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.

There is no change in the behavior.

Link: https://lkml.org/lkml/2016/5/9/950
Signed-off-by: Toshi Kani <redacted>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Jens Axboe <axboe@fb.com>
Cc: Andreas Dilger <adilger.kernel@dilger.ca>
Cc: Jan Kara <jack@suse.cz>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Dan Williams <redacted>
Cc: Ross Zwisler <redacted>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Boaz Harrosh <redacted>
---
 block/ioctl.c          |   30 ------------------------------
 fs/block_dev.c         |   39 +++++++++++++++++++++++++++++++++++++--
 include/linux/blkdev.h |    1 +
 include/linux/fs.h     |    8 --------
 4 files changed, 38 insertions(+), 40 deletions(-)

diff --git a/block/ioctl.c b/block/ioctl.c
index 4ff1f92..7eeda07 100644
--- a/block/ioctl.c
+++ b/block/ioctl.c

@@ -4,7 +4,6 @@
 #include <linux/gfp.h>
 #include <linux/blkpg.h>
 #include <linux/hdreg.h>
-#include <linux/badblocks.h>
 #include <linux/backing-dev.h>
 #include <linux/fs.h>
 #include <linux/blktrace_api.h>

@@ -407,35 +406,6 @@ static inline int is_unrecognized_ioctl(int ret)
                ret == -ENOIOCTLCMD;
 }

-#ifdef CONFIG_FS_DAX
-bool blkdev_dax_capable(struct block_device *bdev)
-{
-       struct gendisk *disk = bdev->bd_disk;
-
-       if (!disk->fops->direct_access)
-               return false;
-
-       /*
-        * If the partition is not aligned on a page boundary, we can't
-        * do dax I/O to it.
-        */
-       if ((bdev->bd_part->start_sect % (PAGE_SIZE / 512))
-                       || (bdev->bd_part->nr_sects % (PAGE_SIZE / 512)))
-               return false;
-
-       /*
-        * If the device has known bad blocks, force all I/O through the
-        * driver / page cache.
-        *
-        * TODO: support finer grained dax error handling
-        */
-       if (disk->bb && disk->bb->count)
-               return false;
-
-       return true;
-}
-#endif
-
 static int blkdev_flushbuf(struct block_device *bdev, fmode_t mode,
                unsigned cmd, unsigned long arg)
 {

diff --git a/fs/block_dev.c b/fs/block_dev.c
index db55638..5d79093 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c

@@ -29,6 +29,7 @@
 #include <linux/log2.h>
 #include <linux/cleancache.h>
 #include <linux/dax.h>
+#include <linux/badblocks.h>
 #include <asm/uaccess.h>
 #include "internal.h"

@@ -554,6 +555,40 @@ int bdev_dax_supported(struct super_block *sb, int blocksize)
 }
 EXPORT_SYMBOL_GPL(bdev_dax_supported);

+/**
+ * bdev_dax_capable() - Return if the raw device is capable for dax
+ * @bdev: The device for raw block device access
+ */
+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;
+
+       dax.sector = 0;
+       if (bdev_direct_access(bdev, &dax) < 0)
+               return false;
+
+       dax.sector = bdev->bd_part->nr_sects - (PAGE_SIZE / 512);
+       if (bdev_direct_access(bdev, &dax) < 0)
+               return false;