Commit ec2e0cc6 authored by Alistair Popple's avatar Alistair Popple Committed by Andrew Morton
Browse files

mm/memory: add vmf_insert_page_mkwrite() 

Currently to map a DAX page the DAX driver calls vmf_insert_pfn.  This
creates a special devmap PTE entry for the pfn but does not take a
reference on the underlying struct page for the mapping.  This is because
DAX page refcounts are treated specially, as indicated by the presence of
a devmap entry.

To allow DAX page refcounts to be managed the same as normal page
refcounts introduce vmf_insert_page_mkwrite().  This will take a reference
on the underlying page much the same as vmf_insert_page, except it also
permits upgrading an existing mapping to be writable if
requested/possible.

Link: https://lkml.kernel.org/r/4ce3aa984c060f370105e0bfef1035869578be47.1740713401.git-series.apopple@nvidia.com


Signed-off-by: default avatarAlistair Popple <apopple@nvidia.com>
Acked-by: default avatarDavid Hildenbrand <david@redhat.com>
Tested-by: default avatarAlison Schofield <alison.schofield@intel.com>
Cc: Alexander Gordeev <agordeev@linux.ibm.com>
Cc: Asahi Lina <lina@asahilina.net>
Cc: Balbir Singh <balbirs@nvidia.com>
Cc: Bjorn Helgaas <bhelgaas@google.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Christian Borntraeger <borntraeger@linux.ibm.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Chunyan Zhang <zhang.lyra@gmail.com>
Cc: Dan Wiliams <dan.j.williams@intel.com>
Cc: "Darrick J. Wong" <djwong@kernel.org>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Dave Jiang <dave.jiang@intel.com>
Cc: Gerald Schaefer <gerald.schaefer@linux.ibm.com>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Huacai Chen <chenhuacai@kernel.org>
Cc: Ira Weiny <ira.weiny@intel.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: linmiaohe <linmiaohe@huawei.com>
Cc: Logan Gunthorpe <logang@deltatee.com>
Cc: Matthew Wilcow (Oracle) <willy@infradead.org>
Cc: Michael "Camp Drill Sergeant" Ellerman <mpe@ellerman.id.au>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Sven Schnelle <svens@linux.ibm.com>
Cc: Ted Ts'o <tytso@mit.edu>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Vishal Verma <vishal.l.verma@intel.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: WANG Xuerui <kernel@xen0n.name>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 15a64311

include/linux/mm.h

+2 −0
Original line number Diff line number Diff line
@@ -3644,6 +3644,8 @@ int vm_map_pages(struct vm_area_struct *vma, struct page **pages, 
				unsigned long num);

int vm_map_pages_zero(struct vm_area_struct *vma, struct page **pages,

				unsigned long num);

vm_fault_t vmf_insert_page_mkwrite(struct vm_fault *vmf, struct page *page,

			bool write);

vm_fault_t vmf_insert_pfn(struct vm_area_struct *vma, unsigned long addr,

			unsigned long pfn);

vm_fault_t vmf_insert_pfn_prot(struct vm_area_struct *vma, unsigned long addr,

mm/memory.c

+20 −0
Original line number Diff line number Diff line
@@ -2643,6 +2643,26 @@ static vm_fault_t __vm_insert_mixed(struct vm_area_struct *vma, 
	return VM_FAULT_NOPAGE;

}



vm_fault_t vmf_insert_page_mkwrite(struct vm_fault *vmf, struct page *page,

			bool write)

{

	pgprot_t pgprot = vmf->vma->vm_page_prot;

	unsigned long addr = vmf->address;

	int err;



	if (addr < vmf->vma->vm_start || addr >= vmf->vma->vm_end)

		return VM_FAULT_SIGBUS;



	err = insert_page(vmf->vma, addr, page, pgprot, write);

	if (err == -ENOMEM)

		return VM_FAULT_OOM;

	if (err < 0 && err != -EBUSY)

		return VM_FAULT_SIGBUS;



	return VM_FAULT_NOPAGE;

}

EXPORT_SYMBOL_GPL(vmf_insert_page_mkwrite);



vm_fault_t vmf_insert_mixed(struct vm_area_struct *vma, unsigned long addr,

		pfn_t pfn)

{