Re: [PATCH v1 1/2] open: add close_range()

[Oleg Nesterov]

On 05/22, Christian Brauner wrote:
>
> +static struct file *pick_file(struct files_struct *files, unsigned fd)
>  {
> -     struct file *file;
> +     struct file *file = NULL;
>       struct fdtable *fdt;
>  
>       spin_lock(&files->file_lock);
> @@ -632,15 +629,65 @@ int __close_fd(struct files_struct *files, unsigned fd)
>               goto out_unlock;
>       rcu_assign_pointer(fdt->fd[fd], NULL);
>       __put_unused_fd(files, fd);
> -     spin_unlock(&files->file_lock);
> -     return filp_close(file, files);
>  
>  out_unlock:
>       spin_unlock(&files->file_lock);
> -     return -EBADF;
> +     return file;

...

> +int __close_range(struct files_struct *files, unsigned fd, unsigned max_fd)
> +{
> +     unsigned int cur_max;
> +
> +     if (fd > max_fd)
> +             return -EINVAL;
> +
> +     rcu_read_lock();
> +     cur_max = files_fdtable(files)->max_fds;
> +     rcu_read_unlock();
> +
> +     /* cap to last valid index into fdtable */
> +     if (max_fd >= cur_max)
> +             max_fd = cur_max - 1;
> +
> +     while (fd <= max_fd) {
> +             struct file *file;
> +
> +             file = pick_file(files, fd++);

Well, how about something like

        static unsigned int find_next_opened_fd(struct fdtable *fdt, unsigned 
start)
        {
                unsigned int maxfd = fdt->max_fds;
                unsigned int maxbit = maxfd / BITS_PER_LONG;
                unsigned int bitbit = start / BITS_PER_LONG;

                bitbit = find_next_bit(fdt->full_fds_bits, maxbit, bitbit) * 
BITS_PER_LONG;
                if (bitbit > maxfd)
                        return maxfd;
                if (bitbit > start)
                        start = bitbit;
                return find_next_bit(fdt->open_fds, maxfd, start);
        }

        unsigned close_next_fd(struct files_struct *files, unsigned start, 
unsigned maxfd)
        {
                unsigned fd;
                struct file *file;
                struct fdtable *fdt;
        
                spin_lock(&files->file_lock);
                fdt = files_fdtable(files);
                fd = find_next_opened_fd(fdt, start);
                if (fd >= fdt->max_fds || fd > maxfd) {
                        fd = -1;
                        goto out;
                }

                file = fdt->fd[fd];
                rcu_assign_pointer(fdt->fd[fd], NULL);
                __put_unused_fd(files, fd);
        out:
                spin_unlock(&files->file_lock);

                if (fd == -1u)
                        return fd;

                filp_close(file, files);
                return fd + 1;
        }

?

Then close_range() can do

        while (fd < max_fd)
                fd = close_next_fd(fd, maxfd);

Oleg.