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authorDan Williams <dan.j.williams@intel.com>2016-01-16 03:56:14 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2016-01-16 04:56:32 +0300
commit34c0fd540e79fb49ef9ce864dae1058cca265780 (patch)
tree7f404f3a644322d0eca02b54daa228261ed24f39 /include/linux/pfn.h
parentba049e93aef7e8c571567088b1b73f4f5b99272a (diff)
downloadlinux-34c0fd540e79fb49ef9ce864dae1058cca265780.tar.xz
mm, dax, pmem: introduce pfn_t
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>
Diffstat (limited to 'include/linux/pfn.h')
-rw-r--r--include/linux/pfn.h9
1 files changed, 9 insertions, 0 deletions
diff --git a/include/linux/pfn.h b/include/linux/pfn.h
index 97f3e88aead4..2d8e49711b63 100644
--- a/include/linux/pfn.h
+++ b/include/linux/pfn.h
@@ -3,6 +3,15 @@
#ifndef __ASSEMBLY__
#include <linux/types.h>
+
+/*
+ * pfn_t: encapsulates a page-frame number that is optionally backed
+ * by memmap (struct page). Whether a pfn_t has a 'struct page'
+ * backing is indicated by flags in the high bits of the value.
+ */
+typedef struct {
+ unsigned long val;
+} pfn_t;
#endif
#define PFN_ALIGN(x) (((unsigned long)(x) + (PAGE_SIZE - 1)) & PAGE_MASK)