// SPDX-License-Identifier: GPL-2.0-only
/*
 * inode.c
 *
 * Copyright (c) 1999 Al Smith
 *
 * Portions derived from work (c) 1995,1996 Christian Vogelgsang,
 *              and from work (c) 1998 Mike Shaver.
 */

#include <linux/buffer_head.h>
#include <linux/module.h>
#include <linux/fs.h>
#include "efs.h"
#include <linux/efs_fs_sb.h>

static int efs_readpage(struct file *file, struct page *page)
{
        return block_read_full_page(page,efs_get_block);
}
static sector_t _efs_bmap(struct address_space *mapping, sector_t block)
{
        return generic_block_bmap(mapping,block,efs_get_block);
}
static const struct address_space_operations efs_aops = {
        .readpage = efs_readpage,
        .bmap = _efs_bmap
};

static inline void extent_copy(efs_extent *src, efs_extent *dst) {
        /*
         * this is slightly evil. it doesn't just copy
         * efs_extent from src to dst, it also mangles
         * the bits so that dst ends up in cpu byte-order.
         */

        dst->cooked.ex_magic  =  (unsigned int) src->raw[0];
        dst->cooked.ex_bn     = ((unsigned int) src->raw[1] << 16) |
                                ((unsigned int) src->raw[2] <<  8) |
                                ((unsigned int) src->raw[3] <<  0);
        dst->cooked.ex_length =  (unsigned int) src->raw[4];
        dst->cooked.ex_offset = ((unsigned int) src->raw[5] << 16) |
                                ((unsigned int) src->raw[6] <<  8) |
                                ((unsigned int) src->raw[7] <<  0);
        return;
}

struct inode *efs_iget(struct super_block *super, unsigned long ino)
{
        int i, inode_index;
        dev_t device;
        u32 rdev;
        struct buffer_head *bh;
        struct efs_sb_info    *sb = SUPER_INFO(super);
        struct efs_inode_info *in;
        efs_block_t block, offset;
        struct efs_dinode *efs_inode;
        struct inode *inode;

        inode = iget_locked(super, ino);
        if (!inode)
                return ERR_PTR(-ENOMEM);
        if (!(inode->i_state & I_NEW))
                return inode;

        in = INODE_INFO(inode);

        /*
        ** EFS layout:
        **
        ** |   cylinder group    |   cylinder group    |   cylinder group ..etc
        ** |inodes|data          |inodes|data          |inodes|data       ..etc
        **
        ** work out the inode block index, (considering initially that the
        ** inodes are stored as consecutive blocks). then work out the block
        ** number of that inode given the above layout, and finally the
        ** offset of the inode within that block.
        */

        inode_index = inode->i_ino /
                (EFS_BLOCKSIZE / sizeof(struct efs_dinode));

        block = sb->fs_start + sb->first_block + 
                (sb->group_size * (inode_index / sb->inode_blocks)) +
                (inode_index % sb->inode_blocks);

        offset = (inode->i_ino %
                        (EFS_BLOCKSIZE / sizeof(struct efs_dinode))) *
                sizeof(struct efs_dinode);

        bh = sb_bread(inode->i_sb, block);
        if (!bh) {
                pr_warn("%s() failed at block %d\n", __func__, block);
                goto read_inode_error;
        }

        efs_inode = (struct efs_dinode *) (bh->b_data + offset);
    
        inode->i_mode  = be16_to_cpu(efs_inode->di_mode);
        set_nlink(inode, be16_to_cpu(efs_inode->di_nlink));
        i_uid_write(inode, (uid_t)be16_to_cpu(efs_inode->di_uid));
        i_gid_write(inode, (gid_t)be16_to_cpu(efs_inode->di_gid));
        inode->i_size  = be32_to_cpu(efs_inode->di_size);
        inode->i_atime.tv_sec = be32_to_cpu(efs_inode->di_atime);
        inode->i_mtime.tv_sec = be32_to_cpu(efs_inode->di_mtime);
        inode->i_ctime.tv_sec = be32_to_cpu(efs_inode->di_ctime);
        inode->i_atime.tv_nsec = inode->i_mtime.tv_nsec = inode->i_ctime.tv_nsec = 0;

        /* this is the number of blocks in the file */
        if (inode->i_size == 0) {
                inode->i_blocks = 0;
        } else {
                inode->i_blocks = ((inode->i_size - 1) >> EFS_BLOCKSIZE_BITS) + 1;
        }

        rdev = be16_to_cpu(efs_inode->di_u.di_dev.odev);
        if (rdev == 0xffff) {
                rdev = be32_to_cpu(efs_inode->di_u.di_dev.ndev);
                if (sysv_major(rdev) > 0xfff)
                        device = 0;
                else
                        device = MKDEV(sysv_major(rdev), sysv_minor(rdev));
        } else
                device = old_decode_dev(rdev);

        /* get the number of extents for this object */
        in->numextents = be16_to_cpu(efs_inode->di_numextents);
        in->lastextent = 0;

