On Tue 10-05-16 10:23:57, Toshi Kani wrote:

blkdev_dax_capable() is similar to bdev_dax_supported(), but needs
to remain as a separate interface for checking dax capability of
a raw block device.

Rename and relocate blkdev_dax_capable() to keep them maintained
consistently, and call bdev_direct_access() for the dax capability
check.

...

+bool bdev_dax_capable(struct block_device *bdev)
+{
+	struct gendisk *disk = bdev->bd_disk;
+	struct blk_dax_ctl dax = {
+		.size = PAGE_SIZE,
+	};
+
+	if (!IS_ENABLED(CONFIG_FS_DAX))
+		return false;

Frankly, I prefer the #ifdef CONFIG_FS_DAX and just compile the code out
when DAX is not enabled (like it was with blkdev_dax_capable()). That way we
don't grow the kernel for people who don't care about DAX.

								Honza
-- 
Jan Kara [off-list ref]
SUSE Labs, CR