// SPDX-License-Identifier: GPL-2.0
/*
 *  linux/fs/hpfs/buffer.c
 *
 *  Mikulas Patocka (mikulas@artax.karlin.mff.cuni.cz), 1998-1999
 *
 *  general buffer i/o
 */
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/blkdev.h>
#include "hpfs_fn.h"

secno hpfs_search_hotfix_map(struct super_block *s, secno sec)
{
        unsigned i;
        struct hpfs_sb_info *sbi = hpfs_sb(s);
        for (i = 0; unlikely(i < sbi->n_hotfixes); i++) {
                if (sbi->hotfix_from[i] == sec) {
                        return sbi->hotfix_to[i];
                }
        }
        return sec;
}

unsigned hpfs_search_hotfix_map_for_range(struct super_block *s, secno sec, unsigned n)
{
        unsigned i;
        struct hpfs_sb_info *sbi = hpfs_sb(s);
        for (i = 0; unlikely(i < sbi->n_hotfixes); i++) {
                if (sbi->hotfix_from[i] >= sec && sbi->hotfix_from[i] < sec + n) {
                        n = sbi->hotfix_from[i] - sec;
                }
        }
        return n;
}

void hpfs_prefetch_sectors(struct super_block *s, unsigned secno, int n)
{
        struct buffer_head *bh;
        struct blk_plug plug;

        if (n <= 0 || unlikely(secno >= hpfs_sb(s)->sb_fs_size))
                return;

        if (unlikely(hpfs_search_hotfix_map_for_range(s, secno, n) != n))
                return;

        bh = sb_find_get_block(s, secno);
        if (bh) {
                if (buffer_uptodate(bh)) {
                        brelse(bh);
                        return;
                }
                brelse(bh);
        }

        blk_start_plug(&plug);
        while (n > 0) {
                if (unlikely(secno >= hpfs_sb(s)->sb_fs_size))
                        break;
                sb_breadahead(s, secno);
                secno++;
                n--;
        }
        blk_finish_plug(&plug);
}

/* Map a sector into a buffer and return pointers to it and to the buffer. */

void *hpfs_map_sector(struct super_block *s, unsigned secno, struct buffer_head **bhp,
                 int ahead)
{
        struct buffer_head *bh;

        hpfs_lock_assert(s);

        hpfs_prefetch_sectors(s, secno, ahead);

        cond_resched();

        *bhp = bh = sb_bread(s, hpfs_search_hotfix_map(s, secno));
        if (bh != NULL)
                return bh->b_data;
        else {
                pr_err("%s(): read error\n", __func__);
                return NULL;
        }
}

/* Like hpfs_map_sector but don't read anything */

void *hpfs_get_sector(struct super_block *s, unsigned secno, struct buffer_head **bhp)
{
        struct buffer_head *bh;
        /*return hpfs_map_sector(s, secno, bhp, 0);*/

        hpfs_lock_assert(s);

        cond_resched();

        if ((*bhp = bh = sb_getblk(s, hpfs_search_hotfix_map(s, secno))) != NULL) {
                if (!buffer_uptodate(bh)) wait_on_buffer(bh);
                set_buffer_uptodate(bh);
                return bh->b_data;
        } else {
                pr_err("%s(): getblk failed\n", __func__);
                return NULL;
        }
}

/* Map 4 sectors into a 4buffer and return pointers to it and to the buffer. */

void *hpfs_map_4sectors(struct super_block *s, unsigned secno, struct quad_buffer_head *qbh,
                   int ahead)
{
        char *data;

        hpfs_lock_assert(s);

        cond_resched();

        if (secno & 3) {
                pr_err("%s(): unaligned read\n", __func__);
                return NULL;
        }

        hpfs_prefetch_sectors(s, secno, 4 + ahead);

        if (!hpfs_map_sector(s, secno + 0, &qbh->bh[0], 0)) goto bail0;
        if (!hpfs_map_sector(s, secno + 1, &qbh->bh[1], 0)) goto bail1;
        if (!hpfs_map_sector(s, secno + 2, &qbh->bh[2], 0)) goto bail2;
        if (!hpfs_map_sector(s, secno + 3, &qbh->bh[3], 0)) goto bail3;

