linux-kernel - Re: [PATCH] ceph: optimize ceph_base64

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Message-ID: <aLf34hrnwULGA+0m@visitorckw-System-Product-Name>
Date: Wed, 3 Sep 2025 16:10:10 +0800
From: Kuan-Wei Chiu <visitorckw@...il.com>
To: Luis Henriques <luis@...lia.com>
Cc: Viacheslav Dubeyko <Slava.Dubeyko@....com>,
	"409411716@....tku.edu.tw" <409411716@....tku.edu.tw>,
	Xiubo Li <xiubli@...hat.com>,
	"idryomov@...il.com" <idryomov@...il.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"ceph-devel@...r.kernel.org" <ceph-devel@...r.kernel.org>
Subject: Re: [PATCH] ceph: optimize ceph_base64_encode() with block processing

On Wed, Sep 03, 2025 at 08:55:36AM +0100, Luis Henriques wrote:
> On Tue, Sep 02, 2025 at 09:21:14PM +0000, Viacheslav Dubeyko wrote:
> > On Wed, 2025-09-03 at 05:05 +0800, Kuan-Wei Chiu wrote:
> > > On Tue, Sep 02, 2025 at 07:37:22PM +0000, Viacheslav Dubeyko wrote:
> > > > On Sat, 2025-08-30 at 21:28 +0800, Guan-Chun Wu wrote:
> > > > > Previously, ceph_base64_encode() used a bitstream approach, handling one
> > > > > input byte at a time and performing extra bit operations. While correct,
> > > > > this method was suboptimal.
> > > > > 
> > > > 
> > > > Sounds interesting!
> > > > 
> > > > Is ceph_base64_decode() efficient then?
> > > > Do we have something in crypto library of Linux kernel? Maybe we can use
> > > > something efficient enough from there?
> > > > 
> > > Hi Viacheslav,
> > > 
> > > FYI, we already have base64 encode/decode implementations in
> > > lib/base64.c. As discussed in another thread [1], I think we can put
> > > the optimized version there and have users switch to call the library
> > > functions.
> > > 
> > > [1]: https://lore.kernel.org/lkml/38753d95-8503-4b72-9590-cb129aa49a41@t-8ch.de/  
> > > 
> > > 
> > 
> > Sounds great! Generalized version of this algorithm is much better than
> > supporting some implementation in Ceph code.
> 
> Please note that ceph can not use the default base64 implementation because
> it uses the '_' character in the encoding, as explained in commit
> 
>   64e86f632bf1 ("ceph: add base64 endcoding routines for encrypted names")
> 
> That's why it implements it's own version according to an IMAP RFC, which
> uses '+' and ',' instead of '-' and '_'.
> 
Perhaps we could modify the API to allow users to provide a custom
base64 table or an extra parameter to specify which RFC standard to use
for encoding/decoding?

Regards,
Kuan-Wei