/*
 *  linux/fs/readdir.c
 *
 *  Copyright (C) 1995  Linus Torvalds
 */

#include <linux/sched.h>
#include <linux/mm.h>
#include <linux/errno.h>
#include <linux/stat.h>
#include <linux/file.h>
#include <linux/smp_lock.h>

#include <asm/uaccess.h>

int vfs_readdir(struct file *file, filldir_t filler, void *buf)
{
        struct inode *inode = file->f_dentry->d_inode;
        int res = -ENOTDIR;
        if (!file->f_op || !file->f_op->readdir)
                goto out;
        down(&inode->i_sem);
        down(&inode->i_zombie);
        res = -ENOENT;
        if (!IS_DEADDIR(inode)) {
                lock_kernel();
                res = file->f_op->readdir(file, buf, filler);
                unlock_kernel();
        }
        up(&inode->i_zombie);
        up(&inode->i_sem);
out:
        return res;
}

int dcache_dir_open(struct inode *inode, struct file *file)
{
        static struct qstr cursor_name = {len:1, name:"."};

        file->private_data = d_alloc(file->f_dentry, &cursor_name);

        return file->private_data ? 0 : -ENOMEM;
}

int dcache_dir_close(struct inode *inode, struct file *file)
{
        dput(file->private_data);
        return 0;
}

loff_t dcache_dir_lseek(struct file *file, loff_t offset, int origin)
{
        down(&file->f_dentry->d_inode->i_sem);
        switch (origin) {
                case 1:
                        offset += file->f_pos;
                case 0:
                        if (offset >= 0)
                                break;
                default:
                        up(&file->f_dentry->d_inode->i_sem);
                        return -EINVAL;
        }
        if (offset != file->f_pos) {
                file->f_pos = offset;
                if (file->f_pos >= 2) {
                        struct list_head *p;
                        struct dentry *cursor = file->private_data;
                        loff_t n = file->f_pos - 2;

                        spin_lock(&dcache_lock);
                        p = file->f_dentry->d_subdirs.next;
                        while (n && p != &file->f_dentry->d_subdirs) {
                                struct dentry *next;
                                next = list_entry(p, struct dentry, d_child);
                                if (!list_empty(&next->d_hash) && next->d_inode)
                                        n--;
                                p = p->next;
                        }
                        list_del(&cursor->d_child);
                        list_add_tail(&cursor->d_child, p);
                        spin_unlock(&dcache_lock);
                }
        }
        up(&file->f_dentry->d_inode->i_sem);
        return offset;
}

int dcache_dir_fsync(struct file * file, struct dentry *dentry, int datasync)
{
        return 0;
}

/*
 * Directory is locked and all positive dentries in it are safe, since
 * for ramfs-type trees they can't go away without unlink() or rmdir(),
 * both impossible due to the lock on directory.
 */

int dcache_readdir(struct file * filp, void * dirent, filldir_t filldir)
{
        struct dentry *dentry = filp->f_dentry;
        struct dentry *cursor = filp->private_data;
        struct list_head *p, *q = &cursor->d_child;
        ino_t ino;
        int i = filp->f_pos;

        switch (i) {
                case 0:
                        ino = dentry->d_inode->i_ino;
                        if (filldir(dirent, ".", 1, i, ino, DT_DIR) < 0)
                                break;
                        filp->f_pos++;
                        i++;
                        /* fallthrough */
                case 1:
                        spin_lock(&dcache_lock);
                        ino = dentry->d_parent->d_inode->i_ino;
                        spin_unlock(&dcache_lock);
                        if (filldir(dirent, "..", 2, i, ino, DT_DIR) < 0)
                                break;
                        filp->f_pos++;
                        i++;
                        /* fallthrough */
                default:
                        spin_lock(&dcache_lock);
                        if (filp->f_pos == 2) {
                                list_del(q);
                                list_add(q, &dentry->d_subdirs);
                        }
                        for (p=q->next; p != &dentry->d_subdirs; p=p->next) {
                                struct dentry *next;
                                next = list_entry(p, struct dentry, d_child);
                                if (list_empty(&next->d_hash) || !next->d_inode)
                                        continue;

                                spin_unlock(&dcache_lock);
                                if (filldir(dirent, next->d_name.name, next->d_name.len, filp->f_pos, next->d_inode->i_ino, DT_UNKNOWN) < 0)
                                        return 0;
                                spin_lock(&dcache_lock);
                                /* next is still alive */
                                list_del(q);
                                list_add(q, p);
                                p = q;
                                filp->f_pos++;
                        }
                        spin_unlock(&dcache_lock);
        }
        return 0;
}

struct file_operations dcache_dir_ops = {
        open:           dcache_dir_open,
        release:        dcache_dir_close,
        llseek:         dcache_dir_lseek,
        read:           generic_read_dir,
        readdir:        dcache_readdir,
        fsync:          dcache_dir_fsync,
};

/*
 * Traditional linux readdir() handling..
 *
 * "count=1" is a special case, meaning that the buffer is one
 * dirent-structure in size and that the code can't handle more
 * anyway. Thus the special "fillonedir()" function for that
 * case (the low-level handlers don't need to care about this).
 */
#define NAME_OFFSET(de) ((int) ((de)->d_name - (char *) (de)))
#define ROUND_UP(x) (((x)+sizeof(long)-1) & ~(sizeof(long)-1))

