// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Squashfs - a compressed read only filesystem for Linux
 *
 * Copyright (c) 2002, 2003, 2004, 2005, 2006, 2007, 2008
 * Phillip Lougher <phillip@squashfs.org.uk>
 *
 * symlink.c
 */

/*
 * This file implements code to handle symbolic links.
 *
 * The data contents of symbolic links are stored inside the symbolic
 * link inode within the inode table.  This allows the normally small symbolic
 * link to be compressed as part of the inode table, achieving much greater
 * compression than if the symbolic link was compressed individually.
 */

#include <linux/fs.h>
#include <linux/vfs.h>
#include <linux/kernel.h>
#include <linux/string.h>
#include <linux/pagemap.h>
#include <linux/xattr.h>

#include "squashfs_fs.h"
#include "squashfs_fs_sb.h"
#include "squashfs_fs_i.h"
#include "squashfs.h"
#include "xattr.h"

static int squashfs_symlink_read_folio(struct file *file, struct folio *folio)
{
        struct inode *inode = folio->mapping->host;
        struct super_block *sb = inode->i_sb;
        struct squashfs_sb_info *msblk = sb->s_fs_info;
        int index = folio_pos(folio);
        u64 block = squashfs_i(inode)->start;
        int offset = squashfs_i(inode)->offset;
        int length = min_t(int, i_size_read(inode) - index, PAGE_SIZE);
        int bytes, copied, error;
        void *pageaddr;
        struct squashfs_cache_entry *entry;

        TRACE("Entered squashfs_symlink_readpage, page index %ld, start block "
                        "%llx, offset %x\n", folio->index, block, offset);

        /*
         * Skip index bytes into symlink metadata.
         */
        if (index) {
                bytes = squashfs_read_metadata(sb, NULL, &block, &offset,
                                                                index);
                if (bytes < 0) {
                        ERROR("Unable to read symlink [%llx:%x]\n",
                                squashfs_i(inode)->start,
                                squashfs_i(inode)->offset);
                        error = bytes;
                        goto out;
                }
        }

        /*
         * Read length bytes from symlink metadata.  Squashfs_read_metadata
         * is not used here because it can sleep and we want to use
         * kmap_local to map the folio.  Instead call the underlying
         * squashfs_cache_get routine.  As length bytes may overlap metadata
         * blocks, we may need to call squashfs_cache_get multiple times.
         */
        for (bytes = 0; bytes < length; offset = 0, bytes += copied) {
                entry = squashfs_cache_get(sb, msblk->block_cache, block, 0);
                if (entry->error) {
                        ERROR("Unable to read symlink [%llx:%x]\n",
                                squashfs_i(inode)->start,
                                squashfs_i(inode)->offset);
                        squashfs_cache_put(entry);
                        error = entry->error;
                        goto out;
                }

                pageaddr = kmap_local_folio(folio, 0);
                copied = squashfs_copy_data(pageaddr + bytes, entry, offset,
                                                                length - bytes);
                if (copied == length - bytes)
                        memset(pageaddr + length, 0, PAGE_SIZE - length);
                else
                        block = entry->next_index;
                kunmap_local(pageaddr);
                squashfs_cache_put(entry);
        }

        flush_dcache_folio(folio);
        error = 0;
out:
        folio_end_read(folio, error == 0);
        return error;
}


const struct address_space_operations squashfs_symlink_aops = {
        .read_folio = squashfs_symlink_read_folio
};

const struct inode_operations squashfs_symlink_inode_ops = {
        .get_link = page_get_link,
        .listxattr = squashfs_listxattr
};