From: Michel Lespinasse <walken@google.com>
To: linux-mm@kvack.org, Andrew Morton <akpm@linux-foundation.org>,
Linus Torvalds <torvalds@linux-foundation.org>
Cc: Tao Ma <tm@tao.ma>,
KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>,
Rik van Riel <riel@redhat.com>, Hugh Dickins <hughd@google.com>
Subject: [PATCH] mlock: operate on any regions with protection != PROT_NONE
Date: Mon, 31 Jan 2011 17:03:41 -0800 [thread overview]
Message-ID: <20110201010341.GA21676@google.com> (raw)
As Tao Ma noticed, change 5ecfda0 breaks blktrace. This is because
blktrace mmaps a file with PROT_WRITE permissions but without PROT_READ,
so my attempt to not unnecessarity break COW during mlock ended up
causing mlock to fail with a permission problem.
I am proposing to let mlock ignore vma protection in all cases except
PROT_NONE. In particular, mlock should not fail for PROT_WRITE regions
(as in the blktrace case, which broke at 5ecfda0) or for PROT_EXEC
regions (which seem to me like they were always broken).
Please review. I am proposing this as a candidate for 2.6.38 inclusion,
because of the behavior change with blktrace.
diff --git a/mm/mlock.c b/mm/mlock.c
index 13e81ee..c3924c7f 100644
--- a/mm/mlock.c
+++ b/mm/mlock.c
@@ -178,6 +178,13 @@ static long __mlock_vma_pages_range(struct vm_area_struct *vma,
if ((vma->vm_flags & (VM_WRITE | VM_SHARED)) == VM_WRITE)
gup_flags |= FOLL_WRITE;
+ /*
+ * We want mlock to succeed for regions that have any permissions
+ * other than PROT_NONE.
+ */
+ if (vma->vm_flags & (VM_READ | VM_WRITE | VM_EXEC))
+ gup_flags |= FOLL_FORCE;
+
if (vma->vm_flags & VM_LOCKED)
gup_flags |= FOLL_MLOCK;
--
Michel "Walken" Lespinasse
A program is never fully debugged until the last user dies.
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next reply other threads:[~2011-02-01 1:03 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-02-01 1:03 Michel Lespinasse [this message]
2011-02-01 1:08 ` [PATCH] mlock: operate on any regions with protection != PROT_NONE Michel Lespinasse
2011-02-01 5:59 ` Linus Torvalds
2011-02-01 6:36 ` Michel Lespinasse
2011-02-01 17:57 ` Rik van Riel
2011-02-01 17:57 ` Rik van Riel
2011-02-03 0:57 ` KOSAKI Motohiro
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