dir.c

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/*
 * OMFS (as used by RIO Karma) directory operations.
 * Copyright (C) 2005 Bob Copeland <[email protected]>
 * Released under GPL v2.
 */

#include <linux/fs.h>
#include <linux/ctype.h>
#include <linux/buffer_head.h>
#include "omfs.h"

static int omfs_hash(const char *name, int namelen, int mod)
{
    int i, hash = 0;
    for (i = 0; i < namelen; i++)
        hash ^= tolower(name[i]) << (i % 24);
    return hash % mod;
}

/*
 * Finds the bucket for a given name and reads the containing block;
 * *ofs is set to the offset of the first list entry.
 */
static struct buffer_head *omfs_get_bucket(struct inode *dir,
        const char *name, int namelen, int *ofs)
{
    int nbuckets = (dir->i_size - OMFS_DIR_START)/8;
    int bucket = omfs_hash(name, namelen, nbuckets);

    *ofs = OMFS_DIR_START + bucket * 8;
    return omfs_bread(dir->i_sb, dir->i_ino);
}

static struct buffer_head *omfs_scan_list(struct inode *dir, u64 block,
                const char *name, int namelen,
                u64 *prev_block)
{
    struct buffer_head *bh;
    struct omfs_inode *oi;
    int err = -ENOENT;
    *prev_block = ~0;

    while (block != ~0) {
        bh = omfs_bread(dir->i_sb, block);
        if (!bh) {
            err = -EIO;
            goto err;
        }

        oi = (struct omfs_inode *) bh->b_data;
        if (omfs_is_bad(OMFS_SB(dir->i_sb), &oi->i_head, block)) {
            brelse(bh);
            goto err;
        }

        if (strncmp(oi->i_name, name, namelen) == 0)
            return bh;

        *prev_block = block;
        block = be64_to_cpu(oi->i_sibling);
        brelse(bh);
    }
err:
    return ERR_PTR(err);
}

static struct buffer_head *omfs_find_entry(struct inode *dir,
                       const char *name, int namelen)
{
    struct buffer_head *bh;
    int ofs;
    u64 block, dummy;

    bh = omfs_get_bucket(dir, name, namelen, &ofs);
    if (!bh)
        return ERR_PTR(-EIO);

    block = be64_to_cpu(*((__be64 *) &bh->b_data[ofs]));
    brelse(bh);

    return omfs_scan_list(dir, block, name, namelen, &dummy);
}

int omfs_make_empty(struct inode *inode, struct super_block *sb)
{
    struct omfs_sb_info *sbi = OMFS_SB(sb);
    struct buffer_head *bh;
    struct omfs_inode *oi;

    bh = omfs_bread(sb, inode->i_ino);
    if (!bh)
        return -ENOMEM;

    memset(bh->b_data, 0, sizeof(struct omfs_inode));

    if (S_ISDIR(inode->i_mode)) {
        memset(&bh->b_data[OMFS_DIR_START], 0xff,
            sbi->s_sys_blocksize - OMFS_DIR_START);
    } else
        omfs_make_empty_table(bh, OMFS_EXTENT_START);

    oi = (struct omfs_inode *) bh->b_data;
    oi->i_head.h_self = cpu_to_be64(inode->i_ino);
    oi->i_sibling = ~cpu_to_be64(0ULL);

    mark_buffer_dirty(bh);
    brelse(bh);
    return 0;
}

static int omfs_add_link(struct dentry *dentry, struct inode *inode)
{
    struct inode *dir = dentry->d_parent->d_inode;
    const char *name = dentry->d_name.name;
    int namelen = dentry->d_name.len;
    struct omfs_inode *oi;
    struct buffer_head *bh;
    u64 block;
    __be64 *entry;
    int ofs;

    /* just prepend to head of queue in proper bucket */
    bh = omfs_get_bucket(dir, name, namelen, &ofs);
    if (!bh)
        goto out;

    entry = (__be64 *) &bh->b_data[ofs];
    block = be64_to_cpu(*entry);
    *entry = cpu_to_be64(inode->i_ino);
    mark_buffer_dirty(bh);
    brelse(bh);

    /* now set the sibling and parent pointers on the new inode */
    bh = omfs_bread(dir->i_sb, inode->i_ino);
    if (!bh)
        goto out;

    oi = (struct omfs_inode *) bh->b_data;
    memcpy(oi->i_name, name, namelen);
    memset(oi->i_name + namelen, 0, OMFS_NAMELEN - namelen);
    oi->i_sibling = cpu_to_be64(block);
    oi->i_parent = cpu_to_be64(dir->i_ino);
    mark_buffer_dirty(bh);
    brelse(bh);

    dir->i_ctime = CURRENT_TIME_SEC;

