Btrfs: add flushoncommit mount option

The 'flushoncommit' mount option forces any data dirtied by a write in a
prior transaction to commit as part of the current commit.  This makes
the committed state a fully consistent view of the file system from the
application's perspective (i.e., it includes all completed file system
operations).  This was previously the behavior only when a snapshot is
created.

This is used by Ceph to ensure that completed writes make it to the
platter along with the metadata operations they are bound to (by
BTRFS_IOC_TRANS_{START,END}).

Signed-off-by: Sage Weil <sage@newdream.net>
Signed-off-by: Chris Mason <chris.mason@oracle.com>

1 files changed, 10 insertions, 4 deletions

diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index 3baa2c109e55..9744af9d71e9 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -68,7 +68,7 @@ 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_notreelog,
-	Opt_err,
+	Opt_flushoncommit, Opt_err,
 };
 
 static match_table_t tokens = {
@@ -86,6 +86,7 @@ static match_table_t tokens = {
 	{Opt_ssd, "ssd"},
 	{Opt_noacl, "noacl"},
 	{Opt_notreelog, "notreelog"},
+	{Opt_flushoncommit, "flushoncommit"},
 	{Opt_err, NULL},
 };
 
@@ -229,6 +230,10 @@ int btrfs_parse_options(struct btrfs_root *root, char *options)
 			printk(KERN_INFO "btrfs: disabling tree log\n");
 			btrfs_set_opt(info->mount_opt, NOTREELOG);
 			break;
+		case Opt_flushoncommit:
+			printk(KERN_INFO "btrfs: turning on flush-on-commit\n");
+			btrfs_set_opt(info->mount_opt, FLUSHONCOMMIT);
+			break;
 		default:
 			break;
 		}
@@ -370,9 +375,8 @@ fail_close:
 int btrfs_sync_fs(struct super_block *sb, int wait)
 {
 	struct btrfs_trans_handle *trans;
-	struct btrfs_root *root;
+	struct btrfs_root *root = btrfs_sb(sb);
 	int ret;
-	root = btrfs_sb(sb);
 
 	if (sb->s_flags & MS_RDONLY)
 		return 0;
@@ -419,7 +423,9 @@ static int btrfs_show_options(struct seq_file *seq, struct vfsmount *vfs)
 	if (btrfs_test_opt(root, SSD))
 		seq_puts(seq, ",ssd");
 	if (btrfs_test_opt(root, NOTREELOG))
-		seq_puts(seq, ",notreelog");
+		seq_puts(seq, ",no-treelog");
+	if (btrfs_test_opt(root, FLUSHONCOMMIT))
+		seq_puts(seq, ",flush-on-commit");
 	if (!(root->fs_info->sb->s_flags & MS_POSIXACL))
 		seq_puts(seq, ",noacl");
 	return 0;