dax: Pass dax_dev instead of bdev to dax_writeback_mapping_range()

As of now dax_writeback_mapping_range() takes "struct block_device" as a
parameter and dax_dev is searched from bdev name. This also involves taking
a fresh reference on dax_dev and putting that reference at the end of
function.

We are developing a new filesystem virtio-fs and using dax to access host
page cache directly. But there is no block device. IOW, we want to make
use of dax but want to get rid of this assumption that there is always
a block device associated with dax_dev.

So pass in "struct dax_device" as parameter instead of bdev.

ext2/ext4/xfs are current users and they already have a reference on
dax_device. So there is no need to take reference and drop reference to
dax_device on each call of this function.

Suggested-by: Christoph Hellwig <hch@infradead.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Link: https://lore.kernel.org/r/20200103183307.GB13350@redhat.com
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

diff --git a/fs/dax.c b/fs/dax.c
index 1f1f020..1a64c19 100644 (file)
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -937,12 +937,11 @@ 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 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;
@@ -953,10 +952,6 @@ 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;
-
        trace_dax_writeback_range(inode, xas.xa_index, end_index);
 
        tag_pages_for_writeback(mapping, xas.xa_index, end_index);
@@ -977,7 +972,6 @@ int dax_writeback_mapping_range(struct address_space *mapping,
                xas_lock_irq(&xas);
        }
        xas_unlock_irq(&xas);
-       put_dax(dax_dev);
        trace_dax_writeback_range_done(inode, xas.xa_index, end_index);
        return ret;
 }

diff --git a/fs/ext2/inode.c b/fs/ext2/inode.c
index 119667e..c885cf7 100644 (file)
--- a/fs/ext2/inode.c
+++ b/fs/ext2/inode.c
@@ -960,8 +960,9 @@ ext2_writepages(struct address_space *mapping, struct writeback_control *wbc)
 static int
 ext2_dax_writepages(struct address_space *mapping, struct writeback_control *wbc)
 {
-       return dax_writeback_mapping_range(mapping,
-                       mapping->host->i_sb->s_bdev, wbc);
+       struct ext2_sb_info *sbi = EXT2_SB(mapping->host->i_sb);
+
+       return dax_writeback_mapping_range(mapping, sbi->s_daxdev, wbc);
 }
 
 const struct address_space_operations ext2_aops = {

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 28f28de..9992af7 100644 (file)
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -2866,7 +2866,7 @@ 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, sbi->s_daxdev, 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 3a688eb..58e937b 100644 (file)
--- a/fs/xfs/xfs_aops.c
+++ b/fs/xfs/xfs_aops.c
@@ -587,7 +587,7 @@ xfs_dax_writepages(
 
        xfs_iflags_clear(ip, XFS_ITRUNCATED);
        return dax_writeback_mapping_range(mapping,
-                       xfs_inode_buftarg(ip)->bt_bdev, wbc);
+                       xfs_inode_buftarg(ip)->bt_daxdev, wbc);
 }
 
 STATIC sector_t

diff --git a/include/linux/dax.h b/include/linux/dax.h
index 9bd8528..d5932e4 100644 (file)
--- a/include/linux/dax.h
+++ b/include/linux/dax.h
@@ -141,7 +141,7 @@ 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 dax_device *dax_dev, struct writeback_control *wbc);
 
 struct page *dax_layout_busy_page(struct address_space *mapping);
 dax_entry_t dax_lock_page(struct page *page);
@@ -180,7 +180,7 @@ 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 dax_device *dax_dev, struct writeback_control *wbc)
 {
        return -EOPNOTSUPP;
 }