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From: Patrick Steinhardt <ps@pks.im>
To: Karthik Nayak <karthik.188@gmail.com>
Cc: git@vger.kernel.org
Subject: Re: [PATCH 5/8] refs/files-backend: add support for symref updates
Date: Tue, 2 Apr 2024 14:20:29 +0200	[thread overview]
Message-ID: <Zgv4DShrInEE30GA@tanuki> (raw)
In-Reply-To: <20240330224623.579457-6-knayak@gitlab.com>

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On Sat, Mar 30, 2024 at 11:46:20PM +0100, Karthik Nayak wrote:
> From: Karthik Nayak <karthik.188@gmail.com>
> 
> Add support for transactional symbolic reference updates in the files
> backend. This also adheres to the config of using symlinks for symbolic
> references.
> 
> While this commit is setting up the files-backend to support symrefs in
> transaction's. It will only be used in a consequent commit, when we wire
> up the `update-symref` option for `git-update-ref`.
> 
> Signed-off-by: Karthik Nayak <karthik.188@gmail.com>
> ---
>  refs/files-backend.c | 45 +++++++++++++++++++++++++++++++++++++++++---
>  1 file changed, 42 insertions(+), 3 deletions(-)
> 
> diff --git a/refs/files-backend.c b/refs/files-backend.c
> index 4dbe73c106..6b4cc80843 100644
> --- a/refs/files-backend.c
> +++ b/refs/files-backend.c
> @@ -2323,7 +2323,7 @@ static int split_head_update(struct ref_update *update,
>  			transaction, "HEAD",
>  			update->flags | REF_LOG_ONLY | REF_NO_DEREF,
>  			&update->new_oid, &update->old_oid,
> -			update->msg, NULL);
> +			update->msg, update->symref_target);
>  
>  	/*
>  	 * Add "HEAD". This insertion is O(N) in the transaction
> @@ -2386,7 +2386,7 @@ static int split_symref_update(struct ref_update *update,
>  	new_update = ref_transaction_add_update(
>  			transaction, referent, new_flags,
>  			&update->new_oid, &update->old_oid,
> -			update->msg, NULL);
> +			update->msg, update->symref_target);
>  
>  	new_update->parent_update = update;
>  
> @@ -2396,7 +2396,7 @@ static int split_symref_update(struct ref_update *update,
>  	 * done when new_update is processed.
>  	 */
>  	update->flags |= REF_LOG_ONLY | REF_NO_DEREF;
> -	update->flags &= ~REF_HAVE_OLD;
> +	update->flags &= ~(REF_HAVE_OLD|REF_UPDATE_SYMREF);
>  
>  	/*
>  	 * Add the referent. This insertion is O(N) in the transaction
> @@ -2567,6 +2567,27 @@ static int lock_ref_for_update(struct files_ref_store *refs,
>  		}
>  	}
>  
> +	if (update->flags & REF_UPDATE_SYMREF) {
> +		if (create_symref_lock(refs, lock, update->refname, update->symref_target)) {
> +			ret = TRANSACTION_GENERIC_ERROR;
> +			goto out;
> +		}
> +
> +		if (close_ref_gently(lock)) {
> +			strbuf_addf(err, "couldn't close '%s.lock'",
> +				    update->refname);
> +			ret = TRANSACTION_GENERIC_ERROR;
> +			goto out;
> +		}
> +
> +		/*
> +		 * Once we have created the symref lock, the commit
> +		 * phase of the transaction only needs to commit the lock.
> +		 */
> +		if (update->flags & REF_UPDATE_SYMREF)
> +			update->flags |= REF_NEEDS_COMMIT;

As far as I can see the `update->flags` aren't ever modified in this
block, which already is guarded via `update->flags = REF_UPDATE_SYMREF`.
This condition should thus be superfluous, and we can instead set
`REF_NEEDS_COMMIT` unconditionally here.

> +	}
> +
>  	if ((update->flags & REF_HAVE_NEW) &&
>  	    !(update->flags & REF_DELETING) &&
>  	    !(update->flags & REF_LOG_ONLY)) {
> @@ -2862,6 +2883,14 @@ static int files_transaction_finish(struct ref_store *ref_store,
>  
>  		if (update->flags & REF_NEEDS_COMMIT ||
>  		    update->flags & REF_LOG_ONLY) {
> +			if (update->flags & REF_UPDATE_SYMREF) {
> +				if (!refs_resolve_ref_unsafe(&refs->base, update->symref_target,
> +							     RESOLVE_REF_READING, &update->new_oid, NULL)) {
> +					strbuf_addf(err, "refname %s not found", update->symref_target);
> +					goto cleanup;
> +				}
> +			}

So we try to resolve the symref target here so that we can provide a
proper new object ID for the reflog entry. What happens though when the
caller tries to create a dangling symref where the target ref does not
exist? Wouldn't we raise an error and abort in that case?

