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 31B03311C15; Mon, 16 Mar 2026 21:13:35 +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=1773695616; cv=none; b=elyws6R+urJxSYlG/MBEoeDC6eTR+dQBlEZDnVRJioxCSzrX7j/Ixw6T6fFUn9YrFacs+iEs7UfVeuR/Jh1nFTkHgEOEDXPfAADkt8ETVhBMYDN62bpvdoPcVRLz2FTBSfChFbuJWaCbx8vfZ4cvj/DjHc+1J6tjylTBaWZiVrw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773695616; c=relaxed/simple; bh=ilMdtysPCdNXPtzF2zNSpIrJ8Gr1Wv5rYS8ynVlNkEU=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=vCqBs9YVdLR9gwuh+Lq44E/jcum0LEFIyO4yo1q59QbD3Z4MmSr8tt/1JttvquZgEArq0Gpt8pBKb9mkuxal7Gb1c26EqJtHbaPA747RjTaCPCt1+0NC0ogJyQ2OHKgTI0AWgNICdIzA8o6IECGjERUMl16ADLrSURnEvTEi6MM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Ntq/l3UG; 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="Ntq/l3UG" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 248B4C19421; Mon, 16 Mar 2026 21:13:35 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1773695615; bh=ilMdtysPCdNXPtzF2zNSpIrJ8Gr1Wv5rYS8ynVlNkEU=; h=From:To:Cc:Subject:Date:From; b=Ntq/l3UGM9JqyJJD9JGa7/yDJgNVnVPNfki9aJRX4uarYRuo6x4Dvl1Nvv2uizzFY PKNBhPwaDwYOT2ryPSG03lQzK/iVm6SI95tlkq8E9XT6eanSVjR8YC7k3x5yHct10Z 0KpqmHVJ//eqjlE2lbzqizxCuq2HekJx0MVEF0CFZiORAS4KC/NJ00mX8hqxEHngbN dN//9WHytXP2+KVpaS88wjMwl7EtwsiLj0M1lgSWEd4oxUmAaUwkJzaE8ngvjhvq+y 1g+fHhAmOGC1WKRn1K9zFe7N/Cc7a3sZPGoqKRVY/lmxStNOEuDKUMfI7PC9kSX4Hr YuQ4yI1r6vyzA== From: "Lorenzo Stoakes (Oracle)" To: Andrew Morton Cc: Jonathan Corbet , Clemens Ladisch , Arnd Bergmann , Greg Kroah-Hartman , "K . Y . Srinivasan" , Haiyang Zhang , Wei Liu , Dexuan Cui , Long Li , Alexander Shishkin , Maxime Coquelin , Alexandre Torgue , Miquel Raynal , Richard Weinberger , Vignesh Raghavendra , Bodo Stroesser , "Martin K . Petersen" , David Howells , Marc Dionne , Alexander Viro , Christian Brauner , Jan Kara , David Hildenbrand , "Liam R . Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Jann Horn , Pedro Falcato , linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-hyperv@vger.kernel.org, linux-stm32@st-md-mailman.stormreply.com, linux-arm-kernel@lists.infradead.org, linux-mtd@lists.infradead.org, linux-staging@lists.linux.dev, linux-scsi@vger.kernel.org, target-devel@vger.kernel.org, linux-afs@lists.infradead.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, Ryan Roberts Subject: [PATCH v2 00/16] mm: expand mmap_prepare functionality and usage Date: Mon, 16 Mar 2026 21:11:56 +0000 Message-ID: X-Mailer: git-send-email 2.53.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit This series expands the mmap_prepare functionality, which is intended to replace the deprecated f_op->mmap hook which has been the source of bugs and security issues for some time. This series starts with some cleanup of existing mmap_prepare logic, then adds documentation for the mmap_prepare call to make it easier for filesystem and driver writers to understand how it works. It then importantly adds a vm_ops->mapped hook, a key feature that was missing from mmap_prepare previously - this is invoked when a driver which specifies mmap_prepare has successfully been mapped but not merged with another VMA. mmap_prepare is invoked prior to a merge being attempted, so you cannot manipulate state such as reference counts as if it were a new mapping. The vm_ops->mapped hook allows a driver to perform tasks required at this stage, and provides symmetry against subsequent vm_ops->open,close calls. The series uses this to correct the afs implementation which wrongly manipulated reference count at mmap_prepare time. It then adds an mmap_prepare equivalent of vm_iomap_memory() - mmap_action_simple_ioremap(), then uses this to update a number of drivers. It then splits out the mmap_prepare compatibility layer (which allows for invocation of mmap_prepare hooks in an mmap() hook) in such a way as to allow for more incremental implementation of mmap_prepare hooks. It then uses this to extend mmap_prepare usage in drivers. Finally it adds an mmap_prepare equivalent of vm_map_pages(), which lays the foundation for future work which will extend mmap_prepare to DMA