#ifndef __ia64__

struct old_linux_dirent {
        unsigned long   d_ino;
        unsigned long   d_offset;
        unsigned short  d_namlen;
        char            d_name[1];
};

struct readdir_callback {
        struct old_linux_dirent * dirent;
        int count;
};

static int fillonedir(void * __buf, const char * name, int namlen, loff_t offset,
                      ino_t ino, unsigned int d_type)
{
        struct readdir_callback * buf = (struct readdir_callback *) __buf;
        struct old_linux_dirent * dirent;

        if (buf->count)
                return -EINVAL;
        buf->count++;
        dirent = buf->dirent;
        put_user(ino, &dirent->d_ino);
        put_user(offset, &dirent->d_offset);
        put_user(namlen, &dirent->d_namlen);
        copy_to_user(dirent->d_name, name, namlen);
        put_user(0, dirent->d_name + namlen);
        return 0;
}

asmlinkage int old_readdir(unsigned int fd, void * dirent, unsigned int count)
{
        int error;
        struct file * file;
        struct readdir_callback buf;

        error = -EBADF;
        file = fget(fd);
        if (!file)
                goto out;

        buf.count = 0;
        buf.dirent = dirent;

        error = vfs_readdir(file, fillonedir, &buf);
        if (error >= 0)
                error = buf.count;

        fput(file);
out:
        return error;
}

#endif /* !__ia64__ */

/*
 * New, all-improved, singing, dancing, iBCS2-compliant getdents()
 * interface. 
 */
struct linux_dirent {
        unsigned long   d_ino;
        unsigned long   d_off;
        unsigned short  d_reclen;
        char            d_name[1];
};

struct getdents_callback {
        struct linux_dirent * current_dir;
        struct linux_dirent * previous;
        int count;
        int error;
};

static int filldir(void * __buf, const char * name, int namlen, loff_t offset,
                   ino_t ino, unsigned int d_type)
{
        struct linux_dirent * dirent;
        struct getdents_callback * buf = (struct getdents_callback *) __buf;
        int reclen = ROUND_UP(NAME_OFFSET(dirent) + namlen + 1);

        buf->error = -EINVAL;   /* only used if we fail.. */
        if (reclen > buf->count)
                return -EINVAL;
        dirent = buf->previous;
        if (dirent)
                put_user(offset, &dirent->d_off);
        dirent = buf->current_dir;
        buf->previous = dirent;
        put_user(ino, &dirent->d_ino);
        put_user(reclen, &dirent->d_reclen);
        copy_to_user(dirent->d_name, name, namlen);
        put_user(0, dirent->d_name + namlen);
        ((char *) dirent) += reclen;
        buf->current_dir = dirent;
        buf->count -= reclen;
        return 0;
}

asmlinkage long sys_getdents(unsigned int fd, void * dirent, unsigned int count)
{
        struct file * file;
        struct linux_dirent * lastdirent;
        struct getdents_callback buf;
        int error;

        error = -EBADF;
        file = fget(fd);
        if (!file)
                goto out;

        buf.current_dir = (struct linux_dirent *) dirent;
        buf.previous = NULL;
        buf.count = count;
        buf.error = 0;

        error = vfs_readdir(file, filldir, &buf);
        if (error < 0)
                goto out_putf;
        error = buf.error;
        lastdirent = buf.previous;
        if (lastdirent) {
                put_user(file->f_pos, &lastdirent->d_off);
                error = count - buf.count;
        }

out_putf:
        fput(file);
out:
        return error;
}

/*
 * And even better one including d_type field and 64bit d_ino and d_off.
 */
struct linux_dirent64 {
        u64             d_ino;
        s64             d_off;
        unsigned short  d_reclen;
        unsigned char   d_type;
        char            d_name[0];
};

#define ROUND_UP64(x) (((x)+sizeof(u64)-1) & ~(sizeof(u64)-1))

struct getdents_callback64 {
        struct linux_dirent64 * current_dir;
        struct linux_dirent64 * previous;
        int count;
        int error;
};

static int filldir64(void * __buf, const char * name, int namlen, loff_t offset,
                     ino_t ino, unsigned int d_type)
{
        struct linux_dirent64 * dirent, d;
        struct getdents_callback64 * buf = (struct getdents_callback64 *) __buf;
        int reclen = ROUND_UP64(NAME_OFFSET(dirent) + namlen + 1);

        buf->error = -EINVAL;   /* only used if we fail.. */
        if (reclen > buf->count)
                return -EINVAL;
        dirent = buf->previous;
        if (dirent) {
                d.d_off = offset;
                copy_to_user(&dirent->d_off, &d.d_off, sizeof(d.d_off));
        }
        dirent = buf->current_dir;
        buf->previous = dirent;
        memset(&d, 0, NAME_OFFSET(&d));
        d.d_ino = ino;
        d.d_reclen = reclen;
        d.d_type = d_type;
        copy_to_user(dirent, &d, NAME_OFFSET(&d));
        copy_to_user(dirent->d_name, name, namlen);
        put_user(0, dirent->d_name + namlen);
        ((char *) dirent) += reclen;
        buf->current_dir = dirent;
        buf->count -= reclen;
        return 0;
}

asmlinkage long sys_getdents64(unsigned int fd, void * dirent, unsigned int count)
{
        struct file * file;
        struct linux_dirent64 * lastdirent;
        struct getdents_callback64 buf;
        int error;

        error = -EBADF;
        file = fget(fd);
        if (!file)
                goto out;

        buf.current_dir = (struct linux_dirent64 *) dirent;
        buf.previous = NULL;
        buf.count = count;
        buf.error = 0;

        error = vfs_readdir(file, filldir64, &buf);
        if (error < 0)
                goto out_putf;
        error = buf.error;
        lastdirent = buf.previous;
        if (lastdirent) {
                struct linux_dirent64 d;
                d.d_off = file->f_pos;
                copy_to_user(&lastdirent->d_off, &d.d_off, sizeof(d.d_off));
                error = count - buf.count;
        }

out_putf:
        fput(file);
out:
        return error;
}