On Fri, Jul 29, 2022 at 06:21:23PM +0100, Al Viro wrote:
> > Hi Al,
> >
> > This changes causes sendfile09 LTP testcase fail in linux-next
> > (up to next-20220727) on s390. In fact, not this change exactly,
> > but rather 92d4d18eecb9 ("new iov_iter flavour - ITER_UBUF") -
> > which differs from what is posted here.
> >
> > AFAICT page_cache_pipe_buf_confirm() encounters !PageUptodate()
> > and !page->mapping page and returns -ENODATA.
> >
> > I am going to narrow the testcase and get more details, but please
> > let me know if I am missing something.
>
> Grrr....
>
> - } else if (iter_is_iovec(to)) {
> + } else if (!user_backed_iter(to)) {
>
> in mm/shmem.c. Spot the typo...
>
> Could you check if replacing that line with
> } else if (user_backed_iter(to)) {
>
> fixes the breakage?
Yes, it does! So just to be sure - this is the fix:
diff --git a/mm/shmem.c b/mm/shmem.c
index 8baf26eda989..5783f11351bb 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -2626,7 +2626,7 @@ static ssize_t shmem_file_read_iter(struct kiocb *iocb, struct iov_iter *to)
ret = copy_page_to_iter(page, offset, nr, to);
put_page(page);
- } else if (!user_backed_iter(to)) {
+ } else if (user_backed_iter(to)) {
/*
* Copy to user tends to be so well optimized, but
* clear_user() not so much, that it is noticeably
Thanks!
