/*
 * Copyright (c) 2000-2001 Christoph Hellwig.
 * 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 =              vxfs_readdir,
};

static inline u_long
dir_blocks(struct inode *ip)
{
        u_long                  bsize = ip->i_sb->s_blocksize;
        return (ip->i_size + bsize - 1) & ~(bsize - 1);
}

/*
 * NOTE! unlike strncmp, vxfs_match returns 1 for success, 0 for failure.
 *
 * len <= VXFS_NAMELEN and de != NULL are guaranteed by caller.
 */
static inline int
vxfs_match(int len, const char * const name, struct vxfs_direct *de)
{
        if (len != de->d_namelen)
                return 0;
        if (!de->d_ino)
                return 0;
        return !memcmp(name, de->d_name, len);
}

static inline struct vxfs_direct *
vxfs_next_entry(struct vxfs_direct *de)
{
        return ((struct vxfs_direct *)((char*)de + de->d_reclen));
}

/**
 * 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                          npages, page, nblocks, pblocks, block;
        u_long                          bsize = ip->i_sb->s_blocksize;
        const char                      *name = dp->d_name.name;
        int                             namelen = dp->d_name.len;

        npages = dir_pages(ip);
        nblocks = dir_blocks(ip);
        pblocks = VXFS_BLOCK_PER_PAGE(ip->i_sb);
        
        for (page = 0; page < npages; page++) {
                caddr_t                 kaddr;
                struct page             *pp;

                pp = vxfs_get_page(ip->i_mapping, page);
                if (IS_ERR(pp))
                        continue;
                kaddr = (caddr_t)page_address(pp);

                for (block = 0; block <= nblocks && block <= pblocks; block++) {
                        caddr_t                 baddr, limit;
                        struct vxfs_dirblk      *dbp;
                        struct vxfs_direct      *de;

                        baddr = kaddr + (block * bsize);
                        limit = baddr + bsize - VXFS_DIRLEN(1);
                        
                        dbp = (struct vxfs_dirblk *)baddr;
                        de = (struct vxfs_direct *)(baddr + VXFS_DIRBLKOV(dbp));

                        for (; (caddr_t)de <= limit; de = vxfs_next_entry(de)) {
                                if (!de->d_reclen)
                                        break;
                                if (!de->d_ino)
                                        continue;
                                if (vxfs_match(namelen, name, de)) {
                                        *ppp = pp;
                                        return (de);
                                }
                        }
                }
                vxfs_put_page(pp);
        }

        return NULL;
}

/**
 * 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 = 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;
        u_long                  page, npages, block, pblocks, nblocks, offset;
        loff_t                  pos;

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

        npages = dir_pages(ip);
        nblocks = dir_blocks(ip);
        pblocks = VXFS_BLOCK_PER_PAGE(sbp);

        page = pos >> PAGE_SHIFT;
        offset = pos & ~PAGE_MASK;
        block = (u_long)(pos >> sbp->s_blocksize_bits) % pblocks;

        for (; page < npages; page++, block = 0) {
                char                    *kaddr;
                struct page             *pp;

                pp = vxfs_get_page(ip->i_mapping, page);
                if (IS_ERR(pp))
                        continue;
                kaddr = (char *)page_address(pp);

                for (; block <= nblocks && block <= pblocks; block++) {
                        char                    *baddr, *limit;
                        struct vxfs_dirblk      *dbp;
                        struct vxfs_direct      *de;

                        baddr = kaddr + (block * bsize);
                        limit = baddr + bsize - VXFS_DIRLEN(1);
        
                        dbp = (struct vxfs_dirblk *)baddr;
                        de = (struct vxfs_direct *)
                                (offset ?
                                 (kaddr + offset) :
                                 (baddr + VXFS_DIRBLKOV(dbp)));

                        for (; (char *)de <= limit; de = vxfs_next_entry(de)) {
                                if (!de->d_reclen)
                                        break;
                                if (!de->d_ino)
                                        continue;

                                offset = (char *)de - kaddr;
                                ctx->pos = ((page << PAGE_SHIFT) | offset) + 2;
                                if (!dir_emit(ctx, de->d_name, de->d_namelen,
                                        de->d_ino, DT_UNKNOWN)) {
                                        vxfs_put_page(pp);
                                        return 0;
                                }
                        }
                        offset = 0;
                }
                vxfs_put_page(pp);
                offset = 0;
        }
        ctx->pos = ((page << PAGE_SHIFT) | offset) + 2;
        return 0;
}