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 841191DE8AE for ; Sat, 30 Aug 2025 18:53:03 +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=1756579983; cv=none; b=f4wr7Z1nwSP3+dsqoj6gUbW5LoQ+xWOU2igzYX+9u6nTxhzk/bdMh8kA/2qYTiSM7vRiq30Og2CdTuiwWoz9brcD8HFXmp7o90qnqvZUoVgaTdWaFoNf7SE1Daj+UnkGGC34UHBRoLW76iawFlEiy8l0zOnc9/FuoRXEHErZKGg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1756579983; c=relaxed/simple; bh=IvQY722kEUSjgUIrvslxkOnXffDG52zgcexjvjT9RuQ=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=cGZnx4b2pMBp2azCQzc/S4uH5q44IaXPGmEFOKKRr3a4rmIenFACyRKk36+uS6VfOtfVFqGoMxHYm/3nVF5/5D7zSRDwvTDbPcbYpLKLy7YInVa+TVh+DzXVNuxUcC1wDaQf7qwsTBQP8VO7awIltrRZmLIKLmBxq2JLwBj3Y14= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=MGBICztY; 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="MGBICztY" Received: by smtp.kernel.org (Postfix) with ESMTPSA id C8DDEC4CEEB; Sat, 30 Aug 2025 18:53:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1756579983; bh=IvQY722kEUSjgUIrvslxkOnXffDG52zgcexjvjT9RuQ=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=MGBICztYVYRFV9V4Fhfw3xBmGQ49KZq5VyFj+6DFCDs+GVKo0nzFYLiUT91NecEVG Fvo5n4RtE6IfME5aE8Ku3TlLy+YSfNk2HllvKbEbCHhZ9An9kdMv/MMMjSqO55h77Z PyRXK2fCOyevFxutPqpsAvsg+dBrBHjVR/zJMHkRJRgEFOZr+QBLmDmWhid0ju0te6 FwablSm9YFFjZbgkln6D/83plJJojKFbCxA1itRZOl/v2ztoTHN9y75E3/J3LMTyQR KzmBOu9D4aEuPAnlE+vhzFFiO3RUYemlJrwGbSmsy12eiaPzinLZ6R9aBLXgOv8kVg grmpKVtjVzyWg== Date: Sat, 30 Aug 2025 14:53:01 -0400 From: Mike Snitzer To: Chuck Lever , Jeff Layton Cc: linux-nfs@vger.kernel.org Subject: Re: [RFC PATCH 0/2] some progress on rpcrdma bug [was: Re: [PATCH v8 5/7] NFSD: issue READs using O_DIRECT even if IO is misaligned] Message-ID: References: <20250830173852.26953-1-snitzer@kernel.org> Precedence: bulk X-Mailing-List: linux-nfs@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250830173852.26953-1-snitzer@kernel.org> On Sat, Aug 30, 2025 at 01:38:50PM -0400, Mike Snitzer wrote: > Hi Chuck, > > Hopeful these 2 patches more clearly demonstrate what I'm finding > needed when using RDMA with my NFSD misaligned DIO READ patch. > > These patches build ontop of my v8 patchset. I've included quite a lot > of context for the data mismatch seen by the NFS client, etc in the > patch headers. > > If I'm understanding you correctly, next step is to look closer at the > rpcrdma code that would skip the throwaway front-pad page from being > mapped to the start of the RDMA READ payload returned to the NFS > client? > > Such important adjustment code would need to know that the rq_bvec[] > that reflects the READ payload doesn't include a bvec that points to > the first page of rqstp->rq_pages (pointed to by rqstp->rq_next_page > on entry to nfsd_iter_read) -- so it must skip past that memory in > the READ payload's RDMA memory returned to NFS client? > > Thanks, > Mike > > Mike Snitzer (2): > NFSD: fix misaligned DIO READ to not use a start_extra_page, exposes rpcrdma bug? > NFSD: use /end/ of rq_pages for front_pad page, simpler workaround for rpcrdma bug > > fs/nfsd/vfs.c | 27 ++++++++------------------- > 1 file changed, 8 insertions(+), 19 deletions(-) > > -- > 2.44.0 > Another important detail to mention, I've been working ontop of a 6.12.24 stable baseline that I've backported all NFS and NFSD changes through 6.17-rc1 + (slightly stale) nfsd-testing to, please see: https://git.kernel.org/pub/scm/linux/kernel/git/snitzer/linux.git/log/?h=kernel-6.12.24/nfsd-testing-snitm.18-testing Not sure if rebasing to the latest nfsd-testing would show this issue... I'm thinking yes, but cannot say for sure. Needing the ability to test/develop Hammerspace and pNFS stuff has prevented me from simply rebasing. But it should be doable without too much effort. Mike