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

#include <linux/blkdev.h>
#include <linux/slab.h>
#include <linux/bitmap.h>
#include <linux/buffer_head.h>
#include <linux/backing-dev.h>

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

#if BITS_PER_LONG == 32
#define __le_long __le32
#define lel_to_cpu(A) le32_to_cpu(A)
#define cpu_to_lel(A) cpu_to_le32(A)
#elif BITS_PER_LONG == 64
#define __le_long __le64
#define lel_to_cpu(A) le64_to_cpu(A)
#define cpu_to_lel(A) cpu_to_le64(A)
#else
#error "BITS_PER_LONG not 32 or 64"
#endif

/*
 *  Allocation Bitmap Management Functions
 */
static bool exfat_test_bitmap_range(struct super_block *sb, unsigned int clu,
                unsigned int count)
{
        struct exfat_sb_info *sbi = EXFAT_SB(sb);
        unsigned int start = clu;
        unsigned int end = clu + count;
        unsigned int ent_idx, i, b;
        unsigned int bit_offset, bits_to_check;
        __le_long *bitmap_le;
        unsigned long mask, word;

        if (!is_valid_cluster(sbi, start) || !is_valid_cluster(sbi, end - 1))
                return false;

        while (start < end) {
                ent_idx = CLUSTER_TO_BITMAP_ENT(start);
                i = BITMAP_OFFSET_SECTOR_INDEX(sb, ent_idx);
                b = BITMAP_OFFSET_BIT_IN_SECTOR(sb, ent_idx);

                bitmap_le = (__le_long *)sbi->vol_amap[i]->b_data;

                /* Calculate how many bits we can check in the current word */
                bit_offset = b % BITS_PER_LONG;
                bits_to_check = min(end - start,
                                    (unsigned int)(BITS_PER_LONG - bit_offset));

                /* Create a bitmask for the range of bits to check */
                if (bits_to_check >= BITS_PER_LONG)
                        mask = ~0UL;
                else
                        mask = ((1UL << bits_to_check) - 1) << bit_offset;
                word = lel_to_cpu(bitmap_le[b / BITS_PER_LONG]);

                /* Check if all bits in the mask are set */
                if ((word & mask) != mask)
                        return false;

                start += bits_to_check;
        }

        return true;
}

static int exfat_allocate_bitmap(struct super_block *sb,
                struct exfat_dentry *ep)
{
        struct exfat_sb_info *sbi = EXFAT_SB(sb);
        struct blk_plug plug;
        long long map_size;
        unsigned int i, j, need_map_size;
        sector_t sector;
        unsigned int max_ra_count;

        sbi->map_clu = le32_to_cpu(ep->dentry.bitmap.start_clu);
        map_size = le64_to_cpu(ep->dentry.bitmap.size);
        need_map_size = ((EXFAT_DATA_CLUSTER_COUNT(sbi) - 1) / BITS_PER_BYTE)
                + 1;
        if (need_map_size != map_size) {
                exfat_err(sb, "bogus allocation bitmap size(need : %u, cur : %lld)",
                          need_map_size, map_size);
                /*
                 * Only allowed when bogus allocation
                 * bitmap size is large
                 */
                if (need_map_size > map_size)
                        return -EIO;
        }
        sbi->map_sectors = ((need_map_size - 1) >>
                        (sb->s_blocksize_bits)) + 1;
        sbi->vol_amap = kvmalloc_objs(struct buffer_head *, sbi->map_sectors);
        if (!sbi->vol_amap)
                return -ENOMEM;

        sector = exfat_cluster_to_sector(sbi, sbi->map_clu);
        max_ra_count = min(sb->s_bdi->ra_pages, sb->s_bdi->io_pages) <<
                (PAGE_SHIFT - sb->s_blocksize_bits);
        for (i = 0; i < sbi->map_sectors; i++) {
                /* Trigger the next readahead in advance. */
                if (max_ra_count && 0 == (i % max_ra_count)) {
                        blk_start_plug(&plug);
                        for (j = i; j < min(max_ra_count, sbi->map_sectors - i) + i; j++)
                                sb_breadahead(sb, sector + j);
                        blk_finish_plug(&plug);
                }

                sbi->vol_amap[i] = sb_bread(sb, sector + i);
                if (!sbi->vol_amap[i])
                        goto err_out;
        }

        if (exfat_test_bitmap_range(sb, sbi->map_clu,
                EXFAT_B_TO_CLU_ROUND_UP(map_size, sbi)) == false)
                goto err_out;

        return 0;

err_out:
        j = 0;
        /* release all buffers and free vol_amap */
        while (j < i)
                brelse(sbi->vol_amap[j++]);

        kvfree(sbi->vol_amap);
        sbi->vol_amap = NULL;
        return -EIO;
}

int exfat_load_bitmap(struct super_block *sb)
{
        unsigned int i, type;
        struct exfat_chain clu;
        struct exfat_sb_info *sbi = EXFAT_SB(sb);

        exfat_chain_set(&clu, sbi->root_dir, 0, ALLOC_FAT_CHAIN);
        while (clu.dir != EXFAT_EOF_CLUSTER) {
                for (i = 0; i < sbi->dentries_per_clu; i++) {
                        struct exfat_dentry *ep;
                        struct buffer_head *bh;

