From: Justin Tobler <jltobler@gmail.com>
Date: Tue, 16 Sep 2025 21:31:04 GMT
Subject: Re: [PATCH v3 2/4] refs/files: use correct error type when lock exists
Message-ID: <672jdldtxegx4y3gdtcyrnsz5nsy4sh6pk76eftqrukwug3f3c@xwso5f4vukn5>
In-Reply-To: <20250913-587-git-fetch-1-fails-fetches-on-case-insensitive-repositories-v3-2-195569740b57@gmail.com>

On 25/09/13 10:54PM, Karthik Nayak wrote:
> When fetching references into a repository, if a lock for a particular
> reference exists, then `lock_raw_ref()` throws:
> 
>     - REF_TRANSACTION_ERROR_CASE_CONFLICT: when there is a conflict
>     because transaction contains conflicting references while being on a

s/transaction/the transaction/

>     case-insensitive filesystem.
> 
>     - REF_TRANSACTION_ERROR_GENERIC: for all other errors.
> 
> The latter causes the entire set of batched updates to fail, even in
> case sensitive filessystems.

Ok so this issue isn't related to case-insensitive filesystems. The
issue is that now we use batch updated, a single pre-existing lockfile
causes the entire transaction to fail. Prior to batch updates, only the
individual update would fail, but wouldn't stop others.

> Instead, return a 'REF_TRANSACTION_ERROR_CREATE_EXISTS' error. This
> allows batched updates to reject the individual update which conflicts
> with the existing file, while updating the rest of the references.

Make sense.

> Signed-off-by: Karthik Nayak <karthik.188@gmail.com>
> ---
>  refs/files-backend.c | 20 +++++++++++++++++---
>  t/t5510-fetch.sh     | 26 ++++++++++++++++++++++++++
>  2 files changed, 43 insertions(+), 3 deletions(-)
> 
> diff --git a/refs/files-backend.c b/refs/files-backend.c
> index 01df32904b..69e50a16db 100644
> --- a/refs/files-backend.c
> +++ b/refs/files-backend.c
> @@ -797,9 +797,23 @@ static enum ref_transaction_error lock_raw_ref(struct files_ref_store *refs,
>  			goto retry;
>  		} else {
>  			unable_to_lock_message(ref_file.buf, myerr, err);
> -			if (myerr == EEXIST && ignore_case &&
> -			    transaction_has_case_conflicting_update(transaction, update))
> -				ret = REF_TRANSACTION_ERROR_CASE_CONFLICT;
> +			if (myerr == EEXIST) {
> +				if (ignore_case &&
> +				    transaction_has_case_conflicting_update(transaction, update))
> +					/*
> +					 * In case-insensitive filesystems, ensure that conflicts within a
> +					 * given transaction are handled. Pre-existing refs on a
> +					 * case-insensitive system will be overridden without any issue.
> +					 */
> +					ret = REF_TRANSACTION_ERROR_CASE_CONFLICT;
> +				else
> +					/*
> +					 * Pre-existing case-conflicting reference locks should also be
> +					 * specially categorized to avoid failing all batched updates.
> +					 */
> +					ret = REF_TRANSACTION_ERROR_CREATE_EXISTS;

IIUC, by returning a non-generic error here the individual reference
will be rejected during batch updates instead of aborting the
transaction.

-Justin