Re: pread() over NFS (again) [1.5.5.4]

> logank@sent.com writes:
> 
> > On Jun 26, 2008, at 1:56 PM, Junio C Hamano wrote:
> >
> >>> "The file shouldn't be short unless someone truncated it, or there
> >>> is a bug in index-pack.  Neither is very likely, but I don't think
> >>> we would want to retry pread'ing the same block forever.
> >>
> >> I don't think we would want to retry even once.  Return value of 0
> >> from
> >> pread is defined to be an EOF, isn't it?
> >
> > No, it seems to be a simple error-out in this case. We have 2.4.20
> > systems with nfs-utils 0.3.3 and used to frequently get the same error
> > while pushing. I made a similar change back in February and haven't
> > had a problem since:
> >
> > diff --git a/index-pack.c b/index-pack.c
> > index 5ac91ba..85c8bdb 100644
> > --- a/index-pack.c
> > +++ b/index-pack.c
> > @@ -313,7 +313,14 @@ static void *get_data_from_pack(struct
> > object_entry *obj)
> > 	src = xmalloc(len);
> > 	data = src;
> > 	do {
> > +		// It appears that if multiple threads read across NFS, the
> > +		// second read will fail. I know this is awful, but we wait for
> > +		// a little bit and try again.
> > 		ssize_t n = pread(pack_fd, data + rdy, len - rdy, from + rdy);
> > +		if (n <= 0) {
> > +			sleep(1);
> > +			n = pread(pack_fd, data + rdy, len - rdy, from + rdy);
> > +		}
> > 		if (n <= 0)
> > 			die("cannot pread pack file: %s", strerror(errno));
> > 		rdy += n;
> >
> > I use a sleep request since it seems less likely that the other thread
> > will have an outstanding request after a second of waiting.
> 
> Gaah.  Don't we have NFS experts in house?  Bruce, perhaps?