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![Linus Torvalds](/assets/img/avatar_default.png)
* DAX broke a fundamental assumption of truncate of file mapped pages. The truncate path assumed that it is safe to disconnect a pinned page from a file and let the filesystem reclaim the physical block. With DAX the page is equivalent to the filesystem block. Introduce dax_layout_busy_page() to enable filesystems to wait for pinned DAX pages to be released. Without this wait a filesystem could allocate blocks under active device-DMA to a new file. * DAX arranges for the block layer to be bypassed and uses dax_direct_access() + copy_to_iter() to satisfy read(2) calls. However, the memcpy_mcsafe() facility is available through the pmem block driver. In order to safely handle media errors, via the DAX block-layer bypass, introduce copy_to_iter_mcsafe(). * Fix cache management policy relative to the ACPI NFIT Platform Capabilities Structure to properly elide cache flushes when they are not necessary. The table indicates whether CPU caches are power-fail protected. Clarify that a deep flush is always performed on REQ_{FUA,PREFLUSH} requests. -----BEGIN PGP SIGNATURE----- iQIcBAABAgAGBQJbGxI7AAoJEB7SkWpmfYgCDjsP/2Lcibu9Kf4tKIzuInsle6iE 6qP29qlkpHVTpDKbhvIxTYTYL9sMU0DNUrpPCJR/EYdeyztLWDFC5EAT1wF240vf maV37s/uP331jSC/2VJnKWzBs2ztQxmKLEIQCxh6aT0qs9cbaOvJgB/WlVu+qtsl aGJFLmb6vdQacp31noU5plKrMgMA1pADyF5qx9I9K2HwowHE7T368ZEFS/3S//c3 LXmpx/Nfq52sGu/qbRbu6B1CTJhIGhmarObyQnvBYoKntK1Ov4e8DS95wD3EhNDe FuRkOCUKhjl6cFy7QVWh1ct1bFm84ny+b4/AtbpOmv9l/+0mveJ7e+5mu8HQTifT wYiEe2xzXJ+OG/xntv8SvlZKMpjP3BqI0jYsTutsjT4oHrciiXdXM186cyS+BiGp KtFmWyncQJgfiTq6+Hj5XpP9BapNS+OYdYgUagw9ZwzdzptuGFYUMSVOBrYrn6c/ fwqtxjubykJoW0P3pkIoT91arFSea7nxOKnGwft06imQ7TwR4ARsI308feQ9itJq 2P2e7/20nYMsw2aRaUDDA70Yu+Lagn1m8WL87IybUGeUDLb1BAkjphAlWa6COJ+u PhvAD2tvyM9m0c7O5Mytvz7iWKG6SVgatoAyOPkaeplQK8khZ+wEpuK58sO6C1w8 4GBvt9ri9i/Ww/A+ppWs =4bfw -----END PGP SIGNATURE----- Merge tag 'libnvdimm-for-4.18' of git://git.kernel.org/pub/scm/linux/kernel/git/nvdimm/nvdimm Pull libnvdimm updates from Dan Williams: "This adds a user for the new 'bytes-remaining' updates to memcpy_mcsafe() that you already received through Ingo via the x86-dax- for-linus pull. Not included here, but still targeting this cycle, is support for handling memory media errors (poison) consumed via userspace dax mappings. Summary: - DAX broke a fundamental assumption of truncate of file mapped pages. The truncate path assumed that it is safe to disconnect a pinned page from a file and let the filesystem reclaim the physical block. With DAX the page is equivalent to the filesystem block. Introduce dax_layout_busy_page() to enable filesystems to wait for pinned DAX pages to be released. Without this wait a filesystem could allocate blocks under active device-DMA to a new file. - DAX arranges for the block layer to be bypassed and uses dax_direct_access() + copy_to_iter() to satisfy read(2) calls. However, the memcpy_mcsafe() facility is available through the pmem block driver. In order to safely handle media errors, via the DAX block-layer bypass, introduce copy_to_iter_mcsafe(). - Fix cache management policy relative to the ACPI NFIT Platform Capabilities Structure to properly elide cache flushes when they are not necessary. The table indicates whether CPU caches are power-fail protected. Clarify that a deep flush is always performed on REQ_{FUA,PREFLUSH} requests" * tag 'libnvdimm-for-4.18' of git://git.kernel.org/pub/scm/linux/kernel/git/nvdimm/nvdimm: (21 commits) dax: Use dax_write_cache* helpers libnvdimm, pmem: Do not flush power-fail protected CPU caches libnvdimm, pmem: Unconditionally deep flush on *sync libnvdimm, pmem: Complete REQ_FLUSH => REQ_PREFLUSH acpi, nfit: Remove ecc_unit_size dax: dax_insert_mapping_entry always succeeds libnvdimm, e820: Register all pmem resources libnvdimm: Debug probe times linvdimm, pmem: Preserve read-only setting for pmem devices x86, nfit_test: Add unit test for memcpy_mcsafe() pmem: Switch to copy_to_iter_mcsafe() dax: Report bytes remaining in dax_iomap_actor() dax: Introduce a ->copy_to_iter dax operation uio, lib: Fix CONFIG_ARCH_HAS_UACCESS_MCSAFE compilation xfs, dax: introduce xfs_break_dax_layouts() xfs: prepare xfs_break_layouts() for another layout type xfs: prepare xfs_break_layouts() to be called with XFS_MMAPLOCK_EXCL mm, fs, dax: handle layout changes to pinned dax mappings mm: fix __gup_device_huge vs unmap mm: introduce MEMORY_DEVICE_FS_DAX and CONFIG_DEV_PAGEMAP_OPS ...
167 lines
5.8 KiB
C
167 lines
5.8 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef _LINUX_MEMREMAP_H_
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#define _LINUX_MEMREMAP_H_
