nilfs_segment_is_active(nilfs, segnum + j)) {
                                ret = -EBUSY;
                                kunmap_local(su2);
                                brelse(su_bh);
                                goto out_header;
                        }
                }
                nc = 0;
                for (su = su2, j = 0; j < n; j++, su = (void *)su + susz) {
                        if (nilfs_segment_usage_error(su)) {
                                nilfs_segment_usage_set_clean(su);
                                nc++;
                        }
                }
                kunmap_local(su2);
                if (nc > 0) {
                        mark_buffer_dirty(su_bh);
                        ncleaned += nc;
                }
                brelse(su_bh);

                if (n == segusages_per_block) {
                        /* make hole */
                        nilfs_sufile_delete_segment_usage_block(sufile, segnum);
                }
        }
        ret = 0;

out_header:
        if (ncleaned > 0) {
                NILFS_SUI(sufile)->ncleansegs += ncleaned;
                nilfs_sufile_mod_counter(header_bh, ncleaned, 0);
                nilfs_mdt_mark_dirty(sufile);
        }
        brelse(header_bh);
out:
        return ret;
}

/**
 * nilfs_sufile_resize - resize segment array
 * @sufile: inode of segment usage file
 * @newnsegs: new number of segments
 *
 * Return: 0 on success, or one of the following negative error codes on
 * failure:
 * * %-EBUSY    - Dirty or active segments exist in the region to be truncated.
 * * %-EIO      - I/O error (including metadata corruption).
 * * %-ENOMEM   - Insufficient memory available.
 * * %-ENOSPC   - Enough free space is not left for shrinking.
 */
int nilfs_sufile_resize(struct inode *sufile, __u64 newnsegs)
{
        struct the_nilfs *nilfs = sufile->i_sb->s_fs_info;
        struct buffer_head *header_bh;
        struct nilfs_sufile_header *header;
        struct nilfs_sufile_info *sui = NILFS_SUI(sufile);
        unsigned long nsegs, nrsvsegs;
        int ret = 0;

        down_write(&NILFS_MDT(sufile)->mi_sem);

        nsegs = nilfs_sufile_get_nsegments(sufile);
        if (nsegs == newnsegs)
                goto out;

        ret = -ENOSPC;
        nrsvsegs = nilfs_nrsvsegs(nilfs, newnsegs);
        if (newnsegs < nsegs && nsegs - newnsegs + nrsvsegs > sui->ncleansegs)
                goto out;

        ret = nilfs_sufile_get_header_block(sufile, &header_bh);
        if (ret < 0)
                goto out;

        if (newnsegs > nsegs) {
                sui->ncleansegs += newnsegs - nsegs;
        } else /* newnsegs < nsegs */ {
                ret = nilfs_sufile_truncate_range(sufile, newnsegs, nsegs - 1);
                if (ret < 0)
                        goto out_header;

                sui->ncleansegs -= nsegs - newnsegs;

                /*
                 * If the sufile is successfully truncated, immediately adjust
                 * the segment allocation space while locking the semaphore
                 * "mi_sem" so that nilfs_sufile_alloc() never allocates
                 * segments in the truncated space.
                 */
                sui->allocmax = newnsegs - 1;
                sui->allocmin = 0;
        }

        header = kmap_local_folio(header_bh->b_folio, 0);
        header->sh_ncleansegs = cpu_to_le64(sui->ncleansegs);
        kunmap_local(header);

        mark_buffer_dirty(header_bh);
        nilfs_mdt_mark_dirty(sufile);
        nilfs_set_nsegments(nilfs, newnsegs);

out_header:
        brelse(header_bh);
out:
        up_write(&NILFS_MDT(sufile)->mi_sem);
        return ret;
}

/**
 * nilfs_sufile_get_suinfo - get segment usage information
 * @sufile: inode of segment usage file
 * @segnum: segment number to start looking
 * @buf:    array of suinfo
 * @sisz:   byte size of suinfo
 * @nsi:    size of suinfo array
 *
 * Return: Count of segment usage info items stored in the output buffer on
 * success, or one of the following negative error codes on failure:
 * * %-EIO      - I/O error (including metadata corruption).
 * * %-ENOMEM   - Insufficient memory available.
 */
ssize_t nilfs_sufile_get_suinfo(struct inode *sufile, __u64 segnum, void *buf,
                                unsigned int sisz, size_t nsi)
{
        struct buffer_head *su_bh;
        struct nilfs_segment_usage *su;
        struct nilfs_suinfo *si = buf;
        size_t susz = NILFS_MDT(sufile)->mi_entry_size;
        struct the_nilfs *nilfs = sufile->i_sb->s_fs_info;
        size_t offset;
        void *kaddr;
        unsigned long nsegs, segusages_per_block;
        ssize_t n;
        int ret, i, j;

