Subject: Re: [PATCH v3 1/6] refs: extract packed_refs_delete_refs() to allow control of transaction

From: Ævar Arnfjörð Bjarmason <[email-masked]>
Date: Thu, 13 Jan 2022 13:43:18 +0100

On Thu, Jan 13 2022, Patrick Steinhardt wrote:

> [[PGP Signed Part:Undecided]]
> When deleting loose refs, then we also have to delete the refs in the
> packed backend. This is done by calling `refs_delete_refs()`, which
> then uses the packed-backend's logic to delete refs. This doesn't allow
> us to exercise any control over the reference transaction which is being
> created in the packed backend, which is required in a subsequent commit.
>
> Extract a new function `packed_refs_delete_refs()`, which hosts most of
> the logic to delete refs except for creating the transaction itself.
> Like this, we can easily create the transaction in the files backend
> and thus exert more control over it.
>
> Signed-off-by: Patrick Steinhardt <[email-masked]>
> ---
>  refs/files-backend.c  | 12 +++++++++---
>  refs/packed-backend.c | 28 +++++++++++++++++++++-------
>  refs/packed-backend.h |  7 +++++++
>  3 files changed, 37 insertions(+), 10 deletions(-)
>
> diff --git a/refs/files-backend.c b/refs/files-backend.c
> index 90b671025a..5795e54020 100644
> --- a/refs/files-backend.c
> +++ b/refs/files-backend.c
> @@ -1249,6 +1249,7 @@ static int files_delete_refs(struct ref_store *ref_store, const char *msg,
>  {
>  	struct files_ref_store *refs =
>  		files_downcast(ref_store, REF_STORE_WRITE, "delete_refs");
> +	struct ref_transaction *transaction = NULL;

nit: "NULL initialization never needed?
(re: https://lore.kernel.org/git/[email-masked]/)

>  	struct strbuf err = STRBUF_INIT;
>  	int i, result = 0;
>  
> @@ -1258,10 +1259,14 @@ static int files_delete_refs(struct ref_store *ref_store, const char *msg,
>  	if (packed_refs_lock(refs->packed_ref_store, 0, &err))
>  		goto error;
>  
> -	if (refs_delete_refs(refs->packed_ref_store, msg, refnames, flags)) {
> -		packed_refs_unlock(refs->packed_ref_store);
> +	transaction = ref_store_transaction_begin(refs->packed_ref_store, &err);
> +	if (!transaction)
> +		goto error;
> +
> +	result = packed_refs_delete_refs(refs->packed_ref_store,
> +					 transaction, msg, refnames, flags);
> +	if (result)
>  		goto error;
> -	}
>  
>  	packed_refs_unlock(refs->packed_ref_store);
>  
> @@ -1288,6 +1293,7 @@ static int files_delete_refs(struct ref_store *ref_store, const char *msg,
>  	else
>  		error(_("could not delete references: %s"), err.buf);
>  
> +	ref_transaction_free(transaction);
>  	strbuf_release(&err);
>  	return -1;
>  }
> diff --git a/refs/packed-backend.c b/refs/packed-backend.c
> index 67152c664e..e97d67f932 100644
> --- a/refs/packed-backend.c
> +++ b/refs/packed-backend.c
> @@ -1522,15 +1522,10 @@ static int packed_initial_transaction_commit(struct ref_store *ref_store,
>  static int packed_delete_refs(struct ref_store *ref_store, const char *msg,
>  			     struct string_list *refnames, unsigned int flags)
>  {
> -	struct packed_ref_store *refs =
> -		packed_downcast(ref_store, REF_STORE_WRITE, "delete_refs");
>  	struct strbuf err = STRBUF_INIT;
>  	struct ref_transaction *transaction;
> -	struct string_list_item *item;
>  	int ret;
>  
> -	(void)refs; /* We need the check above, but don't use the variable */
> -
>  	if (!refnames->nr)
>  		return 0;
>  
> @@ -1544,6 +1539,27 @@ static int packed_delete_refs(struct ref_store *ref_store, const char *msg,
>  	if (!transaction)
>  		return -1;
>  
> +	ret = packed_refs_delete_refs(ref_store, transaction,
> +				      msg, refnames, flags);
> +
> +	ref_transaction_free(transaction);
> +	return ret;
> +}
> +
> +int packed_refs_delete_refs(struct ref_store *ref_store,
> +			    struct ref_transaction *transaction,
> +			    const char *msg,
> +			    struct string_list *refnames,
> +			    unsigned int flags)
> +{
> +	struct packed_ref_store *refs =
> +		packed_downcast(ref_store, REF_STORE_WRITE, "delete_refs");
> +	struct strbuf err = STRBUF_INIT;
> +	struct string_list_item *item;
> +	int ret;
> +
> +	(void)(refs); /* We need the check above, but don't use the variable */
> +
>  	for_each_string_list_item(item, refnames) {
>  		if (ref_transaction_delete(transaction, item->string, NULL,
>  					   flags, msg, &err)) {

I see you're just moving this code around, but FWIW we can just do this
(also in the pre-image):

	int packed_refs_delete_refs(...)
	{
		[declare variables]
                
                /* Assert ref store sanity */
                packed_downcast(ref_store, REF_STORE_WRITE, "delete_refs")

                [...]
	}

Not sure it's good to change it around just for this mostly-move, just a
note...

> @@ -1554,7 +1570,6 @@ static int packed_delete_refs(struct ref_store *ref_store, const char *msg,
>  	}
>  
>  	ret = ref_transaction_commit(transaction, &err);
> -

Stray whitespace change.