From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pf1-f197.google.com (mail-pf1-f197.google.com [209.85.210.197]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 3EF5B4749DA for ; Fri, 14 Aug 2026 14:32:59 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.210.197 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786717983; cv=none; b=SJr8kkBVNNqWxLcbK8LBBleeFEdkThKX4RG12guJqTqqVe2j7kbsYfm+m0T6oh88SwKjmFfTzQ8wl14k5GjKhgqxiI9YdrVYyGeRCy4VuZDdulMI0JVYngBooB7k065Nj3Dk3Z+7IntNBqnD2TdQ4ZrufskdeYg7nnEJfdtSjiQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786717983; c=relaxed/simple; bh=fEf+aoVOmWE9QgWXBBCMkjF2FiCJRCYZ+9VLM2p+ycU=; h=Date:Mime-Version:Message-ID:Subject:From:To:Cc:Content-Type; b=E6PXangX3s37We7q1P+QNIywEhzhz6PdN+fPKs0ktIwAEDzKKTXsTGkWG3NWfGed+eydY8xcMXB74Ys8m0FXbBImFHBN8ZwDXQHoKM/V/CjT8zq1KopbinS7h0GZ8Ro8Hh9ntnB1pMTN8Pr0Y4IN/vATyW1v2C5I2P7FjnVgfMU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--praan.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=MkBwEL5s; arc=none smtp.client-ip=209.85.210.197 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--praan.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="MkBwEL5s" Received: by mail-pf1-f197.google.com with SMTP id d2e1a72fcca58-84870e7f498so1185094b3a.3 for ; Fri, 14 Aug 2026 07:32:59 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20251104; t=1786717978; x=1787322778; darn=vger.kernel.org; h=content-type:cc:to:from:subject:message-id:mime-version:date:from :to:cc:subject:date:message-id:reply-to:content-type; bh=dZBlRjehuCRyYG4VdtgBrAbEd7nP4qKEWqIDe08LiIY=; b=MkBwEL5s0bjOGTQBhMlhEd2kmt0hrng4So5pMERYAVhJvB406e94Kwb+xIpwSXjjka vGS2BtHsGDzx0ubrPOhI/RzDyIPIP4G3cCvCdrSpSXyUO5lIvce8h98FWSds0fjiBBIr Iz5/UjvJd36LjLD76hNjIBzfwyUKghp3Iaio+u/W6O93HjZXtRJfnkCHqGJ/yuwAa2WW st7QHWVzbe+O5RdVPNl7d/quYcOMyH8h3eKX5KjDErUbP5gV9tSIq0r/BUaNc5fZwkmn J7Bll4IFfYqb3ueY8Rz9WERMwPAPnpky9I+is4bb/KThvWyAYH0k1XyucJPXzHyRK/Um CLMA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1786717978; x=1787322778; h=content-type:cc:to:from:subject:message-id:mime-version:date :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to :content-type; bh=dZBlRjehuCRyYG4VdtgBrAbEd7nP4qKEWqIDe08LiIY=; b=XrFWiN9biImeonaqK8O4a7Ey07BaXTQuip14aL80H4ADu6VWuk0i0XYXWURCp0f6YA LtcvBjvXreJKkaewfZNJdknqHBqwYyCwbXLeDVE+ovmXj8h4j7TnPLJN+iVFep7zYNoE 6t+bQh50z6mrQhJ5KndOjd0nW1vtsDOz4Vo28RBPZ3AA30qfDcuWfLc2RWxbfPQRtli2 lYHD0t2BMxoOfwE34v/7Lpe9zkYMm2pjZP9bUPYXhxeW5p+i7Gy2BOWQiqqoloMBGpB2 JektnIRsnNDXBSl0OnnHbDwLZVw1XySENU+5MBBnEtJTj7tr64M2JHkb0/es32G49SGg L2AA== X-Forwarded-Encrypted: i=1; AHgh+Rooz1V0nXbLdEavLIQQeZvVDFUEEy8Uoo92T6fvPsEOmxf6xporpLlIjBJlp/Za/eyVK/wZA2Maudc7ZPQ=@vger.kernel.org X-Gm-Message-State: AOJu0YztnsyeLtFUrt5zoc0clJtB+ImWG9ulNszujhrklXrTyvQqlX53 ElpKDVOmRD9mdF0PaCJSg+Bmay34+58KLK+p9kPLs5rUqjiRz3Rq4aubMMzhJ32DW/6r1TexAx6 QLA== X-Received: from pgdf6.prod.google.com ([2002:a05:6a02:5146:b0:cbb:676d:ab19]) (user=praan job=prod-delivery.src-stubby-dispatcher) by 2002:a05:6a00:1818:b0:848:46a0:3d74 with SMTP id d2e1a72fcca58-84fde3ccf6amr6609292b3a.9.1786717977916; Fri, 14 Aug 2026 07:32:57 -0700 (PDT) Date: Fri, 14 Aug 2026 14:32:50 +0000 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 X-Mailer: git-send-email 2.55.0.691.gc56d675ccc-goog Message-ID: <20260814143255.861084-1-praan@google.com> Subject: [PATCH v6 0/5] nfs: modernize direct I/O path From: Pranjal Shrivastava To: linux-nfs@vger.kernel.org, Trond Myklebust , Anna Schumaker Cc: Chuck Lever , Jeff Layton , linux-kernel@vger.kernel.org, Christoph Hellwig , Logan Gunthorpe , Jason Gunthorpe , linux-pci@vger.kernel.org, linux-rdma@vger.kernel.org, Shivaji Kant , Pranjal Shrivastava Content-Type: text/plain; charset="UTF-8" Modernize the NFS Direct I/O path as a