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charset="utf-8" The .page_mkwrite operator of kernfs just calls file_update_time(). This is the same behaviour that the fault code does if .page_mkwrite is not set. Furthermore, having the page_mkwrite() operator causes writable_file_mapping_allowed() to fail due to vma_needs_dirty_tracking() on the gup flow, which is a pre-requisite for enabling P2PDMA over RDMA. There are no users of .page_mkwrite and no known valid use cases, so just remove the .page_mkwrite from kernfs_ops and WARN_ON() if an mmap() implementation sets .page_mkwrite. Co-developed-by: Logan Gunthorpe Signed-off-by: Logan Gunthorpe Signed-off-by: Martin Oliveira Acked-by: Greg Kroah-Hartman --- fs/kernfs/file.c | 25 ++----------------------- 1 file changed, 2 insertions(+), 23 deletions(-) diff --git a/fs/kernfs/file.c b/fs/kernfs/file.c index 8502ef68459b..90603664de7f 100644 --- a/fs/kernfs/file.c +++ b/fs/kernfs/file.c @@ -386,28 +386,6 @@ static vm_fault_t kernfs_vma_fault(struct vm_fault *vm= f) return ret; } =20 -static vm_fault_t kernfs_vma_page_mkwrite(struct vm_fault *vmf) -{ - struct file *file =3D vmf->vma->vm_file; - struct kernfs_open_file *of =3D kernfs_of(file); - vm_fault_t ret; - - if (!of->vm_ops) - return VM_FAULT_SIGBUS; - - if (!kernfs_get_active(of->kn)) - return VM_FAULT_SIGBUS; - - ret =3D 0; - if (of->vm_ops->page_mkwrite) - ret =3D of->vm_ops->page_mkwrite(vmf); - else - file_update_time(file); - - kernfs_put_active(of->kn); - return ret; -} - static int kernfs_vma_access(struct vm_area_struct *vma, unsigned long add= r, void *buf, int len, int write) { @@ -432,7 +410,6 @@ static int kernfs_vma_access(struct vm_area_struct *vma= , unsigned long addr, static const struct vm_operations_struct kernfs_vm_ops =3D { .open =3D kernfs_vma_open, .fault =3D kernfs_vma_fault, - .page_mkwrite =3D kernfs_vma_page_mkwrite, .access =3D kernfs_vma_access, }; 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Thu, 4 Jul 2024 16:37:51 +0000 From: Martin Oliveira To: linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-rdma@vger.kernel.org Cc: Andrew Morton , Artemy Kovalyov , Greg Kroah-Hartman , Jason Gunthorpe , Leon Romanovsky , Logan Gunthorpe , Martin Oliveira , Michael Guralnik , Mike Marciniszyn , Shiraz Saleem , Tejun Heo , John Hubbard , Dan Williams , David Sloan Subject: [PATCH v3 2/3] mm/gup: allow FOLL_LONGTERM & FOLL_PCI_P2PDMA Date: Thu, 4 Jul 2024 10:37:23 -0600 Message-Id: <20240704163724.2462161-3-martin.oliveira@eideticom.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20240704163724.2462161-1-martin.oliveira@eideticom.com> References: <20240704163724.2462161-1-martin.oliveira@eideticom.com> Content-Transfer-Encoding: quoted-printable X-ClientProxiedBy: MW4PR03CA0078.namprd03.prod.outlook.com (2603:10b6:303:b6::23) To MW3PR19MB4250.namprd19.prod.outlook.com (2603:10b6:303:46::16) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: MW3PR19MB4250:EE_|CH0PR19MB7850:EE_ X-MS-Office365-Filtering-Correlation-Id: ef476c93-f2b4-4e91-ae84-08dc9c47a55d X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|52116014|366016|7416014|376014|1800799024|38350700014; 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charset="utf-8" This check existed originally due to concerns that P2PDMA needed to copy fsdax until pgmap refcounts were fixed (see [1]). The P2PDMA infrastructure will only call unmap_mapping_range() when the underlying device is unbound, and immediately after unmapping it waits for the reference of all ZONE_DEVICE pages to be released before continuing. This does not allow for a page to be reused and no user access fault is therefore possible. It does not have the same problem as fsdax. The one minor concern with FOLL_LONGTERM pins is they will block device unbind until userspace releases them all. Co-developed-by: Logan Gunthorpe Signed-off-by: Logan Gunthorpe Signed-off-by: Martin Oliveira [1]: https://lkml.kernel.org/r/Yy4Ot5MoOhsgYLTQ@ziepe.ca --- mm/gup.c | 5 ----- 1 file changed, 5 deletions(-) diff --git a/mm/gup.c b/mm/gup.c index ca0f5cedce9b..6922e1c38d75 100644 --- a/mm/gup.c +++ b/mm/gup.c @@ -2614,11 +2614,6 @@ static bool is_valid_gup_args(struct page **pages, i= nt *locked, if (WARN_ON_ONCE((gup_flags & (FOLL_GET | FOLL_PIN)) && !pages)) return false; =20 - /* We want to allow the pgmap to be hot-unplugged at all times */ - if (WARN_ON_ONCE((gup_flags & FOLL_LONGTERM) && - (gup_flags & FOLL_PCI_P2PDMA))) - return false; - *gup_flags_p =3D gup_flags; return true; } --=20 2.34.1 From nobody Mon Feb 9 00:26:53 2026 Received: from NAM11-DM6-obe.outbound.protection.outlook.com (mail-dm6nam11on2103.outbound.protection.outlook.com [40.107.223.103]) (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 9252D1B3F09; 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charset="utf-8" If the device supports P2PDMA, add the FOLL_PCI_P2PDMA flag This allows ibv_reg_mr() and friends to use P2PDMA memory that has been mmaped into userspace for MRs in IB and RDMA transactions. Co-developed-by: Logan Gunthorpe Signed-off-by: Logan Gunthorpe Signed-off-by: Martin Oliveira Acked-by: Jason Gunthorpe --- drivers/infiniband/core/umem.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/drivers/infiniband/core/umem.c b/drivers/infiniband/core/umem.c index 07c571c7b699..b59bb6e1475e 100644 --- a/drivers/infiniband/core/umem.c +++ b/drivers/infiniband/core/umem.c @@ -208,6 +208,9 @@ struct ib_umem *ib_umem_get(struct ib_device *device, u= nsigned long addr, if (umem->writable) gup_flags |=3D FOLL_WRITE; =20 + if (ib_dma_pci_p2p_dma_supported(device)) + gup_flags |=3D FOLL_PCI_P2PDMA; + while (npages) { cond_resched(); pinned =3D pin_user_pages_fast(cur_base, --=20 2.34.1