// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Copyright (C) 2012-2013 Samsung Electronics Co., Ltd.
 */

#include <linux/slab.h>
#include <linux/unaligned.h>
#include <linux/buffer_head.h>
#include <linux/blkdev.h>

#include "exfat_raw.h"
#include "exfat_fs.h"

static int exfat_mirror_bh(struct super_block *sb, sector_t sec,
                struct buffer_head *bh)
{
        struct buffer_head *c_bh;
        struct exfat_sb_info *sbi = EXFAT_SB(sb);
        sector_t sec2;
        int err = 0;

        if (sbi->FAT2_start_sector != sbi->FAT1_start_sector) {
                sec2 = sec - sbi->FAT1_start_sector + sbi->FAT2_start_sector;
                c_bh = sb_getblk(sb, sec2);
                if (!c_bh)
                        return -ENOMEM;
                memcpy(c_bh->b_data, bh->b_data, sb->s_blocksize);
                set_buffer_uptodate(c_bh);
                mark_buffer_dirty(c_bh);
                if (sb->s_flags & SB_SYNCHRONOUS)
                        err = sync_dirty_buffer(c_bh);
                brelse(c_bh);
        }

        return err;
}

static int __exfat_ent_get(struct super_block *sb, unsigned int loc,
                unsigned int *content, struct buffer_head **last)
{
        unsigned int off;
        sector_t sec;
        struct buffer_head *bh = last ? *last : NULL;

        sec = FAT_ENT_OFFSET_SECTOR(sb, loc);
        off = FAT_ENT_OFFSET_BYTE_IN_SECTOR(sb, loc);

        if (!bh || bh->b_blocknr != sec || !buffer_uptodate(bh)) {
                brelse(bh);
                bh = sb_bread(sb, sec);
                if (last)
                        *last = bh;
                if (unlikely(!bh))
                        return -EIO;
        }

        *content = le32_to_cpu(*(__le32 *)(&bh->b_data[off]));

        /* remap reserved clusters to simplify code */
        if (*content > EXFAT_BAD_CLUSTER)
                *content = EXFAT_EOF_CLUSTER;

        if (!last)
                brelse(bh);
        return 0;
}

int exfat_ent_set(struct super_block *sb, unsigned int loc,
                unsigned int content)
{
        unsigned int off;
        sector_t sec;
        __le32 *fat_entry;
        struct buffer_head *bh;

        sec = FAT_ENT_OFFSET_SECTOR(sb, loc);
        off = FAT_ENT_OFFSET_BYTE_IN_SECTOR(sb, loc);

        bh = sb_bread(sb, sec);
        if (!bh)
                return -EIO;

        fat_entry = (__le32 *)&(bh->b_data[off]);
        *fat_entry = cpu_to_le32(content);
        exfat_update_bh(bh, sb->s_flags & SB_SYNCHRONOUS);
        exfat_mirror_bh(sb, sec, bh);
        brelse(bh);
        return 0;
}

/*
 * Caller must release the buffer_head if no error return.
 */
int exfat_ent_get(struct super_block *sb, unsigned int loc,
                unsigned int *content, struct buffer_head **last)
{
        struct exfat_sb_info *sbi = EXFAT_SB(sb);

        if (!is_valid_cluster(sbi, loc)) {
                exfat_fs_error_ratelimit(sb,
                        "invalid access to FAT (entry 0x%08x)",
                        loc);
                goto err;
        }

        if (unlikely(__exfat_ent_get(sb, loc, content, last))) {
                exfat_fs_error_ratelimit(sb,
                        "failed to access to FAT (entry 0x%08x)",
                        loc);
                goto err;
        }

        if (unlikely(*content == EXFAT_FREE_CLUSTER)) {
                exfat_fs_error_ratelimit(sb,
                        "invalid access to FAT free cluster (entry 0x%08x)",
                        loc);
                goto err;
        }

        if (unlikely(*content == EXFAT_BAD_CLUSTER)) {
                exfat_fs_error_ratelimit(sb,
                        "invalid access to FAT bad cluster (entry 0x%08x)",
                        loc);
                goto err;
        }

        if (*content != EXFAT_EOF_CLUSTER && !is_valid_cluster(sbi, *content)) {
                exfat_fs_error_ratelimit(sb,
                        "invalid access to FAT (entry 0x%08x) bogus content (0x%08x)",
                        loc, *content);
                goto err;
        }

        return 0;
err:
        if (last) {
                brelse(*last);

