[PATCH 11/12 v3] Btrfs: use the right generation number to read log_root_tree

[Liu Bo <liubo2009@cn.fujitsu.com>]

Currently we use the generation number of the super to read in the log
tree root after a crash.  This doesn't always match the sub trans id and
so it doesn't always match the transid stored in the btree blocks.

We can use log_root_transid to record the log_root_tree's generation
so that when we recover from crash, we can match log_root_tree's btree blocks.

Signed-off-by: Liu Bo <liubo2009@cn.fujitsu.com>
---
 fs/btrfs/disk-io.c  |    3 ++-
 fs/btrfs/tree-log.c |    2 ++
 2 files changed, 4 insertions(+), 1 deletions(-)

diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index d6d71f2..4568317 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -2002,6 +2002,7 @@ struct btrfs_root *open_ctree(struct super_block *sb,
 	if (btrfs_super_log_root(disk_super) != 0 &&
 	    !(fs_info->fs_state & BTRFS_SUPER_FLAG_ERROR)) {
 		u64 bytenr = btrfs_super_log_root(disk_super);
+		u64 log_root_transid = btrfs_super_log_root_transid(disk_super);
 
 		if (fs_devices->rw_devices == 0) {
 			printk(KERN_WARNING "Btrfs log replay required "
@@ -2024,7 +2025,7 @@ struct btrfs_root *open_ctree(struct super_block *sb,
 
 		log_tree_root->node = read_tree_block(tree_root, bytenr,
 						      blocksize,
-						      generation + 1);
+						      log_root_transid);
 		ret = btrfs_recover_log_trees(log_tree_root);
 		BUG_ON(ret);
 
diff --git a/fs/btrfs/tree-log.c b/fs/btrfs/tree-log.c
index 3cf7ed2..166fda5 100644
--- a/fs/btrfs/tree-log.c
+++ b/fs/btrfs/tree-log.c
@@ -2105,6 +2105,8 @@ int btrfs_sync_log(struct btrfs_trans_handle *trans,
 				log_root_tree->node->start);
 	btrfs_set_super_log_root_level(&root->fs_info->super_for_commit,
 				btrfs_header_level(log_root_tree->node));
+	btrfs_set_super_log_root_transid(&root->fs_info->super_for_commit,
+					 trans->transid);
 
 	log_root_tree->log_batch = 0;
 	log_root_tree->log_transid++;
-- 
1.6.5.2