I think we should handle this case gracefully and set the new object ID
to the zero OID. Which is also what happens when deleting the target of
e.g. the `HEAD` symref.

>  			if (files_log_ref_write(refs,
>  						lock->ref_name,
>  						&lock->old_oid,
> @@ -2879,6 +2908,16 @@ static int files_transaction_finish(struct ref_store *ref_store,
>  				goto cleanup;
>  			}
>  		}
> +
> +		/*
> +		 * We try creating a symlink, if that succeeds we continue to the
> +		 * next updated. If not, we try and create a regular symref.
> +		 */
> +		if (update->flags & REF_UPDATE_SYMREF && prefer_symlink_refs)
> +			if (!create_ref_symlink(lock, update->symref_target))
> +				continue;
> +
> +

There's a superfluous newline here.

>  		if (update->flags & REF_NEEDS_COMMIT) {
>  			clear_loose_ref_cache(refs);
>  			if (commit_ref(lock)) {

What is the purpose of `clear_loose_ref_cache()` here, and do we need to
call it when updating symrefs, too?

Patrick

> -- 
> 2.43.GIT
> 

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  reply	other threads:[~2024-04-02 12:20 UTC|newest]

Thread overview: 194+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2024-03-30 22:46 [PATCH 0/8] update-ref: add support for update-symref option Karthik Nayak
2024-03-30 22:46 ` [PATCH 1/8] files-backend: extract out `create_symref_lock` Karthik Nayak
2024-04-02 12:20   ` Patrick Steinhardt
2024-04-03 14:52     ` Karthik Nayak
2024-03-30 22:46 ` [PATCH 2/8] reftable-backend: extract out `write_symref_with_log` Karthik Nayak
2024-04-02 12:20   ` Patrick Steinhardt
2024-03-30 22:46 ` [PATCH 3/8] reftable-backend: move `write_symref_with_log` up Karthik Nayak
2024-03-30 22:46 ` [PATCH 4/8] refs: accept symref in `ref_transaction_add_update` Karthik Nayak
2024-03-30 22:46 ` [PATCH 5/8] refs/files-backend: add support for symref updates Karthik Nayak
2024-04-02 12:20   ` Patrick Steinhardt [this message]
2024-03-30 22:46 ` [PATCH 6/8] refs/reftable-backend: " Karthik Nayak
2024-04-02 12:20   ` Patrick Steinhardt
2024-03-30 22:46 ` [PATCH 7/8] refs: add 'update-symref' command to 'update-ref' Karthik Nayak
2024-03-31 22:08   ` Junio C Hamano
2024-03-31 22:27     ` Chris Torek
2024-03-31 23:14       ` Junio C Hamano
2024-04-01  1:31         ` Junio C Hamano
2024-04-02 12:20           ` Patrick Steinhardt
2024-04-02 16:40             ` Junio C Hamano
2024-04-09 11:55               ` Patrick Steinhardt
2024-04-09 16:15                 ` Karthik Nayak
2024-04-10  4:20                   ` Patrick Steinhardt
2024-04-10 16:06                     ` Junio C Hamano
2024-04-10 17:31                       ` Patrick Steinhardt
2024-04-01 10:38       ` Karthik Nayak
2024-04-01 11:48     ` Karthik Nayak
2024-04-01 16:17       ` Junio C Hamano
2024-04-01 20:40         ` Junio C Hamano
2024-04-01 22:37         ` Karthik Nayak
2024-03-30 22:46 ` [PATCH 8/8] refs: support symrefs in 'reference-transaction' hook Karthik Nayak
2024-04-02 12:20   ` Patrick Steinhardt
2024-04-12  9:59 ` [PATCH v2 0/7] update-ref: add symref oriented commands Karthik Nayak
2024-04-12  9:59   ` [PATCH v2 1/7] refs: accept symref values in `ref_transaction[_add]_update` Karthik Nayak
2024-04-18 14:25     ` Christian Couder
2024-04-19 10:28       ` Karthik Nayak
2024-04-18 15:08     ` Phillip Wood
2024-04-19  9:40       ` Patrick Steinhardt
2024-04-19 15:47       ` Karthik Nayak
2024-05-04 15:15         ` phillip.wood123
2024-04-19  9:40     ` Patrick Steinhardt
