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([2620:10d:c092:600::1:3bd7]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-ac1e5aff06esm218450266b.130.2025.03.04.07.17.00 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 04 Mar 2025 07:17:01 -0800 (PST) Message-ID: <8ad09b2e-7bc6-4379-be68-033e9e164ee8@gmail.com> Date: Tue, 4 Mar 2025 15:18:11 +0000 Precedence: bulk X-Mailing-List: io-uring@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 2/8] io_uring: add infra for importing vectored reg buffers From: Pavel Begunkov To: Caleb Sander Mateos Cc: io-uring@vger.kernel.org, Andres Freund References: <841b4d5b039b9db84aa1e1415a6d249ea57646f6.1741014186.git.asml.silence@gmail.com> <9a5e3d75-afef-4942-881c-444d35472758@gmail.com> Content-Language: en-US In-Reply-To: <9a5e3d75-afef-4942-881c-444d35472758@gmail.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 3/4/25 10:05, Pavel Begunkov wrote: > On 3/3/25 20:49, Caleb Sander Mateos wrote: >> On Mon, Mar 3, 2025 at 7:51 AM Pavel Begunkov wrote: > ... >>> +       for (i = 0; i < nr_iovs; i++) >>> +               max_segs += (iov[i].iov_len >> shift) + 2; >> >> Sees like this may overestimate a bit. I think something like this >> would give the exact number of segments for each iovec? >> (((u64)iov_base & folio_mask) + iov_len + folio_mask) >> folio_shift > > It's overestimated exactly to avoid a beast like this. And it'd be broken as well for 0 len. -- Pavel Begunkov