Re: [PATCH 02/10] Btrfs: fix error handling in btrfs_truncate_inode_items()

[Nikolay Borisov <nborisov@suse.com>]

On 10.05.2018 09:21, Omar Sandoval wrote:
> From: Omar Sandoval <osandov@fb.com>
> 
> btrfs_truncate_inode_items() uses two variables for error handling, ret
> and err. These are not handled consistently, leading to a couple of
> bugs.
> 
> - Errors from btrfs_del_items() are handled but not propagated to the
>   caller
> - If btrfs_run_delayed_refs() fails and aborts the transaction, we
>   continue running
> 
> Just use ret everywhere and simplify things a bit, fixing both of these
> issues.
> 
> Fixes: 79787eaab461 ("btrfs: replace many BUG_ONs with proper error handling")
> Fixes: 1262133b8d6f ("Btrfs: account for crcs in delayed ref processing")
> Signed-off-by: Omar Sandoval <osandov@fb.com>

That function is horrendous so it needs much loving and this is a step
in the right direction.

LGTM:

Reviewed-by: Nikolay Borisov <nborisov@suse.com>

> ---
>  fs/btrfs/inode.c | 55 ++++++++++++++++++++++++------------------------
>  1 file changed, 28 insertions(+), 27 deletions(-)
> 
> diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
> index fef8dbb6a93f..79d1da01a90d 100644
> --- a/fs/btrfs/inode.c
> +++ b/fs/btrfs/inode.c
> @@ -4442,7 +4442,6 @@ int btrfs_truncate_inode_items(struct btrfs_trans_handle *trans,
>  	int pending_del_slot = 0;
>  	int extent_type = -1;
>  	int ret;
> -	int err = 0;
>  	u64 ino = btrfs_ino(BTRFS_I(inode));
>  	u64 bytes_deleted = 0;
>  	bool be_nice = false;
> @@ -4494,22 +4493,19 @@ int btrfs_truncate_inode_items(struct btrfs_trans_handle *trans,
>  	 * up a huge file in a single leaf.  Most of the time that
>  	 * bytes_deleted is > 0, it will be huge by the time we get here
>  	 */
> -	if (be_nice && bytes_deleted > SZ_32M) {
> -		if (btrfs_should_end_transaction(trans)) {
> -			err = -EAGAIN;
> -			goto error;
> -		}
> +	if (be_nice && bytes_deleted > SZ_32M &&
> +	    btrfs_should_end_transaction(trans)) {
> +		ret = -EAGAIN;
> +		goto out;
>  	}
>  
> -
>  	path->leave_spinning = 1;
>  	ret = btrfs_search_slot(trans, root, &key, path, -1, 1);
> -	if (ret < 0) {
> -		err = ret;
> +	if (ret < 0)
>  		goto out;
> -	}
>  
>  	if (ret > 0) {
> +		ret = 0;
>  		/* there are no items in the tree for us to truncate, we're
>  		 * done
>  		 */
> @@ -4620,7 +4616,7 @@ int btrfs_truncate_inode_items(struct btrfs_trans_handle *trans,
>  				 * We have to bail so the last_size is set to
>  				 * just before this extent.
>  				 */
> -				err = NEED_TRUNCATE_BLOCK;
> +				ret = NEED_TRUNCATE_BLOCK;
>  				break;
>  			}
>  
> @@ -4687,7 +4683,7 @@ int btrfs_truncate_inode_items(struct btrfs_trans_handle *trans,
>  						pending_del_nr);
>  				if (ret) {
>  					btrfs_abort_transaction(trans, ret);
> -					goto error;
> +					break;
>  				}
>  				pending_del_nr = 0;
>  			}
> @@ -4698,8 +4694,8 @@ int btrfs_truncate_inode_items(struct btrfs_trans_handle *trans,
>  					trans->delayed_ref_updates = 0;
>  					ret = btrfs_run_delayed_refs(trans,
>  								   updates * 2);
> -					if (ret && !err)
> -						err = ret;
> +					if (ret)
> +						break;
>  				}
>  			}
>  			/*
> @@ -4707,8 +4703,8 @@ int btrfs_truncate_inode_items(struct btrfs_trans_handle *trans,
>  			 * and let the transaction restart
>  			 */
>  			if (should_end) {
> -				err = -EAGAIN;
> -				goto error;
> +				ret = -EAGAIN;
> +				break;
>  			}
>  			goto search_again;
>  		} else {
> @@ -4716,32 +4712,37 @@ int btrfs_truncate_inode_items(struct btrfs_trans_handle *trans,
>  		}
>  	}
>  out:
> -	if (pending_del_nr) {
> -		ret = btrfs_del_items(trans, root, path, pending_del_slot,
> +	if (ret >= 0 && pending_del_nr) {
> +		int err;
> +
> +		err = btrfs_del_items(trans, root, path, pending_del_slot,
>  				      pending_del_nr);
> -		if (ret)
> -			btrfs_abort_transaction(trans, ret);
> +		if (err) {
> +			btrfs_abort_transaction(trans, err);
> +			ret = err;
> +		}
>  	}
> -error:
>  	if (root->root_key.objectid != BTRFS_TREE_LOG_OBJECTID) {
>  		ASSERT(last_size >= new_size);
> -		if (!err && last_size > new_size)
> +		if (!ret && last_size > new_size)
>  			last_size = new_size;
>  		btrfs_ordered_update_i_size(inode, last_size, NULL);
>  	}
>  
>  	btrfs_free_path(path);
>  
> -	if (be_nice && bytes_deleted > SZ_32M) {
> +	if (be_nice && bytes_deleted > SZ_32M && (ret >= 0 || ret == -EAGAIN)) {
>  		unsigned long updates = trans->delayed_ref_updates;
> +		int err;
> +
>  		if (updates) {
>  			trans->delayed_ref_updates = 0;
> -			ret = btrfs_run_delayed_refs(trans, updates * 2);
> -			if (ret && !err)
> -				err = ret;
> +			err = btrfs_run_delayed_refs(trans, updates * 2);
> +			if (err)
> +				ret = err;
>  		}
>  	}
> -	return err;
> +	return ret;
>  }
>  
>  /*
>