fs/nfs/direct.c | 139 ++++++++++++++++++++------------------- fs/nfs/pagelist.c | 62 ++++++++++++++--- fs/nfs/read.c | 2 +- fs/nfs/write.c | 2 +- include/linux/nfs_page.h | 8 ++- 5 files changed, 130 insertions(+), 83 deletions(-)
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/ [v5] - 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 | 62 ++++++++++++++--- fs/nfs/read.c | 2 +- fs/nfs/write.c | 2 +- include/linux/nfs_page.h | 8 ++- 5 files changed, 130 insertions(+), 83 deletions(-) base-commit: 5b57716ed7ad2f4b1724461c8777015c4e4befb1 -- 2.55.0.679.g6767b8d81c-goog
On Mon, Aug 10, 2026 at 07:50:34PM +0000, Pranjal Shrivastava wrote: > 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. > [...] I'm calling out a few typos / non-code mistakes: 1. On the cover letter I missed updating the subject to v5 for this series (the changelog is noted below). 2. I also accidentally dropped Christoph's Reviewed-by tags on patches 1, 2, and 3 during the rebase (given while reviewing v4 [1]). Everything else in the series is correct as per the v5 changelog. Please let me know what the right etiquette is? Shall I resend the series? Apologies for the noise! > > [v5] > - 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 | 62 ++++++++++++++--- > fs/nfs/read.c | 2 +- > fs/nfs/write.c | 2 +- > include/linux/nfs_page.h | 8 ++- > 5 files changed, 130 insertions(+), 83 deletions(-) > > > base-commit: 5b57716ed7ad2f4b1724461c8777015c4e4befb1 > -- > 2.55.0.679.g6767b8d81c-goog > Thanks, Praan [1] https://lore.kernel.org/all/20260720150601.2702700-1-praan@google.com/
On Mon, Aug 10, 2026 at 08:38:49PM +0000, Pranjal Shrivastava wrote: > On Mon, Aug 10, 2026 at 07:50:34PM +0000, Pranjal Shrivastava wrote: > > 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. > > > > [...] > > I'm calling out a few typos / non-code mistakes: > > 1. On the cover letter I missed updating the subject to v5 for this series > (the changelog is noted below). > > 2. I also accidentally dropped Christoph's Reviewed-by tags on patches > 1, 2, and 3 during the rebase (given while reviewing v4 [1]). > > Everything else in the series is correct as per the v5 changelog. > Please let me know what the right etiquette is? Shall I resend the series? > > Apologies for the noise! > Quick update: I've posted a v6 [1] with fixes for unpin bugs reported by Sashiko [2] and with R-bs from Christoph that were dropped mistakenly in v5. Thanks, Praan [1] https://lore.kernel.org/all/20260814143255.861084-1-praan@google.com/ [2] https://sashiko.dev/#/patchset/20260810195040.2877784-1-praan%40google.com
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