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#include <linux/ioport.h>
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#include <linux/percpu-refcount.h>
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#include <asm/pgtable.h>
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struct resource;
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struct device;
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/**
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* struct vmem_altmap - pre-allocated storage for vmemmap_populate
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* @base_pfn: base of the entire dev_pagemap mapping
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* @reserve: pages mapped, but reserved for driver use (relative to @base)
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* @free: free pages set aside in the mapping for memmap storage
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* @align: pages reserved to meet allocation alignments
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* @alloc: track pages consumed, private to vmemmap_populate()
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*/
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struct vmem_altmap {
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const unsigned long base_pfn;
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const unsigned long reserve;
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unsigned long free;
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unsigned long align;
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unsigned long alloc;
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};
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/*
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* Specialize ZONE_DEVICE memory into multiple types each having differents
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* usage.
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*
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* MEMORY_DEVICE_PRIVATE:
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* Device memory that is not directly addressable by the CPU: CPU can neither
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* read nor write private memory. In this case, we do still have struct pages
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* backing the device memory. Doing so simplifies the implementation, but it is
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* important to remember that there are certain points at which the struct page
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* must be treated as an opaque object, rather than a "normal" struct page.
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*
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* A more complete discussion of unaddressable memory may be found in
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* include/linux/hmm.h and Documentation/vm/hmm.rst.
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*
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* MEMORY_DEVICE_PUBLIC:
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* Device memory that is cache coherent from device and CPU point of view. This
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* is use on platform that have an advance system bus (like CAPI or CCIX). A
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* driver can hotplug the device memory using ZONE_DEVICE and with that memory
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* type. Any page of a process can be migrated to such memory. However no one
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* should be allow to pin such memory so that it can always be evicted.
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*
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* MEMORY_DEVICE_FS_DAX:
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* Host memory that has similar access semantics as System RAM i.e. DMA
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* coherent and supports page pinning. In support of coordinating page
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* pinning vs other operations MEMORY_DEVICE_FS_DAX arranges for a
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* wakeup event whenever a page is unpinned and becomes idle. This
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* wakeup is used to coordinate physical address space management (ex:
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* fs truncate/hole punch) vs pinned pages (ex: device dma).
