inode.c

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/*
 *  linux/fs/adfs/inode.c
 *
 *  Copyright (C) 1997-1999 Russell King
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */
#include <linux/buffer_head.h>
#include <linux/writeback.h>
#include "adfs.h"

/*
 * Lookup/Create a block at offset 'block' into 'inode'.  We currently do
 * not support creation of new blocks, so we return -EIO for this case.
 */
static int
adfs_get_block(struct inode *inode, sector_t block, struct buffer_head *bh,
           int create)
{
    if (!create) {
        if (block >= inode->i_blocks)
            goto abort_toobig;

        block = __adfs_block_map(inode->i_sb, inode->i_ino, block);
        if (block)
            map_bh(bh, inode->i_sb, block);
        return 0;
    }
    /* don't support allocation of blocks yet */
    return -EIO;

abort_toobig:
    return 0;
}

static int adfs_writepage(struct page *page, struct writeback_control *wbc)
{
    return block_write_full_page(page, adfs_get_block, wbc);
}

static int adfs_readpage(struct file *file, struct page *page)
{
    return block_read_full_page(page, adfs_get_block);
}

static int adfs_write_begin(struct file *file, struct address_space *mapping,
            loff_t pos, unsigned len, unsigned flags,
            struct page **pagep, void **fsdata)
{
    int ret;

    *pagep = NULL;
    ret = cont_write_begin(file, mapping, pos, len, flags, pagep, fsdata,
                adfs_get_block,
                &ADFS_I(mapping->host)->mmu_private);
    if (unlikely(ret)) {
        loff_t isize = mapping->host->i_size;
        if (pos + len > isize)
            vmtruncate(mapping->host, isize);
    }

    return ret;
}

static sector_t _adfs_bmap(struct address_space *mapping, sector_t block)
{
    return generic_block_bmap(mapping, block, adfs_get_block);
}

static const struct address_space_operations adfs_aops = {
    .readpage   = adfs_readpage,
    .writepage  = adfs_writepage,
    .write_begin    = adfs_write_begin,
    .write_end  = generic_write_end,
    .bmap       = _adfs_bmap
};

/*
 * Convert ADFS attributes and filetype to Linux permission.
 */
static umode_t
adfs_atts2mode(struct super_block *sb, struct inode *inode)
{
    unsigned int attr = ADFS_I(inode)->attr;
    umode_t mode, rmask;
    struct adfs_sb_info *asb = ADFS_SB(sb);

    if (attr & ADFS_NDA_DIRECTORY) {
        mode = S_IRUGO & asb->s_owner_mask;
        return S_IFDIR | S_IXUGO | mode;
    }

    switch (ADFS_I(inode)->filetype) {
    case 0xfc0: /* LinkFS */
        return S_IFLNK|S_IRWXUGO;

    case 0xfe6: /* UnixExec */
        rmask = S_IRUGO | S_IXUGO;
        break;

    default:
        rmask = S_IRUGO;
    }

    mode = S_IFREG;

    if (attr & ADFS_NDA_OWNER_READ)
        mode |= rmask & asb->s_owner_mask;

    if (attr & ADFS_NDA_OWNER_WRITE)
        mode |= S_IWUGO & asb->s_owner_mask;

    if (attr & ADFS_NDA_PUBLIC_READ)
        mode |= rmask & asb->s_other_mask;

    if (attr & ADFS_NDA_PUBLIC_WRITE)
        mode |= S_IWUGO & asb->s_other_mask;
    return mode;
}

/*
 * Convert Linux permission to ADFS attribute.  We try to do the reverse
 * of atts2mode, but there is not a 1:1 translation.
 */
static int
adfs_mode2atts(struct super_block *sb, struct inode *inode)
{
    umode_t mode;
    int attr;
    struct adfs_sb_info *asb = ADFS_SB(sb);

