inode.c

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/*
 * 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 (IS_ERR(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) {
        printk(KERN_WARNING "EFS: bread() failed at block %d\n", 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) {
            printk(KERN_WARNING "EFS: extent %d has bad magic number in inode %lu\n", i, inode->i_ino);
            brelse(bh);
            goto read_inode_error;
        }
    }

    brelse(bh);
   
#ifdef DEBUG
    printk(KERN_DEBUG "EFS: efs_iget(): inode %lu, extents %d, mode %o\n",
        inode->i_ino, in->numextents, inode->i_mode);
#endif

    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->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:
            printk(KERN_WARNING "EFS: unsupported inode mode %o\n", inode->i_mode);
            goto read_inode_error;
            break;
    }

    unlock_new_inode(inode);
    return inode;
        
read_inode_error:
    printk(KERN_WARNING "EFS: 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) {
            printk(KERN_ERR "EFS: map_block() failed to map (1 extent)\n");
            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;
            }
        }

        printk(KERN_ERR "EFS: map_block() failed to map block %u (dir)\n", block);
        return 0;
    }

#ifdef DEBUG
    printk(KERN_DEBUG "EFS: map_block(): indirect search for logical block %u\n", block);
#endif
    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 */
            printk(KERN_ERR "EFS: 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) {
                printk(KERN_ERR "EFS: bread() failed at block %d\n", iblock);
                return 0;
            }
#ifdef DEBUG
            printk(KERN_DEBUG "EFS: map_block(): read indirect extent block %d\n", iblock);
#endif
            first = 0;
            lastblock = iblock;
        }

        exts = (efs_extent *) bh->b_data;

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

        if (ext.cooked.ex_magic != 0) {
            printk(KERN_ERR "EFS: 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);
    printk(KERN_ERR "EFS: map_block() failed to map block %u (indir)\n", block);
    return 0;
}  

MODULE_LICENSE("GPL");