Btrfs: change how we track dirty roots

I've been overloading root->dirty_list to keep track of dirty roots and which
roots need to have their commit roots switched at transaction commit time.  This
could cause us to lose an update to the root which could corrupt the file
system.  To fix this use a state bit to know if the root is dirty, and if it
isn't set we go ahead and move the root to the dirty list.  This way if we
re-dirty the root after adding it to the switch_commit list we make sure to
update it.  This also makes it so that the extent root is always the last root
on the dirty list to try and keep the amount of churn down at this point in the
commit.  Thanks,

Signed-off-by: Josef Bacik <jbacik@fb.com>
Signed-off-by: Chris Mason <clm@fb.com>

diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c
index 14a72ed14ef7b1c2a5b78688c0b316d129b2bb72..97a98fc07cfcbc5fe960e2e903f5f05f8e3c1339 100644 (file)
--- a/fs/btrfs/ctree.c
+++ b/fs/btrfs/ctree.c
@@ -213,11 +213,19 @@ static struct extent_buffer *btrfs_read_lock_root_node(struct btrfs_root *root)
  */
 static void add_root_to_dirty_list(struct btrfs_root *root)
 {
+       if (test_bit(BTRFS_ROOT_DIRTY, &root->state) ||
+           !test_bit(BTRFS_ROOT_TRACK_DIRTY, &root->state))
+               return;
+
        spin_lock(&root->fs_info->trans_lock);
-       if (test_bit(BTRFS_ROOT_TRACK_DIRTY, &root->state) &&
-           list_empty(&root->dirty_list)) {
-               list_add(&root->dirty_list,
-                        &root->fs_info->dirty_cowonly_roots);
+       if (!test_and_set_bit(BTRFS_ROOT_DIRTY, &root->state)) {
+               /* Want the extent tree to be the last on the list */
+               if (root->objectid == BTRFS_EXTENT_TREE_OBJECTID)
+                       list_move_tail(&root->dirty_list,
+                                      &root->fs_info->dirty_cowonly_roots);
+               else
+                       list_move(&root->dirty_list,
+                                 &root->fs_info->dirty_cowonly_roots);
        }
        spin_unlock(&root->fs_info->trans_lock);
 }

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 7e607416755a880fef1a06d3a8a3482417c0b364..45ed4dc6a0cef90589d10222b6051f93dc3b2885 100644 (file)
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -1775,6 +1775,7 @@ struct btrfs_subvolume_writers {
 #define BTRFS_ROOT_DEFRAG_RUNNING      6
 #define BTRFS_ROOT_FORCE_COW           7
 #define BTRFS_ROOT_MULTI_LOG_TASKS     8
+#define BTRFS_ROOT_DIRTY               9
 
 /*
  * in ram representation of the tree.  extent_root is used for all allocations

diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c
index a605d4e2f2bca98e14c430c31514588c1b7982f1..aa2219ebecc9b94ab9c66055ced26609806c0e39 100644 (file)
--- a/fs/btrfs/transaction.c
+++ b/fs/btrfs/transaction.c
@@ -1020,6 +1020,7 @@ static int update_cowonly_root(struct btrfs_trans_handle *trans,
        u64 old_root_bytenr;
        u64 old_root_used;
        struct btrfs_root *tree_root = root->fs_info->tree_root;
+       bool extent_root = (root->objectid == BTRFS_EXTENT_TREE_OBJECTID);
 
        old_root_used = btrfs_root_used(&root->root_item);
        btrfs_write_dirty_block_groups(trans, root);
@@ -1038,7 +1039,12 @@ static int update_cowonly_root(struct btrfs_trans_handle *trans,
                        return ret;
 
                old_root_used = btrfs_root_used(&root->root_item);
-               ret = btrfs_write_dirty_block_groups(trans, root);
+               if (extent_root) {
+                       ret = btrfs_write_dirty_block_groups(trans, root);
+                       if (ret)
+                               return ret;
+               }
+               ret = btrfs_run_delayed_refs(trans, root, (unsigned long)-1);
                if (ret)
                        return ret;
        }
@@ -1097,6 +1103,7 @@ static noinline int commit_cowonly_roots(struct btrfs_trans_handle *trans,
                next = fs_info->dirty_cowonly_roots.next;
                list_del_init(next);
                root = list_entry(next, struct btrfs_root, dirty_list);
+               clear_bit(BTRFS_ROOT_DIRTY, &root->state);
 
                if (root != fs_info->extent_root)
                        list_add_tail(&root->dirty_list,