btrfs: replace many BUG_ONs with proper error handling

 btrfs currently handles most errors with BUG_ON. This patch is a work-in-
 progress but aims to handle most errors other than internal logic
 errors and ENOMEM more gracefully.

 This iteration prevents most crashes but can run into lockups with
 the page lock on occasion when the timing "works out."

Signed-off-by: Jeff Mahoney <jeffm@suse.com>

1 files changed, 23 insertions, 13 deletions

diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c
index 5a4999aa8fe..63f835aa978 100644
--- a/fs/btrfs/transaction.c
+++ b/fs/btrfs/transaction.c
@@ -949,18 +949,19 @@ static noinline int create_pending_snapshot(struct btrfs_trans_handle *trans,
 				dentry->d_name.name, dentry->d_name.len,
 				parent_inode, &key,
 				BTRFS_FT_DIR, index);
-	if (ret) {
+	if (ret == -EEXIST) {
 		pending->error = -EEXIST;
 		dput(parent);
 		goto fail;
-	} else if (ret)
-		goto abort_trans;
+	} else if (ret) {
+		goto abort_trans_dput;
+	}
 
 	btrfs_i_size_write(parent_inode, parent_inode->i_size +
 					 dentry->d_name.len * 2);
 	ret = btrfs_update_inode(trans, parent_root, parent_inode);
 	if (ret)
-		goto abort_trans;
+		goto abort_trans_dput;
 
 	/*
 	 * pull in the delayed directory update
@@ -969,8 +970,10 @@ static noinline int create_pending_snapshot(struct btrfs_trans_handle *trans,
 	 * snapshot
 	 */
 	ret = btrfs_run_delayed_items(trans, root);
-	if (ret) /* Transaction aborted */
+	if (ret) { /* Transaction aborted */
+		dput(parent);
 		goto fail;
+	}
 
 	record_root_in_trans(trans, root);
 	btrfs_set_root_last_snapshot(&root->root_item, trans->transid);
@@ -986,17 +989,20 @@ static noinline int create_pending_snapshot(struct btrfs_trans_handle *trans,
 
 	old = btrfs_lock_root_node(root);
 	ret = btrfs_cow_block(trans, root, old, NULL, 0, &old);
-	if (ret)
-		goto abort_trans;
+	if (ret) {
+		btrfs_tree_unlock(old);
+		free_extent_buffer(old);
+		goto abort_trans_dput;
+	}
 
 	btrfs_set_lock_blocking(old);
 
 	ret = btrfs_copy_root(trans, root, old, &tmp, objectid);
-	if (ret)
-		goto abort_trans;
-
+	/* clean up in any case */
 	btrfs_tree_unlock(old);
 	free_extent_buffer(old);
+	if (ret)
+		goto abort_trans_dput;
 
 	/* see comments in should_cow_block() */
 	root->force_cow = 1;
@@ -1009,7 +1015,7 @@ static noinline int create_pending_snapshot(struct btrfs_trans_handle *trans,
 	btrfs_tree_unlock(tmp);
 	free_extent_buffer(tmp);
 	if (ret)
-		goto abort_trans;
+		goto abort_trans_dput;
 
 	/*
 	 * insert root back/forward references
@@ -1018,14 +1024,16 @@ static noinline int create_pending_snapshot(struct btrfs_trans_handle *trans,
 				 parent_root->root_key.objectid,
 				 btrfs_ino(parent_inode), index,
 				 dentry->d_name.name, dentry->d_name.len);
+	dput(parent);
 	if (ret)
 		goto fail;
-	dput(parent);
 
 	key.offset = (u64)-1;
 	pending->snap = btrfs_read_fs_root_no_name(root->fs_info, &key);
-	if (IS_ERR(pending->snap))
+	if (IS_ERR(pending->snap)) {
+		ret = PTR_ERR(pending->snap);
 		goto abort_trans;
+	}
 
 	ret = btrfs_reloc_post_snapshot(trans, pending);
 	if (ret)
@@ -1037,6 +1045,8 @@ fail:
 	btrfs_block_rsv_release(root, &pending->block_rsv, (u64)-1);
 	return ret;
 
+abort_trans_dput:
+	dput(parent);
 abort_trans:
 	btrfs_abort_transaction(trans, root, ret);
 	goto fail;