Btrfs: notreelog mount option

Add a 'notreelog' mount option to disable the tree log (used by fsync,
O_SYNC writes).  This is much slower, but the tree logging produces
inconsistent views into the FS for ceph.
Signed-off-by: Sage Weil <sage@newdream.net>
Signed-off-by: Chris Mason <chris.mason@oracle.com>

fs/btrfs/ctree.h

@@ -1036,6 +1036,7 @@ struct btrfs_root {
 #define BTRFS_MOUNT_SSD			(1 << 3)
 #define BTRFS_MOUNT_DEGRADED		(1 << 4)
 #define BTRFS_MOUNT_COMPRESS		(1 << 5)
+#define BTRFS_MOUNT_NOTREELOG           (1 << 6)
 
 #define btrfs_clear_opt(o, opt)		((o) &= ~BTRFS_MOUNT_##opt)
 #define btrfs_set_opt(o, opt)		((o) |= BTRFS_MOUNT_##opt)

fs/btrfs/super.c

@@ -67,7 +67,8 @@ static void btrfs_put_super(struct super_block *sb)
 enum {
 	Opt_degraded, Opt_subvol, Opt_device, Opt_nodatasum, Opt_nodatacow,
 	Opt_max_extent, Opt_max_inline, Opt_alloc_start, Opt_nobarrier,
-	Opt_ssd, Opt_thread_pool, Opt_noacl,  Opt_compress, Opt_err,
+	Opt_ssd, Opt_thread_pool, Opt_noacl,  Opt_compress, Opt_notreelog,
+	Opt_err,
 };
 
 static match_table_t tokens = {
@@ -84,6 +85,7 @@ static match_table_t tokens = {
 	{Opt_compress, "compress"},
 	{Opt_ssd, "ssd"},
 	{Opt_noacl, "noacl"},
+	{Opt_notreelog, "notreelog"},
 	{Opt_err, NULL},
 };
 
@@ -223,6 +225,10 @@ int btrfs_parse_options(struct btrfs_root *root, char *options)
 		case Opt_noacl:
 			root->fs_info->sb->s_flags &= ~MS_POSIXACL;
 			break;
+		case Opt_notreelog:
+			printk(KERN_INFO "btrfs: disabling tree log\n");
+			btrfs_set_opt(info->mount_opt, NOTREELOG);
+			break;
 		default:
 			break;
 		}
@@ -412,6 +418,8 @@ static int btrfs_show_options(struct seq_file *seq, struct vfsmount *vfs)
 		seq_puts(seq, ",compress");
 	if (btrfs_test_opt(root, SSD))
 		seq_puts(seq, ",ssd");
+	if (btrfs_test_opt(root, NOTREELOG))
+		seq_puts(seq, ",notreelog");
 	if (!(root->fs_info->sb->s_flags & MS_POSIXACL))
 		seq_puts(seq, ",noacl");
 	return 0;

fs/btrfs/tree-log.c

@@ -2898,6 +2898,11 @@ int btrfs_log_inode_parent(struct btrfs_trans_handle *trans,
 
 	sb = inode->i_sb;
 
+	if (btrfs_test_opt(root, NOTREELOG)) {
+		ret = 1;
+		goto end_no_trans;
+	}
+
 	if (root->fs_info->last_trans_log_full_commit >
 	    root->fs_info->last_trans_committed) {
 		ret = 1;