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Date:   Tue, 9 Aug 2022 14:37:22 +0200
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Subject: Re: [PATCH 03/16] lib/test_bitmap: don't test bitmap_set if nbits ==
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To:     Yury Norov <yury.norov@gmail.com>, linux-kernel@vger.kernel.org,
        Alexander Lobakin <alexandr.lobakin@intel.com>,
        Alexei Starovoitov <ast@kernel.org>,
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        Andrii Nakryiko <andrii@kernel.org>,
        Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
        Ben Segall <bsegall@google.com>,
        Christoph Lameter <cl@linux.com>,
        Dan Williams <dan.j.williams@intel.com>,
        Daniel Borkmann <daniel@iogearbox.net>,
        Daniel Bristot de Oliveira <bristot@redhat.com>,
        Dennis Zhou <dennis@kernel.org>,
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        Frederic Weisbecker <fweisbec@gmail.com>,
        Guenter Roeck <linux@roeck-us.net>,
        Ingo Molnar <mingo@redhat.com>,
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        John Fastabend <john.fastabend@gmail.com>,
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        Juri Lelli <juri.lelli@redhat.com>,
        KP Singh <kpsingh@kernel.org>,
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References: <20220718192844.1805158-1-yury.norov@gmail.com>
 <20220718192844.1805158-4-yury.norov@gmail.com>
From:   Rasmus Villemoes <linux@rasmusvillemoes.dk>
In-Reply-To: <20220718192844.1805158-4-yury.norov@gmail.com>
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On 18/07/2022 21.28, Yury Norov wrote:
> Don't test bitmap_set(bitmap, start, 0) as it's useless, most probably
> a sign of error in real code, 

No it's not. The nbits can easily be the result of some computation that
ended up resulting in 0 being the right number to copy (or set, or
whatnot), and it's not unreasonable to _not_ check in the caller for
that special case, but rather rely on bitmap_set() to behave sanely - it
has perfectly well-defined semantics to "set 0 bits starting at @start".

The same way that memset() and memcpy() and memcmp() and countless other
functions have perfectly well-defined semantics with a length of 0, and
we don't add caller-side checks for those either.

NAK on this series.

Rasmus