        down_read(&NILFS_MDT(sufile)->mi_sem);

        segusages_per_block = nilfs_sufile_segment_usages_per_block(sufile);
        nsegs = min_t(unsigned long,
                      nilfs_sufile_get_nsegments(sufile) - segnum,
                      nsi);
        for (i = 0; i < nsegs; i += n, segnum += n) {
                n = min_t(unsigned long,
                          segusages_per_block -
                                  nilfs_sufile_get_offset(sufile, segnum),
                          nsegs - i);
                ret = nilfs_sufile_get_segment_usage_block(sufile, segnum, 0,
                                                           &su_bh);
                if (ret < 0) {
                        if (ret != -ENOENT)
                                goto out;
                        /* hole */
                        memset(si, 0, sisz * n);
                        si = (void *)si + sisz * n;
                        continue;
                }

                offset = nilfs_sufile_segment_usage_offset(sufile, segnum,
                                                           su_bh);
                su = kaddr = kmap_local_folio(su_bh->b_folio, offset);
                for (j = 0; j < n;
                     j++, su = (void *)su + susz, si = (void *)si + sisz) {
                        si->sui_lastmod = le64_to_cpu(su->su_lastmod);
                        si->sui_nblocks = le32_to_cpu(su->su_nblocks);
                        si->sui_flags = le32_to_cpu(su->su_flags) &
                                ~BIT(NILFS_SEGMENT_USAGE_ACTIVE);
                        if (nilfs_segment_is_active(nilfs, segnum + j))
                                si->sui_flags |=
                                        BIT(NILFS_SEGMENT_USAGE_ACTIVE);
                }
                kunmap_local(kaddr);
                brelse(su_bh);
        }
        ret = nsegs;

 out:
        up_read(&NILFS_MDT(sufile)->mi_sem);
        return ret;
}

/**
 * nilfs_sufile_set_suinfo - sets segment usage info
 * @sufile: inode of segment usage file
 * @buf: array of suinfo_update
 * @supsz: byte size of suinfo_update
 * @nsup: size of suinfo_update array
 *
 * Description: Takes an array of nilfs_suinfo_update structs and updates
 * segment usage accordingly. Only the fields indicated by the sup_flags
 * are updated.
 *
 * Return: 0 on success, or one of the following negative error codes on
 * failure:
 * * %-EINVAL   - Invalid values in input (segment number, flags or nblocks).
 * * %-EIO      - I/O error (including metadata corruption).
 * * %-ENOMEM   - Insufficient memory available.
 */
ssize_t nilfs_sufile_set_suinfo(struct inode *sufile, void *buf,
                                unsigned int supsz, size_t nsup)
{
        struct the_nilfs *nilfs = sufile->i_sb->s_fs_info;
        struct buffer_head *header_bh, *bh;
        struct nilfs_suinfo_update *sup, *supend = buf + supsz * nsup;
        struct nilfs_segment_usage *su;
        size_t offset;
        unsigned long blkoff, prev_blkoff;
        int cleansi, cleansu, dirtysi, dirtysu;
        long ncleaned = 0, ndirtied = 0;
        int ret = 0;

        if (unlikely(nsup == 0))
                return ret;

        for (sup = buf; sup < supend; sup = (void *)sup + supsz) {
                if (sup->sup_segnum >= nilfs->ns_nsegments
                        || (sup->sup_flags &
                                (~0UL << __NR_NILFS_SUINFO_UPDATE_FIELDS))
                        || (nilfs_suinfo_update_nblocks(sup) &&
                                sup->sup_sui.sui_nblocks >
                                nilfs->ns_blocks_per_segment))
                        return -EINVAL;
        }

        down_write(&NILFS_MDT(sufile)->mi_sem);

        ret = nilfs_sufile_get_header_block(sufile, &header_bh);
        if (ret < 0)
                goto out_sem;

        sup = buf;
        blkoff = nilfs_sufile_get_blkoff(sufile, sup->sup_segnum);
        ret = nilfs_mdt_get_block(sufile, blkoff, 1, NULL, &bh);
        if (ret < 0)
                goto out_header;

        for (;;) {
                offset = nilfs_sufile_segment_usage_offset(
                        sufile, sup->sup_segnum, bh);
                su = kmap_local_folio(bh->b_folio, offset);

                if (nilfs_suinfo_update_lastmod(sup))
                        su->su_lastmod = cpu_to_le64(sup->sup_sui.sui_lastmod);

                if (nilfs_suinfo_update_nblocks(sup))
                        su->su_nblocks = cpu_to_le32(sup->sup_sui.sui_nblocks);

                if (nilfs_suinfo_update_flags(sup)) {
                        /*
                         * Active flag is a virtual flag projected by running
                         * nilfs kernel code - drop it not to write it to
                         * disk.
                         */
                        sup->sup_sui.sui_flags &=
                                        ~BIT(NILFS_SEGMENT_USAGE_ACTIVE);