                        ep = exfat_get_dentry(sb, &clu, i, &bh);
                        if (!ep)
                                return -EIO;

                        type = exfat_get_entry_type(ep);
                        if (type == TYPE_BITMAP &&
                            ep->dentry.bitmap.flags == 0x0) {
                                int err;

                                err = exfat_allocate_bitmap(sb, ep);
                                brelse(bh);
                                return err;
                        }
                        brelse(bh);

                        if (type == TYPE_UNUSED)
                                return -EINVAL;
                }

                if (exfat_get_next_cluster(sb, &clu.dir))
                        return -EIO;
        }

        return -EINVAL;
}

void exfat_free_bitmap(struct exfat_sb_info *sbi)
{
        int i;

        for (i = 0; i < sbi->map_sectors; i++)
                __brelse(sbi->vol_amap[i]);

        kvfree(sbi->vol_amap);
}

int exfat_set_bitmap(struct super_block *sb, unsigned int clu, bool sync)
{
        int i, b;
        unsigned int ent_idx;
        struct exfat_sb_info *sbi = EXFAT_SB(sb);

        if (!is_valid_cluster(sbi, clu))
                return -EINVAL;

        ent_idx = CLUSTER_TO_BITMAP_ENT(clu);
        i = BITMAP_OFFSET_SECTOR_INDEX(sb, ent_idx);
        b = BITMAP_OFFSET_BIT_IN_SECTOR(sb, ent_idx);

        set_bit_le(b, sbi->vol_amap[i]->b_data);
        exfat_update_bh(sbi->vol_amap[i], sync);
        return 0;
}

int exfat_clear_bitmap(struct super_block *sb, unsigned int clu, bool sync)
{
        int i, b;
        unsigned int ent_idx;
        struct exfat_sb_info *sbi = EXFAT_SB(sb);

        if (!is_valid_cluster(sbi, clu))
                return -EIO;

        ent_idx = CLUSTER_TO_BITMAP_ENT(clu);
        i = BITMAP_OFFSET_SECTOR_INDEX(sb, ent_idx);
        b = BITMAP_OFFSET_BIT_IN_SECTOR(sb, ent_idx);

        if (!test_bit_le(b, sbi->vol_amap[i]->b_data))
                return -EIO;

        clear_bit_le(b, sbi->vol_amap[i]->b_data);

        exfat_update_bh(sbi->vol_amap[i], sync);

        return 0;
}

bool exfat_test_bitmap(struct super_block *sb, unsigned int clu)
{
        int i, b;
        unsigned int ent_idx;
        struct exfat_sb_info *sbi = EXFAT_SB(sb);

        if (!sbi->vol_amap)
                return true;

        if (!is_valid_cluster(sbi, clu))
                return false;

        ent_idx = CLUSTER_TO_BITMAP_ENT(clu);
        i = BITMAP_OFFSET_SECTOR_INDEX(sb, ent_idx);
        b = BITMAP_OFFSET_BIT_IN_SECTOR(sb, ent_idx);

        if (!test_bit_le(b, sbi->vol_amap[i]->b_data))
                return false;

        return true;
}

/*
 * If the value of "clu" is 0, it means cluster 2 which is the first cluster of
 * the cluster heap.
 */
unsigned int exfat_find_free_bitmap(struct super_block *sb, unsigned int clu)
{
        unsigned int i, map_i, map_b, ent_idx;
        unsigned int clu_base, clu_free;
        unsigned long clu_bits, clu_mask;
        struct exfat_sb_info *sbi = EXFAT_SB(sb);
        __le_long bitval;

        WARN_ON(clu < EXFAT_FIRST_CLUSTER);
        ent_idx = ALIGN_DOWN(CLUSTER_TO_BITMAP_ENT(clu), BITS_PER_LONG);
        clu_base = BITMAP_ENT_TO_CLUSTER(ent_idx);
        clu_mask = IGNORED_BITS_REMAINED(clu, clu_base);

        map_i = BITMAP_OFFSET_SECTOR_INDEX(sb, ent_idx);
        map_b = BITMAP_OFFSET_BYTE_IN_SECTOR(sb, ent_idx);

