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From: Bruce Fields <bfields@fieldses.org>
To: Chuck Lever <chuck.lever@oracle.com>
Cc: Arnd Bergmann <arnd@arndb.de>,
	Linux NFS Mailing List <linux-nfs@vger.kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	y2038 Mailman List <y2038@lists.linaro.org>
Subject: Re: [PATCH v2 10/12] nfsd: use boottime for lease expiry alculation
Date: Fri, 13 Dec 2019 16:13:11 -0500	[thread overview]
Message-ID: <20191213211311.GA12391@fieldses.org> (raw)
In-Reply-To: <BBB37836-D835-4EB7-8593-080BF60BDA38@oracle.com>

On Fri, Dec 13, 2019 at 01:23:08PM -0500, Chuck Lever wrote:
> 
> 
> > On Dec 13, 2019, at 11:40 AM, Arnd Bergmann <arnd@arndb.de> wrote:
> > 
> > On Fri, Dec 13, 2019 at 5:26 PM Chuck Lever <chuck.lever@oracle.com> wrote:
> >>> On Dec 13, 2019, at 9:10 AM, Arnd Bergmann <arnd@arndb.de> wrote:
> > 
> >>> diff --git a/fs/nfsd/nfs4callback.c b/fs/nfsd/nfs4callback.c
> >>> index 24534db87e86..508d7c6c00b5 100644
> >>> --- a/fs/nfsd/nfs4callback.c
> >>> +++ b/fs/nfsd/nfs4callback.c
> >>> @@ -823,7 +823,12 @@ static const struct rpc_program cb_program = {
> >>> static int max_cb_time(struct net *net)
> >>> {
> >>>      struct nfsd_net *nn = net_generic(net, nfsd_net_id);
> >>> -     return max(nn->nfsd4_lease/10, (time_t)1) * HZ;
> >>> +
> >>> +     /* nfsd4_lease is set to at most one hour */
> >>> +     if (WARN_ON_ONCE(nn->nfsd4_lease > 3600))
> >>> +             return 360 * HZ;
> >> 
> >> Why is the WARN_ON_ONCE added here? Is it really necessary?
> > 
> > This is to ensure the kernel doesn't change to a larger limit that
> > requires a 64-bit division on a 32-bit architecture.
> > 
> > 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. ;-)

Note that __nfsd4_write_time() already limits nfsd4_lease to 3600.

We could just use a smaller type for nfsd4_lease if that'd help.

--b.

  parent reply	other threads:[~2019-12-13 21:13 UTC|newest]

Thread overview: 23+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-12-13 14:10 [PATCH v2 00/12] nfsd: avoid 32-bit time_t Arnd Bergmann
2019-12-13 14:10 ` [PATCH v2 01/12] nfsd: use ktime_get_seconds() for timestamps Arnd Bergmann
2019-12-13 14:10 ` [PATCH v2 02/12] nfsd: print 64-bit timestamps in client_info_show Arnd Bergmann
2019-12-13 14:10 ` [PATCH v2 03/12] nfsd: handle nfs3 timestamps as unsigned Arnd Bergmann
2019-12-13 14:10 ` [PATCH v2 04/12] nfsd: use timespec64 in encode_time_delta Arnd Bergmann
2019-12-13 14:10 ` [PATCH v2 05/12] nfsd: make 'boot_time' 64-bit wide Arnd Bergmann
2019-12-13 14:10 ` [PATCH v2 06/12] nfsd: pass a 64-bit guardtime to nfsd_setattr() Arnd Bergmann
2019-12-13 14:10 ` [PATCH v2 07/12] nfsd: use time64_t in nfsd_proc_setattr() check Arnd Bergmann
2019-12-13 14:10 ` [PATCH v2 08/12] nfsd: fix delay timer on 32-bit architectures Arnd Bergmann
2019-12-13 14:10 ` [PATCH v2 09/12] nfsd: fix jiffies/time_t mixup in LRU list Arnd Bergmann
2019-12-13 14:10 ` [PATCH v2 10/12] nfsd: use boottime for lease expiry alculation Arnd Bergmann
2019-12-13 16:26   ` Chuck Lever
2019-12-13 16:40     ` Arnd Bergmann
2019-12-13 18:23       ` Chuck Lever
2019-12-13 21:09         ` Arnd Bergmann
2019-12-13 21:13         ` Bruce Fields [this message]
2019-12-13 21:19           ` Arnd Bergmann
2019-12-20  2:57   ` J. Bruce Fields
2019-12-13 14:10 ` [PATCH v2 11/12] nfsd: use ktime_get_real_seconds() in nfs4_verifier Arnd Bergmann
2019-12-13 14:10 ` [PATCH v2 12/12] nfsd: remove nfs4_reset_lease() declarations Arnd Bergmann
2019-12-18 17:21 ` [PATCH v2 00/12] nfsd: avoid 32-bit time_t Arnd Bergmann
2019-12-18 17:24   ` J. Bruce Fields
2019-12-18 18:05     ` Arnd Bergmann

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