symlink.c

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/*
 * symlink.c
 *
 * PURPOSE
 *  Symlink handling routines for the OSTA-UDF(tm) filesystem.
 *
 * COPYRIGHT
 *  This file is distributed under the terms of the GNU General Public
 *  License (GPL). Copies of the GPL can be obtained from:
 *      ftp://prep.ai.mit.edu/pub/gnu/GPL
 *  Each contributing author retains all rights to their own work.
 *
 *  (C) 1998-2001 Ben Fennema
 *  (C) 1999 Stelias Computing Inc
 *
 * HISTORY
 *
 *  04/16/99 blf  Created.
 *
 */

#include "udfdecl.h"
#include <asm/uaccess.h>
#include <linux/errno.h>
#include <linux/fs.h>
#include <linux/time.h>
#include <linux/mm.h>
#include <linux/stat.h>
#include <linux/pagemap.h>
#include <linux/buffer_head.h>
#include "udf_i.h"

static void udf_pc_to_char(struct super_block *sb, unsigned char *from,
               int fromlen, unsigned char *to)
{
    struct pathComponent *pc;
    int elen = 0;
    unsigned char *p = to;

    while (elen < fromlen) {
        pc = (struct pathComponent *)(from + elen);
        switch (pc->componentType) {
        case 1:
            /*
             * Symlink points to some place which should be agreed
             * upon between originator and receiver of the media. Ignore.
             */
            if (pc->lengthComponentIdent > 0)
                break;
            /* Fall through */
        case 2:
            p = to;
            *p++ = '/';
            break;
        case 3:
            memcpy(p, "../", 3);
            p += 3;
            break;
        case 4:
            memcpy(p, "./", 2);
            p += 2;
            /* that would be . - just ignore */
            break;
        case 5:
            p += udf_get_filename(sb, pc->componentIdent, p,
                          pc->lengthComponentIdent);
            *p++ = '/';
            break;
        }
        elen += sizeof(struct pathComponent) + pc->lengthComponentIdent;
    }
    if (p > to + 1)
        p[-1] = '\0';
    else
        p[0] = '\0';
}

static int udf_symlink_filler(struct file *file, struct page *page)
{
    struct inode *inode = page->mapping->host;
    struct buffer_head *bh = NULL;
    unsigned char *symlink;
    int err = -EIO;
    unsigned char *p = kmap(page);
    struct udf_inode_info *iinfo;
    uint32_t pos;

    iinfo = UDF_I(inode);
    pos = udf_block_map(inode, 0);

    down_read(&iinfo->i_data_sem);
    if (iinfo->i_alloc_type == ICBTAG_FLAG_AD_IN_ICB) {
        symlink = iinfo->i_ext.i_data + iinfo->i_lenEAttr;
    } else {
        bh = sb_bread(inode->i_sb, pos);

        if (!bh)
            goto out;

        symlink = bh->b_data;
    }

    udf_pc_to_char(inode->i_sb, symlink, inode->i_size, p);
    brelse(bh);

    up_read(&iinfo->i_data_sem);
    SetPageUptodate(page);
    kunmap(page);
    unlock_page(page);
    return 0;

out:
    up_read(&iinfo->i_data_sem);
    SetPageError(page);
    kunmap(page);
    unlock_page(page);
    return err;
}

/*
 * symlinks can't do much...
 */
const struct address_space_operations udf_symlink_aops = {
    .readpage       = udf_symlink_filler,
};