mm: introduce find_dev_pagemap()
There are several scenarios where we need to retrieve and update metadata associated with a given devm_memremap_pages() mapping, and the only lookup key available is a pfn in the range: 1/ We want to augment vmemmap_populate() (called via arch_add_memory()) to allocate memmap storage from pre-allocated pages reserved by the device driver. At vmemmap_alloc_block_buf() time it grabs device pages rather than page allocator pages. This is in support of devm_memremap_pages() mappings where the memmap is too large to fit in main memory (i.e. large persistent memory devices). 2/ Taking a reference against the mapping when inserting device pages into the address_space radix of a given inode. This facilitates unmap_mapping_range() and truncate_inode_pages() operations when the driver is tearing down the mapping. 3/ get_user_pages() operations on ZONE_DEVICE memory require taking a reference against the mapping so that the driver teardown path can revoke and drain usage of device pages. Signed-off-by: Dan Williams <dan.j.williams@intel.com> Tested-by: Logan Gunthorpe <logang@deltatee.com> Cc: Christoph Hellwig <hch@lst.de> Cc: Dave Chinner <david@fromorbit.com> Cc: Ross Zwisler <ross.zwisler@linux.intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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include/linux/memremap.h
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