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SubjectRe: [regression?] distcc says: (dcc_pump_sendfile) ERROR: sendfile returned 0? can't cope (bisected)
On Thu, May 08 2008, Tom Zanussi wrote:
>
> On Thu, 2008-05-08 at 02:21 -0500, Tom Zanussi wrote:
> > On Wed, 2008-05-07 at 23:16 +0200, Jens Axboe wrote:
> > > On Wed, May 07 2008, Dan Williams wrote:
> > > > Hi Tom, Jens,
> > > >
> > > > My build system started reporting these error messages recently.
> > > > Reverting commit c3270e577c18b3d0e984c3371493205a4807db9d on top of
> > > > 2.6.26-rc1 gets things working for me again.
> > >
> > > Irk, that patch did scare me a bit (hence I asked Tom to double check as
> > > wel :-). I'll take a look in the morning, all test boxes are off at this
> > > point in time.
> > >
> >
> > I did, and it still looks ok to me, but obviously it's not, so I'll have
> > to do some more digging.
> >
> > The only thing I can think of right now that might be a possible cause
> > would be in splice_direct_to_actor(), if we had an incomplete transfer,
> > the sd->pos returned and assigned would have the value set by the failed
> > actor(). Maybe something like the following would take care of that
> > case, but I haven't had a chance to test it yet - will do that tomorrow
> > night...
> >
>
> Looks like I was on the right track - can you try this patch out
> instead? It makes sure sd.pos is updated correctly if the transfer was
> incomplete or failed. I ran some kernel compiles using distcc while
> running blktrace in sendfile mode and didn't see any problems with
> either.

Dan, can I talk you into re-trying current git with this patch applied?
It's basically the (now) reverted broken bits plus the fix from Tom from
this email.

diff --git a/fs/splice.c b/fs/splice.c
index 7815003..a048ad2 100644
--- a/fs/splice.c
+++ b/fs/splice.c
@@ -983,7 +983,7 @@ ssize_t splice_direct_to_actor(struct file *in, struct splice_desc *sd,

while (len) {
size_t read_len;
- loff_t pos = sd->pos;
+ loff_t pos = sd->pos, prev_pos = pos;

ret = do_splice_to(in, &pos, pipe, len, flags);
if (unlikely(ret <= 0))
@@ -998,15 +998,19 @@ ssize_t splice_direct_to_actor(struct file *in, struct splice_desc *sd,
* could get stuck data in the internal pipe:
*/
ret = actor(pipe, sd);
- if (unlikely(ret <= 0))
+ if (unlikely(ret <= 0)) {
+ sd->pos = prev_pos;
goto out_release;
+ }

bytes += ret;
len -= ret;
sd->pos = pos;

- if (ret < read_len)
+ if (ret < read_len) {
+ sd->pos = prev_pos + ret;
goto out_release;
+ }
}

done:
@@ -1072,7 +1076,7 @@ long do_splice_direct(struct file *in, loff_t *ppos, struct file *out,

ret = splice_direct_to_actor(in, &sd, direct_splice_actor);
if (ret > 0)
- *ppos += ret;
+ *ppos = sd.pos;

return ret;
}
diff --git a/kernel/relay.c b/kernel/relay.c
index bc24dcd..7de644c 100644
--- a/kernel/relay.c
+++ b/kernel/relay.c
@@ -1191,7 +1191,7 @@ static ssize_t relay_file_splice_read(struct file *in,
ret = 0;
spliced = 0;

- while (len) {
+ while (len && !spliced) {
ret = subbuf_splice_actor(in, ppos, pipe, len, flags, &nonpad_ret);
if (ret < 0)
break;
--
Jens Axboe



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