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, 13 insertions, 12 deletions

diff --git a/fs/ext4/ialloc.c b/fs/ext4/ialloc.c
index 6e60528..9dd21b7 100644
--- a/fs/ext4/ialloc.c
+++ b/fs/ext4/ialloc.c
@@ -253,12 +253,12 @@ void ext4_free_inode(handle_t *handle, struct inode *inode)
 				spin_unlock(sb_bgl_lock(sbi, flex_group));
 			}
 		}
-		BUFFER_TRACE(bh2, "call ext4_journal_dirty_metadata");
-		err = ext4_journal_dirty_metadata(handle, bh2);
+		BUFFER_TRACE(bh2, "call ext4_handle_dirty_metadata");
+		err = ext4_handle_dirty_metadata(handle, NULL, bh2);
 		if (!fatal) fatal = err;
 	}
-	BUFFER_TRACE(bitmap_bh, "call ext4_journal_dirty_metadata");
-	err = ext4_journal_dirty_metadata(handle, bitmap_bh);
+	BUFFER_TRACE(bitmap_bh, "call ext4_handle_dirty_metadata");
+	err = ext4_handle_dirty_metadata(handle, NULL, bitmap_bh);
 	if (!fatal)
 		fatal = err;
 	sb->s_dirt = 1;
@@ -656,15 +656,16 @@ repeat_in_this_group:
 						ino, bitmap_bh->b_data)) {
 				/* we won it */
 				BUFFER_TRACE(bitmap_bh,
-					"call ext4_journal_dirty_metadata");
-				err = ext4_journal_dirty_metadata(handle,
+					"call ext4_handle_dirty_metadata");
+				err = ext4_handle_dirty_metadata(handle,
+								inode,
 								bitmap_bh);
 				if (err)
 					goto fail;
 				goto got;
 			}
 			/* we lost it */
-			jbd2_journal_release_buffer(handle, bitmap_bh);
+			ext4_handle_release_buffer(handle, bitmap_bh);
 
 			if (++ino < EXT4_INODES_PER_GROUP(sb))
 				goto repeat_in_this_group;
@@ -726,7 +727,8 @@ got:
 		/* Don't need to dirty bitmap block if we didn't change it */
 		if (free) {
 			BUFFER_TRACE(block_bh, "dirty block bitmap");
-			err = ext4_journal_dirty_metadata(handle, block_bh);
+			err = ext4_handle_dirty_metadata(handle,
+							NULL, block_bh);
 		}
 
 		brelse(block_bh);
@@ -771,8 +773,8 @@ got:
 	}
 	gdp->bg_checksum = ext4_group_desc_csum(sbi, group, gdp);
 	spin_unlock(sb_bgl_lock(sbi, group));
-	BUFFER_TRACE(bh2, "call ext4_journal_dirty_metadata");
-	err = ext4_journal_dirty_metadata(handle, bh2);
+	BUFFER_TRACE(bh2, "call ext4_handle_dirty_metadata");
+	err = ext4_handle_dirty_metadata(handle, NULL, bh2);
 	if (err) goto fail;
 
 	percpu_counter_dec(&sbi->s_freeinodes_counter);
@@ -825,7 +827,7 @@ got:
 
 	ext4_set_inode_flags(inode);
 	if (IS_DIRSYNC(inode))
-		handle->h_sync = 1;
+		ext4_handle_sync(handle);
 	if (insert_inode_locked(inode) < 0) {
 		err = -EINVAL;
 		goto fail_drop;
@@ -1028,4 +1030,3 @@ unsigned long ext4_count_dirs(struct super_block * sb)
 	}
 	return count;
 }
-