[PATCH 3/3] ext4: call block_flush_device() on fsync

["Fernando Luis Vázquez Cao" <fernando@oss.ntt.co.jp>]

To ensure that bits are truly on-disk after an fsync or fdatasync, we
should force a disk flush explicitly when there is dirty data/metadata
and the journal didn't emit a write barrier (either because metadata is
not being synched or barriers are disabled).

Signed-off-by: Fernando Luis Vazquez Cao <fernando@oss.ntt.co.jp>
---

diff -urNp linux-2.6.29-rc5-orig/fs/ext4/fsync.c linux-2.6.29-rc5/fs/ext4/fsync.c
--- linux-2.6.29-rc5-orig/fs/ext4/fsync.c	2008-12-25 08:26:37.000000000 +0900
+++ linux-2.6.29-rc5/fs/ext4/fsync.c	2009-02-16 15:52:56.000000000 +0900
@@ -48,6 +48,7 @@ int ext4_sync_file(struct file *file, st
 {
 	struct inode *inode = dentry->d_inode;
 	journal_t *journal = EXT4_SB(inode->i_sb)->s_journal;
+	unsigned long i_state = inode->i_state;
 	int ret = 0;
 
 	J_ASSERT(ext4_journal_current_handle() == NULL);
@@ -76,25 +77,30 @@ int ext4_sync_file(struct file *file, st
 	 */
 	if (ext4_should_journal_data(inode)) {
 		ret = ext4_force_commit(inode->i_sb);
-		goto out;
+		if (!(journal->j_flags & JBD2_BARRIER))
+			block_flush_device(inode->i_sb);
+		return ret;
 	}
 
-	if (datasync && !(inode->i_state & I_DIRTY_DATASYNC))
-		goto out;
+	if (datasync && !(i_state & I_DIRTY_DATASYNC)) {
+		if (i_state & I_DIRTY_PAGES)
+			block_flush_device(inode->i_sb);
+		return ret;
+	}
 
 	/*
 	 * The VFS has written the file data.  If the inode is unaltered
 	 * then we need not start a commit.
 	 */
-	if (inode->i_state & (I_DIRTY_SYNC|I_DIRTY_DATASYNC)) {
+	if (i_state & (I_DIRTY_SYNC|I_DIRTY_DATASYNC)) {
 		struct writeback_control wbc = {
 			.sync_mode = WB_SYNC_ALL,
 			.nr_to_write = 0, /* sys_fsync did this */
 		};
 		ret = sync_inode(inode, &wbc);
-		if (journal && (journal->j_flags & JBD2_BARRIER))
-			blkdev_issue_flush(inode->i_sb->s_bdev, NULL);
+		if (journal && !(journal->j_flags & JBD2_BARRIER))
+			block_flush_device(inode->i_sb);
 	}
-out:
+
 	return ret;
 }