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mm: add PHYS_PFN, use it in __phys_to_pfn()

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__phys_to_pfn and __pfn_to_phys are symmetric, PHYS_PFN and PFN_PHYS are
semmetric:

 - y = (phys_addr_t)x << PAGE_SHIFT

 - y >> PAGE_SHIFT = (phys_add_t)x

 - (unsigned long)(y >> PAGE_SHIFT) = x

[akpm@linux-foundation.org: use macro arg name `x']
[arnd@arndb.de: include linux/pfn.h for PHYS_PFN definition]
Signed-off-by: Chen Gang <gang.chen.5i5j@gmail.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Chen Gang 2016-01-14 15:18:33 -08:00 • committed by Linus Torvalds
parent 3aa2385111
commit 8f235d1a3e
2 changed files with 4 additions and 1 deletions
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1
include/linux/pfn.h
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@ -9,5 +9,6 @@
#define PFN_UP(x) (((x) + PAGE_SIZE-1) >> PAGE_SHIFT)
#define PFN_DOWN(x) ((x) >> PAGE_SHIFT)
#define PFN_PHYS(x) ((phys_addr_t)(x) << PAGE_SHIFT)
#define PHYS_PFN(x) ((unsigned long)((x) >> PAGE_SHIFT))
#endif