fs: add sync_inode_metadata

Add a new helper to write out the inode using the writeback code,
that is including the correct dirty bit and list manipulation.  A few
of filesystems already opencode this, and a lot of others should be
using it instead of using write_inode_now which also writes out the
data.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 20 insertions, 0 deletions

diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index ab38fef1c9a1..29e3f409bbd0 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -1198,3 +1198,23 @@ int sync_inode(struct inode *inode, struct writeback_control *wbc)
         return ret;
 }
 EXPORT_SYMBOL(sync_inode);
+
+/**
+ * sync_inode - write an inode to disk
+ * @inode: the inode to sync
+ * @wait: wait for I/O to complete.
+ *
+ * Write an inode to disk and adjust it's dirty state after completion.
+ *
+ * Note: only writes the actual inode, no associated data or other metadata.
+ */
+int sync_inode_metadata(struct inode *inode, int wait)
+{
+        struct writeback_control wbc = {
+                .sync_mode = wait ? WB_SYNC_ALL : WB_SYNC_NONE,
+                .nr_to_write = 0, /* metadata-only */
+        };
+
+        return sync_inode(inode, &wbc);
+}
+EXPORT_SYMBOL(sync_inode_metadata);