ext4: Allow ext4 to run without a journal

A few weeks ago I posted a patch for discussion that allowed ext4 to run
without a journal.  Since that time I've integrated the excellent
comments from Andreas and fixed several serious bugs.  We're currently
running with this patch and generating some performance numbers against
both ext2 (with backported reservations code) and ext4 with and without
a journal.  It just so happens that running without a journal is
slightly faster for most everything.

We did
	iozone -T -t 4 s 2g -r 256k -T -I -i0 -i1 -i2

which creates 4 threads, each of which create and do reads and writes on
a 2G file, with a buffer size of 256K, using O_DIRECT for all file opens
to bypass the page cache.  Results:

                     ext2        ext4, default   ext4, no journal
  initial writes   13.0 MB/s        15.4 MB/s          15.7 MB/s
  rewrites         13.1 MB/s        15.6 MB/s          15.9 MB/s
  reads            15.2 MB/s        16.9 MB/s          17.2 MB/s
  re-reads         15.3 MB/s        16.9 MB/s          17.2 MB/s
  random readers    5.6 MB/s         5.6 MB/s           5.7 MB/s
  random writers    5.1 MB/s         5.3 MB/s           5.4 MB/s 

So it seems that, so far, this was a useful exercise.

Signed-off-by: Frank Mayhar <fmayhar@google.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

1 files changed, 7 insertions, 5 deletions

diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index 0917be51f102..743e3feb3e50 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -97,6 +97,8 @@ static int ext4_ext_journal_restart(handle_t *handle, int needed)
 {
 	int err;
 
+	if (!ext4_handle_valid(handle))
+		return 0;
 	if (handle->h_buffer_credits > needed)
 		return 0;
 	err = ext4_journal_extend(handle, needed);
@@ -134,7 +136,7 @@ static int ext4_ext_dirty(handle_t *handle, struct inode *inode,
 	int err;
 	if (path->p_bh) {
 		/* path points to block */
-		err = ext4_journal_dirty_metadata(handle, path->p_bh);
+		err = ext4_handle_dirty_metadata(handle, inode, path->p_bh);
 	} else {
 		/* path points to leaf/index in inode body */
 		err = ext4_mark_inode_dirty(handle, inode);
@@ -780,7 +782,7 @@ static int ext4_ext_split(handle_t *handle, struct inode *inode,
 	set_buffer_uptodate(bh);
 	unlock_buffer(bh);
 
-	err = ext4_journal_dirty_metadata(handle, bh);
+	err = ext4_handle_dirty_metadata(handle, inode, bh);
 	if (err)
 		goto cleanup;
 	brelse(bh);
@@ -859,7 +861,7 @@ static int ext4_ext_split(handle_t *handle, struct inode *inode,
 		set_buffer_uptodate(bh);
 		unlock_buffer(bh);
 
-		err = ext4_journal_dirty_metadata(handle, bh);
+		err = ext4_handle_dirty_metadata(handle, inode, bh);
 		if (err)
 			goto cleanup;
 		brelse(bh);
@@ -955,7 +957,7 @@ static int ext4_ext_grow_indepth(handle_t *handle, struct inode *inode,
 	set_buffer_uptodate(bh);
 	unlock_buffer(bh);
 
-	err = ext4_journal_dirty_metadata(handle, bh);
+	err = ext4_handle_dirty_metadata(handle, inode, bh);
 	if (err)
 		goto out;
 
@@ -2947,7 +2949,7 @@ void ext4_ext_truncate(struct inode *inode)
 	 * transaction synchronous.
 	 */
 	if (IS_SYNC(inode))
-		handle->h_sync = 1;
+		ext4_handle_sync(handle);
 
 out_stop:
 	up_write(&EXT4_I(inode)->i_data_sem);