ext4: call blkdev_issue_flush on fsync

[Fernando Luis Vázquez Cao]

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@xxxxxxxxxxxxx>
---

--- linux-2.6.29-rc1-orig/fs/ext4/fsync.c	2008-12-25 08:26:37.000000000 +0900
+++ linux-2.6.29-rc1/fs/ext4/fsync.c	2009-01-16 22:18:51.000000000 +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 +77,33 @@ int ext4_sync_file(struct file *file, st
 	 */
 	if (ext4_should_journal_data(inode)) {
 		ret = ext4_force_commit(inode->i_sb);
+		if (!(journal->j_flags & JBD2_BARRIER))
+			goto no_journal_barrier;
 		goto out;
 	}
 
-	if (datasync && !(inode->i_state & I_DIRTY_DATASYNC))
-		goto out;
+	if (datasync && !(i_state & I_DIRTY_DATASYNC))
+		goto flush_blkdev;
 
 	/*
 	 * 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))
+			goto no_journal_barrier;
 	}
+
+flush_blkdev:
+	if (!(i_state & I_DIRTY_PAGES))
+		goto out;
+no_journal_barrier:
+	blkdev_issue_flush(inode->i_sb->s_bdev, NULL);
 out:
 	return ret;
 }


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