4.4-stable review patch. If anyone has any objections, please let me know.
------------------ From: Dave Hansen <[email protected]> commit ace7fab7a6cdd363a615ec537f2aa94dbc761ee2 upstream A recent patch changed the format of a swap PTE. The comment explaining the format of the swap PTE is wrong about the bits used for the swap type field. Amusingly, the ASCII art and the patch description are correct, but the comment itself is wrong. As I was looking at this, I also noticed that the SWP_OFFSET_FIRST_BIT has an off-by-one error. This does not really hurt anything. It just wasted a bit of space in the PTE, giving us 2^59 bytes of addressable space in our swapfiles instead of 2^60. But, it doesn't match with the comments, and it wastes a bit of space, so fix it. Signed-off-by: Dave Hansen <[email protected]> Cc: Andrew Morton <[email protected]> Cc: Andy Lutomirski <[email protected]> Cc: Borislav Petkov <[email protected]> Cc: Brian Gerst <[email protected]> Cc: Dave Hansen <[email protected]> Cc: Denys Vlasenko <[email protected]> Cc: H. Peter Anvin <[email protected]> Cc: Josh Poimboeuf <[email protected]> Cc: Linus Torvalds <[email protected]> Cc: Luis R. Rodriguez <[email protected]> Cc: Peter Zijlstra <[email protected]> Cc: Thomas Gleixner <[email protected]> Cc: Toshi Kani <[email protected]> Fixes: 00839ee3b299 ("x86/mm: Move swap offset/type up in PTE to work around erratum") Link: http://lkml.kernel.org/r/[email protected] Signed-off-by: Ingo Molnar <[email protected]> Signed-off-by: Guenter Roeck <[email protected]> Signed-off-by: Greg Kroah-Hartman <[email protected]> --- arch/x86/include/asm/pgtable_64.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) --- a/arch/x86/include/asm/pgtable_64.h +++ b/arch/x86/include/asm/pgtable_64.h @@ -168,7 +168,7 @@ static inline int pgd_large(pgd_t pgd) { * * | ... | 11| 10| 9|8|7|6|5| 4| 3|2|1|0| <- bit number * | ... |SW3|SW2|SW1|G|L|D|A|CD|WT|U|W|P| <- bit names - * | OFFSET (14->63) | TYPE (10-13) |0|X|X|X| X| X|X|X|0| <- swp entry + * | OFFSET (14->63) | TYPE (9-13) |0|X|X|X| X| X|X|X|0| <- swp entry * * G (8) is aliased and used as a PROT_NONE indicator for * !present ptes. We need to start storing swap entries above @@ -179,7 +179,7 @@ static inline int pgd_large(pgd_t pgd) { #define SWP_TYPE_FIRST_BIT (_PAGE_BIT_PROTNONE + 1) #define SWP_TYPE_BITS 5 /* Place the offset above the type: */ -#define SWP_OFFSET_FIRST_BIT (SWP_TYPE_FIRST_BIT + SWP_TYPE_BITS + 1) +#define SWP_OFFSET_FIRST_BIT (SWP_TYPE_FIRST_BIT + SWP_TYPE_BITS) #define MAX_SWAPFILES_CHECK() BUILD_BUG_ON(MAX_SWAPFILES_SHIFT > SWP_TYPE_BITS)