2024-04-19 18:09       ` Karthik Nayak
2024-04-23  6:31         ` Patrick Steinhardt
2024-04-23 10:48           ` Karthik Nayak
2024-04-12  9:59   ` [PATCH v2 2/7] update-ref: add support for symref-verify Karthik Nayak
2024-04-18 14:26     ` Christian Couder
2024-04-19 21:21       ` Karthik Nayak
2024-04-19  9:40     ` Patrick Steinhardt
2024-04-19 21:53       ` Karthik Nayak
2024-04-12  9:59   ` [PATCH v2 3/7] update-ref: add support for symref-delete Karthik Nayak
2024-04-18 14:52     ` Christian Couder
2024-04-21 10:43       ` Karthik Nayak
2024-04-19  9:40     ` Patrick Steinhardt
2024-04-21 10:45       ` Karthik Nayak
2024-04-12  9:59   ` [PATCH v2 4/7] files-backend: extract out `create_symref_lock` Karthik Nayak
2024-04-12  9:59   ` [PATCH v2 5/7] update-ref: add support for symref-create Karthik Nayak
2024-04-19  9:40     ` Patrick Steinhardt
2024-04-19 15:48       ` Junio C Hamano
2024-04-21 12:50       ` Karthik Nayak
2024-04-21 15:57         ` Karthik Nayak
2024-04-23  6:39         ` Patrick Steinhardt
2024-04-23 10:52           ` Karthik Nayak
2024-04-12  9:59   ` [PATCH v2 6/7] update-ref: add support for symref-update Karthik Nayak
2024-04-19  9:40     ` Patrick Steinhardt
2024-04-21 19:00       ` Karthik Nayak
2024-04-23  6:49         ` Patrick Steinhardt
2024-04-23 11:30           ` Karthik Nayak
2024-04-12  9:59   ` [PATCH v2 7/7] refs: support symrefs in 'reference-transaction' hook Karthik Nayak
2024-04-12 18:01   ` [PATCH v2 0/7] update-ref: add symref oriented commands Junio C Hamano
2024-04-12 18:49     ` Karthik Nayak
2024-04-18 15:05   ` Christian Couder
2024-04-21 19:06     ` Karthik Nayak
2024-04-20  6:16   ` Patrick Steinhardt
2024-04-21 19:11     ` Karthik Nayak
2024-04-23 21:28   ` [PATCH v3 0/8] refs: add symref support to 'git-update-ref' Karthik Nayak
2024-04-23 21:28     ` [PATCH v3 1/8] refs: accept symref values in `ref_transaction[_add]_update` Karthik Nayak
2024-04-23 21:28     ` [PATCH v3 2/8] update-ref: support parsing ref targets in `parse_next_oid` Karthik Nayak
2024-04-23 21:28     ` [PATCH v3 3/8] files-backend: extract out `create_symref_lock` Karthik Nayak
2024-04-23 21:28     ` [PATCH v3 4/8] update-ref: support symrefs in the verify command Karthik Nayak
2024-04-23 21:28     ` [PATCH v3 5/8] update-ref: support symrefs in the delete command Karthik Nayak
2024-04-23 21:28     ` [PATCH v3 6/8] update-ref: support symrefs in the create command Karthik Nayak
2024-04-23 21:28     ` [PATCH v3 7/8] update-ref: support symrefs in the update command Karthik Nayak
2024-04-23 21:28     ` [PATCH v3 8/8] ref: support symrefs in 'reference-transaction' hook Karthik Nayak
2024-04-23 22:03     ` [PATCH v3 0/8] refs: add symref support to 'git-update-ref' Jeff King
2024-04-24  1:17       ` Junio C Hamano
2024-04-24 16:25       ` Karthik Nayak
2024-04-25  6:40         ` Patrick Steinhardt
2024-04-25 21:12           ` Karthik Nayak
2024-04-25 18:01         ` Junio C Hamano
2024-04-25 21:14           ` Karthik Nayak
2024-04-25 21:55             ` Junio C Hamano
2024-04-26 12:48               ` Karthik Nayak
2024-04-26 20:41         ` Jeff King
2024-04-25 17:09     ` Junio C Hamano
2024-04-25 21:07       ` Karthik Nayak
2024-04-26 15:24     ` [PATCH v4 0/7] add symref-* commands to 'git-update-ref --stdin' Karthik Nayak
2024-04-26 15:24       ` [PATCH v4 1/7] refs: accept symref values in `ref_transaction[_add]_update` Karthik Nayak
