dax: move writeback calls into the filesystems

Previously calls to dax_writeback_mapping_range() for all DAX filesystems
(ext2, ext4 & xfs) were centralized in filemap_write_and_wait_range().

dax_writeback_mapping_range() needs a struct block_device, and it used
to get that from inode->i_sb->s_bdev.  This is correct for normal inodes
mounted on ext2, ext4 and XFS filesystems, but is incorrect for DAX raw
block devices and for XFS real-time files.

Instead, call dax_writeback_mapping_range() directly from the filesystem
->writepages function so that it can supply us with a valid block
device.  This also fixes DAX code to properly flush caches in response
to sync(2).

Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Cc: Al Viro <viro@ftp.linux.org.uk>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Jens Axboe <axboe@fb.com>
Cc: Matthew Wilcox <matthew.r.wilcox@intel.com>
Cc: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 12 insertions, 1 deletions

diff --git a/fs/block_dev.c b/fs/block_dev.c
index 31c6d1090f11..826b164a4b5b 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -1697,13 +1697,24 @@ static int blkdev_releasepage(struct page *page, gfp_t wait)
         return try_to_free_buffers(page);
 }
 
+static int blkdev_writepages(struct address_space *mapping,
+                             struct writeback_control *wbc)
+{
+        if (dax_mapping(mapping)) {
+                struct block_device *bdev = I_BDEV(mapping->host);
+
+                return dax_writeback_mapping_range(mapping, bdev, wbc);
+        }
+        return generic_writepages(mapping, wbc);
+}
+
 static const struct address_space_operations def_blk_aops = {
         .readpage       = blkdev_readpage,
         .readpages      = blkdev_readpages,
         .writepage      = blkdev_writepage,
         .write_begin    = blkdev_write_begin,
         .write_end      = blkdev_write_end,
-        .writepages     = generic_writepages,
+        .writepages     = blkdev_writepages,
         .releasepage    = blkdev_releasepage,
         .direct_IO      = blkdev_direct_IO,
         .is_dirty_writeback = buffer_check_dirty_writeback,