device-dax: implement ->pagesize() for smaps to report MMUPageSize

Given that device-dax is making similar page mapping size guarantees as
hugetlbfs, emit the size in smaps and any other kernel path that
requests the mapping size of a vma.

Link: http://lkml.kernel.org/r/151996255287.27922.18397777516059080245.stgit@dwillia2-desk3.amr.corp.intel.com
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Reported-by: Jane Chu <jane.chu@oracle.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Paul Mackerras <paulus@samba.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 10 insertions, 0 deletions

diff --git a/drivers/dax/device.c b/drivers/dax/device.c
index 2137dbc29877..0b61f48f21a6 100644
--- a/drivers/dax/device.c
+++ b/drivers/dax/device.c
@@ -439,10 +439,20 @@ static int dev_dax_split(struct vm_area_struct *vma, unsigned long addr)
         return 0;
 }
 
+static unsigned long dev_dax_pagesize(struct vm_area_struct *vma)
+{
+        struct file *filp = vma->vm_file;
+        struct dev_dax *dev_dax = filp->private_data;
+        struct dax_region *dax_region = dev_dax->region;
+
+        return dax_region->align;
+}
+
 static const struct vm_operations_struct dax_vm_ops = {
         .fault = dev_dax_fault,
         .huge_fault = dev_dax_huge_fault,
         .split = dev_dax_split,
+        .pagesize = dev_dax_pagesize,
 };
 
 static int dax_mmap(struct file *filp, struct vm_area_struct *vma)