linux-kernel - Re: [RFC 04/11] ext4: Convert mballoc cr (criteria) to enum

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Message-ID: <ZB8IB14yLaoY4+19@li-bb2b2a4c-3307-11b2-a85c-8fa5c3a69313.ibm.com>
Date:   Sat, 25 Mar 2023 20:12:36 +0530
From:   Ojaswin Mujoo <ojaswin@...ux.ibm.com>
To:     Jan Kara <jack@...e.cz>
Cc:     linux-ext4@...r.kernel.org, "Theodore Ts'o" <tytso@....edu>,
        Ritesh Harjani <riteshh@...ux.ibm.com>,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        Ritesh Harjani <ritesh.list@...il.com>
Subject: Re: [RFC 04/11] ext4: Convert mballoc cr (criteria) to enum

On Thu, Mar 23, 2023 at 11:55:37AM +0100, Jan Kara wrote:
> On Fri 17-03-23 15:56:46, Ojaswin Mujoo wrote:
> > On Thu, Mar 09, 2023 at 01:11:22PM +0100, Jan Kara wrote:
> > > Also when going for symbolic allocator scan names maybe we could actually
> > > make names sensible instead of CR[0-4]? Perhaps like CR_ORDER2_ALIGNED,
> > > CR_BEST_LENGHT_FAST, CR_BEST_LENGTH_ALL, CR_ANY_FREE. And probably we could
> > > deal with ordered comparisons like in:
> > I like this idea, it should make the code a bit more easier to
> > understand. However just wondering if I should do it as a part of this
> > series or a separate patch since we'll be touching code all around and 
> > I don't want to confuse people with the noise :) 
> 
> I guess a mechanical rename should not be really confusing. It just has to
> be a separate patch.
Alright, got it.
> 
> > > 
> > >                 if (cr < 2 &&
> > >                     (!sbi->s_log_groups_per_flex ||
> > >                      ((group & ((1 << sbi->s_log_groups_per_flex) - 1)) != 0)) &
> > >                     !(ext4_has_group_desc_csum(sb) &&
> > >                       (gdp->bg_flags & cpu_to_le16(EXT4_BG_BLOCK_UNINIT))))
> > >                         return 0;
> > > 
> > > to declare CR_FAST_SCAN = 2, or something like that. What do you think?
> > About this, wont it be better to just use something like
> > 
> > cr < CR_BEST_LENGTH_ALL 
> > 
> > instead of defining a new CR_FAST_SCAN = 2.
> 
> Yeah, that works as well.
> 
> > The only concern is that if we add a new "fast" CR (say between
> > CR_BEST_LENGTH_FAST and CR_BEST_LENGTH_ALL) then we'll need to make
> > sure we also update CR_FAST_SCAN to 3 which is easy to miss.
> 
> Well, you have that problem with any naming scheme (and even with numbers).
> So as long as names are all defined together, there's reasonable chance
> you'll remember to verify the limits still hold :)
haha that's true. Anyways, I'll try a few things and see what looks
good. Thanks for the suggestions.

Regards,
ojaswin
> 
> 								Honza
> -- 
> Jan Kara <jack@...e.com>
> SUSE Labs, CR