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Re: [PATCH] files-backend: unlock packed store only if locked




On Tue, Feb 06, 2018 at 12:36:15PM -0800, Jonathan Tan wrote:

> In commit 42c7f7ff9685 ("commit_packed_refs(): remove call to
> `packed_refs_unlock()`", 2017-06-23), a call to packed_refs_unlock() was
> added to files_initial_transaction_commit() in order to compensate for
> removing that call from commit_packed_refs(). However, that call was
> added in the cleanup section, which is run even if the packed_ref_store
> was never locked (which happens if an error occurs earlier in the
> function).
> 
> Create a new cleanup goto target which runs packed_refs_unlock(), and
> ensure that only goto statements after a successful invocation of
> packed_refs_lock() jump there.

The explanation and patch look good to me.

But this all seemed strangely familiar... I think this is the same bug
as:

  https://public-inbox.org/git/20180118143841.1a4c674d@novascotia/

which is queued as mr/packed-ref-store-fix. It's listed as "will merge
to next" in the "what's cooking" from Jan 31st.

> diff --git a/refs/files-backend.c b/refs/files-backend.c
> index f75d960e1..89bc5584a 100644
> --- a/refs/files-backend.c
> +++ b/refs/files-backend.c
> @@ -2931,13 +2931,14 @@ static int files_initial_transaction_commit(struct ref_store *ref_store,
>  
>  	if (initial_ref_transaction_commit(packed_transaction, err)) {
>  		ret = TRANSACTION_GENERIC_ERROR;
> -		goto cleanup;
> +		goto locked_cleanup;
>  	}
>  
> +locked_cleanup:
> +	packed_refs_unlock(refs->packed_ref_store);
>  cleanup:
>  	if (packed_transaction)
>  		ref_transaction_free(packed_transaction);
> -	packed_refs_unlock(refs->packed_ref_store);

I actually like this double-label a bit more than what is queued on
mr/packed-ref-store-fix, though I am OK with either solution.

-Peff