[Qemu-devel] [PATCH v10 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 <address@hidden>
---
 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 cde3b49b2a91..1cce626ff576 100644
--- a/drivers/md/dm-table.c
+++ b/drivers/md/dm-table.c
@@ -886,10 +886,17 @@ static int device_supports_dax(struct dm_target *ti, 
struct dm_dev *dev,
        return bdev_dax_supported(dev->bdev, PAGE_SIZE);
 }
 
+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);
+}
+
 static bool dm_table_supports_dax(struct dm_table *t)
 {
        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++) {
@@ -901,7 +908,14 @@ static bool dm_table_supports_dax(struct dm_table *t)
                if (!ti->type->iterate_devices ||
                    !ti->type->iterate_devices(ti, device_supports_dax, NULL))
                        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