    /* mark affected inodes dirty to rebuild checksums */
    mark_inode_dirty(dir);
    mark_inode_dirty(inode);
    return 0;
out:
    return -ENOMEM;
}

static int omfs_delete_entry(struct dentry *dentry)
{
    struct inode *dir = dentry->d_parent->d_inode;
    struct inode *dirty;
    const char *name = dentry->d_name.name;
    int namelen = dentry->d_name.len;
    struct omfs_inode *oi;
    struct buffer_head *bh, *bh2;
    __be64 *entry, next;
    u64 block, prev;
    int ofs;
    int err = -ENOMEM;

    /* delete the proper node in the bucket's linked list */
    bh = omfs_get_bucket(dir, name, namelen, &ofs);
    if (!bh)
        goto out;

    entry = (__be64 *) &bh->b_data[ofs];
    block = be64_to_cpu(*entry);

    bh2 = omfs_scan_list(dir, block, name, namelen, &prev);
    if (IS_ERR(bh2)) {
        err = PTR_ERR(bh2);
        goto out_free_bh;
    }

    oi = (struct omfs_inode *) bh2->b_data;
    next = oi->i_sibling;
    brelse(bh2);

    if (prev != ~0) {
        /* found in middle of list, get list ptr */
        brelse(bh);
        bh = omfs_bread(dir->i_sb, prev);
        if (!bh)
            goto out;

        oi = (struct omfs_inode *) bh->b_data;
        entry = &oi->i_sibling;
    }

    *entry = next;
    mark_buffer_dirty(bh);

    if (prev != ~0) {
        dirty = omfs_iget(dir->i_sb, prev);
        if (!IS_ERR(dirty)) {
            mark_inode_dirty(dirty);
            iput(dirty);
        }
    }

    err = 0;
out_free_bh:
    brelse(bh);
out:
    return err;
}

static int omfs_dir_is_empty(struct inode *inode)
{
    int nbuckets = (inode->i_size - OMFS_DIR_START) / 8;
    struct buffer_head *bh;
    u64 *ptr;
    int i;

    bh = omfs_bread(inode->i_sb, inode->i_ino);

    if (!bh)
        return 0;

    ptr = (u64 *) &bh->b_data[OMFS_DIR_START];

    for (i = 0; i < nbuckets; i++, ptr++)
        if (*ptr != ~0)
            break;

    brelse(bh);
    return *ptr != ~0;
}

static int omfs_remove(struct inode *dir, struct dentry *dentry)
{
    struct inode *inode = dentry->d_inode;
    int ret;


    if (S_ISDIR(inode->i_mode) &&
        !omfs_dir_is_empty(inode))
        return -ENOTEMPTY;

    ret = omfs_delete_entry(dentry);
    if (ret)
        return ret;
    
    clear_nlink(inode);
    mark_inode_dirty(inode);
    mark_inode_dirty(dir);
    return 0;
}

static int omfs_add_node(struct inode *dir, struct dentry *dentry, umode_t mode)
{
    int err;
    struct inode *inode = omfs_new_inode(dir, mode);

    if (IS_ERR(inode))
        return PTR_ERR(inode);

    err = omfs_make_empty(inode, dir->i_sb);
    if (err)
        goto out_free_inode;

    err = omfs_add_link(dentry, inode);
    if (err)
        goto out_free_inode;

    d_instantiate(dentry, inode);
    return 0;

out_free_inode:
    iput(inode);
    return err;
}

static int omfs_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
{
    return omfs_add_node(dir, dentry, mode | S_IFDIR);
}

static int omfs_create(struct inode *dir, struct dentry *dentry, umode_t mode,
        bool excl)
{
    return omfs_add_node(dir, dentry, mode | S_IFREG);
}

static struct dentry *omfs_lookup(struct inode *dir, struct dentry *dentry,
                  unsigned int flags)
{
    struct buffer_head *bh;
    struct inode *inode = NULL;

    if (dentry->d_name.len > OMFS_NAMELEN)
        return ERR_PTR(-ENAMETOOLONG);

    bh = omfs_find_entry(dir, dentry->d_name.name, dentry->d_name.len);
    if (!IS_ERR(bh)) {
        struct omfs_inode *oi = (struct omfs_inode *)bh->b_data;
        ino_t ino = be64_to_cpu(oi->i_head.h_self);
        brelse(bh);
        inode = omfs_iget(dir->i_sb, ino);
        if (IS_ERR(inode))
            return ERR_CAST(inode);
    }
    d_add(dentry, inode);
    return NULL;
}