                /* Avoid double release */
                *last = NULL;
        }
        return -EIO;
}

int exfat_chain_cont_cluster(struct super_block *sb, unsigned int chain,
                unsigned int len)
{
        if (!len)
                return 0;

        while (len > 1) {
                if (exfat_ent_set(sb, chain, chain + 1))
                        return -EIO;
                chain++;
                len--;
        }

        if (exfat_ent_set(sb, chain, EXFAT_EOF_CLUSTER))
                return -EIO;
        return 0;
}

static inline void exfat_discard_cluster(struct super_block *sb,
                unsigned int clu, unsigned int num_clusters)
{
        int ret;
        struct exfat_sb_info *sbi = EXFAT_SB(sb);

        ret = sb_issue_discard(sb, exfat_cluster_to_sector(sbi, clu),
                        sbi->sect_per_clus * num_clusters, GFP_NOFS, 0);
        if (ret == -EOPNOTSUPP) {
                exfat_err(sb, "discard not supported by device, disabling");
                sbi->options.discard = 0;
        }
}

/* This function must be called with bitmap_lock held */
static int __exfat_free_cluster(struct inode *inode, struct exfat_chain *p_chain)
{
        struct super_block *sb = inode->i_sb;
        struct exfat_sb_info *sbi = EXFAT_SB(sb);
        int cur_cmap_i, next_cmap_i;
        unsigned int num_clusters = 0;
        unsigned int clu;

        /* invalid cluster number */
        if (p_chain->dir == EXFAT_FREE_CLUSTER ||
            p_chain->dir == EXFAT_EOF_CLUSTER ||
            p_chain->dir < EXFAT_FIRST_CLUSTER)
                return 0;

        /* no cluster to truncate */
        if (p_chain->size == 0)
                return 0;

        /* check cluster validation */
        if (!is_valid_cluster(sbi, p_chain->dir)) {
                exfat_err(sb, "invalid start cluster (%u)", p_chain->dir);
                return -EIO;
        }

        clu = p_chain->dir;

        cur_cmap_i = next_cmap_i =
                BITMAP_OFFSET_SECTOR_INDEX(sb, CLUSTER_TO_BITMAP_ENT(clu));

        if (p_chain->flags == ALLOC_NO_FAT_CHAIN) {
                int err;
                unsigned int last_cluster = p_chain->dir + p_chain->size - 1;

                do {
                        bool sync = false;

                        if (clu < last_cluster)
                                next_cmap_i =
                                  BITMAP_OFFSET_SECTOR_INDEX(sb, CLUSTER_TO_BITMAP_ENT(clu+1));

                        /* flush bitmap only if index would be changed or for last cluster */
                        if (clu == last_cluster || cur_cmap_i != next_cmap_i) {
                                sync = true;
                                cur_cmap_i = next_cmap_i;
                        }

                        err = exfat_clear_bitmap(sb, clu, (sync && IS_DIRSYNC(inode)));
                        if (err)
                                break;
                        clu++;
                        num_clusters++;
                } while (num_clusters < p_chain->size);

                if (sbi->options.discard)
                        exfat_discard_cluster(sb, p_chain->dir, p_chain->size);
        } else {
                unsigned int nr_clu = 1;

                do {
                        bool sync = false;
                        unsigned int n_clu = clu;
                        int err = exfat_get_next_cluster(sb, &n_clu);

                        if (err || n_clu == EXFAT_EOF_CLUSTER)
                                sync = true;
                        else
                                next_cmap_i =
                                  BITMAP_OFFSET_SECTOR_INDEX(sb, CLUSTER_TO_BITMAP_ENT(n_clu));

                        if (cur_cmap_i != next_cmap_i) {
                                sync = true;
                                cur_cmap_i = next_cmap_i;
                        }

                        if (exfat_clear_bitmap(sb, clu, (sync && IS_DIRSYNC(inode))))
                                break;

                        if (sbi->options.discard) {
                                if (n_clu == clu + 1)
                                        nr_clu++;
                                else {
                                        exfat_discard_cluster(sb, clu - nr_clu + 1, nr_clu);
                                        nr_clu = 1;
                                }
                        }

                        clu = n_clu;
                        num_clusters++;

                        if (err)
                                break;

                        if (num_clusters >= sbi->num_clusters - EXFAT_FIRST_CLUSTER) {
                                /*
                                 * The cluster chain includes a loop, scan the
                                 * bitmap to get the number of used clusters.
                                 */
                                exfat_count_used_clusters(sb, &sbi->used_clusters);

                                return 0;
                        }
                } while (clu != EXFAT_EOF_CLUSTER);
        }

        sbi->used_clusters -= num_clusters;
        return 0;
}

int exfat_free_cluster(struct inode *inode, struct exfat_chain *p_chain)
{
        int ret = 0;

        mutex_lock(&EXFAT_SB(inode->i_sb)->bitmap_lock);
        ret = __exfat_free_cluster(inode, p_chain);
        mutex_unlock(&EXFAT_SB(inode->i_sb)->bitmap_lock);

        return ret;
}

int exfat_find_last_cluster(struct super_block *sb, struct exfat_chain *p_chain,
                unsigned int *ret_clu)
{
        struct buffer_head *bh = NULL;
        unsigned int clu, next;
        unsigned int count = 0;

        next = p_chain->dir;
        if (p_chain->flags == ALLOC_NO_FAT_CHAIN) {
                *ret_clu = next + p_chain->size - 1;
                return 0;
        }

        do {
                count++;
                clu = next;
                if (exfat_ent_get(sb, clu, &next, &bh))
                        return -EIO;
        } while (next != EXFAT_EOF_CLUSTER && count <= p_chain->size);

        brelse(bh);
        if (p_chain->size != count) {
                exfat_fs_error(sb,
                        "bogus directory size (clus : ondisk(%d) != counted(%d))",
                        p_chain->size, count);
                return -EIO;
        }

        *ret_clu = clu;
        return 0;
}

int exfat_zeroed_cluster(struct inode *dir, unsigned int clu)
{
        struct super_block *sb = dir->i_sb;
        struct exfat_sb_info *sbi = EXFAT_SB(sb);
        struct buffer_head *bh;
        sector_t blknr, last_blknr, i;

        blknr = exfat_cluster_to_sector(sbi, clu);
        last_blknr = blknr + sbi->sect_per_clus;

        if (last_blknr > sbi->num_sectors && sbi->num_sectors > 0) {
                exfat_fs_error_ratelimit(sb,
                        "%s: out of range(sect:%llu len:%u)",
                        __func__, (unsigned long long)blknr,
                        sbi->sect_per_clus);
                return -EIO;
        }

        /* Zeroing the unused blocks on this cluster */
        for (i = blknr; i < last_blknr; i++) {
                bh = sb_getblk(sb, i);
                if (!bh)
                        return -ENOMEM;

                memset(bh->b_data, 0, sb->s_blocksize);
                set_buffer_uptodate(bh);
                mark_buffer_dirty(bh);
                brelse(bh);
        }

        if (IS_DIRSYNC(dir))
                return sync_blockdev_range(sb->s_bdev,
                                EXFAT_BLK_TO_B(blknr, sb),
                                EXFAT_BLK_TO_B(last_blknr, sb) - 1);

        return 0;
}

int exfat_alloc_cluster(struct inode *inode, unsigned int num_alloc,
                struct exfat_chain *p_chain, bool sync_bmap)
{
        int ret = -ENOSPC;
        unsigned int total_cnt;
        unsigned int hint_clu, new_clu, last_clu = EXFAT_EOF_CLUSTER;
        struct super_block *sb = inode->i_sb;
        struct exfat_sb_info *sbi = EXFAT_SB(sb);

        total_cnt = EXFAT_DATA_CLUSTER_COUNT(sbi);

        if (unlikely(total_cnt < sbi->used_clusters)) {
                exfat_fs_error_ratelimit(sb,
                        "%s: invalid used clusters(t:%u,u:%u)\n",
                        __func__, total_cnt, sbi->used_clusters);
                return -EIO;
        }

        if (num_alloc > total_cnt - sbi->used_clusters)
                return -ENOSPC;

        mutex_lock(&sbi->bitmap_lock);

        hint_clu = p_chain->dir;
        /* find new cluster */
        if (hint_clu == EXFAT_EOF_CLUSTER) {
                if (sbi->clu_srch_ptr < EXFAT_FIRST_CLUSTER) {
                        exfat_err(sb, "sbi->clu_srch_ptr is invalid (%u)",
                                  sbi->clu_srch_ptr);
                        sbi->clu_srch_ptr = EXFAT_FIRST_CLUSTER;
                }

                hint_clu = exfat_find_free_bitmap(sb, sbi->clu_srch_ptr);
                if (hint_clu == EXFAT_EOF_CLUSTER) {
                        ret = -ENOSPC;
                        goto unlock;
                }
        }

