linux-kernel - [PATCH 2/2] mm: thp: kill the bogus ->def_flags check in hugepage

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Date:	Wed, 22 Jan 2014 18:46:46 +0100
From:	Oleg Nesterov <oleg@...hat.com>
To:	Alex Thorlton <athorlton@....com>,
	Andrew Morton <akpm@...ux-foundation.org>
Cc:	"Kirill A. Shutemov" <kirill@...temov.name>,
	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Rik van Riel <riel@...hat.com>,
	Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Andy Lutomirski <luto@...capital.net>,
	Al Viro <viro@...iv.linux.org.uk>,
	Kees Cook <keescook@...omium.org>,
	Andrea Arcangeli <aarcange@...hat.com>
Subject: [PATCH 2/2] mm: thp: kill the bogus ->def_flags check in
	hugepage_madvise()

hugepage_madvise() checks "mm->def_flags & VM_NOHUGEPAGE" but
this can be never true, currently mm->def_flags can only have
VM_LOCKED.

And otoh we might want to add VM_NOHUGEPAGE into ->def_flags
but override it in vma->vm_flags via madvise(MADV_HUGEPAGE).

Signed-off-by: Oleg Nesterov <oleg@...hat.com>
---
 mm/huge_memory.c |    2 --
 1 files changed, 0 insertions(+), 2 deletions(-)

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index bccd5a6..e8b656c 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1941,8 +1941,6 @@ int hugepage_madvise(struct vm_area_struct *vma,
 		 */
 		if (*vm_flags & (VM_HUGEPAGE | VM_NO_THP))
 			return -EINVAL;
-		if (mm->def_flags & VM_NOHUGEPAGE)
-			return -EINVAL;
 		*vm_flags &= ~VM_NOHUGEPAGE;
 		*vm_flags |= VM_HUGEPAGE;
 		/*
-- 
1.5.5.1


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