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From:   Liam Howlett <liam.howlett@oracle.com>
To:     Lukas Bulwahn <lukas.bulwahn@gmail.com>
CC:     Matthew Wilcox <willy@infradead.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        "linux-mm@kvack.org" <linux-mm@kvack.org>,
        "kernel-janitors@vger.kernel.org" <kernel-janitors@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "maple-tree@lists.infradead.org" <maple-tree@lists.infradead.org>
Subject: Re: [PATCH 0/1] Dead stores in maple-tree
Thread-Topic: [PATCH 0/1] Dead stores in maple-tree
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Date:   Wed, 26 Oct 2022 14:23:19 +0000
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References: <20221026120029.12555-1-lukas.bulwahn@gmail.com>
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* Lukas Bulwahn <lukas.bulwahn@gmail.com> [221026 08:01]:
> Dear maple-tree authors, dear Liam, dear Matthew,
>=20
> there are some Dead Stores that clang-analyzer reports:
>=20
> lib/maple_tree.c:2906:2: warning: Value stored to 'last' is never read [c=
lang-analyzer-deadcode.DeadStores]
> lib/maple_tree.c:2907:2: warning: Value stored to 'prev_min' is never rea=
d [clang-analyzer-deadcode.DeadStores]
>=20
> I addressed these two cases, which were most obvious and clear to fix;
> see patch of this one-element series.
>=20
> Further, clang-analyzer reports more, which I did not address:
>=20
> lib/maple_tree.c:332:2: warning: Value stored to 'node' is never read [cl=
ang-analyzer-deadcode.DeadStores]
> lib/maple_tree.c:337:2: warning: Value stored to 'node' is never read [cl=
ang-analyzer-deadcode.DeadStores]
>=20
> Unclear to me if the tool is wrong or right in its analysis here for the =
two functions above.

The tool is correct but these aren't going anywhere.  They are compiled
out and are needed for the future.

>=20
> lib/maple_tree.c:1212:23: warning: Value stored to 'nodep' during its ini=
tialization is never read [clang-analyzer-deadcode.DeadStores]
>=20
> A lot of pointer magic. Unclear to me if the tool is wrong or right in it=
s analysis here.

Agreed, this is unclear.. I don't like it and it needs to be removed.
I'll send something out shortly. This was refactoring by the looks of it.

>=20
> lib/maple_tree.c:5014:5: warning: Value stored to 'count' is never read [=
clang-analyzer-deadcode.DeadStores]
>=20
> Unclear if the code is intended as it is now.
>=20
> In mas_anode_descend(), the variable count is really just assigned and us=
ed once
> effectively. The second assignment is never read. So, the variable count =
could
> just be removed in mas_anode_descend().

This was probably left over from refactoring as well.  I will fix this
as well, thanks.

>=20
>=20
> Maybe these further warnings are helpful to clean up the code or find an =
issue
> that was overlooked so far.

Much appreciated,
Liam=