preparatory step to enable PCI Peer-to-Peer DMA (P2PDMA) support. Following feedback on the initial RFC [1], the modernization and architectural changes are split into different series. Additionally, based on the discussion in the v2 [2] of this series, the migration of NFS Direct I/O to folios would be handled in a separate follow-up series. Currently, NFS O_DIRECT relies on the legacy iov_iter_get_pages_alloc2() API which does not support the pinning requirements for P2P memory. The implementation moves NFS to the modern iov_iter_extract_pages() API. Design ====== 1. Pin-Awareness Standard NFS requests use get_page() and put_page() for memory management. However, memory extracted via iov_iter_extract_pages() requires explicit pinning. Introduce a PG_PINNED flag and a wb_nr_pinned count to struct nfs_page. This allows the request lifecycle to track ownership of physical pins and ensure that unpinning is performed only when the I/O is complete. 2. API Migration Migrate the Direct I/O path to the modern iov_iter_extract_pages() API. This aligns NFS with the modern extraction model and serves as the foundation for passing ITER_ALLOW_P2PDMA in a follow-up series. Upcoming Work / Roadmap ================================ As decided in the RFC [1] & v2 [2], there will be separate series for P2PDMA Enablement and Migrating NFS Direct I/O to use folios. This series lays the necessary groundwork for the upcoming work. Following this, two additional series are planned: 1. Migrating NFS Direct I/O to Folios A series that introduces and exports helper from iov_iter.c to allow the nfs_direct_extract_pages() helper introduced here to aggregate multiple pages into a single large folio-based request, aiming to reduce the RPC overhead for hugepage I/O. 2. P2PDMA Enablement for NFS Enabling ITER_ALLOW_P2PDMA for the Direct I/O path and introducing transport-level negotiation (discovery of P2P-capable RDMA/NVMe devices). This will build upon the PG_PINNED infrastructure introduced by this series. Testing ======= This series has been tested with xfstests [3] on RDMA & TCP transports by running the quick test suite for each transport vs. version combo: ./check -g quick -s rdma3 -s rdma40 -s rdma41 -s rdma42 -s tcp3 -s tcp40 -s tcp41 -s tcp42 The tests were run before & after applying the series. No regressions were observed. The following summary was tabulated via a custom script [4] (on github) to depict that the tests failing in v1 [5] are now passing. python3 display.py results/*/check.log +--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+ | testcase | rdma-sys-3 | rdma-sys-4.0 | rdma-sys-4.1 | rdma-sys-4.2 | tcp-sys-3 | tcp-sys-4.0 | tcp-sys-4.1 | tcp-sys-4.2 | +--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+ | generic/091 | pass | pass | pass | pass | pass | pass | pass | pass | | generic/130 | pass | pass | pass | pass | pass | pass | pass | pass | | generic/139 | pass | pass | pass | pass | pass | pass | pass | pass | | generic/143 | pass | pass | pass | pass | pass | pass | pass | pass | | generic/154 | pass | pass | pass | pass | pass | pass | pass | pass | | generic/155 | pass | pass | pass | pass | pass | pass | pass | pass | | generic/183 | skipped | skipped | skipped | pass | skipped | skipped | skipped | pass | | generic/188 | skipped | skipped | skipped | pass | skipped | skipped | skipped | pass | | generic/190 | skipped | skipped | skipped | pass | skipped | skipped | skipped | pass | | generic/196 | skipped | skipped | skipped | pass | skipped | skipped | skipped | pass | | generic/198 | pass | pass | pass | pass | pass | pass | pass | pass | | generic/203 | skipped | skipped | skipped | pass | skipped | skipped | skipped | pass | | generic/214 | pass | pass | pass | pass | pass | pass | pass | pass | | generic/240 | pass | pass | pass | pass | pass | pass | pass | pass | | generic/263 | pass | pass | pass | pass | pass | pass | pass | pass | | generic/287 | skipped | skipped | skipped | pass | skipped | skipped | skipped | pass | | generic/290 | skipped | skipped | skipped | pass | skipped | skipped | skipped | pass | | generic/292 | skipped | skipped | skipped | pass | skipped | skipped | skipped | pass | | generic/330 | skipped | skipped | skipped | pass | skipped | skipped | skipped | pass | | generic/444 | skipped | skipped | skipped | skipped | skipped | skipped | skipped | skipped | | generic/450 | pass | pass | pass | pass | pass | pass | pass | pass | | generic/451 | pass | pass | pass | pass | pass | pass | pass | pass | | generic/586 | pass | pass | pass | pass | pass | pass | pass | pass | | generic/647 | pass | pass | pass | pass | pass | pass | pass | pass | | generic/708 | pass | pass | pass | pass | pass | pass | pass | pass | | generic/729 | pass | pass | pass | pass | pass | pass | pass | pass | | generic/760 | pass | pass | pass | pass | pass | pass | pass | pass | +--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+ Thanks, Praan [1] https://lore.kernel.org/all/20260401194501.2269200-1-praan@google.com/ [2] https://lore.kernel.org/all/ak8-NMsNPOB3zpF-@infradead.org/ [3] https://git.kernel.org/pub/scm/fs/xfs/xfstests-dev.git [4] https://github.com/pran005/tools/blob/main/display.py [5] https://lore.kernel.org/all/29a0511d-5216-46f2-a7e4-9c04ae9b1890@app.fastmail.com/ [v6] - Fixed double unpin bugs pointed out by Sashiko: https://sashiko.dev/#/patchset/20260810195040.2877784-1-praan%40google.com - Added R-bs from Christoph (due since v4) [v5] - https://lore.kernel.org/all/20260810195040.2877784-1-praan@google.com/ - Fixed an iov_iter_revert oops in nfs_direct_extract_pages(). - Fixed a refcount underflow in nfs_direct_release_pages() during swap-over-NFS by ensuring we do not call put_page() on unpinned memory. - Rebased on fs-next [v4] - https://lore.kernel.org/all/20260720150601.2702700-1-praan@google.com/ - Dropped superfluous externs in include/linux/nfs_page.h - Scoped `req` locally inside the loop in nfs_release_request_list() - Wrapped >80 character lines in Patch 1 to adhere to coding style. - Fixed typos and capitalization convention in the commit msgs - Collected Reviewed-by tags from Christoph and Shivaji - Rebased on fs-next [v3] - https://lore.kernel.org/all/20260715143540.3597616-1-praan@google.com/ - Dropped patches that added folio support for NFS Direct I/O - Folded requested_bytes accounting in patch 5 due to dropped folio support - Rebased on fs-next [v2] - https://lore.kernel.org/all/20260616134000.2733403-1-praan@google.com/ - Fix data corruption in nfs_direct_extract_pages() by correctly calculating intra-page offsets using offset_in_page(). - Fix requested_bytes accounting in direct read/write paths to only increment after successful RPC scheduling. - Add missing kernel-doc descriptions for the @pinned parameter in nfs_page_create_from_page() and nfs_page_create_from_folio(). - Rebase on fs-next/ [v1] https://lore.kernel.org/all/20260603053033.3300318-1-praan@google.com/ Pranjal Shrivastava (5): nfs: make nfs_page pin-aware nfs: track number of pinned pages in nfs_page nfs: introduce nfs_release_request_list helper nfs: migrate direct I/O to iov_iter_extract_pages nfs: introduce nfs_direct_extract_pages helper fs/nfs/direct.c | 139 ++++++++++++++++++++------------------- fs/nfs/pagelist.c | 66 ++++++++++++++++--- fs/nfs/read.c | 2 +- fs/nfs/write.c | 2 +- include/linux/nfs_page.h | 8 ++- 5 files changed, 134 insertions(+), 83 deletions(-) base-commit: 15db403711f3cd9b7b764716ddf5909091b604bf -- 2.55.0.691.gc56d675ccc-goog