dir.c

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/*
 * QNX6 file system, Linux implementation.
 *
 * Version : 1.0.0
 *
 * History :
 *
 * 01-02-2012 by Kai Bankett ([email protected]) : first release.
 * 16-02-2012 pagemap extension by Al Viro
 *
 */

#include "qnx6.h"

static unsigned qnx6_lfile_checksum(char *name, unsigned size)
{
    unsigned crc = 0;
    char *end = name + size;
    while (name < end) {
        crc = ((crc >> 1) + *(name++)) ^
            ((crc & 0x00000001) ? 0x80000000 : 0);
    }
    return crc;
}

static struct page *qnx6_get_page(struct inode *dir, unsigned long n)
{
    struct address_space *mapping = dir->i_mapping;
    struct page *page = read_mapping_page(mapping, n, NULL);
    if (!IS_ERR(page))
        kmap(page);
    return page;
}

static inline unsigned long dir_pages(struct inode *inode)
{
    return (inode->i_size+PAGE_CACHE_SIZE-1)>>PAGE_CACHE_SHIFT;
}

static unsigned last_entry(struct inode *inode, unsigned long page_nr)
{
    unsigned long last_byte = inode->i_size;
    last_byte -= page_nr << PAGE_CACHE_SHIFT;
    if (last_byte > PAGE_CACHE_SIZE)
        last_byte = PAGE_CACHE_SIZE;
    return last_byte / QNX6_DIR_ENTRY_SIZE;
}

static struct qnx6_long_filename *qnx6_longname(struct super_block *sb,
                     struct qnx6_long_dir_entry *de,
                     struct page **p)
{
    struct qnx6_sb_info *sbi = QNX6_SB(sb);
    u32 s = fs32_to_cpu(sbi, de->de_long_inode); /* in block units */
    u32 n = s >> (PAGE_CACHE_SHIFT - sb->s_blocksize_bits); /* in pages */
    /* within page */
    u32 offs = (s << sb->s_blocksize_bits) & ~PAGE_CACHE_MASK;
    struct address_space *mapping = sbi->longfile->i_mapping;
    struct page *page = read_mapping_page(mapping, n, NULL);
    if (IS_ERR(page))
        return ERR_CAST(page);
    kmap(*p = page);
    return (struct qnx6_long_filename *)(page_address(page) + offs);
}

static int qnx6_dir_longfilename(struct inode *inode,
            struct qnx6_long_dir_entry *de,
            void *dirent, loff_t pos,
            unsigned de_inode, filldir_t filldir)
{
    struct qnx6_long_filename *lf;
    struct super_block *s = inode->i_sb;
    struct qnx6_sb_info *sbi = QNX6_SB(s);
    struct page *page;
    int lf_size;

    if (de->de_size != 0xff) {
        /* error - long filename entries always have size 0xff
           in direntry */
        printk(KERN_ERR "qnx6: invalid direntry size (%i).\n",
                de->de_size);
        return 0;
    }
    lf = qnx6_longname(s, de, &page);
    if (IS_ERR(lf)) {
        printk(KERN_ERR "qnx6:Error reading longname\n");
        return 0;
    }

    lf_size = fs16_to_cpu(sbi, lf->lf_size);

    if (lf_size > QNX6_LONG_NAME_MAX) {
        QNX6DEBUG((KERN_INFO "file %s\n", lf->lf_fname));
        printk(KERN_ERR "qnx6:Filename too long (%i)\n", lf_size);
        qnx6_put_page(page);
        return 0;
    }

    /* calc & validate longfilename checksum
       mmi 3g filesystem does not have that checksum */
    if (!test_opt(s, MMI_FS) && fs32_to_cpu(sbi, de->de_checksum) !=
            qnx6_lfile_checksum(lf->lf_fname, lf_size))
        printk(KERN_INFO "qnx6: long filename checksum error.\n");

    QNX6DEBUG((KERN_INFO "qnx6_readdir:%.*s inode:%u\n",
                    lf_size, lf->lf_fname, de_inode));
    if (filldir(dirent, lf->lf_fname, lf_size, pos, de_inode,
            DT_UNKNOWN) < 0) {
        qnx6_put_page(page);
        return 0;
    }

    qnx6_put_page(page);
    /* success */
    return 1;
}

static int qnx6_readdir(struct file *filp, void *dirent, filldir_t filldir)
{
    struct inode *inode = filp->f_path.dentry->d_inode;
    struct super_block *s = inode->i_sb;
    struct qnx6_sb_info *sbi = QNX6_SB(s);
    loff_t pos = filp->f_pos & (QNX6_DIR_ENTRY_SIZE - 1);
    unsigned long npages = dir_pages(inode);
    unsigned long n = pos >> PAGE_CACHE_SHIFT;
    unsigned start = (pos & ~PAGE_CACHE_MASK) / QNX6_DIR_ENTRY_SIZE;
    bool done = false;

