Btrfs: Find and remove dead roots the first time a root is loaded.

Dead roots are trees left over after a crash, and they were either in the
process of being removed or were waiting to be removed when the box crashed.
Before, a search of the entire tree of root pointers was done on mount
looking for dead roots.  Now, the search is done the first time we load
a root.

This makes mount faster when there are a large number of snapshots, and it
enables the block accounting code to properly update the block counts on
the latest root as old versions of the root are reaped after a crash.

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

1 files changed, 2 insertions, 1 deletions

diff --git a/fs/btrfs/transaction.h b/fs/btrfs/transaction.h
index e451783a1a4d..4bc328cbb24c 100644
--- a/fs/btrfs/transaction.h
+++ b/fs/btrfs/transaction.h
@@ -78,7 +78,8 @@ void btrfs_transaction_flush_work(struct btrfs_root *root);
 void btrfs_transaction_queue_work(struct btrfs_root *root, int delay);
 void btrfs_init_transaction_sys(void);
 void btrfs_exit_transaction_sys(void);
-int btrfs_add_dead_root(struct btrfs_root *root, struct list_head *dead_list);
+int btrfs_add_dead_root(struct btrfs_root *root, struct btrfs_root *latest,
+                        struct list_head *dead_list);
 int btrfs_defrag_dirty_roots(struct btrfs_fs_info *info);
 int btrfs_defrag_root(struct btrfs_root *root, int cacheonly);
 int btrfs_clean_old_snapshots(struct btrfs_root *root);