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Message-ID: <CADvbK_fOv0+9bx1APO4rPwnRjYYC=Mov_803zCLAVAU7TgpekQ@mail.gmail.com>
Date: Tue, 27 Nov 2018 19:30:49 +0900
From: Xin Long <lucien.xin@...il.com>
To: Neil Horman <nhorman@...driver.com>
Cc: network dev <netdev@...r.kernel.org>, linux-sctp@...r.kernel.org,
davem <davem@...emloft.net>,
Marcelo Ricardo Leitner <marcelo.leitner@...il.com>
Subject: Re: [PATCH net] sctp: check and update stream->out_curr when
allocating stream_out
On Mon, Nov 26, 2018 at 10:59 PM Neil Horman <nhorman@...driver.com> wrote:
>
> On Mon, Nov 26, 2018 at 10:46:33PM +0900, Xin Long wrote:
> > On Mon, Nov 26, 2018 at 9:54 PM Neil Horman <nhorman@...driver.com> wrote:
> > >
> > > On Mon, Nov 26, 2018 at 07:22:05PM +0800, Xin Long wrote:
> > > > Now when using stream reconfig to add out streams, stream->out
> > > > will get re-allocated, and all old streams' information will
> > > > be copied to the new ones and the old ones will be freed.
> > > >
> > > > So without stream->out_curr updated, next time when trying to
> > > > send from stream->out_curr stream, a panic would be caused.
> > > >
> > > > This patch is to define sctp_stream_out_copy used to update the
> > > > stream->out_curr pointer to the new stream when copying the old
> > > > streams' information.
> > > >
> > > > While at it, rename fa_copy to sctp_stream_in_copy.
> > > >
> > > > Fixes: 5bbbbe32a431 ("sctp: introduce stream scheduler foundations")
> > > > Reported-by: Ying Xu <yinxu@...hat.com>
> > > > Reported-by: syzbot+e33a3a138267ca119c7d@...kaller.appspotmail.com
> > > > Signed-off-by: Xin Long <lucien.xin@...il.com>
> > > > ---
> > > > net/sctp/stream.c | 46 ++++++++++++++++++++++++++++++++--------------
> > > > 1 file changed, 32 insertions(+), 14 deletions(-)
> > > >
> > > > diff --git a/net/sctp/stream.c b/net/sctp/stream.c
> > > > index 3892e76..0687eeb 100644
> > > > --- a/net/sctp/stream.c
> > > > +++ b/net/sctp/stream.c
> > > > @@ -61,18 +61,6 @@ static void fa_free(struct flex_array *fa)
> > > > flex_array_free(fa);
> > > > }
> > > >
> > > > -static void fa_copy(struct flex_array *fa, struct flex_array *from,
> > > > - size_t index, size_t count)
> > > > -{
> > > > - void *elem;
> > > > -
> > > > - while (count--) {
> > > > - elem = flex_array_get(from, index);
> > > > - flex_array_put(fa, index, elem, 0);
> > > > - index++;
> > > > - }
> > > > -}
> > > > -
> > > > static void fa_zero(struct flex_array *fa, size_t index, size_t count)
> > > > {
> > > > void *elem;
> > > > @@ -135,6 +123,36 @@ static void sctp_stream_outq_migrate(struct sctp_stream *stream,
> > > > kfree(SCTP_SO(stream, i)->ext);
> > > > }
> > > >
> > > > +static void sctp_stream_in_copy(struct flex_array *fa,
> > > > + struct sctp_stream *stream, __u16 count)
> > > > +{
> > > > + size_t index = 0;
> > > > + void *elem;
> > > > +
> > > > + count = min(count, stream->incnt);
> > > > + while (count--) {
> > > > + elem = flex_array_get(stream->in, index);
> > > > + flex_array_put(fa, index, elem, 0);
> > > > + index++;
> > > > + }
> > > > +}
> > > > +
> > > > +static void sctp_stream_out_copy(struct flex_array *fa,
> > > > + struct sctp_stream *stream, __u16 count)
> > > > +{
> > > > + size_t index = 0;
> > > > + void *elem;
> > > > +
> > > > + count = min(count, stream->outcnt);
> > > > + while (count--) {
> > > > + elem = flex_array_get(stream->out, index);
> > > > + flex_array_put(fa, index, elem, 0);
> > > > + if (stream->out_curr == elem)
> > > > + stream->out_curr = flex_array_get(fa, index);
> > > > + index++;
> > > > + }
> > > > +}
> > > > +
> > > Seems like you are duplicating code here. I think you would be better off
> > > moving the fa_copy routine to the flex_array api (perhaps renaming it
> > > flex_array_copy), and then codig sctp_stream_*_copy as static inlines that just
> > > call the flex_array api to do the copy. As for setting the out_curr pointer,
> > > perhaps you should convert that to an index, so it can be looked up on demand,
> > changing to use index only for this may not worth it.
> > there is no API from flex_array to convert element to index either
> > the index is also the stream_id, but we didn't save it into stream_out
> > either, too.
> >
> Right, I'm saying it would be valuable to augment the flex_array api to include
> a copy function, as well as a pointer to index lookup element, that could have
> use beyond just sctp.
What do you think of this?
It's not called in tx/rx path, so no performance problem caused.
Since only SCTP is using fa_xxx(), I will not move any to
lib/flex_array.c for now.
+static size_t fa_index(struct flex_array *fa, void *elem, size_t count)
+{
+ size_t index = 0;
+
+ while (count--)
+ if (elem == flex_array_get(fa, index++))
+ break;
+
+ return index;
+}
+
/* Migrates chunks from stream queues to new stream queues if needed,
* but not across associations. Also, removes those chunks to streams
* higher than the new max.
@@ -147,6 +158,13 @@ static int sctp_stream_alloc_out(struct
sctp_stream *stream, __u16 outcnt,
if (stream->out) {
fa_copy(out, stream->out, 0, min(outcnt, stream->outcnt));
+ if (stream->out_curr) {
+ size_t index = fa_index(stream->out, stream->out_curr,
+ stream->outcnt);
+
+ BUG_ON(index == stream->outcnt);
+ stream->out_curr = flex_array_get(out, index);
+ }
fa_free(stream->out);
}
>
> > > so that it doesn't have to be updated here at all, or alternatively, just set it
> > > back to NULL here so that the selected scheduler will be forced to do the next
> > > lookup.
> > We can't set it back to NULL. Otherwise, the scheduler may go to
> > send other msg if the last msg (with multiple chunks) is not yet sent
> > out completely, which is not allowed when it's not I-Data chunk.
> >
> If setting it back to NULL isn't valid, then the above is your solution.
>
> > This is not much duplicating, and this can reduce few params.
> > I'm actually ok with this.
> >
> I know your ok with it, you wrote the patch :). I however, am not really ok
> with the duplication. I would like to see it collapsed, if its not going to
> create a significant performance impact.
>
> Neil
>
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