The patch titled
mlock: operate on any regions with protection != PROT_NONE
has been added to the -mm tree. Its filename is
mlock-operate-on-any-regions-with-protection-=-prot_none.patch
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------------------------------------------------------
Subject: mlock: operate on any regions with protection != PROT_NONE
From: Michel Lespinasse <walken@xxxxxxxxxx>
As Tao Ma noticed, 5ecfda0 ("mlock: avoid dirtying pages and triggering
writeback") 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.
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).
Signed-off-by: Michel Lespinasse <walken@xxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Reported-by: Tao Ma <tm@xxxxxx>
Cc: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx>
Acked-by: Rik van Riel <riel@xxxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/mlock.c | 7 +++++++
1 file changed, 7 insertions(+)
diff -puN mm/mlock.c~mlock-operate-on-any-regions-with-protection-=-prot_none mm/mlock.c
--- a/mm/mlock.c~mlock-operate-on-any-regions-with-protection-=-prot_none
+++ a/mm/mlock.c
@@ -178,6 +178,13 @@ static long __mlock_vma_pages_range(stru
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;
_
Patches currently in -mm which might be from walken@xxxxxxxxxx are
mlock-operate-on-any-regions-with-protection-=-prot_none.patch
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