        /* copy the extents contained within the inode to memory */
        for(i = 0; i < EFS_DIRECTEXTENTS; i++) {
                extent_copy(&(efs_inode->di_u.di_extents[i]), &(in->extents[i]));
                if (i < in->numextents && in->extents[i].cooked.ex_magic != 0) {
                        pr_warn("extent %d has bad magic number in inode %lu\n",
                                i, inode->i_ino);
                        brelse(bh);
                        goto read_inode_error;
                }
        }

        brelse(bh);
        pr_debug("efs_iget(): inode %lu, extents %d, mode %o\n",
                 inode->i_ino, in->numextents, inode->i_mode);
        switch (inode->i_mode & S_IFMT) {
                case S_IFDIR: 
                        inode->i_op = &efs_dir_inode_operations; 
                        inode->i_fop = &efs_dir_operations; 
                        break;
                case S_IFREG:
                        inode->i_fop = &generic_ro_fops;
                        inode->i_data.a_ops = &efs_aops;
                        break;
                case S_IFLNK:
                        inode->i_op = &page_symlink_inode_operations;
                        inode_nohighmem(inode);
                        inode->i_data.a_ops = &efs_symlink_aops;
                        break;
                case S_IFCHR:
                case S_IFBLK:
                case S_IFIFO:
                        init_special_inode(inode, inode->i_mode, device);
                        break;
                default:
                        pr_warn("unsupported inode mode %o\n", inode->i_mode);
                        goto read_inode_error;
                        break;
        }

        unlock_new_inode(inode);
        return inode;
        
read_inode_error:
        pr_warn("failed to read inode %lu\n", inode->i_ino);
        iget_failed(inode);
        return ERR_PTR(-EIO);
}

static inline efs_block_t
efs_extent_check(efs_extent *ptr, efs_block_t block, struct efs_sb_info *sb) {
        efs_block_t start;
        efs_block_t length;
        efs_block_t offset;

        /*
         * given an extent and a logical block within a file,
         * can this block be found within this extent ?
         */
        start  = ptr->cooked.ex_bn;
        length = ptr->cooked.ex_length;
        offset = ptr->cooked.ex_offset;

        if ((block >= offset) && (block < offset+length)) {
                return(sb->fs_start + start + block - offset);
        } else {
                return 0;
        }
}

efs_block_t efs_map_block(struct inode *inode, efs_block_t block) {
        struct efs_sb_info    *sb = SUPER_INFO(inode->i_sb);
        struct efs_inode_info *in = INODE_INFO(inode);
        struct buffer_head    *bh = NULL;

        int cur, last, first = 1;
        int ibase, ioffset, dirext, direxts, indext, indexts;
        efs_block_t iblock, result = 0, lastblock = 0;
        efs_extent ext, *exts;

        last = in->lastextent;

        if (in->numextents <= EFS_DIRECTEXTENTS) {
                /* first check the last extent we returned */
                if ((result = efs_extent_check(&in->extents[last], block, sb)))
                        return result;
    
                /* if we only have one extent then nothing can be found */
                if (in->numextents == 1) {
                        pr_err("%s() failed to map (1 extent)\n", __func__);
                        return 0;
                }

                direxts = in->numextents;

                /*
                 * check the stored extents in the inode
                 * start with next extent and check forwards
                 */
                for(dirext = 1; dirext < direxts; dirext++) {
                        cur = (last + dirext) % in->numextents;
                        if ((result = efs_extent_check(&in->extents[cur], block, sb))) {
                                in->lastextent = cur;
                                return result;
                        }
                }

                pr_err("%s() failed to map block %u (dir)\n", __func__, block);
                return 0;
        }

        pr_debug("%s(): indirect search for logical block %u\n",
                 __func__, block);
        direxts = in->extents[0].cooked.ex_offset;
        indexts = in->numextents;

        for(indext = 0; indext < indexts; indext++) {
                cur = (last + indext) % indexts;

                /*
                 * work out which direct extent contains `cur'.
                 *
                 * also compute ibase: i.e. the number of the first
                 * indirect extent contained within direct extent `cur'.
                 *
                 */
                ibase = 0;
                for(dirext = 0; cur < ibase && dirext < direxts; dirext++) {
                        ibase += in->extents[dirext].cooked.ex_length *
                                (EFS_BLOCKSIZE / sizeof(efs_extent));
                }

                if (dirext == direxts) {
                        /* should never happen */
                        pr_err("couldn't find direct extent for indirect extent %d (block %u)\n",
                               cur, block);
                        if (bh) brelse(bh);
                        return 0;
                }
                
                /* work out block number and offset of this indirect extent */
                iblock = sb->fs_start + in->extents[dirext].cooked.ex_bn +
                        (cur - ibase) /
                        (EFS_BLOCKSIZE / sizeof(efs_extent));
                ioffset = (cur - ibase) %
                        (EFS_BLOCKSIZE / sizeof(efs_extent));

                if (first || lastblock != iblock) {
                        if (bh) brelse(bh);

                        bh = sb_bread(inode->i_sb, iblock);
                        if (!bh) {
                                pr_err("%s() failed at block %d\n",
                                       __func__, iblock);
                                return 0;
                        }
                        pr_debug("%s(): read indirect extent block %d\n",
                                 __func__, iblock);
                        first = 0;
                        lastblock = iblock;
                }

                exts = (efs_extent *) bh->b_data;

                extent_copy(&(exts[ioffset]), &ext);

                if (ext.cooked.ex_magic != 0) {
                        pr_err("extent %d has bad magic number in block %d\n",
                               cur, iblock);
                        if (bh) brelse(bh);
                        return 0;
                }

                if ((result = efs_extent_check(&ext, block, sb))) {
                        if (bh) brelse(bh);
                        in->lastextent = cur;
                        return result;
                }
        }
        if (bh) brelse(bh);
        pr_err("%s() failed to map block %u (indir)\n", __func__, block);
        return 0;
}  

MODULE_LICENSE("GPL");