2024-04-26 19:31         ` Junio C Hamano
2024-04-26 21:15           ` Jeff King
2024-04-29  7:02             ` Patrick Steinhardt
2024-04-29  7:55               ` Jeff King
2024-04-29  9:29                 ` phillip.wood123
2024-04-29  9:32             ` phillip.wood123
2024-04-29 16:18               ` Junio C Hamano
2024-04-30 10:33                 ` Jeff King
2024-04-30 10:30               ` Jeff King
2024-04-28 19:36           ` Karthik Nayak
2024-04-29 13:38         ` Phillip Wood
2024-04-29 14:01           ` Karthik Nayak
2024-04-26 15:24       ` [PATCH v4 2/7] files-backend: extract out `create_symref_lock` Karthik Nayak
2024-04-26 21:39         ` Junio C Hamano
2024-04-28 19:57           ` Karthik Nayak
2024-04-26 15:24       ` [PATCH v4 3/7] update-ref: add support for 'symref-verify' command Karthik Nayak
2024-04-26 22:51         ` Junio C Hamano
2024-04-28 22:28           ` Karthik Nayak
2024-04-26 15:24       ` [PATCH v4 4/7] update-ref: add support for 'symref-delete' command Karthik Nayak
2024-04-26 15:24       ` [PATCH v4 5/7] update-ref: add support for 'symref-create' command Karthik Nayak
2024-04-26 15:24       ` [PATCH v4 6/7] update-ref: add support for 'symref-update' command Karthik Nayak
2024-04-26 15:24       ` [PATCH v4 7/7] ref: support symrefs in 'reference-transaction' hook Karthik Nayak
2024-04-30 10:14       ` [PATCH v4 0/7] add symref-* commands to 'git-update-ref --stdin' Karthik Nayak
2024-05-01 20:22       ` [PATCH v5 0/7] refs: add support for transactional symref updates Karthik Nayak
2024-05-01 20:22         ` [PATCH v5 1/7] refs: accept symref values in `ref_transaction_update()` Karthik Nayak
2024-05-01 20:22         ` [PATCH v5 2/7] files-backend: extract out `create_symref_lock()` Karthik Nayak
2024-05-01 22:06           ` Junio C Hamano
2024-05-02  7:47             ` Patrick Steinhardt
2024-05-02 11:05               ` Karthik Nayak
2024-05-02 16:49               ` Junio C Hamano
2024-05-01 20:22         ` [PATCH v5 3/7] refs: support symrefs in 'reference-transaction' hook Karthik Nayak
2024-05-01 23:05           ` Junio C Hamano
2024-05-02  5:32             ` Karthik Nayak
2024-05-01 20:22         ` [PATCH v5 4/7] refs: add support for transactional symref updates Karthik Nayak
2024-05-01 23:52           ` Junio C Hamano
2024-05-02  5:50             ` Karthik Nayak
2024-05-02  7:47               ` Patrick Steinhardt
2024-05-02 11:10                 ` Karthik Nayak
2024-05-02 16:51                 ` Junio C Hamano
2024-05-02 16:00               ` Junio C Hamano
2024-05-02 17:53           ` Junio C Hamano
2024-05-01 20:22         ` [PATCH v5 5/7] refs: use transaction in `refs_create_symref()` Karthik Nayak
2024-05-02  7:47           ` Patrick Steinhardt
2024-05-01 20:22         ` [PATCH v5 6/7] refs: rename `refs_create_symref()` to `refs_update_symref()` Karthik Nayak
2024-05-02  7:47           ` Patrick Steinhardt
2024-05-02 11:34             ` Karthik Nayak
2024-05-01 20:22         ` [PATCH v5 7/7] refs: remove `create_symref` and associated dead code Karthik Nayak
2024-05-02  7:47           ` Patrick Steinhardt
2024-05-02 16:53             ` Junio C Hamano
2024-05-02  0:20         ` [PATCH v5 0/7] refs: add support for transactional symref updates Junio C Hamano
2024-05-02  5:53           ` Karthik Nayak
2024-05-03 12:41         ` [PATCH v6 " Karthik Nayak
2024-05-03 12:41           ` [PATCH v6 1/7] refs: accept symref values in `ref_transaction_update()` Karthik Nayak