        for (i = EXFAT_FIRST_CLUSTER; i < sbi->num_clusters;
             i += BITS_PER_LONG) {
                bitval = *(__le_long *)(sbi->vol_amap[map_i]->b_data + map_b);
                if (clu_mask > 0) {
                        bitval |= cpu_to_lel(clu_mask);
                        clu_mask = 0;
                }
                if (lel_to_cpu(bitval) != ULONG_MAX) {
                        clu_bits = lel_to_cpu(bitval);
                        clu_free = clu_base + ffz(clu_bits);
                        if (clu_free < sbi->num_clusters)
                                return clu_free;
                }
                clu_base += BITS_PER_LONG;
                map_b += sizeof(long);

                if (map_b >= sb->s_blocksize ||
                    clu_base >= sbi->num_clusters) {
                        if (++map_i >= sbi->map_sectors) {
                                clu_base = EXFAT_FIRST_CLUSTER;
                                map_i = 0;
                        }
                        map_b = 0;
                }
        }

        return EXFAT_EOF_CLUSTER;
}

int exfat_count_used_clusters(struct super_block *sb, unsigned int *ret_count)
{
        struct exfat_sb_info *sbi = EXFAT_SB(sb);
        unsigned int count = 0;
        unsigned int i, map_i = 0, map_b = 0;
        unsigned int total_clus = EXFAT_DATA_CLUSTER_COUNT(sbi);
        unsigned int last_mask = total_clus & (BITS_PER_LONG - 1);
        unsigned long *bitmap, clu_bits;

        total_clus &= ~last_mask;
        for (i = 0; i < total_clus; i += BITS_PER_LONG) {
                bitmap = (void *)(sbi->vol_amap[map_i]->b_data + map_b);
                count += hweight_long(*bitmap);
                map_b += sizeof(long);
                if (map_b >= (unsigned int)sb->s_blocksize) {
                        map_i++;
                        map_b = 0;
                }
        }

        if (last_mask) {
                bitmap = (void *)(sbi->vol_amap[map_i]->b_data + map_b);
                clu_bits = lel_to_cpu(*(__le_long *)bitmap);
                count += hweight_long(clu_bits & BITMAP_LAST_WORD_MASK(last_mask));
        }

        *ret_count = count;
        return 0;
}

int exfat_trim_fs(struct inode *inode, struct fstrim_range *range)
{
        unsigned int trim_begin, trim_end, count, next_free_clu;
        u64 clu_start, clu_end, trim_minlen, trimmed_total = 0;
        struct super_block *sb = inode->i_sb;
        struct exfat_sb_info *sbi = EXFAT_SB(sb);
        int err = 0;

        clu_start = max_t(u64, range->start >> sbi->cluster_size_bits,
                                EXFAT_FIRST_CLUSTER);
        clu_end = clu_start + (range->len >> sbi->cluster_size_bits) - 1;
        trim_minlen = range->minlen >> sbi->cluster_size_bits;

        if (clu_start >= sbi->num_clusters || range->len < sbi->cluster_size)
                return -EINVAL;

        if (clu_end >= sbi->num_clusters)
                clu_end = sbi->num_clusters - 1;

        mutex_lock(&sbi->bitmap_lock);

        trim_begin = trim_end = exfat_find_free_bitmap(sb, clu_start);
        if (trim_begin == EXFAT_EOF_CLUSTER)
                goto unlock;

        next_free_clu = exfat_find_free_bitmap(sb, trim_end + 1);
        if (next_free_clu == EXFAT_EOF_CLUSTER)
                goto unlock;

        do {
                if (next_free_clu == trim_end + 1) {
                        /* extend trim range for continuous free cluster */
                        trim_end++;
                } else {
                        /* trim current range if it's larger than trim_minlen */
                        count = trim_end - trim_begin + 1;
                        if (count >= trim_minlen) {
                                err = sb_issue_discard(sb,
                                        exfat_cluster_to_sector(sbi, trim_begin),
                                        count * sbi->sect_per_clus, GFP_NOFS, 0);
                                if (err)
                                        goto unlock;

                                trimmed_total += count;
                        }

                        /* set next start point of the free hole */
                        trim_begin = trim_end = next_free_clu;
                }

                if (next_free_clu >= clu_end)
                        break;

                if (fatal_signal_pending(current)) {
                        err = -ERESTARTSYS;
                        goto unlock;
                }

                next_free_clu = exfat_find_free_bitmap(sb, next_free_clu + 1);
        } while (next_free_clu != EXFAT_EOF_CLUSTER &&
                        next_free_clu > trim_end);

        /* try to trim remainder */
        count = trim_end - trim_begin + 1;
        if (count >= trim_minlen) {
                err = sb_issue_discard(sb, exfat_cluster_to_sector(sbi, trim_begin),
                        count * sbi->sect_per_clus, GFP_NOFS, 0);
                if (err)
                        goto unlock;

                trimmed_total += count;
        }

unlock:
        mutex_unlock(&sbi->bitmap_lock);
        range->len = trimmed_total << sbi->cluster_size_bits;

        return err;
}