[PATCH 38/44] btrfs: hold a ref on the root in open_ctree

[Josef Bacik <josef@toxicpanda.com>]

We lookup the fs_root and put it in our fs_info directly, we should hold
a ref on this root for the lifetime of the fs_info.  Rework the free'ing
function so that it calls btrfs_put_fs_root() on the root at free time
with all of the other global trees.

Signed-off-by: Josef Bacik <josef@toxicpanda.com>
---
 fs/btrfs/ctree.h   | 17 -----------------
 fs/btrfs/disk-io.c | 26 ++++++++++++++++++++++++++
 fs/btrfs/disk-io.h |  1 +
 fs/btrfs/super.c   |  6 +++---
 4 files changed, 30 insertions(+), 20 deletions(-)

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index b2e8fd8a8e59..8578c65890b2 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -2648,23 +2648,6 @@ static inline int btrfs_need_cleaner_sleep(struct btrfs_fs_info *fs_info)
 	return fs_info->sb->s_flags & SB_RDONLY || btrfs_fs_closing(fs_info);
 }
 
-static inline void free_fs_info(struct btrfs_fs_info *fs_info)
-{
-	kfree(fs_info->balance_ctl);
-	kfree(fs_info->delayed_root);
-	kfree(fs_info->extent_root);
-	kfree(fs_info->tree_root);
-	kfree(fs_info->chunk_root);
-	kfree(fs_info->dev_root);
-	kfree(fs_info->csum_root);
-	kfree(fs_info->quota_root);
-	kfree(fs_info->uuid_root);
-	kfree(fs_info->free_space_root);
-	kfree(fs_info->super_copy);
-	kfree(fs_info->super_for_commit);
-	kvfree(fs_info);
-}
-
 /* tree mod log functions from ctree.c */
 u64 btrfs_get_tree_mod_seq(struct btrfs_fs_info *fs_info,
 			   struct seq_list *elem);
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index dfeeabfc341b..9435d4aa1668 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -1525,6 +1525,25 @@ int btrfs_insert_fs_root(struct btrfs_fs_info *fs_info,
 	return ret;
 }
 
+void btrfs_free_fs_info(struct btrfs_fs_info *fs_info)
+{
+	kfree(fs_info->balance_ctl);
+	kfree(fs_info->delayed_root);
+	kfree(fs_info->extent_root);
+	kfree(fs_info->tree_root);
+	kfree(fs_info->chunk_root);
+	kfree(fs_info->dev_root);
+	kfree(fs_info->csum_root);
+	kfree(fs_info->quota_root);
+	kfree(fs_info->uuid_root);
+	kfree(fs_info->free_space_root);
+	kfree(fs_info->super_copy);
+	kfree(fs_info->super_for_commit);
+	btrfs_put_fs_root(fs_info->fs_root);
+	kvfree(fs_info);
+}
+
+
 struct btrfs_root *btrfs_get_fs_root(struct btrfs_fs_info *fs_info,
 				     struct btrfs_key *location,
 				     bool check_ref)
@@ -3188,6 +3207,13 @@ int __cold open_ctree(struct super_block *sb,
 		goto fail_qgroup;
 	}
 
+	if (!btrfs_grab_fs_root(fs_info->fs_root)) {
+		fs_info->fs_root = NULL;
+		err = -ENOENT;
+		btrfs_warn(fs_info, "failed to grab a ref on the fs tree");
+		goto fail_qgroup;
+	}
+
 	if (sb_rdonly(sb))
 		return 0;
 
diff --git a/fs/btrfs/disk-io.h b/fs/btrfs/disk-io.h
index 1685dd2cf7ab..8fa0c8748db9 100644
--- a/fs/btrfs/disk-io.h
+++ b/fs/btrfs/disk-io.h
@@ -68,6 +68,7 @@ struct btrfs_root *btrfs_get_fs_root(struct btrfs_fs_info *fs_info,
 				     struct btrfs_key *key,
 				     bool check_ref);
 
+void btrfs_free_fs_info(struct btrfs_fs_info *fs_info);
 int btrfs_cleanup_fs_roots(struct btrfs_fs_info *fs_info);
 void btrfs_btree_balance_dirty(struct btrfs_fs_info *fs_info);
 void btrfs_btree_balance_dirty_nodelay(struct btrfs_fs_info *fs_info);
diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index 9c50bee71de9..cc411304e2c9 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -1559,7 +1559,7 @@ static struct dentry *btrfs_mount_root(struct file_system_type *fs_type,
 
 	if (s->s_root) {
 		btrfs_close_devices(fs_devices);
-		free_fs_info(fs_info);
+		btrfs_free_fs_info(fs_info);
 		if ((flags ^ s->s_flags) & SB_RDONLY)
 			error = -EBUSY;
 	} else {
@@ -1582,7 +1582,7 @@ static struct dentry *btrfs_mount_root(struct file_system_type *fs_type,
 error_close_devices:
 	btrfs_close_devices(fs_devices);
 error_fs_info:
-	free_fs_info(fs_info);
+	btrfs_free_fs_info(fs_info);
 error_sec_opts:
 	security_free_mnt_opts(&new_sec_opts);
 	return ERR_PTR(error);
@@ -2138,7 +2138,7 @@ static void btrfs_kill_super(struct super_block *sb)
 {
 	struct btrfs_fs_info *fs_info = btrfs_sb(sb);
 	kill_anon_super(sb);
-	free_fs_info(fs_info);
+	btrfs_free_fs_info(fs_info);
 }
 
 static struct file_system_type btrfs_fs_type = {
-- 
2.23.0