ext2, ext4, xfs: retrieve dax_device for iomap operations

In preparation for converting fs/dax.c to use dax_direct_access()
instead of bdev_direct_access(), add the plumbing to retrieve the
dax_device associated with a given block_device.

Signed-off-by: Dan Williams <dan.j.williams@intel.com>

1 files changed, 8 insertions, 1 deletions

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 4247d8d25687..2cb2634daa99 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -3305,6 +3305,7 @@ static int ext4_releasepage(struct page *page, gfp_t wait)
 static int ext4_iomap_begin(struct inode *inode, loff_t offset, loff_t length,
                             unsigned flags, struct iomap *iomap)
 {
+        struct block_device *bdev;
         unsigned int blkbits = inode->i_blkbits;
         unsigned long first_block = offset >> blkbits;
         unsigned long last_block = (offset + length - 1) >> blkbits;
@@ -3373,7 +3374,12 @@ retry:
         }
 
         iomap->flags = 0;
-        iomap->bdev = inode->i_sb->s_bdev;
+        bdev = inode->i_sb->s_bdev;
+        iomap->bdev = bdev;
+        if (blk_queue_dax(bdev->bd_queue))
+                iomap->dax_dev = dax_get_by_host(bdev->bd_disk->disk_name);
+        else
+                iomap->dax_dev = NULL;
         iomap->offset = first_block << blkbits;
 
         if (ret == 0) {
@@ -3406,6 +3412,7 @@ static int ext4_iomap_end(struct inode *inode, loff_t offset, loff_t length,
         int blkbits = inode->i_blkbits;
         bool truncate = false;
 
+        put_dax(iomap->dax_dev);
         if (!(flags & IOMAP_WRITE) || (flags & IOMAP_FAULT))
                 return 0;