                        cleansi = nilfs_suinfo_clean(&sup->sup_sui);
                        cleansu = nilfs_segment_usage_clean(su);
                        dirtysi = nilfs_suinfo_dirty(&sup->sup_sui);
                        dirtysu = nilfs_segment_usage_dirty(su);

                        if (cleansi && !cleansu)
                                ++ncleaned;
                        else if (!cleansi && cleansu)
                                --ncleaned;

                        if (dirtysi && !dirtysu)
                                ++ndirtied;
                        else if (!dirtysi && dirtysu)
                                --ndirtied;

                        su->su_flags = cpu_to_le32(sup->sup_sui.sui_flags);
                }

                kunmap_local(su);

                sup = (void *)sup + supsz;
                if (sup >= supend)
                        break;

                prev_blkoff = blkoff;
                blkoff = nilfs_sufile_get_blkoff(sufile, sup->sup_segnum);
                if (blkoff == prev_blkoff)
                        continue;

                /* get different block */
                mark_buffer_dirty(bh);
                put_bh(bh);
                ret = nilfs_mdt_get_block(sufile, blkoff, 1, NULL, &bh);
                if (unlikely(ret < 0))
                        goto out_mark;
        }
        mark_buffer_dirty(bh);
        put_bh(bh);

 out_mark:
        if (ncleaned || ndirtied) {
                nilfs_sufile_mod_counter(header_bh, (u64)ncleaned,
                                (u64)ndirtied);
                NILFS_SUI(sufile)->ncleansegs += ncleaned;
        }
        nilfs_mdt_mark_dirty(sufile);
 out_header:
        put_bh(header_bh);
 out_sem:
        up_write(&NILFS_MDT(sufile)->mi_sem);
        return ret;
}

/**
 * nilfs_sufile_trim_fs() - trim ioctl handle function
 * @sufile: inode of segment usage file
 * @range: fstrim_range structure
 *
 * start:       First Byte to trim
 * len:         number of Bytes to trim from start
 * minlen:      minimum extent length in Bytes
 *
 * Decription: nilfs_sufile_trim_fs goes through all segments containing bytes
 * from start to start+len. start is rounded up to the next block boundary
 * and start+len is rounded down. For each clean segment blkdev_issue_discard
 * function is invoked.
 *
 * Return: 0 on success, or a negative error code on failure.
 */
int nilfs_sufile_trim_fs(struct inode *sufile, struct fstrim_range *range)
{
        struct the_nilfs *nilfs = sufile->i_sb->s_fs_info;
        struct buffer_head *su_bh;
        struct nilfs_segment_usage *su;
        size_t offset;
        void *kaddr;
        size_t n, i, susz = NILFS_MDT(sufile)->mi_entry_size;
        sector_t seg_start, seg_end, start_block, end_block;
        sector_t start = 0, nblocks = 0;
        u64 segnum, segnum_end, minlen, len, max_blocks, ndiscarded = 0;
        int ret = 0;
        unsigned int sects_per_block;

        sects_per_block = (1 << nilfs->ns_blocksize_bits) /
                        bdev_logical_block_size(nilfs->ns_bdev);
        len = range->len >> nilfs->ns_blocksize_bits;
        minlen = range->minlen >> nilfs->ns_blocksize_bits;
        max_blocks = ((u64)nilfs->ns_nsegments * nilfs->ns_blocks_per_segment);

        if (!len || range->start >= max_blocks << nilfs->ns_blocksize_bits)
                return -EINVAL;

        start_block = (range->start + nilfs->ns_blocksize - 1) >>
                        nilfs->ns_blocksize_bits;

        /*
         * range->len can be very large (actually, it is set to
         * ULLONG_MAX by default) - truncate upper end of the range
         * carefully so as not to overflow.
         */
        if (max_blocks - start_block < len)
                end_block = max_blocks - 1;
        else
                end_block = start_block + len - 1;

        if (end_block < nilfs->ns_first_data_block)
                goto out;

        segnum = nilfs_get_segnum_of_block(nilfs, start_block);
        segnum_end = nilfs_get_segnum_of_block(nilfs, end_block);

        down_read(&NILFS_MDT(sufile)->mi_sem);

        while (segnum <= segnum_end) {
                n = nilfs_sufile_segment_usages_in_block(sufile, segnum,
                                segnum_end);

                ret = nilfs_sufile_get_segment_usage_block(sufile, segnum, 0,
                                                           &su_bh);
                if (ret < 0) {
                        if (ret != -ENOENT)
                                goto out_sem;
                        /* hole */
                        segnum += n;
                        continue;
                }

                offset = nilfs_sufile_segment_usage_offset(sufile, segnum,
                                                           su_bh);
                su = kaddr = kmap_local_folio(su_bh->b_folio, offset);
                for (i = 0; i < n; ++i, ++segnum, su = (void *)su + susz) {
                        if (!nilfs_segment_usage_clean(su))
                                continue;