        /* check cluster validation */
        if (!is_valid_cluster(sbi, hint_clu)) {
                if (hint_clu != sbi->num_clusters)
                        exfat_err(sb, "hint_cluster is invalid (%u), rewind to the first cluster",
                                        hint_clu);
                hint_clu = EXFAT_FIRST_CLUSTER;
                p_chain->flags = ALLOC_FAT_CHAIN;
        }

        p_chain->dir = EXFAT_EOF_CLUSTER;

        while ((new_clu = exfat_find_free_bitmap(sb, hint_clu)) !=
               EXFAT_EOF_CLUSTER) {
                if (new_clu != hint_clu &&
                    p_chain->flags == ALLOC_NO_FAT_CHAIN) {
                        if (exfat_chain_cont_cluster(sb, p_chain->dir,
                                        p_chain->size)) {
                                ret = -EIO;
                                goto free_cluster;
                        }
                        p_chain->flags = ALLOC_FAT_CHAIN;
                }

                /* update allocation bitmap */
                if (exfat_set_bitmap(sb, new_clu, sync_bmap)) {
                        ret = -EIO;
                        goto free_cluster;
                }

                /* update FAT table */
                if (p_chain->flags == ALLOC_FAT_CHAIN) {
                        if (exfat_ent_set(sb, new_clu, EXFAT_EOF_CLUSTER)) {
                                ret = -EIO;
                                goto free_cluster;
                        }
                }

                if (p_chain->dir == EXFAT_EOF_CLUSTER) {
                        p_chain->dir = new_clu;
                } else if (p_chain->flags == ALLOC_FAT_CHAIN) {
                        if (exfat_ent_set(sb, last_clu, new_clu)) {
                                ret = -EIO;
                                goto free_cluster;
                        }
                }
                p_chain->size++;

                last_clu = new_clu;

                if (p_chain->size == num_alloc) {
                        sbi->clu_srch_ptr = hint_clu;
                        sbi->used_clusters += num_alloc;

                        mutex_unlock(&sbi->bitmap_lock);
                        return 0;
                }

                hint_clu = new_clu + 1;
                if (hint_clu >= sbi->num_clusters) {
                        hint_clu = EXFAT_FIRST_CLUSTER;

                        if (p_chain->flags == ALLOC_NO_FAT_CHAIN) {
                                if (exfat_chain_cont_cluster(sb, p_chain->dir,
                                                p_chain->size)) {
                                        ret = -EIO;
                                        goto free_cluster;
                                }
                                p_chain->flags = ALLOC_FAT_CHAIN;
                        }
                }
        }
free_cluster:
        __exfat_free_cluster(inode, p_chain);
unlock:
        mutex_unlock(&sbi->bitmap_lock);
        return ret;
}

int exfat_count_num_clusters(struct super_block *sb,
                struct exfat_chain *p_chain, unsigned int *ret_count)
{
        unsigned int i, count;
        unsigned int clu;
        struct exfat_sb_info *sbi = EXFAT_SB(sb);
        struct buffer_head *bh = NULL;

        if (!p_chain->dir || p_chain->dir == EXFAT_EOF_CLUSTER) {
                *ret_count = 0;
                return 0;
        }

        if (p_chain->flags == ALLOC_NO_FAT_CHAIN) {
                *ret_count = p_chain->size;
                return 0;
        }

        clu = p_chain->dir;
        count = 0;
        for (i = EXFAT_FIRST_CLUSTER; i < sbi->num_clusters; i++) {
                count++;
                if (exfat_ent_get(sb, clu, &clu, &bh))
                        return -EIO;
                if (clu == EXFAT_EOF_CLUSTER)
                        break;
        }

        brelse(bh);
        *ret_count = count;

        /*
         * since exfat_count_used_clusters() is not called, sbi->used_clusters
         * cannot be used here.
         */
        if (unlikely(i == sbi->num_clusters && clu != EXFAT_EOF_CLUSTER)) {
                exfat_fs_error(sb, "The cluster chain has a loop");
                return -EIO;
        }

        return 0;
}