    /* FIXME: should we be able to alter a link? */
    if (S_ISLNK(inode->i_mode))
        return ADFS_I(inode)->attr;

    if (S_ISDIR(inode->i_mode))
        attr = ADFS_NDA_DIRECTORY;
    else
        attr = 0;

    mode = inode->i_mode & asb->s_owner_mask;
    if (mode & S_IRUGO)
        attr |= ADFS_NDA_OWNER_READ;
    if (mode & S_IWUGO)
        attr |= ADFS_NDA_OWNER_WRITE;

    mode = inode->i_mode & asb->s_other_mask;
    mode &= ~asb->s_owner_mask;
    if (mode & S_IRUGO)
        attr |= ADFS_NDA_PUBLIC_READ;
    if (mode & S_IWUGO)
        attr |= ADFS_NDA_PUBLIC_WRITE;

    return attr;
}

/*
 * Convert an ADFS time to Unix time.  ADFS has a 40-bit centi-second time
 * referenced to 1 Jan 1900 (til 2248) so we need to discard 2208988800 seconds
 * of time to convert from RISC OS epoch to Unix epoch.
 */
static void
adfs_adfs2unix_time(struct timespec *tv, struct inode *inode)
{
    unsigned int high, low;
    /* 01 Jan 1970 00:00:00 (Unix epoch) as nanoseconds since
     * 01 Jan 1900 00:00:00 (RISC OS epoch)
     */
    static const s64 nsec_unix_epoch_diff_risc_os_epoch =
                            2208988800000000000LL;
    s64 nsec;

    if (ADFS_I(inode)->stamped == 0)
        goto cur_time;

    high = ADFS_I(inode)->loadaddr & 0xFF; /* top 8 bits of timestamp */
    low  = ADFS_I(inode)->execaddr;    /* bottom 32 bits of timestamp */

    /* convert 40-bit centi-seconds to 32-bit seconds
     * going via nanoseconds to retain precision
     */
    nsec = (((s64) high << 32) | (s64) low) * 10000000; /* cs to ns */

    /* Files dated pre  01 Jan 1970 00:00:00. */
    if (nsec < nsec_unix_epoch_diff_risc_os_epoch)
        goto too_early;

    /* convert from RISC OS to Unix epoch */
    nsec -= nsec_unix_epoch_diff_risc_os_epoch;

    *tv = ns_to_timespec(nsec);
    return;

 cur_time:
    *tv = CURRENT_TIME;
    return;

 too_early:
    tv->tv_sec = tv->tv_nsec = 0;
    return;
}

/*
 * Convert an Unix time to ADFS time.  We only do this if the entry has a
 * time/date stamp already.
 */
static void
adfs_unix2adfs_time(struct inode *inode, unsigned int secs)
{
    unsigned int high, low;

    if (ADFS_I(inode)->stamped) {
        /* convert 32-bit seconds to 40-bit centi-seconds */
        low  = (secs & 255) * 100;
        high = (secs / 256) * 100 + (low >> 8) + 0x336e996a;

        ADFS_I(inode)->loadaddr = (high >> 24) |
                (ADFS_I(inode)->loadaddr & ~0xff);
        ADFS_I(inode)->execaddr = (low & 255) | (high << 8);
    }
}

/*
 * Fill in the inode information from the object information.
 *
 * Note that this is an inode-less filesystem, so we can't use the inode
 * number to reference the metadata on the media.  Instead, we use the
 * inode number to hold the object ID, which in turn will tell us where
 * the data is held.  We also save the parent object ID, and with these
 * two, we can locate the metadata.
 *
 * This does mean that we rely on an objects parent remaining the same at
 * all times - we cannot cope with a cross-directory rename (yet).
 */
struct inode *
adfs_iget(struct super_block *sb, struct object_info *obj)
{
    struct inode *inode;

    inode = new_inode(sb);
    if (!inode)
        goto out;

    inode->i_uid     = ADFS_SB(sb)->s_uid;
    inode->i_gid     = ADFS_SB(sb)->s_gid;
    inode->i_ino     = obj->file_id;
    inode->i_size    = obj->size;
    set_nlink(inode, 2);
    inode->i_blocks  = (inode->i_size + sb->s_blocksize - 1) >>
                sb->s_blocksize_bits;

