Re: [PATCH 5/6] aio: implement IOCB_CMD_FSYNC and IOCB_CMD_FDSYNC

[Al Viro]

On Wed, Mar 28, 2018 at 09:26:38AM +0200, Christoph Hellwig wrote:
> +static int aio_fsync(struct fsync_iocb *req, struct iocb *iocb, bool 
> datasync)
> +{
> +     int ret;
> +
> +     if (iocb->aio_buf)
> +             return -EINVAL;
> +     if (iocb->aio_offset || iocb->aio_nbytes || iocb->aio_rw_flags)
> +             return -EINVAL;
> +
> +     req->file = fget(iocb->aio_fildes);
> +     if (unlikely(!req->file))
> +             return -EBADF;
> +
> +     ret = -EINVAL;
> +     if (!req->file->f_op->fsync)
> +             goto out_fput;
> +
> +     req->datasync = datasync;
> +     INIT_WORK(&req->work, aio_fsync_work);
> +     schedule_work(&req->work);
> +     return -EIOCBQUEUED;
> +out_fput:
> +     if (unlikely(ret && ret != -EIOCBQUEUED))

Really?  The only way to get there is if we got NULL ->f_op->fsync.
So this "if (unlikely(...))" is actually if (true) and I'm not
sure we want that separated anyway - simply

        if (unlikely(!req->file->f_op->fsync)) {
                fput(req->file);
                return -EINVAL;
        }

> +             fput(req->file);

> +     return ret;
> +}