Btrfs: Add a write ahead tree log to optimize synchronous operations

File syncs and directory syncs are optimized by copying their
items into a special (copy-on-write) log tree.  There is one log tree per
subvolume and the btrfs super block points to a tree of log tree roots.

After a crash, items are copied out of the log tree and back into the
subvolume.  See tree-log.c for all the details.

Signed-off-by: Chris Mason <chris.mason@oracle.com>

1 files changed, 8 insertions, 0 deletions

diff --git a/fs/btrfs/btrfs_inode.h b/fs/btrfs/btrfs_inode.h
index 111f90524ae..fcc8cf27e90 100644
--- a/fs/btrfs/btrfs_inode.h
+++ b/fs/btrfs/btrfs_inode.h
@@ -33,6 +33,7 @@ struct btrfs_inode {
 	struct extent_io_tree io_failure_tree;
 	struct mutex csum_mutex;
 	struct mutex extent_mutex;
+	struct mutex log_mutex;
 	struct inode vfs_inode;
 	struct btrfs_ordered_inode_tree ordered_tree;
 
@@ -44,10 +45,17 @@ struct btrfs_inode {
 
 	struct list_head delalloc_inodes;
 
+	/* full 64 bit generation number */
+	u64 generation;
+
 	/*
 	 * transid of the trans_handle that last modified this inode
 	 */
 	u64 last_trans;
+	/*
+	 * transid that last logged this inode
+	 */
+	u64 logged_trans;
 	u64 delalloc_bytes;
 	u64 disk_i_size;
 	u32 flags;