[PATCH 1/6] genhd: Add GENHD_FL_DAX to gendisk flags

[Toshi Kani <toshi.kani@hpe.com>]

Currently, presence of direct_access() in block_device_operations
indicates support of DAX on its block device.  Because
block_device_operations is instantiated with 'const', this DAX
capablity may not be enabled conditinally.

In preparation for supporting DAX to device-mapper devices, add
GENHD_FL_DAX to gendisk flags to indicate that this block device
supports DAX.  This will allow to set the DAX capability based on
how mapped device is composed.

Signed-off-by: Toshi Kani <toshi.kani@hpe.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: <linux-s390@vger.kernel.org>
---
 drivers/block/brd.c          |    2 +-
 drivers/nvdimm/pmem.c        |    2 +-
 drivers/s390/block/dcssblk.c |    1 +
 include/linux/genhd.h        |    2 +-
 4 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/block/brd.c b/drivers/block/brd.c
index c04bd9b..43a6765 100644
--- a/drivers/block/brd.c
+++ b/drivers/block/brd.c
@@ -518,7 +518,7 @@ static struct brd_device *brd_alloc(int i)
 	disk->fops		= &brd_fops;
 	disk->private_data	= brd;
 	disk->queue		= brd->brd_queue;
-	disk->flags		= GENHD_FL_EXT_DEVT;
+	disk->flags		= GENHD_FL_EXT_DEVT | GENHD_FL_DAX;
 	sprintf(disk->disk_name, "ram%d", i);
 	set_capacity(disk, rd_size * 2);
 
diff --git a/drivers/nvdimm/pmem.c b/drivers/nvdimm/pmem.c
index 608fc44..3847449 100644
--- a/drivers/nvdimm/pmem.c
+++ b/drivers/nvdimm/pmem.c
@@ -295,7 +295,7 @@ static int pmem_attach_disk(struct device *dev,
 
 	disk->fops		= &pmem_fops;
 	disk->queue		= q;
-	disk->flags		= GENHD_FL_EXT_DEVT;
+	disk->flags		= GENHD_FL_EXT_DEVT | GENHD_FL_DAX;
 	nvdimm_namespace_disk_name(ndns, disk->disk_name);
 	disk->driverfs_dev = dev;
 	set_capacity(disk, (pmem->size - pmem->pfn_pad - pmem->data_offset)
diff --git a/drivers/s390/block/dcssblk.c b/drivers/s390/block/dcssblk.c
index bed53c4..60b1857 100644
--- a/drivers/s390/block/dcssblk.c
+++ b/drivers/s390/block/dcssblk.c
@@ -616,6 +616,7 @@ dcssblk_add_store(struct device *dev, struct device_attribute *attr, const char
 	dev_info->gd->queue = dev_info->dcssblk_queue;
 	dev_info->gd->private_data = dev_info;
 	dev_info->gd->driverfs_dev = &dev_info->dev;
+	dev_info->gd->flags = GENHD_FL_DAX;
 	blk_queue_make_request(dev_info->dcssblk_queue, dcssblk_make_request);
 	blk_queue_logical_block_size(dev_info->dcssblk_queue, 4096);
 
diff --git a/include/linux/genhd.h b/include/linux/genhd.h
index 359a8e4..9dc3a3d 100644
--- a/include/linux/genhd.h
+++ b/include/linux/genhd.h
@@ -131,7 +131,7 @@ struct hd_struct {
 };
 
 #define GENHD_FL_REMOVABLE			1
-/* 2 is unused */
+#define GENHD_FL_DAX				2
 #define GENHD_FL_MEDIA_CHANGE_NOTIFY		4
 #define GENHD_FL_CD				8
 #define GENHD_FL_UP				16