Re: iov_iter_pipe warning.

[Al Viro]

On Fri, Apr 28, 2017 at 06:20:25PM +0100, Al Viro wrote:
> On Fri, Apr 28, 2017 at 12:50:24PM -0400, Dave Jones wrote:
> > currently running v4.11-rc8-75-gf83246089ca0
> > 
> > sunrpc bit is for the other unrelated problem I'm chasing.
> > 
> > note also, I saw the backtrace without the fs/splice.c changes.
> 
>       Interesting...  Could you add this and see if that triggers?

Gyah...  It's a bloody dumb braino in iov_iter_revert() for pipe-backed
ones.  Sorry, the oneliner below should fix it.

diff --git a/lib/iov_iter.c b/lib/iov_iter.c
index f7c93568ec99..4952311422c1 100644
--- a/lib/iov_iter.c
+++ b/lib/iov_iter.c
@@ -798,7 +798,7 @@ void iov_iter_revert(struct iov_iter *i, size_t unroll)
                while (1) {
                        size_t n = off - pipe->bufs[idx].offset;
                        if (unroll < n) {
-                               off -= (n - unroll);
+                               off -= unroll;
                                break;
                        }
                        unroll -= n;