/*
 * Copyright (c) 2000-2001 Christoph Hellwig.
 * Copyright (c) 2016 Krzysztof Blaszkowski
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions, and the following disclaimer,
 *    without modification.
 * 2. The name of the author may not be used to endorse or promote products
 *    derived from this software without specific prior written permission.
 *
 * Alternatively, this software may be distributed under the terms of the
 * GNU General Public License ("GPL").
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE FOR
 * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

/*
 * Veritas filesystem driver - lookup and other directory related code.
 */
#include <linux/fs.h>
#include <linux/time.h>
#include <linux/mm.h>
#include <linux/highmem.h>
#include <linux/kernel.h>
#include <linux/pagemap.h>

#include "vxfs.h"
#include "vxfs_dir.h"
#include "vxfs_inode.h"
#include "vxfs_extern.h"

/*
 * Number of VxFS blocks per page.
 */
#define VXFS_BLOCK_PER_PAGE(sbp)  ((PAGE_SIZE / (sbp)->s_blocksize))


static struct dentry *  vxfs_lookup(struct inode *, struct dentry *, unsigned int);
static int              vxfs_readdir(struct file *, struct dir_context *);

const struct inode_operations vxfs_dir_inode_ops = {
        .lookup =               vxfs_lookup,
};

const struct file_operations vxfs_dir_operations = {
        .llseek =               generic_file_llseek,
        .read =                 generic_read_dir,
        .iterate_shared =       vxfs_readdir,
};


/**
 * vxfs_find_entry - find a mathing directory entry for a dentry
 * @ip:         directory inode
 * @dp:         dentry for which we want to find a direct
 * @ppp:        gets filled with the page the return value sits in
 *
 * Description:
 *   vxfs_find_entry finds a &struct vxfs_direct for the VFS directory
 *   cache entry @dp.  @ppp will be filled with the page the return
 *   value resides in.
 *
 * Returns:
 *   The wanted direct on success, else a NULL pointer.
 */
static struct vxfs_direct *
vxfs_find_entry(struct inode *ip, struct dentry *dp, struct page **ppp)
{
        u_long bsize = ip->i_sb->s_blocksize;
        const char *name = dp->d_name.name;
        int namelen = dp->d_name.len;
        loff_t limit = VXFS_DIRROUND(ip->i_size);
        struct vxfs_direct *de_exit = NULL;
        loff_t pos = 0;
        struct vxfs_sb_info *sbi = VXFS_SBI(ip->i_sb);

        while (pos < limit) {
                struct page *pp;
                char *kaddr;
                int pg_ofs = pos & ~PAGE_MASK;

                pp = vxfs_get_page(ip->i_mapping, pos >> PAGE_SHIFT);
                if (IS_ERR(pp))
                        return NULL;
                kaddr = (char *)page_address(pp);

                while (pg_ofs < PAGE_SIZE && pos < limit) {
                        struct vxfs_direct *de;

                        if ((pos & (bsize - 1)) < 4) {
                                struct vxfs_dirblk *dbp =
                                        (struct vxfs_dirblk *)
                                         (kaddr + (pos & ~PAGE_MASK));
                                int overhead = VXFS_DIRBLKOV(sbi, dbp);

                                pos += overhead;
                                pg_ofs += overhead;
                        }
                        de = (struct vxfs_direct *)(kaddr + pg_ofs);

                        if (!de->d_reclen) {
                                pos += bsize - 1;
                                pos &= ~(bsize - 1);
                                break;
                        }

                        pg_ofs += fs16_to_cpu(sbi, de->d_reclen);
                        pos += fs16_to_cpu(sbi, de->d_reclen);
                        if (!de->d_ino)
                                continue;

                        if (namelen != fs16_to_cpu(sbi, de->d_namelen))
                                continue;
                        if (!memcmp(name, de->d_name, namelen)) {
                                *ppp = pp;
                                de_exit = de;
                                break;
                        }
                }
                if (!de_exit)
                        vxfs_put_page(pp);
                else
                        break;
        }

        return de_exit;
}

/**
 * vxfs_inode_by_name - find inode number for dentry
 * @dip:        directory to search in
 * @dp:         dentry we search for
 *
 * Description:
 *   vxfs_inode_by_name finds out the inode number of
 *   the path component described by @dp in @dip.
 *
 * Returns:
 *   The wanted inode number on success, else Zero.
 */
static ino_t
vxfs_inode_by_name(struct inode *dip, struct dentry *dp)
{
        struct vxfs_direct              *de;
        struct page                     *pp;
        ino_t                           ino = 0;

