BFS could fail to properly write out inode on fsync(2) due to races with
WB_SYNC_NONE writeback. Several racing fsyncs could also result in some
fsync returning earlier than all metadata buffers were properly
persisted.

Fix all these issues by using new .sync_inode_metadata method which
makes sure all inode related metadata is written to disk during any
WB_SYNC_ALL writeback.

Signed-off-by: Jan Kara <jack@suse.cz>
---
 fs/bfs/dir.c   |  9 +--------
 fs/bfs/inode.c | 30 ++++++++++++++++++++++++------
 2 files changed, 25 insertions(+), 14 deletions(-)

diff --git a/fs/bfs/dir.c b/fs/bfs/dir.c
index 5b40ab09a796..9b37ec4bd89a 100644
--- a/fs/bfs/dir.c
+++ b/fs/bfs/dir.c
@@ -68,17 +68,10 @@ static int bfs_readdir(struct file *f, struct dir_context *ctx)
 	return 0;
 }
 
-static int bfs_fsync(struct file *file, loff_t start, loff_t end, int datasync)
-{
-	return mmb_fsync(file,
-			&BFS_I(file->f_mapping->host)->i_metadata_bhs,
-			start, end, datasync);
-}
-
 const struct file_operations bfs_dir_operations = {
 	.read		= generic_read_dir,
 	.iterate_shared	= bfs_readdir,
-	.fsync		= bfs_fsync,
+	.fsync		= simple_fsync,
 	.llseek		= generic_file_llseek,
 };
 
diff --git a/fs/bfs/inode.c b/fs/bfs/inode.c
index e41efdd35db9..cacc7eff9c33 100644
--- a/fs/bfs/inode.c
+++ b/fs/bfs/inode.c
@@ -136,7 +136,6 @@ static int bfs_write_inode(struct inode *inode, struct writeback_control *wbc)
 	unsigned long i_sblock;
 	struct bfs_inode *di;
 	struct buffer_head *bh;
-	int err = 0;
 
 	dprintf("ino=%08x\n", ino);
 
@@ -165,13 +164,31 @@ static int bfs_write_inode(struct inode *inode, struct writeback_control *wbc)
 	di->i_eoffset = cpu_to_le32(i_sblock * BFS_BSIZE + inode->i_size - 1);
 
 	mark_buffer_dirty(bh);
-	if (wbc->sync_mode == WB_SYNC_ALL) {
-		sync_dirty_buffer(bh);
-		if (buffer_req(bh) && !buffer_uptodate(bh))
-			err = -EIO;
-	}
 	brelse(bh);
 	mutex_unlock(&info->bfs_lock);
+	set_inode_metadata_writeback(inode);
+	return 0;
+}
+
+static int bfs_sync_inode_metadata(struct inode *inode,
+				   struct writeback_control *wbc)
+{
+	int err = 0;
+	struct bfs_inode *di;
+	struct buffer_head *bh;
+
+	di = find_inode(inode->i_sb, (u16)inode->ino, &bh);
+	if (IS_ERR(di))
+		return PTR_ERR(di);
+
+	sync_dirty_buffer(bh);
+	if (buffer_write_io_error(bh)) {
+		err = -EIO;
+		goto out;
+	}
+	err = mmb_sync(&BFS_I(inode)->i_metadata_bhs);
+out:
+	brelse(bh);
 	return err;
 }
 
@@ -302,6 +319,7 @@ static const struct super_operations bfs_sops = {
 	.alloc_inode	= bfs_alloc_inode,
 	.free_inode	= bfs_free_inode,
 	.write_inode	= bfs_write_inode,
+	.sync_inode_metadata = bfs_sync_inode_metadata,
 	.evict_inode	= bfs_evict_inode,
 	.put_super	= bfs_put_super,
 	.statfs		= bfs_statfs,
-- 
2.51.0