On Mon, Dec 23, 2019 at 09:08:55PM +0000, Sargun Dhillon wrote:
> This introduces a function which can be used to fetch a file, given an
> arbitrary task. As long as the user holds a reference (refcnt) to the
> task_struct it is safe to call, and will either return NULL on failure,
> or a pointer to the file, with a refcnt.
>
> Signed-off-by: Sargun Dhillon <sargun@xxxxxxxxx>
> ---
> fs/file.c | 22 ++++++++++++++++++++--
> include/linux/file.h | 2 ++
> 2 files changed, 22 insertions(+), 2 deletions(-)
>
> diff --git a/fs/file.c b/fs/file.c
> index 2f4fcf985079..0ceeb046f4f3 100644
> --- a/fs/file.c
> +++ b/fs/file.c
> @@ -706,9 +706,9 @@ void do_close_on_exec(struct files_struct *files)
> spin_unlock(&files->file_lock);
> }
>
> -static struct file *__fget(unsigned int fd, fmode_t mask, unsigned int refs)
> +static struct file *__fget_files(struct files_struct *files, unsigned int fd,
> + fmode_t mask, unsigned int refs)
> {
> - struct files_struct *files = current->files;
> struct file *file;
>
> rcu_read_lock();
> @@ -729,6 +729,11 @@ static struct file *__fget(unsigned int fd, fmode_t mask, unsigned int refs)
> return file;
> }
>
> +static struct file *__fget(unsigned int fd, fmode_t mask, unsigned int refs)
> +{
> + return __fget_files(current->files, fd, mask, refs);
> +}
> +
> struct file *fget_many(unsigned int fd, unsigned int refs)
> {
> return __fget(fd, FMODE_PATH, refs);
> @@ -746,6 +751,19 @@ struct file *fget_raw(unsigned int fd)
> }
> EXPORT_SYMBOL(fget_raw);
>
> +struct file *fget_task(struct task_struct *task, unsigned int fd)
> +{
> + struct file *file = NULL;
> +
> + task_lock(task);
> + if (task->files)
> + file = __fget_files(task->files, fd, 0, 1);
> +
> + task_unlock(task);
Nit: remove the \n:
task_lock(task);
if (task->files)
file = __fget_files(task->files, fd, 0, 1);
task_unlock(task);
Christian
