From: Josef Bacik <josef@toxicpanda.com>
Date: Fri, 14 Feb 2020 16:11:43 -0500
Git-commit: 5c8fd99fec9d9265ed8fb732120a2ffd2bbab9b8
Patch-mainline: 5.7-rc1
References: bsc#1176019
Subject: [PATCH] btrfs: make inodes hold a ref on their roots

If we make sure all the inodes have refs on their root we don't have to
worry about the root disappearing while we have open inodes.

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 | 2 +-
 fs/btrfs/inode.c   | 8 +++++---
 2 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 242c072d69a7..5db76264b07f 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -2096,7 +2096,7 @@ static void btrfs_init_btree_inode(struct btrfs_fs_info *fs_info)
 
 	BTRFS_I(inode)->io_tree.ops = &btree_extent_io_ops;
 
-	BTRFS_I(inode)->root = fs_info->tree_root;
+	BTRFS_I(inode)->root = btrfs_grab_root(fs_info->tree_root);
 	memset(&BTRFS_I(inode)->location, 0, sizeof(struct btrfs_key));
 	set_bit(BTRFS_INODE_DUMMY, &BTRFS_I(inode)->runtime_flags);
 	btrfs_insert_inode_hash(inode);
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index d31543350799..683bb20c1d0f 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -5235,7 +5235,8 @@ static int btrfs_init_locked_inode(struct inode *inode, void *p)
 	inode->i_ino = args->location->objectid;
 	memcpy(&BTRFS_I(inode)->location, args->location,
 	       sizeof(*args->location));
-	BTRFS_I(inode)->root = args->root;
+	BTRFS_I(inode)->root = btrfs_grab_root(args->root);
+	BUG_ON(args->root && !BTRFS_I(inode)->root);
 	return 0;
 }
 
@@ -5316,7 +5317,7 @@ static struct inode *new_simple_dir(struct super_block *s,
 	if (!inode)
 		return ERR_PTR(-ENOMEM);
 
-	BTRFS_I(inode)->root = root;
+	BTRFS_I(inode)->root = btrfs_grab_root(root);
 	memcpy(&BTRFS_I(inode)->location, key, sizeof(*key));
 	set_bit(BTRFS_INODE_DUMMY, &BTRFS_I(inode)->runtime_flags);
 
@@ -5884,7 +5885,7 @@ static struct inode *btrfs_new_inode(struct btrfs_trans_handle *trans,
 	 */
 	BTRFS_I(inode)->index_cnt = 2;
 	BTRFS_I(inode)->dir_index = *index;
-	BTRFS_I(inode)->root = root;
+	BTRFS_I(inode)->root = btrfs_grab_root(root);
 	BTRFS_I(inode)->generation = trans->transid;
 	inode->i_generation = BTRFS_I(inode)->generation;
 
@@ -8926,6 +8927,7 @@ void btrfs_destroy_inode(struct inode *inode)
 	inode_tree_del(inode);
 	btrfs_drop_extent_cache(BTRFS_I(inode), 0, (u64)-1, 0);
 	btrfs_inode_clear_file_extent_range(BTRFS_I(inode), 0, (u64)-1);
+	btrfs_put_root(BTRFS_I(inode)->root);
 }
 
 int btrfs_drop_inode(struct inode *inode)
-- 
2.26.2