    if (filp->f_pos >= inode->i_size)
        return 0;

    for ( ; !done && n < npages; n++, start = 0) {
        struct page *page = qnx6_get_page(inode, n);
        int limit = last_entry(inode, n);
        struct qnx6_dir_entry *de;
        int i = start;

        if (IS_ERR(page)) {
            printk(KERN_ERR "qnx6_readdir: read failed\n");
            filp->f_pos = (n + 1) << PAGE_CACHE_SHIFT;
            return PTR_ERR(page);
        }
        de = ((struct qnx6_dir_entry *)page_address(page)) + start;
        for (; i < limit; i++, de++, pos += QNX6_DIR_ENTRY_SIZE) {
            int size = de->de_size;
            u32 no_inode = fs32_to_cpu(sbi, de->de_inode);

            if (!no_inode || !size)
                continue;

            if (size > QNX6_SHORT_NAME_MAX) {
                /* long filename detected
                   get the filename from long filename
                   structure / block */
                if (!qnx6_dir_longfilename(inode,
                    (struct qnx6_long_dir_entry *)de,
                    dirent, pos, no_inode,
                    filldir)) {
                    done = true;
                    break;
                }
            } else {
                QNX6DEBUG((KERN_INFO "qnx6_readdir:%.*s"
                   " inode:%u\n", size, de->de_fname,
                            no_inode));
                if (filldir(dirent, de->de_fname, size,
                      pos, no_inode, DT_UNKNOWN)
                    < 0) {
                    done = true;
                    break;
                }
            }
        }
        qnx6_put_page(page);
    }
    filp->f_pos = pos;
    return 0;
}

/*
 * check if the long filename is correct.
 */
static unsigned qnx6_long_match(int len, const char *name,
            struct qnx6_long_dir_entry *de, struct inode *dir)
{
    struct super_block *s = dir->i_sb;
    struct qnx6_sb_info *sbi = QNX6_SB(s);
    struct page *page;
    int thislen;
    struct qnx6_long_filename *lf = qnx6_longname(s, de, &page);

    if (IS_ERR(lf))
        return 0;

    thislen = fs16_to_cpu(sbi, lf->lf_size);
    if (len != thislen) {
        qnx6_put_page(page);
        return 0;
    }
    if (memcmp(name, lf->lf_fname, len) == 0) {
        qnx6_put_page(page);
        return fs32_to_cpu(sbi, de->de_inode);
    }
    qnx6_put_page(page);
    return 0;
}

/*
 * check if the filename is correct.
 */
static unsigned qnx6_match(struct super_block *s, int len, const char *name,
            struct qnx6_dir_entry *de)
{
    struct qnx6_sb_info *sbi = QNX6_SB(s);
    if (memcmp(name, de->de_fname, len) == 0)
        return fs32_to_cpu(sbi, de->de_inode);
    return 0;
}


unsigned qnx6_find_entry(int len, struct inode *dir, const char *name,
             struct page **res_page)
{
    struct super_block *s = dir->i_sb;
    struct qnx6_inode_info *ei = QNX6_I(dir);
    struct page *page = NULL;
    unsigned long start, n;
    unsigned long npages = dir_pages(dir);
    unsigned ino;
    struct qnx6_dir_entry *de;
    struct qnx6_long_dir_entry *lde;

    *res_page = NULL;

    if (npages == 0)
        return 0;
    start = ei->i_dir_start_lookup;
    if (start >= npages)
        start = 0;
    n = start;

    do {
        page = qnx6_get_page(dir, n);
        if (!IS_ERR(page)) {
            int limit = last_entry(dir, n);
            int i;

            de = (struct qnx6_dir_entry *)page_address(page);
            for (i = 0; i < limit; i++, de++) {
                if (len <= QNX6_SHORT_NAME_MAX) {
                    /* short filename */
                    if (len != de->de_size)
                        continue;
                    ino = qnx6_match(s, len, name, de);
                    if (ino)
                        goto found;
                } else if (de->de_size == 0xff) {
                    /* deal with long filename */
                    lde = (struct qnx6_long_dir_entry *)de;
                    ino = qnx6_long_match(len,
                                name, lde, dir);
                    if (ino)
                        goto found;
                } else
                    printk(KERN_ERR "qnx6: undefined "
                        "filename size in inode.\n");
            }
            qnx6_put_page(page);
        }

        if (++n >= npages)
            n = 0;
    } while (n != start);
    return 0;

found:
    *res_page = page;
    ei->i_dir_start_lookup = n;
    return ino;
}

const struct file_operations qnx6_dir_operations = {
    .llseek     = generic_file_llseek,
    .read       = generic_read_dir,
    .readdir    = qnx6_readdir,
    .fsync      = generic_file_fsync,
};

const struct inode_operations qnx6_dir_inode_operations = {
    .lookup     = qnx6_lookup,
};