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Date:   Wed, 3 Mar 2021 13:38:23 -0500
From:   Bruce Fields <bfields@fieldses.org>
To:     Chuck Lever <chuck.lever@oracle.com>
Cc:     Linux NFS Mailing List <linux-nfs@vger.kernel.org>
Subject: Re: [PATCH v1 19/42] SUNRPC: Fix xdr_get_next_encode_buffer() page
 boundary handling
Message-ID: <20210303183823.GD1282@fieldses.org>
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On Wed, Mar 03, 2021 at 06:30:40PM +0000, Chuck Lever wrote:
> 
> 
> > On Mar 3, 2021, at 1:27 PM, Chuck Lever <chuck.lever@oracle.com> wrote:
> > 
> > 
> > 
> >> On Mar 3, 2021, at 1:25 PM, Bruce Fields <bfields@fieldses.org> wrote:
> >> 
> >> On Wed, Mar 03, 2021 at 06:19:33PM +0000, Chuck Lever wrote:
> >>> 
> >>> 
> >>>> On Mar 3, 2021, at 11:52 AM, Bruce Fields <bfields@fieldses.org> wrote:
> >>>> 
> >>>> On Wed, Mar 03, 2021 at 03:43:28PM +0000, Chuck Lever wrote:
> >>>>> Why would that not be OK? the next call to xdr_get_next_encode_buffer()
> >>>>> should do the right thing and bounce the new encoded data from the
> >>>>> next page into this one again.
> >>>>> 
> >>>>> So far I have not encountered any problems. Would such a problem show
> >>>>> up with some frequency under normal use, or would it be especially
> >>>>> subtle?
> >>>> 
> >>>> I mainly just want to make sure we've got a coherent idea what this code
> >>>> is doing....
> >>> 
> >>> Agreed, that's a good thing.
> >> 
> >> I'm also a little vague on what exactly the problem is you're running
> >> into.  (Probably because I haven't really looked at the v3 readdir
> >> encoding.)
> >> 
> >> Is it approaching the end of a page, or is it running out of buflen?
> >> How exactly does it fail?
> > 
> > I don't recall exactly, it was a late last summer when I wrote all these.
> > 
> > Approaching the end of a page, IIRC, the unpatched code would leave
> > a gap in the directory entry stream.
> 
> Well, when I converted the entry encoders to use xdr_stream, it would
> have a problem around the end of a page. The existing encoders are
> open-coded to deal with this case.

We're not seeing v4 readdir bugs, though, I wonder what's different?

--b.