Messages in this thread Patch in this message | | | Date | Thu, 3 Jul 2008 14:44:33 -0700 (PDT) | From | David Rientjes <> | Subject | Re: [bug ?] do_get_mempolicy() |
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On Thu, 3 Jul 2008, John Blackwood wrote:
> Hi Lee, > > I'm having unexpected results with get_mempolicy(2) in 2.6.26, and > I am hoping that you can either agree with me, or maybe comment on my > misconceptions. > > When I have a task with no special task mempolicy (the default mempolicy), > when I call get_mempolicy(2), it returns a policy value of 2 (MPOL_BIND) > with a NULL nodemask. > > I believe that this is because of the code in do_get_mempolicy() that does: > > *policy |= pol->flags; > > in the else case when flags do not contain MPOL_F_NODE. > > I guess I don't understand why we are ORing in the pol->flags into the > *policy value. For example, when this is for the default_policy, the > MPOL_F_LOCAL flag (which has a value of 2) gets stuffed into the *policy > location, and a get_mempolicy(2) caller sees this as the MPOL_BIND > mempolicy. > > Maybe the "*policy |= pol->flags;" line should be removed ? >
You're right, the flags member of struct mempolicy has subsequently changed to carry "internal" flags that are not supposed to be exposed to userspace via the get_mempolicy() API.
The following patch probably fixes it.
Lee?
Signed-off-by: David Rientjes <rientjes@google.com> --- mm/mempolicy.c | 2 +- 1 files changed, 1 insertions(+), 1 deletions(-)
diff --git a/mm/mempolicy.c b/mm/mempolicy.c --- a/mm/mempolicy.c +++ b/mm/mempolicy.c @@ -729,7 +729,7 @@ static long do_get_mempolicy(int *policy, nodemask_t *nmask, } else { *policy = pol == &default_policy ? MPOL_DEFAULT : pol->mode; - *policy |= pol->flags; + *policy |= (pol->flags & MPOL_MODE_FLAGS); } if (vma) {
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