[PATCH 31/52] dax: Pass dax_dev to dax_writeback_mapping_range()

[Vivek Goyal <vgoyal@xxxxxxxxxx>]

Right now dax_writeback_mapping_range() is passed a bdev and dax_dev
is searched from that bdev name.

virtio-fs does not have a bdev. So pass in dax_dev also to
dax_writeback_mapping_range(). If dax_dev is passed in, bdev is not
used otherwise dax_dev is searched using bdev.

Signed-off-by: Vivek Goyal <vgoyal@xxxxxxxxxx>
---
 fs/dax.c            | 16 ++++++++++------
 fs/ext4/inode.c     |  2 +-
 fs/xfs/xfs_aops.c   |  2 +-
 include/linux/dax.h |  6 ++++--
 4 files changed, 16 insertions(+), 10 deletions(-)

diff --git a/fs/dax.c b/fs/dax.c
index 6431c3aba182..1ae3a60c17d4 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -911,12 +911,12 @@ static int dax_writeback_one(struct xa_state *xas, struct dax_device *dax_dev,
  * on persistent storage prior to completion of the operation.
  */
 int dax_writeback_mapping_range(struct address_space *mapping,
-		struct block_device *bdev, struct writeback_control *wbc)
+		struct block_device *bdev, struct dax_device *dax_dev,
+		struct writeback_control *wbc)
 {
 	XA_STATE(xas, &mapping->i_pages, wbc->range_start >> PAGE_SHIFT);
 	struct inode *inode = mapping->host;
 	pgoff_t end_index = wbc->range_end >> PAGE_SHIFT;
-	struct dax_device *dax_dev;
 	void *entry;
 	int ret = 0;
 	unsigned int scanned = 0;
@@ -927,9 +927,12 @@ int dax_writeback_mapping_range(struct address_space *mapping,
 	if (!mapping->nrexceptional || wbc->sync_mode != WB_SYNC_ALL)
 		return 0;
 
-	dax_dev = dax_get_by_host(bdev->bd_disk->disk_name);
-	if (!dax_dev)
-		return -EIO;
+	if (bdev) {
+		WARN_ON(dax_dev);
+		dax_dev = dax_get_by_host(bdev->bd_disk->disk_name);
+		if (!dax_dev)
+			return -EIO;
+	}
 
 	trace_dax_writeback_range(inode, xas.xa_index, end_index);
 
@@ -951,7 +954,8 @@ int dax_writeback_mapping_range(struct address_space *mapping,
 		xas_lock_irq(&xas);
 	}
 	xas_unlock_irq(&xas);
-	put_dax(dax_dev);
+	if (bdev)
+		put_dax(dax_dev);
 	trace_dax_writeback_range_done(inode, xas.xa_index, end_index);
 	return ret;
 }
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 22a9d8159720..3569c260a3bd 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -2978,7 +2978,7 @@ static int ext4_dax_writepages(struct address_space *mapping,
 	percpu_down_read(&sbi->s_journal_flag_rwsem);
 	trace_ext4_writepages(inode, wbc);
 
-	ret = dax_writeback_mapping_range(mapping, inode->i_sb->s_bdev, wbc);
+	ret = dax_writeback_mapping_range(mapping, inode->i_sb->s_bdev, NULL, wbc);
 	trace_ext4_writepages_result(inode, wbc, ret,
 				     nr_to_write - wbc->nr_to_write);
 	percpu_up_read(&sbi->s_journal_flag_rwsem);
diff --git a/fs/xfs/xfs_aops.c b/fs/xfs/xfs_aops.c
index 338b9d9984e0..b1947beec50a 100644
--- a/fs/xfs/xfs_aops.c
+++ b/fs/xfs/xfs_aops.c
@@ -951,7 +951,7 @@ xfs_dax_writepages(
 {
 	xfs_iflags_clear(XFS_I(mapping->host), XFS_ITRUNCATED);
 	return dax_writeback_mapping_range(mapping,
-			xfs_find_bdev_for_inode(mapping->host), wbc);
+			xfs_find_bdev_for_inode(mapping->host), NULL, wbc);
 }
 
 STATIC int
diff --git a/include/linux/dax.h b/include/linux/dax.h
index 450b28db9533..a8461841f148 100644
--- a/include/linux/dax.h
+++ b/include/linux/dax.h
@@ -85,7 +85,8 @@ static inline void fs_put_dax(struct dax_device *dax_dev)
 
 struct dax_device *fs_dax_get_by_bdev(struct block_device *bdev);
 int dax_writeback_mapping_range(struct address_space *mapping,
-		struct block_device *bdev, struct writeback_control *wbc);
+		struct block_device *bdev, struct dax_device *dax_dev,
+		struct writeback_control *wbc);
 
 struct page *dax_layout_busy_page(struct address_space *mapping);
 bool dax_lock_mapping_entry(struct page *page);
@@ -117,7 +118,8 @@ static inline struct page *dax_layout_busy_page(struct address_space *mapping)
 }
 
 static inline int dax_writeback_mapping_range(struct address_space *mapping,
-		struct block_device *bdev, struct writeback_control *wbc)
+		struct block_device *bdev, struct dax_device *dax_dev,
+		struct writeback_control *wbc)
 {
 	return -EOPNOTSUPP;
 }
-- 
2.13.6