| Message ID | 1489660329-22501-3-git-send-email-aneesh.kumar@linux.vnet.ibm.com (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
On Thu, Mar 16, 2017 at 04:02:00PM +0530, Aneesh Kumar K.V wrote: > For low slice max addr should be less that 4G ^^^^ than A more verbose explanation of the off-by-1 error that you are fixing is needed here. Tell us what goes wrong with the current code and why your fix is the correct one. > > Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com> For the code change: Reviewed-by: Paul Mackerras <paulus@ozlabs.org>
Paul Mackerras <paulus@ozlabs.org> writes: > On Thu, Mar 16, 2017 at 04:02:00PM +0530, Aneesh Kumar K.V wrote: >> For low slice max addr should be less that 4G > ^^^^ than > > A more verbose explanation of the off-by-1 error that you are fixing > is needed here. Tell us what goes wrong with the current code and why > your fix is the correct one. How about powerpc/mm/slice: when computing slice mask limit low slice max addr correctly For low slice, max addr should be less that 4G. Without limiting this correctly we will end up with a low slice mask which has 17th bit set. This is not a problem with the current code because our low slice mask is of type u16. But in later patch I am switching low slice mask to u64 type and having the 17bit set result in wrong slice mask which in turn results in mmap failures. > >> >> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com> > > For the code change: > > Reviewed-by: Paul Mackerras <paulus@ozlabs.org>
diff --git a/arch/powerpc/mm/slice.c b/arch/powerpc/mm/slice.c index 2b27458902ee..bf150557dba8 100644 --- a/arch/powerpc/mm/slice.c +++ b/arch/powerpc/mm/slice.c @@ -83,11 +83,10 @@ static struct slice_mask slice_range_to_mask(unsigned long start, struct slice_mask ret = { 0, 0 }; if (start < SLICE_LOW_TOP) { - unsigned long mend = min(end, SLICE_LOW_TOP); - unsigned long mstart = min(start, SLICE_LOW_TOP); + unsigned long mend = min(end, (SLICE_LOW_TOP - 1)); ret.low_slices = (1u << (GET_LOW_SLICE_INDEX(mend) + 1)) - - (1u << GET_LOW_SLICE_INDEX(mstart)); + - (1u << GET_LOW_SLICE_INDEX(start)); } if ((start + len) > SLICE_LOW_TOP)
For low slice max addr should be less that 4G Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com> --- arch/powerpc/mm/slice.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-)