                        nilfs_get_segment_range(nilfs, segnum, &seg_start,
                                                &seg_end);

                        if (!nblocks) {
                                /* start new extent */
                                start = seg_start;
                                nblocks = seg_end - seg_start + 1;
                                continue;
                        }

                        if (start + nblocks == seg_start) {
                                /* add to previous extent */
                                nblocks += seg_end - seg_start + 1;
                                continue;
                        }

                        /* discard previous extent */
                        if (start < start_block) {
                                nblocks -= start_block - start;
                                start = start_block;
                        }

                        if (nblocks >= minlen) {
                                kunmap_local(kaddr);

                                ret = blkdev_issue_discard(nilfs->ns_bdev,
                                                start * sects_per_block,
                                                nblocks * sects_per_block,
                                                GFP_NOFS);
                                if (ret < 0) {
                                        put_bh(su_bh);
                                        goto out_sem;
                                }

                                ndiscarded += nblocks;
                                offset = nilfs_sufile_segment_usage_offset(
                                        sufile, segnum, su_bh);
                                su = kaddr = kmap_local_folio(su_bh->b_folio,
                                                              offset);
                        }

                        /* start new extent */
                        start = seg_start;
                        nblocks = seg_end - seg_start + 1;
                }
                kunmap_local(kaddr);
                put_bh(su_bh);
        }


        if (nblocks) {
                /* discard last extent */
                if (start < start_block) {
                        nblocks -= start_block - start;
                        start = start_block;
                }
                if (start + nblocks > end_block + 1)
                        nblocks = end_block - start + 1;

                if (nblocks >= minlen) {
                        ret = blkdev_issue_discard(nilfs->ns_bdev,
                                        start * sects_per_block,
                                        nblocks * sects_per_block,
                                        GFP_NOFS);
                        if (!ret)
                                ndiscarded += nblocks;
                }
        }

out_sem:
        up_read(&NILFS_MDT(sufile)->mi_sem);

out:
        range->len = ndiscarded << nilfs->ns_blocksize_bits;
        return ret;
}

/**
 * nilfs_sufile_read - read or get sufile inode
 * @sb: super block instance
 * @susize: size of a segment usage entry
 * @raw_inode: on-disk sufile inode
 * @inodep: buffer to store the inode
 *
 * Return: 0 on success, or a negative error code on failure.
 */
int nilfs_sufile_read(struct super_block *sb, size_t susize,
                      struct nilfs_inode *raw_inode, struct inode **inodep)
{
        struct inode *sufile;
        struct nilfs_sufile_info *sui;
        struct buffer_head *header_bh;
        struct nilfs_sufile_header *header;
        int err;

        if (susize > sb->s_blocksize) {
                nilfs_err(sb, "too large segment usage size: %zu bytes",
                          susize);
                return -EINVAL;
        } else if (susize < NILFS_MIN_SEGMENT_USAGE_SIZE) {
                nilfs_err(sb, "too small segment usage size: %zu bytes",
                          susize);
                return -EINVAL;
        }

        sufile = nilfs_iget_locked(sb, NULL, NILFS_SUFILE_INO);
        if (unlikely(!sufile))
                return -ENOMEM;
        if (!(inode_state_read_once(sufile) & I_NEW))
                goto out;

        err = nilfs_mdt_init(sufile, NILFS_MDT_GFP, sizeof(*sui));
        if (err)
                goto failed;

        nilfs_mdt_set_entry_size(sufile, susize,
                                 sizeof(struct nilfs_sufile_header));

        err = nilfs_read_inode_common(sufile, raw_inode);
        if (err)
                goto failed;

        err = nilfs_mdt_get_block(sufile, 0, 0, NULL, &header_bh);
        if (unlikely(err)) {
                if (err == -ENOENT) {
                        nilfs_err(sb,
                                  "missing header block in segment usage metadata");
                        err = -EINVAL;
                }
                goto failed;
        }

        sui = NILFS_SUI(sufile);
        header = kmap_local_folio(header_bh->b_folio, 0);
        sui->ncleansegs = le64_to_cpu(header->sh_ncleansegs);
        kunmap_local(header);
        brelse(header_bh);

        sui->allocmax = nilfs_sufile_get_nsegments(sufile) - 1;
        sui->allocmin = 0;

        unlock_new_inode(sufile);
 out:
        *inodep = sufile;
        return 0;
 failed:
        iget_failed(sufile);
        return err;
}