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*/
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enum memory_type {
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MEMORY_DEVICE_PRIVATE = 1,
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MEMORY_DEVICE_PUBLIC,
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MEMORY_DEVICE_FS_DAX,
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};
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/*
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* For MEMORY_DEVICE_PRIVATE we use ZONE_DEVICE and extend it with two
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* callbacks:
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* page_fault()
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* page_free()
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*
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* Additional notes about MEMORY_DEVICE_PRIVATE may be found in
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* include/linux/hmm.h and Documentation/vm/hmm.rst. There is also a brief
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* explanation in include/linux/memory_hotplug.h.
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*
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* The page_fault() callback must migrate page back, from device memory to
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* system memory, so that the CPU can access it. This might fail for various
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* reasons (device issues, device have been unplugged, ...). When such error
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* conditions happen, the page_fault() callback must return VM_FAULT_SIGBUS and
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* set the CPU page table entry to "poisoned".
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*
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* Note that because memory cgroup charges are transferred to the device memory,
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* this should never fail due to memory restrictions. However, allocation
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* of a regular system page might still fail because we are out of memory. If
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* that happens, the page_fault() callback must return VM_FAULT_OOM.
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*
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* The page_fault() callback can also try to migrate back multiple pages in one
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* chunk, as an optimization. It must, however, prioritize the faulting address
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* over all the others.
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*
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*
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* The page_free() callback is called once the page refcount reaches 1
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* (ZONE_DEVICE pages never reach 0 refcount unless there is a refcount bug.
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* This allows the device driver to implement its own memory management.)
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*
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* For MEMORY_DEVICE_PUBLIC only the page_free() callback matter.
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*/
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typedef int (*dev_page_fault_t)(struct vm_area_struct *vma,
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unsigned long addr,
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const struct page *page,
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unsigned int flags,
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pmd_t *pmdp);
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typedef void (*dev_page_free_t)(struct page *page, void *data);
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/**
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* struct dev_pagemap - metadata for ZONE_DEVICE mappings
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* @page_fault: callback when CPU fault on an unaddressable device page
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* @page_free: free page callback when page refcount reaches 1
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* @altmap: pre-allocated/reserved memory for vmemmap allocations
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* @res: physical address range covered by @ref
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* @ref: reference count that pins the devm_memremap_pages() mapping
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* @dev: host device of the mapping for debug
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* @data: private data pointer for page_free()
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* @type: memory type: see MEMORY_* in memory_hotplug.h
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*/
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struct dev_pagemap {
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dev_page_fault_t page_fault;
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dev_page_free_t page_free;
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struct vmem_altmap altmap;
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bool altmap_valid;
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struct resource res;
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struct percpu_ref *ref;
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struct device *dev;
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void *data;
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enum memory_type type;
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};
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#ifdef CONFIG_ZONE_DEVICE
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void *devm_memremap_pages(struct device *dev, struct dev_pagemap *pgmap);
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struct dev_pagemap *get_dev_pagemap(unsigned long pfn,
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struct dev_pagemap *pgmap);
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unsigned long vmem_altmap_offset(struct vmem_altmap *altmap);
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void vmem_altmap_free(struct vmem_altmap *altmap, unsigned long nr_pfns);
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#else
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static inline void *devm_memremap_pages(struct device *dev,
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struct dev_pagemap *pgmap)
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{
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/*
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* Fail attempts to call devm_memremap_pages() without
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* ZONE_DEVICE support enabled, this requires callers to fall
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* back to plain devm_memremap() based on config
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*/
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WARN_ON_ONCE(1);
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return ERR_PTR(-ENXIO);
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}
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static inline struct dev_pagemap *get_dev_pagemap(unsigned long pfn,
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struct dev_pagemap *pgmap)
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{
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return NULL;
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}
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static inline unsigned long vmem_altmap_offset(struct vmem_altmap *altmap)
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{
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return 0;
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}
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static inline void vmem_altmap_free(struct vmem_altmap *altmap,
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unsigned long nr_pfns)
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{
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}
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#endif /* CONFIG_ZONE_DEVICE */
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static inline void put_dev_pagemap(struct dev_pagemap *pgmap)
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{
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if (pgmap)
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percpu_ref_put(pgmap->ref);
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}
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#endif /* _LINUX_MEMREMAP_H_ */
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