linux-kernel - Re: [PATCH v2 10/12] nfsd: use boottime for lease expiry alculation

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Message-ID: <CAK8P3a3W3o6K_BGPaDre29Y1v=ZUMVv4+_mJr68vNkppKuuZrA@mail.gmail.com>
Date:   Fri, 13 Dec 2019 22:09:48 +0100
From:   Arnd Bergmann <arnd@...db.de>
To:     Chuck Lever <chuck.lever@...cle.com>
Cc:     Bruce Fields <bfields@...ldses.org>,
        Linux NFS Mailing List <linux-nfs@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        y2038 Mailman List <y2038@...ts.linaro.org>
Subject: Re: [PATCH v2 10/12] nfsd: use boottime for lease expiry alculation

On Fri, Dec 13, 2019 at 7:23 PM Chuck Lever <chuck.lever@...cle.com> wrote:
> > On Dec 13, 2019, at 11:40 AM, Arnd Bergmann <arnd@...db.de> wrote:
> >
> > On Fri, Dec 13, 2019 at 5:26 PM Chuck Lever <chuck.lever@...cle.com> wrote:
> >>> On Dec 13, 2019, at 9:10 AM, Arnd Bergmann <arnd@...db.de> wrote:
> >
> >>> diff --git a/fs/nfsd/nfs4callback.c b/fs/nfsd/nfs4callback.c
> >>> index 24534db87e86..508d7c6c00b5 100644
> >
> > With the old code, dividing by 10 was always fast as
> > nn->nfsd4_lease was the size of an integer register. Now it
> > is 64 bit wide, and I check that truncating it to 32 bit again
> > is safe.
>
> OK. That comment should state this reason rather than just repeating
> what the code does. ;-)

I changed the comment now to:

+       /*
+        * nfsd4_lease is set to at most one hour in __nfsd4_write_time,
+        * so we can use 32-bit math on it. Warn if that assumption
+        * ever stops being true.
+        */

Modified branch pushed to
git://git.kernel.org/pub/scm/linux/kernel/git/arnd/playground.git y2038-nfsd-v2

        Arnd