[PATCH] x86/pat: no need to check overlaps with more than one entry in chk_conflict

[PATCH] x86/pat: no need to check overlaps with more than one entry in chk_conflict

[Xiaotian Feng]

memtype list is built via reserve_memtype, for the overlapped areas, they're
all the same type, otherwise reserve_memtype will fail to insert it into the
list. So there's no need to check overlaps with more than one entry in the
chk_conflict code.

Signed-off-by: Xiaotian Feng <dfeng@redhat.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Suresh Siddha <suresh.b.siddha@intel.com>
Cc: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
---
 arch/x86/mm/pat.c |    7 -------
 1 files changed, 0 insertions(+), 7 deletions(-)

diff --git a/arch/x86/mm/pat.c b/arch/x86/mm/pat.c
index 81fb753..8178763 100644
--- a/arch/x86/mm/pat.c
+++ b/arch/x86/mm/pat.c
@@ -247,13 +247,6 @@ chk_conflict(struct memtype *new, struct memtype *entry, unsigned long *type)
 			goto conflict;
 	}
 
-	 /* check overlaps with more than one entry in the list */
-	list_for_each_entry_continue(entry, &memtype_list, nd) {
-		if (new->end <= entry->start)
-			break;
-		else if (new->type != entry->type)
-			goto conflict;
-	}
 	return 0;
 
  conflict:
-- 
1.6.2.5

RE: [PATCH] x86/pat: no need to check overlaps with more than one entry in chk_conflict

[Pallipadi, Venkatesh]

>-----Original Message-----
>From: linux-kernel-owner@vger.kernel.org 
>[mailto:linux-kernel-owner@vger.kernel.org] On Behalf Of Xiaotian Feng
>Sent: Tuesday, November 17, 2009 6:48 PM
>To: x86@kernel.org
>Cc: linux-kernel@vger.kernel.org; Xiaotian Feng; Ingo Molnar; 
>Siddha, Suresh B; Pallipadi, Venkatesh
>Subject: [PATCH] x86/pat: no need to check overlaps with more 
>than one entry in chk_conflict
>
>memtype list is built via reserve_memtype, for the overlapped 
>areas, they're
>all the same type, otherwise reserve_memtype will fail to 
>insert it into the
>list. So there's no need to check overlaps with more than one 
>entry in the
>chk_conflict code.

NAK.

The reason we have to check for more than one entry is for the cases
like this.

New entry:                   s-------------------e
Existing entries:         s----e     s-----e   s----e
(s=start, e=end)

Thanks,
Venki