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/ext2/inode.c b/fs/ext2/inode.c
index 128cce540645..4c9d2d44e879 100644
--- a/fs/ext2/inode.c
+++ b/fs/ext2/inode.c
@@ -799,6 +799,7 @@ int ext2_get_block(struct inode *inode, sector_t iblock,
 static int ext2_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 max_blocks = (length + (1 << blkbits) - 1) >> blkbits;
@@ -812,8 +813,13 @@ static int ext2_iomap_begin(struct inode *inode, loff_t offset, loff_t length,
                 return ret;
 
         iomap->flags = 0;
-        iomap->bdev = inode->i_sb->s_bdev;
+        bdev = inode->i_sb->s_bdev;
+        iomap->bdev = bdev;
         iomap->offset = (u64)first_block << blkbits;
+        if (blk_queue_dax(bdev->bd_queue))
+                iomap->dax_dev = dax_get_by_host(bdev->bd_disk->disk_name);
+        else
+                iomap->dax_dev = NULL;
 
         if (ret == 0) {
                 iomap->type = IOMAP_HOLE;
@@ -835,6 +841,7 @@ static int
 ext2_iomap_end(struct inode *inode, loff_t offset, loff_t length,
                 ssize_t written, unsigned flags, struct iomap *iomap)
 {
+        put_dax(iomap->dax_dev);
         if (iomap->type == IOMAP_MAPPED &&
             written < length &&
             (flags & IOMAP_WRITE))