coherent mappings. v2: * Rebased on https://lore.kernel.org/all/cover.1773665966.git.ljs@kernel.org/ to make Andrew's life easier :) * Folded all interim fixes into series (thanks Randy for many doc fixes!)) * As per Suren, removed a comment about allocations too small to fail. * As per Randy, fixed up typo in documentation for vm_area_desc. * Fixed mmap_action_prepare() not returning if invalid action->type specified, as updated from Andrew's interim fix (thanks!) and also reported by kernel test bot. * Updated mmap_action_prepare() and specific prepare functions to only pass vm_area_desc parameter as per Suren. * Fixed up whitespace as per Suren. * Updated vm_op->open comment in vm_operations_struct to reference forking as per Suren. * Added a commit to check that input range is within VMA on remap as per Suren (this also covers I/O remap and all other cases already asserted). * Updated AFS to not incorrectly reference count on mmap prepare as per Usama. * Also updated various static AFS functions to be consistent with each other. * Updated AFS commit message to reflect mmap_prepare being before any VMA merging as per Suren. * Updated __compat_vma_mapped() to check for NULL vm_ops as per Usama. * Updated __compat_vma_mapped() to not reference an unmapped VMA's fields as per Usama. * Updated __vma_check_mmap_hook() to check for NULL vm_ops as per Usama. * Dropped comment about preferring mmap_prepare as seems overly confusing, as per Suren. * Updated the mmap lock assert in unmap_vma_locked() to a write lock assert as per Suren. * Copied vm_ops->open comment over to VMA tests in appropriate patch as per Suren. * Updated mmap_prepare documentation to reflect the fact that no resources should be allocated upon mmap_prepare. * Updated mmap_prepare documentation to reference the vm_ops->mapped callback. * Fixed stray markdown '## How to use' in documentation. * Fixed bug reported by kernel test bot re: overlooked vma_desc_test_flags() -> vma_desc_test() in MTD driver for nommu. v1: https://lore.kernel.org/linux-mm/cover.1773346620.git.ljs@kernel.org/ Lorenzo Stoakes (Oracle) (16): mm: various small mmap_prepare cleanups mm: add documentation for the mmap_prepare file operation callback mm: document vm_operations_struct->open the same as close() mm: add vm_ops->mapped hook fs: afs: correctly drop reference count on mapping failure mm: add mmap_action_simple_ioremap() misc: open-dice: replace deprecated mmap hook with mmap_prepare hpet: replace deprecated mmap hook with mmap_prepare mtdchar: replace deprecated mmap hook with mmap_prepare, clean up stm: replace deprecated mmap hook with mmap_prepare staging: vme_user: replace deprecated mmap hook with mmap_prepare mm: allow handling of stacked mmap_prepare hooks in more drivers drivers: hv: vmbus: replace deprecated mmap hook with mmap_prepare uio: replace deprecated mmap hook with mmap_prepare in uio_info mm: add mmap_action_map_kernel_pages[_full]() mm: on remap assert that input range within the proposed VMA Documentation/driver-api/vme.rst | 2 +- Documentation/filesystems/index.rst | 1 + Documentation/filesystems/mmap_prepare.rst | 168 ++++++++++++++++ drivers/char/hpet.c | 12 +- drivers/hv/hyperv_vmbus.h | 4 +- drivers/hv/vmbus_drv.c | 27 ++- drivers/hwtracing/stm/core.c | 31 ++- drivers/misc/open-dice.c | 19 +- drivers/mtd/mtdchar.c | 21 +- drivers/staging/vme_user/vme.c | 20 +- drivers/staging/vme_user/vme.h | 2 +- drivers/staging/vme_user/vme_user.c | 51 +++-- drivers/target/target_core_user.c | 26 ++- drivers/uio/uio.c | 10 +- drivers/uio/uio_hv_generic.c | 11 +- fs/afs/file.c | 36 +++- include/linux/fs.h | 14 +- include/linux/hyperv.h | 4 +- include/linux/mm.h | 158 +++++++++++++-- include/linux/mm_types.h | 17 +- include/linux/uio_driver.h | 4 +- mm/internal.h | 37 ++-- mm/memory.c | 177 ++++++++++++----- mm/util.c | 219 +++++++++++++++------ mm/vma.c | 59 ++++-- mm/vma.h | 2 +- tools/testing/vma/include/dup.h | 141 +++++++++---- tools/testing/vma/include/stubs.h | 8 +- 28 files changed, 970 insertions(+), 311 deletions(-) create mode 100644 Documentation/filesystems/mmap_prepare.rst -- 2.53.0