From: Josef Bacik <josef@toxicpanda.com>
Date: Fri, 14 Feb 2020 16:11:44 -0500
Git-commit: dc9492c14c758639d7b2468d4ed3c77e785c1a35
Patch-mainline: 5.7-rc1
References: bsc#1176019
Subject: [PATCH] btrfs: hold a ref on the root on the dead roots list

At the point we add a root to the dead roots list we have no open inodes
for that root, so we need to hold a ref on that root to keep it from
disappearing.

Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
---
 fs/btrfs/disk-io.c     | 3 +--
 fs/btrfs/transaction.c | 5 ++++-
 2 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 5db76264b07f..831755a867ce 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -2035,8 +2035,7 @@ void btrfs_free_fs_roots(struct btrfs_fs_info *fs_info)
 
 		if (test_bit(BTRFS_ROOT_IN_RADIX, &gang[0]->state))
 			btrfs_drop_and_free_fs_root(fs_info, gang[0]);
-		else
-			btrfs_put_root(gang[0]);
+		btrfs_put_root(gang[0]);
 	}
 
 	while (1) {
diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c
index d2c667465fd4..8cede6eb9843 100644
--- a/fs/btrfs/transaction.c
+++ b/fs/btrfs/transaction.c
@@ -1264,8 +1264,10 @@ void btrfs_add_dead_root(struct btrfs_root *root)
 	struct btrfs_fs_info *fs_info = root->fs_info;
 
 	spin_lock(&fs_info->trans_lock);
-	if (list_empty(&root->root_list))
+	if (list_empty(&root->root_list)) {
+		btrfs_grab_root(root);
 		list_add_tail(&root->root_list, &fs_info->dead_roots);
+	}
 	spin_unlock(&fs_info->trans_lock);
 }
 
@@ -2435,6 +2437,7 @@ int btrfs_clean_one_deleted_snapshot(struct btrfs_root *root)
 	else
 		ret = btrfs_drop_snapshot(root, 1, 0);
 
+	btrfs_put_root(root);
 	return (ret < 0) ? 0 : 1;
 }
 
-- 
2.26.2