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, 16 insertions, 15 deletions

diff --git a/fs/ext4/resize.c b/fs/ext4/resize.c
index d448eb1..1665aa1 100644
--- a/fs/ext4/resize.c
+++ b/fs/ext4/resize.c
@@ -149,7 +149,7 @@ static int extend_or_restart_transaction(handle_t *handle, int thresh,
 {
 	int err;
 
-	if (handle->h_buffer_credits >= thresh)
+	if (ext4_handle_has_enough_credits(handle, thresh))
 		return 0;
 
 	err = ext4_journal_extend(handle, EXT4_MAX_TRANS_DATA);
@@ -232,7 +232,7 @@ static int setup_new_group_blocks(struct super_block *sb,
 		memcpy(gdb->b_data, sbi->s_group_desc[i]->b_data, gdb->b_size);
 		set_buffer_uptodate(gdb);
 		unlock_buffer(gdb);
-		ext4_journal_dirty_metadata(handle, gdb);
+		ext4_handle_dirty_metadata(handle, NULL, gdb);
 		ext4_set_bit(bit, bh->b_data);
 		brelse(gdb);
 	}
@@ -251,7 +251,7 @@ static int setup_new_group_blocks(struct super_block *sb,
 			err = PTR_ERR(bh);
 			goto exit_bh;
 		}
-		ext4_journal_dirty_metadata(handle, gdb);
+		ext4_handle_dirty_metadata(handle, NULL, gdb);
 		ext4_set_bit(bit, bh->b_data);
 		brelse(gdb);
 	}
@@ -276,7 +276,7 @@ static int setup_new_group_blocks(struct super_block *sb,
 			err = PTR_ERR(it);
 			goto exit_bh;
 		}
-		ext4_journal_dirty_metadata(handle, it);
+		ext4_handle_dirty_metadata(handle, NULL, it);
 		brelse(it);
 		ext4_set_bit(bit, bh->b_data);
 	}
@@ -286,7 +286,7 @@ static int setup_new_group_blocks(struct super_block *sb,
 
 	mark_bitmap_end(input->blocks_count, EXT4_BLOCKS_PER_GROUP(sb),
 			bh->b_data);
-	ext4_journal_dirty_metadata(handle, bh);
+	ext4_handle_dirty_metadata(handle, NULL, bh);
 	brelse(bh);
 
 	/* Mark unused entries in inode bitmap used */
@@ -299,7 +299,7 @@ static int setup_new_group_blocks(struct super_block *sb,
 
 	mark_bitmap_end(EXT4_INODES_PER_GROUP(sb), EXT4_BLOCKS_PER_GROUP(sb),
 			bh->b_data);
-	ext4_journal_dirty_metadata(handle, bh);
+	ext4_handle_dirty_metadata(handle, NULL, bh);
 exit_bh:
 	brelse(bh);
 
@@ -486,12 +486,12 @@ static int add_new_gdb(handle_t *handle, struct inode *inode,
 	 * reserved inode, and will become GDT blocks (primary and backup).
 	 */
 	data[gdb_num % EXT4_ADDR_PER_BLOCK(sb)] = 0;
-	ext4_journal_dirty_metadata(handle, dind);
+	ext4_handle_dirty_metadata(handle, NULL, dind);
 	brelse(dind);
 	inode->i_blocks -= (gdbackups + 1) * sb->s_blocksize >> 9;
 	ext4_mark_iloc_dirty(handle, inode, &iloc);
 	memset((*primary)->b_data, 0, sb->s_blocksize);
-	ext4_journal_dirty_metadata(handle, *primary);
+	ext4_handle_dirty_metadata(handle, NULL, *primary);
 
 	o_group_desc = EXT4_SB(sb)->s_group_desc;
 	memcpy(n_group_desc, o_group_desc,
@@ -502,7 +502,7 @@ static int add_new_gdb(handle_t *handle, struct inode *inode,
 	kfree(o_group_desc);
 
 	le16_add_cpu(&es->s_reserved_gdt_blocks, -1);
-	ext4_journal_dirty_metadata(handle, EXT4_SB(sb)->s_sbh);
+	ext4_handle_dirty_metadata(handle, NULL, EXT4_SB(sb)->s_sbh);
 
 	return 0;
 
@@ -618,7 +618,7 @@ static int reserve_backup_gdb(handle_t *handle, struct inode *inode,
 		       primary[i]->b_blocknr, gdbackups,
 		       blk + primary[i]->b_blocknr); */
 		data[gdbackups] = cpu_to_le32(blk + primary[i]->b_blocknr);
-		err2 = ext4_journal_dirty_metadata(handle, primary[i]);
+		err2 = ext4_handle_dirty_metadata(handle, NULL, primary[i]);
 		if (!err)
 			err = err2;
 	}
@@ -676,7 +676,8 @@ static void update_backups(struct super_block *sb,
 		struct buffer_head *bh;
 
 		/* Out of journal space, and can't get more - abort - so sad */
-		if (handle->h_buffer_credits == 0 &&
+		if (ext4_handle_valid(handle) &&
+		    handle->h_buffer_credits == 0 &&
 		    ext4_journal_extend(handle, EXT4_MAX_TRANS_DATA) &&
 		    (err = ext4_journal_restart(handle, EXT4_MAX_TRANS_DATA)))
 			break;
@@ -696,7 +697,7 @@ static void update_backups(struct super_block *sb,
 			memset(bh->b_data + size, 0, rest);
 		set_buffer_uptodate(bh);
 		unlock_buffer(bh);
-		ext4_journal_dirty_metadata(handle, bh);
+		ext4_handle_dirty_metadata(handle, NULL, bh);
 		brelse(bh);
 	}
 	if ((err2 = ext4_journal_stop(handle)) && !err)
@@ -916,7 +917,7 @@ int ext4_group_add(struct super_block *sb, struct ext4_new_group_data *input)
 	/* Update the global fs size fields */
 	sbi->s_groups_count++;
 
-	ext4_journal_dirty_metadata(handle, primary);
+	ext4_handle_dirty_metadata(handle, NULL, primary);
 
 	/* Update the reserved block counts only once the new group is
 	 * active. */
@@ -938,7 +939,7 @@ int ext4_group_add(struct super_block *sb, struct ext4_new_group_data *input)
 			EXT4_INODES_PER_GROUP(sb);
 	}
 
-	ext4_journal_dirty_metadata(handle, sbi->s_sbh);
+	ext4_handle_dirty_metadata(handle, NULL, sbi->s_sbh);
 	sb->s_dirt = 1;
 
 exit_journal:
@@ -1072,7 +1073,7 @@ int ext4_group_extend(struct super_block *sb, struct ext4_super_block *es,
 		goto exit_put;
 	}
 	ext4_blocks_count_set(es, o_blocks_count + add);
-	ext4_journal_dirty_metadata(handle, EXT4_SB(sb)->s_sbh);
+	ext4_handle_dirty_metadata(handle, NULL, EXT4_SB(sb)->s_sbh);
 	sb->s_dirt = 1;
 	unlock_super(sb);
 	ext4_debug("freeing blocks %llu through %llu\n", o_blocks_count,