        de = vxfs_find_entry(dip, dp, &pp);
        if (de) {
                ino = fs32_to_cpu(VXFS_SBI(dip->i_sb), de->d_ino);
                kunmap(pp);
                put_page(pp);
        }
        
        return (ino);
}

/**
 * vxfs_lookup - lookup pathname component
 * @dip:        dir in which we lookup
 * @dp:         dentry we lookup
 * @flags:      lookup flags
 *
 * Description:
 *   vxfs_lookup tries to lookup the pathname component described
 *   by @dp in @dip.
 *
 * Returns:
 *   A NULL-pointer on success, else a negative error code encoded
 *   in the return pointer.
 */
static struct dentry *
vxfs_lookup(struct inode *dip, struct dentry *dp, unsigned int flags)
{
        struct inode            *ip = NULL;
        ino_t                   ino;
                         
        if (dp->d_name.len > VXFS_NAMELEN)
                return ERR_PTR(-ENAMETOOLONG);
                                 
        ino = vxfs_inode_by_name(dip, dp);
        if (ino) {
                ip = vxfs_iget(dip->i_sb, ino);
                if (IS_ERR(ip))
                        return ERR_CAST(ip);
        }
        d_add(dp, ip);
        return NULL;
}

/**
 * vxfs_readdir - read a directory
 * @fp:         the directory to read
 * @retp:       return buffer
 * @filler:     filldir callback
 *
 * Description:
 *   vxfs_readdir fills @retp with directory entries from @fp
 *   using the VFS supplied callback @filler.
 *
 * Returns:
 *   Zero.
 */
static int
vxfs_readdir(struct file *fp, struct dir_context *ctx)
{
        struct inode            *ip = file_inode(fp);
        struct super_block      *sbp = ip->i_sb;
        u_long                  bsize = sbp->s_blocksize;
        loff_t                  pos, limit;
        struct vxfs_sb_info     *sbi = VXFS_SBI(sbp);

        if (ctx->pos == 0) {
                if (!dir_emit_dot(fp, ctx))
                        goto out;
                ctx->pos++;
        }
        if (ctx->pos == 1) {
                if (!dir_emit(ctx, "..", 2, VXFS_INO(ip)->vii_dotdot, DT_DIR))
                        goto out;
                ctx->pos++;
        }

        limit = VXFS_DIRROUND(ip->i_size);
        if (ctx->pos > limit)
                goto out;

        pos = ctx->pos & ~3L;

        while (pos < limit) {
                struct page *pp;
                char *kaddr;
                int pg_ofs = pos & ~PAGE_MASK;
                int rc = 0;

                pp = vxfs_get_page(ip->i_mapping, pos >> PAGE_SHIFT);
                if (IS_ERR(pp))
                        return -ENOMEM;

                kaddr = (char *)page_address(pp);

                while (pg_ofs < PAGE_SIZE && pos < limit) {
                        struct vxfs_direct *de;

                        if ((pos & (bsize - 1)) < 4) {
                                struct vxfs_dirblk *dbp =
                                        (struct vxfs_dirblk *)
                                         (kaddr + (pos & ~PAGE_MASK));
                                int overhead = VXFS_DIRBLKOV(sbi, dbp);

                                pos += overhead;
                                pg_ofs += overhead;
                        }
                        de = (struct vxfs_direct *)(kaddr + pg_ofs);

                        if (!de->d_reclen) {
                                pos += bsize - 1;
                                pos &= ~(bsize - 1);
                                break;
                        }

                        pg_ofs += fs16_to_cpu(sbi, de->d_reclen);
                        pos += fs16_to_cpu(sbi, de->d_reclen);
                        if (!de->d_ino)
                                continue;

                        rc = dir_emit(ctx, de->d_name,
                                        fs16_to_cpu(sbi, de->d_namelen),
                                        fs32_to_cpu(sbi, de->d_ino),
                                        DT_UNKNOWN);
                        if (!rc) {
                                /* the dir entry was not read, fix pos. */
                                pos -= fs16_to_cpu(sbi, de->d_reclen);
                                break;
                        }
                }
                vxfs_put_page(pp);
                if (!rc)
                        break;
        }

        ctx->pos = pos | 2;

out:
        return 0;
}