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 9E94219D8A3 for ; Tue, 23 Sep 2025 03:18:19 +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=1758597499; cv=none; b=byDgjIKs0OaaluKXXG1QJNHXB69RZIGksdkj3FTWEy3G4VEbmaOge67Vogca37wsdXAb/KoxCQTL2/kXyavC4ZMwD2f4HFdUgakMuK9qggSv34kUfGL9Kut9wngYW/3QP67f/eEBxoEHepQFmFPcaERZaigJ2eRo8aZGPNTcxQ4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1758597499; c=relaxed/simple; bh=Ylpf9pqASQEyrYcB/9DK0jCV2Ic/3RAg7j0A1HoBPCE=; h=Date:To:From:Subject:Message-Id; b=oEWwfj2MZUgVNdzN12yg8EaZPJgkfRsXEe75CNlaTHrfeoK4V0sZIszE37jb8FzoXQ14k8SYb8RxPGhl07mVGuzcMHgvCmlADfn8CgII63MFiVUeVrcs5ClH2varIjZtipRGOaipvxuM8sF3V2m/fGR0F06yOwOKIBodZo7LAEc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b=NbvbLlM3; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b="NbvbLlM3" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6C4DFC4CEF0; Tue, 23 Sep 2025 03:18:19 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1758597499; bh=Ylpf9pqASQEyrYcB/9DK0jCV2Ic/3RAg7j0A1HoBPCE=; h=Date:To:From:Subject:From; b=NbvbLlM3jmPsWa/uzgasyKDx+C3+Sc+YTC9cEyYsECY4gsEk1plyCZC1bfyXIlBhM jSj4Eyb/v2D31fuXgie8qF9WmBLvyshpW1Zurj7WnyZCVbOBdg164AMIofWxs3h4ud fnwWptIV8TL6vGk+AAfsQHwvbnk48PSQEtib2hOw= Date: Mon, 22 Sep 2025 20:18:18 -0700 To: mm-commits@vger.kernel.org,willy@infradead.org,will@kernel.org,vishal.l.verma@intel.com,viro@zeniv.linux.org.uk,vgoyal@redhat.com,vbabka@suse.cz,urezki@gmail.com,tsbogend@alpha.franken.de,tony.luck@intel.com,svens@linux.ibm.com,surenb@google.com,rppt@kernel.org,robin.murphy@arm.com,reinette.chatre@intel.com,pfalcato@suse.de,osalvador@suse.de,nico@fluxnic.net,muchun.song@linux.dev,mhocko@suse.com,liam.howlett@oracle.com,kevin.tian@intel.com,jgg@nvidia.com,jannh@google.com,james.morse@arm.com,jack@suse.cz,hughd@google.com,hca@linux.ibm.com,guoren@kernel.org,gregkh@linuxfoundation.org,gor@linux.ibm.com,dyoung@redhat.com,dvyukov@google.com,david@redhat.com,davem@davemloft.net,dave.martin@arm.com,dave.jiang@intel.com,dan.j.williams@intel.com,corbet@lwn.net,brauner@kernel.org,borntraeger@linux.ibm.com,bhe@redhat.com,baolin.wang@linux.alibaba.com,arnd@arndb.de,andreyknvl@gmail.com,andreas@gaisler.com,almaz.alexandrovich@paragon-software.com,agordeev@linux.ibm.com,lorenzo.stoakes@oracle.com,akpm@linux-foundation.org From: Andrew Morton Subject: [merged mm-stable] mm-update-mem-char-driver-to-use-mmap_prepare.patch removed from -mm tree Message-Id: <20250923031819.6C4DFC4CEF0@smtp.kernel.org> Precedence: bulk X-Mailing-List: mm-commits@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: The quilt patch titled Subject: mm: update mem char driver to use mmap_prepare has been removed from the -mm tree. Its filename was mm-update-mem-char-driver-to-use-mmap_prepare.patch This patch was dropped because it was merged into the mm-stable branch of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm ------------------------------------------------------ From: Lorenzo Stoakes Subject: mm: update mem char driver to use mmap_prepare Date: Wed, 17 Sep 2025 20:11:15 +0100 Update the mem char driver (backing /dev/mem and /dev/zero) to use f_op->mmap_prepare hook rather than the deprecated f_op->mmap. The /dev/zero implementation has a very unique and rather concerning characteristic in that it converts MAP_PRIVATE mmap() mappings anonymous when they are, in fact, not. The new f_op->mmap_prepare() can support this, but rather than introducing a helper function to perform this hack (and risk introducing other users), utilise the success hook to do so. We utilise the newly introduced shmem_zero_setup_desc() to allow for the shared mapping case via an f_op->mmap_prepare() hook. We also use the desc->action_error_hook to filter the remap error to -EAGAIN to keep behaviour consistent. Link: https://lkml.kernel.org/r/14cdf181c4145a298a2249946b753276bdc11167.1758135681.git.lorenzo.stoakes@oracle.com Signed-off-by: Lorenzo Stoakes Reviewed-by: Jason Gunthorpe Cc: Alexander Gordeev Cc: Al Viro Cc: Andreas Larsson Cc: Andrey Konovalov Cc: Arnd Bergmann Cc: Baolin Wang Cc: Baoquan He Cc: Chatre, Reinette Cc: Christian Borntraeger Cc: Christian Brauner Cc: Dan Williams Cc: Dave Jiang Cc: Dave Martin Cc: Dave Young Cc: David Hildenbrand Cc: David S. Miller Cc: Dmitriy Vyukov Cc: Greg Kroah-Hartman Cc: Guo Ren Cc: Heiko Carstens Cc: Hugh Dickins Cc: James Morse Cc: Jan Kara Cc: Jann Horn Cc: Jonathan Corbet Cc: Kevin Tian Cc: Konstantin Komarov Cc: Liam Howlett Cc: "Luck, Tony" Cc: Matthew Wilcox (Oracle) Cc: Michal Hocko Cc: Mike Rapoport Cc: Muchun Song Cc: Nicolas Pitre Cc: Oscar Salvador Cc: Pedro Falcato Cc: Robin Murohy Cc: Suren Baghdasaryan Cc: Sven Schnelle Cc: Thomas Bogendoerfer Cc: "Uladzislau Rezki (Sony)" Cc: Vasily Gorbik Cc: Vishal Verma Cc: Vivek Goyal Cc: Vlastimil Babka Cc: Will Deacon Signed-off-by: Andrew Morton --- drivers/char/mem.c | 88 +++++++++++++++++++++++++------------------ 1 file changed, 52 insertions(+), 36 deletions(-) --- a/drivers/char/mem.c~mm-update-mem-char-driver-to-use-mmap_prepare +++ a/drivers/char/mem.c @@ -304,13 +304,13 @@ static unsigned zero_mmap_capabilities(s } /* can't do an in-place private mapping if there's no MMU */ -static inline int private_mapping_ok(struct vm_area_struct *vma) +static inline int private_mapping_ok(struct vm_area_desc *desc) { - return is_nommu_shared_mapping(vma->vm_flags); + return is_nommu_shared_mapping(desc->vm_flags); } #else -static inline int private_mapping_ok(struct vm_area_struct *vma) +static inline int private_mapping_ok(struct vm_area_desc *desc) { return 1; } @@ -322,46 +322,49 @@ static const struct vm_operations_struct #endif }; -static int mmap_mem(struct file *file, struct vm_area_struct *vma) +static int mmap_filter_error(int err) { - size_t size = vma->vm_end - vma->vm_start; - phys_addr_t offset = (phys_addr_t)vma->vm_pgoff << PAGE_SHIFT; + return -EAGAIN; +} + +static int mmap_mem_prepare(struct vm_area_desc *desc) +{ + struct file *file = desc->file; + const size_t size = vma_desc_size(desc); + const phys_addr_t offset = (phys_addr_t)desc->pgoff << PAGE_SHIFT; /* Does it even fit in phys_addr_t? */ - if (offset >> PAGE_SHIFT != vma->vm_pgoff) + if (offset >> PAGE_SHIFT != desc->pgoff) return -EINVAL; /* It's illegal to wrap around the end of the physical address space. */ if (offset + (phys_addr_t)size - 1 < offset) return -EINVAL; - if (!valid_mmap_phys_addr_range(vma->vm_pgoff, size)) + if (!valid_mmap_phys_addr_range(desc->pgoff, size)) return -EINVAL; - if (!private_mapping_ok(vma)) + if (!private_mapping_ok(desc)) return -ENOSYS; - if (!range_is_allowed(vma->vm_pgoff, size)) + if (!range_is_allowed(desc->pgoff, size)) return -EPERM; - if (!phys_mem_access_prot_allowed(file, vma->vm_pgoff, size, - &vma->vm_page_prot)) + if (!phys_mem_access_prot_allowed(file, desc->pgoff, size, + &desc->page_prot)) return -EINVAL; - vma->vm_page_prot = phys_mem_access_prot(file, vma->vm_pgoff, - size, - vma->vm_page_prot); - - vma->vm_ops = &mmap_mem_ops; - - /* Remap-pfn-range will mark the range VM_IO */ - if (remap_pfn_range(vma, - vma->vm_start, - vma->vm_pgoff, - size, - vma->vm_page_prot)) { - return -EAGAIN; - } + desc->page_prot = phys_mem_access_prot(file, desc->pgoff, + size, + desc->page_prot); + + desc->vm_ops = &mmap_mem_ops; + + /* Remap-pfn-range will mark the range VM_IO. */ + mmap_action_remap_full(desc, desc->pgoff); + /* We filter remap errors to -EAGAIN. */ + desc->action.error_hook = mmap_filter_error; + return 0; } @@ -501,14 +504,26 @@ static ssize_t read_zero(struct file *fi return cleared; } -static int mmap_zero(struct file *file, struct vm_area_struct *vma) +static int mmap_zero_private_success(const struct vm_area_struct *vma) +{ + /* + * This is a highly unique situation where we mark a MAP_PRIVATE mapping + * of /dev/zero anonymous, despite it not being. + */ + vma_set_anonymous((struct vm_area_struct *)vma); + + return 0; +} + +static int mmap_zero_prepare(struct vm_area_desc *desc) { #ifndef CONFIG_MMU return -ENOSYS; #endif - if (vma->vm_flags & VM_SHARED) - return shmem_zero_setup(vma); - vma_set_anonymous(vma); + if (desc->vm_flags & VM_SHARED) + return shmem_zero_setup_desc(desc); + + desc->action.success_hook = mmap_zero_private_success; return 0; } @@ -526,10 +541,11 @@ static unsigned long get_unmapped_area_z { if (flags & MAP_SHARED) { /* - * mmap_zero() will call shmem_zero_setup() to create a file, - * so use shmem's get_unmapped_area in case it can be huge; - * and pass NULL for file as in mmap.c's get_unmapped_area(), - * so as not to confuse shmem with our handle on "/dev/zero". + * mmap_zero_prepare() will call shmem_zero_setup() to create a + * file, so use shmem's get_unmapped_area in case it can be + * huge; and pass NULL for file as in mmap.c's + * get_unmapped_area(), so as not to confuse shmem with our + * handle on "/dev/zero". */ return shmem_get_unmapped_area(NULL, addr, len, pgoff, flags); } @@ -632,7 +648,7 @@ static const struct file_operations __ma .llseek = memory_lseek, .read = read_mem, .write = write_mem, - .mmap = mmap_mem, + .mmap_prepare = mmap_mem_prepare, .open = open_mem, #ifndef CONFIG_MMU .get_unmapped_area = get_unmapped_area_mem, @@ -668,7 +684,7 @@ static const struct file_operations zero .write_iter = write_iter_zero, .splice_read = copy_splice_read, .splice_write = splice_write_zero, - .mmap = mmap_zero, + .mmap_prepare = mmap_zero_prepare, .get_unmapped_area = get_unmapped_area_zero, #ifndef CONFIG_MMU .mmap_capabilities = zero_mmap_capabilities, _ Patches currently in -mm which might be from lorenzo.stoakes@oracle.com are