dm thin: clean up compiler warning

Clean up "warning: dubious: !x & y".  Also make it clear that
__snapshotted_since() returns a bool and that dm_thin_lookup_result's
'shared' member is a flag.
Signed-off-by: NMike Snitzer <snitzer@redhat.com>
Signed-off-by: NAlasdair G Kergon <agk@redhat.com>

drivers/md/dm-thin-metadata.c

@@ -1262,7 +1262,7 @@ dm_thin_id dm_thin_dev_id(struct dm_thin_device *td)
 	return td->id;
 }
 
-static int __snapshotted_since(struct dm_thin_device *td, uint32_t time)
+static bool __snapshotted_since(struct dm_thin_device *td, uint32_t time)
 {
 	return td->snapshotted_time > time;
 }

drivers/md/dm-thin-metadata.h

@@ -119,7 +119,7 @@ dm_thin_id dm_thin_dev_id(struct dm_thin_device *td);
 
 struct dm_thin_lookup_result {
 	dm_block_t block;
-	int shared;
+	unsigned shared:1;
 };
 
 /*

drivers/md/dm-thin.c

@@ -1218,7 +1218,7 @@ static void process_discard(struct thin_c *tc, struct bio *bio)
 			 */
 			m = get_next_mapping(pool);
 			m->tc = tc;
-			m->pass_discard = (!lookup_result.shared) & pool->pf.discard_passdown;
+			m->pass_discard = (!lookup_result.shared) && pool->pf.discard_passdown;
 			m->virt_block = block;
 			m->data_block = lookup_result.block;
 			m->cell = cell;