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[85.228.45.68]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-c4cabe4a5f5sm377975966b.50.2026.11.02.03.23.04 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 02 Nov 2026 03:23:05 -0800 (PST) Message-ID: <24af6daf-dbf3-5c47-beb7-077c4473ea7e@outbound.gmail.com> Date: Mon, 2 Nov 2026 12:23:02 +0100 X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.10.0 From: Eli Billauer Subject: Re: [PATCH] char: xillybus: use stream_open for stream semantics To: mdshahid03@gmail.com Cc: arnd@arndb.de, gregkh@linuxfoundation.org, linux-kernel@vger.kernel.org References: <20261031083610.87160-1-mdshahid03@gmail.com> Content-Language: en-US In-Reply-To: <20261031083610.87160-1-mdshahid03@gmail.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Hello Mohammad, On 31/10/2026 9:36, mdshahid03@gmail.com wrote: > Use stream_open() to mark these channels as streams and > disable unnecessary file position handling, The difference between stream_open() and nonseekable_open() is that the former sets FMODE_STREAM and clears FMODE_ATOMIC_POS. I made a quick test run, and FMODE_ATOMIC_POS isn't set in either case. As FMODE_ATOMIC_POS is clear, no lock is taken while updating fpos either way. So in effect, the only difference is that FMODE_STREAM is set. Frankly speaking, I'm not sure in what way this matters, if at all. > allowing read > and write operations to run concurrently. I checked that with hardware. There's no problem running read() and write() concurrently even before this patch. And I don't see why there would be a problem. It seems like FMODE_STREAM was supposed to replace FMODE_ATOMIC_POS somewhere back in 2019 with Linus' commit 0be0ee71816b ("vfs: properly and reliably lock f_pos in fdget_pos()"). That is where he urged the move towards stream_open(). But then he reverted it with commit 2be7d348fe92 soon afterwards. All in all, I don't know what to say about this. Calling stream_open() does sound more correct, and nothing broke with this patch. But I'm generally unhappy fiddling with code unless it fixes something. Regards, Eli