        if (likely(qbh->bh[1]->b_data == qbh->bh[0]->b_data + 1 * 512) &&
            likely(qbh->bh[2]->b_data == qbh->bh[0]->b_data + 2 * 512) &&
            likely(qbh->bh[3]->b_data == qbh->bh[0]->b_data + 3 * 512)) {
                return qbh->data = qbh->bh[0]->b_data;
        }

        qbh->data = data = kmalloc(2048, GFP_NOFS);
        if (!data) {
                pr_err("%s(): out of memory\n", __func__);
                goto bail4;
        }

        memcpy(data + 0 * 512, qbh->bh[0]->b_data, 512);
        memcpy(data + 1 * 512, qbh->bh[1]->b_data, 512);
        memcpy(data + 2 * 512, qbh->bh[2]->b_data, 512);
        memcpy(data + 3 * 512, qbh->bh[3]->b_data, 512);

        return data;

 bail4:
        brelse(qbh->bh[3]);
 bail3:
        brelse(qbh->bh[2]);
 bail2:
        brelse(qbh->bh[1]);
 bail1:
        brelse(qbh->bh[0]);
 bail0:
        return NULL;
}

/* Don't read sectors */

void *hpfs_get_4sectors(struct super_block *s, unsigned secno,
                          struct quad_buffer_head *qbh)
{
        cond_resched();

        hpfs_lock_assert(s);

        if (secno & 3) {
                pr_err("%s(): unaligned read\n", __func__);
                return NULL;
        }

        if (!hpfs_get_sector(s, secno + 0, &qbh->bh[0])) goto bail0;
        if (!hpfs_get_sector(s, secno + 1, &qbh->bh[1])) goto bail1;
        if (!hpfs_get_sector(s, secno + 2, &qbh->bh[2])) goto bail2;
        if (!hpfs_get_sector(s, secno + 3, &qbh->bh[3])) goto bail3;

        if (likely(qbh->bh[1]->b_data == qbh->bh[0]->b_data + 1 * 512) &&
            likely(qbh->bh[2]->b_data == qbh->bh[0]->b_data + 2 * 512) &&
            likely(qbh->bh[3]->b_data == qbh->bh[0]->b_data + 3 * 512)) {
                return qbh->data = qbh->bh[0]->b_data;
        }

        if (!(qbh->data = kmalloc(2048, GFP_NOFS))) {
                pr_err("%s(): out of memory\n", __func__);
                goto bail4;
        }
        return qbh->data;

bail4:
        brelse(qbh->bh[3]);
bail3:
        brelse(qbh->bh[2]);
bail2:
        brelse(qbh->bh[1]);
bail1:
        brelse(qbh->bh[0]);
bail0:
        return NULL;
}
        

void hpfs_brelse4(struct quad_buffer_head *qbh)
{
        if (unlikely(qbh->data != qbh->bh[0]->b_data))
                kfree(qbh->data);
        brelse(qbh->bh[0]);
        brelse(qbh->bh[1]);
        brelse(qbh->bh[2]);
        brelse(qbh->bh[3]);
}       

void hpfs_mark_4buffers_dirty(struct quad_buffer_head *qbh)
{
        if (unlikely(qbh->data != qbh->bh[0]->b_data)) {
                memcpy(qbh->bh[0]->b_data, qbh->data + 0 * 512, 512);
                memcpy(qbh->bh[1]->b_data, qbh->data + 1 * 512, 512);
                memcpy(qbh->bh[2]->b_data, qbh->data + 2 * 512, 512);
                memcpy(qbh->bh[3]->b_data, qbh->data + 3 * 512, 512);
        }
        mark_buffer_dirty(qbh->bh[0]);
        mark_buffer_dirty(qbh->bh[1]);
        mark_buffer_dirty(qbh->bh[2]);
        mark_buffer_dirty(qbh->bh[3]);
}