34c0fd540e
For the purpose of communicating the optional presence of a 'struct page' for the pfn returned from ->direct_access(), introduce a type that encapsulates a page-frame-number plus flags. These flags contain the historical "page_link" encoding for a scatterlist entry, but can also denote "device memory". Where "device memory" is a set of pfns that are not part of the kernel's linear mapping by default, but are accessed via the same memory controller as ram. The motivation for this new type is large capacity persistent memory that needs struct page entries in the 'memmap' to support 3rd party DMA (i.e. O_DIRECT I/O with a persistent memory source/target). However, we also need it in support of maintaining a list of mapped inodes which need to be unmapped at driver teardown or freeze_bdev() time. Signed-off-by: Dan Williams <dan.j.williams@intel.com> Cc: Christoph Hellwig <hch@lst.de> Cc: Dave Hansen <dave@sr71.net> 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>
24 lines
637 B
C
24 lines
637 B
C
#ifndef _LINUX_PFN_H_
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#define _LINUX_PFN_H_
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#ifndef __ASSEMBLY__
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#include <linux/types.h>
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/*
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* pfn_t: encapsulates a page-frame number that is optionally backed
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* by memmap (struct page). Whether a pfn_t has a 'struct page'
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* backing is indicated by flags in the high bits of the value.
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*/
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typedef struct {
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unsigned long val;
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} pfn_t;
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#endif
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#define PFN_ALIGN(x) (((unsigned long)(x) + (PAGE_SIZE - 1)) & PAGE_MASK)
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#define PFN_UP(x) (((x) + PAGE_SIZE-1) >> PAGE_SHIFT)
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#define PFN_DOWN(x) ((x) >> PAGE_SHIFT)
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#define PFN_PHYS(x) ((phys_addr_t)(x) << PAGE_SHIFT)
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#define PHYS_PFN(x) ((unsigned long)((x) >> PAGE_SHIFT))
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#endif
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