[PATCH v11 4/7] dm: enable synchronous dax

[Pankaj Gupta]

 This patch sets dax device 'DAXDEV_SYNC' flag if all the target
 devices of device mapper support synchrononous DAX. If device
 mapper consists of both synchronous and asynchronous dax devices,
 we don't set 'DAXDEV_SYNC' flag.

Signed-off-by: Pankaj Gupta <pagupta@xxxxxxxxxx>
---
 drivers/md/dm-table.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/drivers/md/dm-table.c b/drivers/md/dm-table.c
index 350cf0451456..c5160d846fe6 100644
--- a/drivers/md/dm-table.c
+++ b/drivers/md/dm-table.c
@@ -890,10 +890,17 @@ static int device_supports_dax(struct dm_target *ti, struct dm_dev *dev,
 			start, len);
 }
 
+static int device_synchronous(struct dm_target *ti, struct dm_dev *dev,
+				       sector_t start, sector_t len, void *data)
+{
+	return dax_synchronous(dev->dax_dev);
+}
+
 bool dm_table_supports_dax(struct dm_table *t, int blocksize)
 {
 	struct dm_target *ti;
 	unsigned i;
+	bool dax_sync = true;
 
 	/* Ensure that all targets support DAX. */
 	for (i = 0; i < dm_table_get_num_targets(t); i++) {
@@ -906,7 +913,14 @@ bool dm_table_supports_dax(struct dm_table *t, int blocksize)
 		    !ti->type->iterate_devices(ti, device_supports_dax,
 			    &blocksize))
 			return false;
+
+		/* Check devices support synchronous DAX */
+		if (dax_sync &&
+		    !ti->type->iterate_devices(ti, device_synchronous, NULL))
+			dax_sync = false;
 	}
+	if (dax_sync)
+		set_dax_synchronous(t->md->dax_dev);
 
 	return true;
 }
-- 
2.20.1