Commit fdf4c587 authored Jan 31, 2011 by Michel Lespinasse Committed by Linus Torvalds Feb 02, 2011

mlock: operate on any regions with protection != PROT_NONE



As Tao Ma noticed, change 5ecfda04 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 5ecfda04) or for PROT_EXEC
regions (which seem to me like they were always broken).

Signed-off-by: Michel Lespinasse <walken@google.com>
Acked-by: Rik van Riel <riel@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 69bc70d4

mm/mlock.c

+7 −0

Original line number	Diff line number	Diff line
		@@ -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;