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 111f90524ae1..fcc8cf27e906 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;