/*
 * linux/fs/9p/vfs_dir.c
 *
 * This file contains vfs directory ops for the 9P2000 protocol.
 *
 *  Copyright (C) 2004 by Eric Van Hensbergen <ericvh@gmail.com>
 *  Copyright (C) 2002 by Ron Minnich <rminnich@lanl.gov>
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License version 2
 *  as published by the Free Software Foundation.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program; if not, write to:
 *  Free Software Foundation
 *  51 Franklin Street, Fifth Floor
 *  Boston, MA  02111-1301  USA
 *
 */

#include <linux/module.h>
#include <linux/errno.h>
#include <linux/fs.h>
#include <linux/file.h>
#include <linux/stat.h>
#include <linux/string.h>
#include <linux/sched.h>
#include <linux/inet.h>
#include <linux/idr.h>
#include <linux/slab.h>
#include <linux/uio.h>
#include <net/9p/9p.h>
#include <net/9p/client.h>

#include "v9fs.h"
#include "v9fs_vfs.h"
#include "fid.h"

/**
 * struct p9_rdir - readdir accounting
 * @head: start offset of current dirread buffer
 * @tail: end offset of current dirread buffer
 * @buf: dirread buffer
 *
 * private structure for keeping track of readdir
 * allocated on demand
 */

struct p9_rdir {
        int head;
        int tail;
        uint8_t buf[];
};

/**
 * dt_type - return file type
 * @mistat: mistat structure
 *
 */

static inline int dt_type(struct p9_wstat *mistat)
{
        unsigned long perm = mistat->mode;
        int rettype = DT_REG;

        if (perm & P9_DMDIR)
                rettype = DT_DIR;
        if (perm & P9_DMSYMLINK)
                rettype = DT_LNK;

        return rettype;
}

static void p9stat_init(struct p9_wstat *stbuf)
{
        stbuf->name  = NULL;
        stbuf->uid   = NULL;
        stbuf->gid   = NULL;
        stbuf->muid  = NULL;
        stbuf->extension = NULL;
}

/**
 * v9fs_alloc_rdir_buf - Allocate buffer used for read and readdir
 * @filp: opened file structure
 * @buflen: Length in bytes of buffer to allocate
 *
 */

static struct p9_rdir *v9fs_alloc_rdir_buf(struct file *filp, int buflen)
{
        struct p9_fid *fid = filp->private_data;
        if (!fid->rdir)
                fid->rdir = kzalloc(sizeof(struct p9_rdir) + buflen, GFP_KERNEL);
        return fid->rdir;
}

/**
 * v9fs_dir_readdir - iterate through a directory
 * @file: opened file structure
 * @ctx: actor we feed the entries to
 *
 */

static int v9fs_dir_readdir(struct file *file, struct dir_context *ctx)
{
        bool over;
        struct p9_wstat st;
        int err = 0;
        struct p9_fid *fid;
        int buflen;
        int reclen = 0;
        struct p9_rdir *rdir;
        struct kvec kvec;

        p9_debug(P9_DEBUG_VFS, "name %pD\n", file);
        fid = file->private_data;

        buflen = fid->clnt->msize - P9_IOHDRSZ;

        rdir = v9fs_alloc_rdir_buf(file, buflen);
        if (!rdir)
                return -ENOMEM;
        kvec.iov_base = rdir->buf;
        kvec.iov_len = buflen;

        while (1) {
                if (rdir->tail == rdir->head) {
                        struct iov_iter to;
                        int n;
                        iov_iter_kvec(&to, READ | ITER_KVEC, &kvec, 1, buflen);
                        n = p9_client_read(file->private_data, ctx->pos, &to,
                                           &err);
                        if (err)
                                return err;
                        if (n == 0)
                                return 0;

                        rdir->head = 0;
                        rdir->tail = n;
                }
                while (rdir->head < rdir->tail) {
                        p9stat_init(&st);
                        err = p9stat_read(fid->clnt, rdir->buf + rdir->head,
                                          rdir->tail - rdir->head, &st);
                        if (err) {
                                p9_debug(P9_DEBUG_VFS, "returned %d\n", err);
                                p9stat_free(&st);
                                return -EIO;
                        }
                        reclen = st.size+2;

                        over = !dir_emit(ctx, st.name, strlen(st.name),
                                         v9fs_qid2ino(&st.qid), dt_type(&st));
                        p9stat_free(&st);
                        if (over)
                                return 0;

                        rdir->head += reclen;
                        ctx->pos += reclen;
                }
        }
}

/**
 * v9fs_dir_readdir_dotl - iterate through a directory
 * @file: opened file structure
 * @ctx: actor we feed the entries to
 *
 */
static int v9fs_dir_readdir_dotl(struct file *file, struct dir_context *ctx)
{
        int err = 0;
        struct p9_fid *fid;
        int buflen;
        struct p9_rdir *rdir;
        struct p9_dirent curdirent;

        p9_debug(P9_DEBUG_VFS, "name %pD\n", file);
        fid = file->private_data;

        buflen = fid->clnt->msize - P9_READDIRHDRSZ;

        rdir = v9fs_alloc_rdir_buf(file, buflen);
        if (!rdir)
                return -ENOMEM;

        while (1) {
                if (rdir->tail == rdir->head) {
                        err = p9_client_readdir(fid, rdir->buf, buflen,
                                                ctx->pos);
                        if (err <= 0)
                                return err;

                        rdir->head = 0;
                        rdir->tail = err;
                }

                while (rdir->head < rdir->tail) {

                        err = p9dirent_read(fid->clnt, rdir->buf + rdir->head,
                                            rdir->tail - rdir->head,
                                            &curdirent);
                        if (err < 0) {
                                p9_debug(P9_DEBUG_VFS, "returned %d\n", err);
                                return -EIO;
                        }

                        if (!dir_emit(ctx, curdirent.d_name,
                                      strlen(curdirent.d_name),
                                      v9fs_qid2ino(&curdirent.qid),
                                      curdirent.d_type))
                                return 0;

                        ctx->pos = curdirent.d_off;
                        rdir->head += err;
                }
        }
}


/**
 * v9fs_dir_release - close a directory
 * @inode: inode of the directory
 * @filp: file pointer to a directory
 *
 */

int v9fs_dir_release(struct inode *inode, struct file *filp)
{
        struct p9_fid *fid;

        fid = filp->private_data;
        p9_debug(P9_DEBUG_VFS, "inode: %p filp: %p fid: %d\n",
                 inode, filp, fid ? fid->fid : -1);
        if (fid)
                p9_client_clunk(fid);
        return 0;
}

const struct file_operations v9fs_dir_operations = {
        .read = generic_read_dir,
        .llseek = generic_file_llseek,
        .iterate_shared = v9fs_dir_readdir,
        .open = v9fs_file_open,
        .release = v9fs_dir_release,
};

const struct file_operations v9fs_dir_operations_dotl = {
        .read = generic_read_dir,
        .llseek = generic_file_llseek,
        .iterate_shared = v9fs_dir_readdir_dotl,
        .open = v9fs_file_open,
        .release = v9fs_dir_release,
        .fsync = v9fs_file_fsync_dotl,
};