// SPDX-License-Identifier: GPL-2.0-only
/*
 * 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>
 */

#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/slab.h>
#include <linux/uio.h>
#include <linux/fscache.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;
}

/**
 * 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;
        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, ITER_DEST, &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) {
                        err = p9stat_read(fid->clnt, rdir->buf + rdir->head,
                                          rdir->tail - rdir->head, &st);
                        if (err <= 0) {
                                p9_debug(P9_DEBUG_VFS, "returned %d\n", err);
                                return -EIO;
                        }

                        over = !dir_emit(ctx, st.name, strlen(st.name),
                                        QID2INO(&st.qid), dt_type(&st));
                        p9stat_free(&st);
                        if (over)
                                return 0;

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

/**
 * 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),
                                      QID2INO(&curdirent.qid),
                                      curdirent.d_type))
                                return 0;

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


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

int v9fs_dir_release(struct inode *inode, struct file *filp)
{
        struct v9fs_inode *v9inode = V9FS_I(inode);
        struct p9_fid *fid;
        __le32 version;
        loff_t i_size;
        int retval = 0, put_err;

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

        if (fid) {
                if ((S_ISREG(inode->i_mode)) && (filp->f_mode & FMODE_WRITE))
                        retval = filemap_fdatawrite(inode->i_mapping);

                spin_lock(&inode->i_lock);
                hlist_del(&fid->ilist);
                spin_unlock(&inode->i_lock);
                put_err = p9_fid_put(fid);
                retval = retval < 0 ? retval : put_err;
        }

        if ((filp->f_mode & FMODE_WRITE)) {
                version = cpu_to_le32(v9inode->qid.version);
                i_size = i_size_read(inode);
                fscache_unuse_cookie(v9fs_inode_cookie(v9inode),
                                     &version, &i_size);
        } else {
                fscache_unuse_cookie(v9fs_inode_cookie(v9inode), NULL, NULL);
        }
        return retval;
}

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,
};