From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id A4C1A1F2380; Wed, 12 Nov 2025 08:43:09 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1762936991; cv=none; b=iXC+OexdlOJAD2qCSTRt2/QR+/xG8pFgQwXnbBMLExNJT/ud7dcWgdb0MhQKfn2jXS0Eej6JFDv752kyn3e+5IskFl+lJzLc+E7DhaYbDCdblGplrToi5n9dpa0QGH33K3R4KOGW5sGHwaznynFVb62LupQhjIkzmdshQYOrHRc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1762936991; c=relaxed/simple; bh=/LczoiltHHVY6BkCv9TZVd8sVoWtwDEUK3HjIAwFlwU=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=EqT2jeA0OydNPXoYgUimykSHx7ZMx0kZajUAnQ0EZonMfgJ23/7xmWmAzGmc5baB3cpgCu46rwDzVuP2pcUn7v2zd6U/7TpSclJVgaWs0cshgGbg+ldnfhzpciGZb1ysRmec60TbeQAHSo92NnPVAgRq84Qh85T1v7CuddGTds4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=MV9dyKuN; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="MV9dyKuN" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3B6DBC4CEF5; Wed, 12 Nov 2025 08:43:07 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1762936989; bh=/LczoiltHHVY6BkCv9TZVd8sVoWtwDEUK3HjIAwFlwU=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=MV9dyKuNGr0RyS1A32gUCODKaSsjbECo8tbz5ZuCyw2R9pYGU0+Kbo3BujT3URIMQ WhorLU3/ctmiM10PjyJHG2Rb/1KhcRL+j4oZrwzI4lPL2tlGvpzRUR7tyhYRPD84fv 1gkFDp5J17d1nWFsEq6JoWQGMn0x2JIyTZHue6uIXS1dOwLbd1Udb1gjJ7yJb8dk+w Yw9aRbRVBOvpXN6Vl5ih5+uQDZdi/OZ3PT6chK094k/JF7NcLa1/glLAA0+DV7KToC gSk5UCURFAkLkqN6+zxF0vJj6QAM/aYImAUEsMYZHq8ObH9YS9gw/EiqcKzrLjyBmJ fz5LHOPOU8Jrg== Message-ID: <8c957ed5-ce4e-4207-8757-47b8ac168832@kernel.org> Date: Wed, 12 Nov 2025 17:43:05 +0900 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: enable iomap dio write completions from interrupt context To: Christoph Hellwig , Christian Brauner Cc: Alexander Viro , "Darrick J. Wong" , Jan Kara , Jens Axboe , Avi Kivity , Naohiro Aota , Johannes Thumshirn , linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org, io-uring@vger.kernel.org References: <20251112072214.844816-1-hch@lst.de> Content-Language: en-US From: Damien Le Moal Organization: Western Digital Research In-Reply-To: <20251112072214.844816-1-hch@lst.de> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 11/12/25 16:21, Christoph Hellwig wrote: > Hi all, > > Currently iomap defers all write completions to interrupt context. This > was based on my assumption that no one cares about the latency of those > to simplify the code vs the old direct-io.c. It turns out someone cared, > as Avi reported a lot of context switches with ScyllaDB, which at least > in older kernels with workqueue scheduling issues caused really high > tail latencies. > > Fortunately allowing the direct completions is pretty easy with all the > other iomap changes we had since. > > While doing this I've also found dead code which gets removed (patch 1) > and an incorrect assumption in zonefs that read completions are called > in user context, which it assumes for it's error handling. Fix this by > always calling error completions from user context (patch 2). > > Against the vfs/vfs-6.19.iomap branch. > > Diffstat: > Documentation/filesystems/iomap/operations.rst | 4 > fs/backing-file.c | 6 - > fs/iomap/direct-io.c | 149 +++++++++++-------------- > include/linux/fs.h | 43 +------ > io_uring/rw.c | 16 -- > 5 files changed, 81 insertions(+), 137 deletions(-) Where is the zonefs change ? Missing a patch ? -- Damien Le Moal Western Digital Research