From: Josef Bacik <josef@toxicpanda.com>
Date: Fri, 24 Jan 2020 09:32:27 -0500
Git-commit: af01d2e53f3343e9f22495e79f07b107374b05a1
Patch-mainline: 5.7-rc1
References: bsc#1176019
Subject: [PATCH] btrfs: hold a ref on fs roots while they're in the radix tree

If the root is sitting in the radix tree, we should probably have a ref
for the radix tree.  Grab a ref on the root when we insert it, and drop
it when it gets deleted.

Reviewed-by: Nikolay Borisov <nborisov@suse.com>
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 | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 67e7b0ccdea0..43af9f9b8583 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -1513,8 +1513,10 @@ int btrfs_insert_fs_root(struct btrfs_fs_info *fs_info,
 	ret = radix_tree_insert(&fs_info->fs_roots_radix,
 				(unsigned long)root->root_key.objectid,
 				root);
-	if (ret == 0)
+	if (ret == 0) {
+		btrfs_grab_fs_root(root);
 		set_bit(BTRFS_ROOT_IN_RADIX, &root->state);
+	}
 	spin_unlock(&fs_info->fs_roots_radix_lock);
 	radix_tree_preload_end();
 
@@ -3817,6 +3819,8 @@ void btrfs_drop_and_free_fs_root(struct btrfs_fs_info *fs_info,
 	spin_lock(&fs_info->fs_roots_radix_lock);
 	radix_tree_delete(&fs_info->fs_roots_radix,
 			  (unsigned long)root->root_key.objectid);
+	if (test_and_clear_bit(BTRFS_ROOT_IN_RADIX, &root->state))
+		btrfs_put_fs_root(root);
 	spin_unlock(&fs_info->fs_roots_radix_lock);
 
 	if (btrfs_root_refs(&root->root_item) == 0)
-- 
2.26.2