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From:   "Fabio M. De Francesco" <fmdefrancesco@gmail.com>
To:     David Sterba <dsterba@suse.com>,
        Andrew Morton <akpm@linux-foundation.org>
Cc:     Ira Weiny <ira.weiny@intel.com>, dsterba@suse.cz,
        Chris Mason <clm@fb.com>, Josef Bacik <josef@toxicpanda.com>,
        Nick Terrell <terrelln@fb.com>, linux-btrfs@vger.kernel.org,
        linux-kernel@vger.kernel.org, Filipe Manana <fdmanana@kernel.org>
Subject: Re: [PATCH] btrfs: Replace kmap() with kmap_local_page() in zstd.c
Date:   Wed, 15 Jun 2022 07:29:55 +0200
Message-ID: <3619537.MHq7AAxBmi@opensuse>
In-Reply-To: <YqjAVq+1PIpVIr0p@iweiny-desk3>
References: <20220611135203.27992-1-fmdefrancesco@gmail.com> <8952566.CDJkKcVGEf@opensuse> <YqjAVq+1PIpVIr0p@iweiny-desk3>
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On marted=C3=AC 14 giugno 2022 19:07:34 CEST Ira Weiny wrote:
> On Tue, Jun 14, 2022 at 06:28:48PM +0200, Fabio M. De Francesco wrote:
> > On marted=C3=AC 14 giugno 2022 16:25:21 CEST David Sterba wrote:
> > > On Tue, Jun 14, 2022 at 01:22:50AM +0200, Fabio M. De Francesco=20
wrote:
> > > > On luned=C3=AC 13 giugno 2022 20:39:13 CEST David Sterba wrote:
> > > > > On Sat, Jun 11, 2022 at 03:52:03PM +0200, Fabio M. De Francesco=20
> > >=20
>=20
> [snip]
>=20
> > > > A better solution is changing the prototype of __kunmap_local(); I
> > > > suppose that Andrew won't object, but who knows?
> > > >=20
> > > > (+Cc Andrew Morton).
> > > >=20
> > > > I was waiting for your comments. At now I've done about 15=20
conversions=20
> > > > across the kernel but it's the first time I had to pass a pointer=20
to=20
> > const=20
> > > > void to kunmap_local(). Therefore, I was not sure if changing the=20
API=20
> > were=20
> > > > better suited (however I have already discussed this with Ira).
> > >=20
> > > IMHO it should be fixed in the API.
> > >=20
> > I agree with you in full.
> >=20
> > At the same time when you sent this email I submitted a patch to change=
=20
> > kunmap_local() and kunmap_atomic().
> >=20
> > After Andrew takes them I'll send v2 of this patch to zstd.c without=20
those=20
> > unnecessary casts.
>=20
> David,
>=20
> Would you be willing to take this through your tree as a pre-patch to the=
=20
kmap
> changes in btrfs?
>=20
> That would be easier for Fabio and probably you and Andrew in the long=20
run.
>=20
> Ira

David,

Please drop the first version of the changes[1] to the API and instead take=
=20
my second version.[2] I've only reworked the commit message (and subject,=20
but this was involuntary) to make explicit that the fundamental reason=20
behind these changes are semantic correctness.

Thanks,

=46abio

[1] https://lore.kernel.org/lkml/20220614142531.16478-1-fmdefrancesco@gmail=
=2Ecom/

[2] https://lore.kernel.org/lkml/20220615051256.31466-1-fmdefrancesco@gmail=
=2Ecom/