    /*
     * we need to save the parent directory ID so that
     * write_inode can update the directory information
     * for this file.  This will need special handling
     * for cross-directory renames.
     */
    ADFS_I(inode)->parent_id = obj->parent_id;
    ADFS_I(inode)->loadaddr  = obj->loadaddr;
    ADFS_I(inode)->execaddr  = obj->execaddr;
    ADFS_I(inode)->attr      = obj->attr;
    ADFS_I(inode)->filetype  = obj->filetype;
    ADFS_I(inode)->stamped   = ((obj->loadaddr & 0xfff00000) == 0xfff00000);

    inode->i_mode    = adfs_atts2mode(sb, inode);
    adfs_adfs2unix_time(&inode->i_mtime, inode);
    inode->i_atime = inode->i_mtime;
    inode->i_ctime = inode->i_mtime;

    if (S_ISDIR(inode->i_mode)) {
        inode->i_op = &adfs_dir_inode_operations;
        inode->i_fop    = &adfs_dir_operations;
    } else if (S_ISREG(inode->i_mode)) {
        inode->i_op = &adfs_file_inode_operations;
        inode->i_fop    = &adfs_file_operations;
        inode->i_mapping->a_ops = &adfs_aops;
        ADFS_I(inode)->mmu_private = inode->i_size;
    }

    insert_inode_hash(inode);

out:
    return inode;
}

/*
 * Validate and convert a changed access mode/time to their ADFS equivalents.
 * adfs_write_inode will actually write the information back to the directory
 * later.
 */
int
adfs_notify_change(struct dentry *dentry, struct iattr *attr)
{
    struct inode *inode = dentry->d_inode;
    struct super_block *sb = inode->i_sb;
    unsigned int ia_valid = attr->ia_valid;
    int error;
    
    error = inode_change_ok(inode, attr);

    /*
     * we can't change the UID or GID of any file -
     * we have a global UID/GID in the superblock
     */
    if ((ia_valid & ATTR_UID && !uid_eq(attr->ia_uid, ADFS_SB(sb)->s_uid)) ||
        (ia_valid & ATTR_GID && !gid_eq(attr->ia_gid, ADFS_SB(sb)->s_gid)))
        error = -EPERM;

    if (error)
        goto out;

    /* XXX: this is missing some actual on-disk truncation.. */
    if (ia_valid & ATTR_SIZE)
        truncate_setsize(inode, attr->ia_size);

    if (ia_valid & ATTR_MTIME) {
        inode->i_mtime = attr->ia_mtime;
        adfs_unix2adfs_time(inode, attr->ia_mtime.tv_sec);
    }
    /*
     * FIXME: should we make these == to i_mtime since we don't
     * have the ability to represent them in our filesystem?
     */
    if (ia_valid & ATTR_ATIME)
        inode->i_atime = attr->ia_atime;
    if (ia_valid & ATTR_CTIME)
        inode->i_ctime = attr->ia_ctime;
    if (ia_valid & ATTR_MODE) {
        ADFS_I(inode)->attr = adfs_mode2atts(sb, inode);
        inode->i_mode = adfs_atts2mode(sb, inode);
    }

    /*
     * FIXME: should we be marking this inode dirty even if
     * we don't have any metadata to write back?
     */
    if (ia_valid & (ATTR_SIZE | ATTR_MTIME | ATTR_MODE))
        mark_inode_dirty(inode);
out:
    return error;
}

/*
 * write an existing inode back to the directory, and therefore the disk.
 * The adfs-specific inode data has already been updated by
 * adfs_notify_change()
 */
int adfs_write_inode(struct inode *inode, struct writeback_control *wbc)
{
    struct super_block *sb = inode->i_sb;
    struct object_info obj;
    int ret;

    obj.file_id = inode->i_ino;
    obj.name_len    = 0;
    obj.parent_id   = ADFS_I(inode)->parent_id;
    obj.loadaddr    = ADFS_I(inode)->loadaddr;
    obj.execaddr    = ADFS_I(inode)->execaddr;
    obj.attr    = ADFS_I(inode)->attr;
    obj.size    = inode->i_size;

    ret = adfs_dir_update(sb, &obj, wbc->sync_mode == WB_SYNC_ALL);
    return ret;
}