/* sanity check block's self pointer */
int omfs_is_bad(struct omfs_sb_info *sbi, struct omfs_header *header,
    u64 fsblock)
{
    int is_bad;
    u64 ino = be64_to_cpu(header->h_self);
    is_bad = ((ino != fsblock) || (ino < sbi->s_root_ino) ||
        (ino > sbi->s_num_blocks));

    if (is_bad)
        printk(KERN_WARNING "omfs: bad hash chain detected\n");

    return is_bad;
}

static int omfs_fill_chain(struct file *filp, void *dirent, filldir_t filldir,
        u64 fsblock, int hindex)
{
    struct inode *dir = filp->f_dentry->d_inode;
    struct buffer_head *bh;
    struct omfs_inode *oi;
    u64 self;
    int res = 0;
    unsigned char d_type;

    /* follow chain in this bucket */
    while (fsblock != ~0) {
        bh = omfs_bread(dir->i_sb, fsblock);
        if (!bh)
            goto out;

        oi = (struct omfs_inode *) bh->b_data;
        if (omfs_is_bad(OMFS_SB(dir->i_sb), &oi->i_head, fsblock)) {
            brelse(bh);
            goto out;
        }

        self = fsblock;
        fsblock = be64_to_cpu(oi->i_sibling);

        /* skip visited nodes */
        if (hindex) {
            hindex--;
            brelse(bh);
            continue;
        }

        d_type = (oi->i_type == OMFS_DIR) ? DT_DIR : DT_REG;

        res = filldir(dirent, oi->i_name, strnlen(oi->i_name,
            OMFS_NAMELEN), filp->f_pos, self, d_type);
        brelse(bh);
        if (res < 0)
            break;
        filp->f_pos++;
    }
out:
    return res;
}

static int omfs_rename(struct inode *old_dir, struct dentry *old_dentry,
        struct inode *new_dir, struct dentry *new_dentry)
{
    struct inode *new_inode = new_dentry->d_inode;
    struct inode *old_inode = old_dentry->d_inode;
    int err;

    if (new_inode) {
        /* overwriting existing file/dir */
        err = omfs_remove(new_dir, new_dentry);
        if (err)
            goto out;
    }

    /* since omfs locates files by name, we need to unlink _before_
     * adding the new link or we won't find the old one */
    err = omfs_delete_entry(old_dentry);
    if (err)
        goto out;

    mark_inode_dirty(old_dir);
    err = omfs_add_link(new_dentry, old_inode);
    if (err)
        goto out;

    old_inode->i_ctime = CURRENT_TIME_SEC;
    mark_inode_dirty(old_inode);
out:
    return err;
}

static int omfs_readdir(struct file *filp, void *dirent, filldir_t filldir)
{
    struct inode *dir = filp->f_dentry->d_inode;
    struct buffer_head *bh;
    loff_t offset, res;
    unsigned int hchain, hindex;
    int nbuckets;
    u64 fsblock;
    int ret = -EINVAL;

    if (filp->f_pos >> 32)
        goto success;

    switch ((unsigned long) filp->f_pos) {
    case 0:
        if (filldir(dirent, ".", 1, 0, dir->i_ino, DT_DIR) < 0)
            goto success;
        filp->f_pos++;
        /* fall through */
    case 1:
        if (filldir(dirent, "..", 2, 1,
            parent_ino(filp->f_dentry), DT_DIR) < 0)
            goto success;
        filp->f_pos = 1 << 20;
        /* fall through */
    }

    nbuckets = (dir->i_size - OMFS_DIR_START) / 8;

    /* high 12 bits store bucket + 1 and low 20 bits store hash index */
    hchain = (filp->f_pos >> 20) - 1;
    hindex = filp->f_pos & 0xfffff;

    bh = omfs_bread(dir->i_sb, dir->i_ino);
    if (!bh)
        goto out;

    offset = OMFS_DIR_START + hchain * 8;

    for (; hchain < nbuckets; hchain++, offset += 8) {
        fsblock = be64_to_cpu(*((__be64 *) &bh->b_data[offset]));

        res = omfs_fill_chain(filp, dirent, filldir, fsblock, hindex);
        hindex = 0;
        if (res < 0)
            break;

        filp->f_pos = (hchain+2) << 20;
    }
    brelse(bh);
success:
    ret = 0;
out:
    return ret;
}

const struct inode_operations omfs_dir_inops = {
    .lookup = omfs_lookup,
    .mkdir = omfs_mkdir,
    .rename = omfs_rename,
    .create = omfs_create,
    .unlink = omfs_remove,
    .rmdir = omfs_remove,
};

const struct file_operations omfs_dir_operations = {
    .read = generic_read_dir,
    .readdir = omfs_readdir,
    .llseek = generic_file_llseek,
};