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authorDave Hansen <dave.hansen@linux.intel.com>2016-08-10 10:23:25 -0700
committerIngo Molnar <mingo@kernel.org>2016-08-11 11:04:10 +0200
commitace7fab7a6cdd363a615ec537f2aa94dbc761ee2 (patch)
treea79d363c5a4f6c17a633fe0b02e31f5a2a44b032 /arch
parent62d16b5a3fca4d186e13215e0d7d2f6d36191796 (diff)
x86/mm: Fix swap entry comment and macro
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 <dave.hansen@linux.intel.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Andy Lutomirski <luto@kernel.org> Cc: Borislav Petkov <bp@alien8.de> Cc: Brian Gerst <brgerst@gmail.com> Cc: Dave Hansen <dave@sr71.net> Cc: Denys Vlasenko <dvlasenk@redhat.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Josh Poimboeuf <jpoimboe@redhat.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Luis R. Rodriguez <mcgrof@suse.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Toshi Kani <toshi.kani@hp.com> Fixes: 00839ee3b299 ("x86/mm: Move swap offset/type up in PTE to work around erratum") Link: http://lkml.kernel.org/r/20160810172325.E56AD7DA@viggo.jf.intel.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'arch')
-rw-r--r--arch/x86/include/asm/pgtable_64.h4
1 files changed, 2 insertions, 2 deletions
diff --git a/arch/x86/include/asm/pgtable_64.h b/arch/x86/include/asm/pgtable_64.h
index 7e8ec7ae10fa..1cc82ece9ac1 100644
--- a/arch/x86/include/asm/pgtable_64.h
+++ b/arch/x86/include/asm/pgtable_64.h
@@ -145,7 +145,7 @@ static inline int pgd_large(pgd_t pgd) { return 0; }
*
* | ... | 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
@@ -156,7 +156,7 @@ static inline int pgd_large(pgd_t pgd) { return 0; }
#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)