On Thu, 2 Jun 2022 16:21:29 +0800 Yu Kuai <yukuai3@xxxxxxxxxx> wrote:
> In filemap_read(), 'ra->prev_pos' is set to 'iocb->ki_pos + copied',
> while it should be 'iocb->ki_ops'. For consequence,
> folio_mark_accessed() will not be called for 'fbatch.folios[0]' since
> 'iocb->ki_pos' is always equal to 'ra->prev_pos'.
>
> ...
>
> --- a/mm/filemap.c
> +++ b/mm/filemap.c
> @@ -2728,10 +2728,11 @@ ssize_t filemap_read(struct kiocb *iocb, struct iov_iter *iter,
> flush_dcache_folio(folio);
>
> copied = copy_folio_to_iter(folio, offset, bytes, iter);
> -
> - already_read += copied;
> - iocb->ki_pos += copied;
> - ra->prev_pos = iocb->ki_pos;
> + if (copied) {
> + ra->prev_pos = iocb->ki_pos;
> + already_read += copied;
> + iocb->ki_pos += copied;
> + }
>
> if (copied < bytes) {
> error = -EFAULT;
It seems tidier, but does it matter? If copied==0 we're going to break
out and return -EFAULT anyway?
