linux-kernel - [PATCH 0/1] Dead stores in maple-tree

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Date:   Wed, 26 Oct 2022 14:00:28 +0200
From:   Lukas Bulwahn <lukas.bulwahn@...il.com>
To:     "Liam R . Howlett" <Liam.Howlett@...cle.com>,
        Matthew Wilcox <willy@...radead.org>,
        Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org
Cc:     kernel-janitors@...r.kernel.org, linux-kernel@...r.kernel.org,
        Lukas Bulwahn <lukas.bulwahn@...il.com>
Subject: [PATCH 0/1] Dead stores in maple-tree

Dear maple-tree authors, dear Liam, dear Matthew,

there are some Dead Stores that clang-analyzer reports:

lib/maple_tree.c:2906:2: warning: Value stored to 'last' is never read [clang-analyzer-deadcode.DeadStores]
lib/maple_tree.c:2907:2: warning: Value stored to 'prev_min' is never read [clang-analyzer-deadcode.DeadStores]

I addressed these two cases, which were most obvious and clear to fix;
see patch of this one-element series.

Further, clang-analyzer reports more, which I did not address:

lib/maple_tree.c:332:2: warning: Value stored to 'node' is never read [clang-analyzer-deadcode.DeadStores]
lib/maple_tree.c:337:2: warning: Value stored to 'node' is never read [clang-analyzer-deadcode.DeadStores]

Unclear to me if the tool is wrong or right in its analysis here for the two functions above.

lib/maple_tree.c:1212:23: warning: Value stored to 'nodep' during its initialization is never read [clang-analyzer-deadcode.DeadStores]

A lot of pointer magic. Unclear to me if the tool is wrong or right in its analysis here.

lib/maple_tree.c:5014:5: warning: Value stored to 'count' is never read [clang-analyzer-deadcode.DeadStores]

Unclear if the code is intended as it is now.

In mas_anode_descend(), the variable count is really just assigned and used once
effectively. The second assignment is never read. So, the variable count could
just be removed in mas_anode_descend().

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

Best regards,

Lukas

Lukas Bulwahn (1):
  lib: maple_tree: remove unneeded initialization in mtree_range_walk()

 lib/maple_tree.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

-- 
2.17.1