2024-05-04 15:18             ` Phillip Wood
2024-05-05 15:10               ` Karthik Nayak
2024-05-05 15:19                 ` phillip.wood123
2024-05-03 12:41           ` [PATCH v6 2/7] files-backend: extract out `create_symref_lock()` Karthik Nayak
2024-05-03 12:41           ` [PATCH v6 3/7] refs: support symrefs in 'reference-transaction' hook Karthik Nayak
2024-05-03 12:41           ` [PATCH v6 4/7] refs: add support for transactional symref updates Karthik Nayak
2024-05-05 14:09             ` Phillip Wood
2024-05-05 16:09               ` Karthik Nayak
2024-05-06  9:35                 ` Phillip Wood
2024-05-06 11:19                   ` Karthik Nayak
2024-05-06 13:19                     ` Phillip Wood
2024-05-06  9:54                 ` Phillip Wood
2024-05-06 11:22                   ` Karthik Nayak
2024-05-06 13:17                     ` Phillip Wood
2024-05-03 12:41           ` [PATCH v6 5/7] refs: use transaction in `refs_create_symref()` Karthik Nayak
2024-05-03 12:41           ` [PATCH v6 6/7] refs: rename `refs_create_symref()` to `refs_update_symref()` Karthik Nayak
2024-05-03 12:41           ` [PATCH v6 7/7] refs: remove `create_symref` and associated dead code Karthik Nayak
2024-05-03 23:09             ` Junio C Hamano
2024-05-04  9:30               ` Karthik Nayak
2024-05-03 16:45           ` [PATCH v6 0/7] refs: add support for transactional symref updates Junio C Hamano
2024-05-06  7:36           ` Patrick Steinhardt
2024-05-07  6:00           ` [PATCH v7 0/8] " Karthik Nayak
2024-05-07  6:00             ` [PATCH v7 1/8] refs: accept symref values in `ref_transaction_update()` Karthik Nayak
2024-05-07  6:00             ` [PATCH v7 2/8] files-backend: extract out `create_symref_lock()` Karthik Nayak
2024-05-07  6:00             ` [PATCH v7 3/8] refs: support symrefs in 'reference-transaction' hook Karthik Nayak
2024-05-07  6:00             ` [PATCH v7 4/8] refs: move `original_update_refname` to 'refs.c' Karthik Nayak
2024-05-07  6:00             ` [PATCH v7 5/8] refs: add support for transactional symref updates Karthik Nayak
2024-05-07  6:00             ` [PATCH v7 6/8] refs: use transaction in `refs_create_symref()` Karthik Nayak
2024-05-07  6:00             ` [PATCH v7 7/8] refs: rename `refs_create_symref()` to `refs_update_symref()` Karthik Nayak
2024-05-07  6:00             ` [PATCH v7 8/8] refs: remove `create_symref` and associated dead code Karthik Nayak
2024-05-07  6:25             ` [PATCH v7 0/8] refs: add support for transactional symref updates Junio C Hamano
2024-05-07  6:31               ` Junio C Hamano
2024-05-07 12:58             ` [PATCH v8 " Karthik Nayak
2024-05-07 12:58               ` [PATCH v8 1/8] refs: accept symref values in `ref_transaction_update()` Karthik Nayak
2024-05-07 12:58               ` [PATCH v8 2/8] files-backend: extract out `create_symref_lock()` Karthik Nayak
2024-05-07 12:58               ` [PATCH v8 3/8] refs: support symrefs in 'reference-transaction' hook Karthik Nayak
2024-05-07 12:58               ` [PATCH v8 4/8] refs: move `original_update_refname` to 'refs.c' Karthik Nayak
2024-05-07 12:58               ` [PATCH v8 5/8] refs: add support for transactional symref updates Karthik Nayak
2024-05-07 12:58               ` [PATCH v8 6/8] refs: use transaction in `refs_create_symref()` Karthik Nayak
2024-05-07 12:58               ` [PATCH v8 7/8] refs: rename `refs_create_symref()` to `refs_update_symref()` