mm/hmm: merge hmm_range_snapshot into hmm_range_fault

Add a HMM_FAULT_SNAPSHOT flag so that hmm_range_snapshot can be merged
into the almost identical hmm_range_fault function.

Link: https://lore.kernel.org/r/20190726005650.2566-5-rcampbell@nvidia.com
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Ralph Campbell <rcampbell@nvidia.com>
Reviewed-by: Jason Gunthorpe <jgg@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
diff --git a/include/linux/hmm.h b/include/linux/hmm.h
index 89a1410..90dc594 100644
--- a/include/linux/hmm.h
+++ b/include/linux/hmm.h
@@ -413,7 +413,9 @@ void hmm_range_unregister(struct hmm_range *range);
  */
 #define HMM_FAULT_ALLOW_RETRY		(1 << 0)
 
-long hmm_range_snapshot(struct hmm_range *range);
+/* Don't fault in missing PTEs, just snapshot the current state. */
+#define HMM_FAULT_SNAPSHOT		(1 << 1)
+
 long hmm_range_fault(struct hmm_range *range, unsigned int flags);
 
 long hmm_range_dma_map(struct hmm_range *range,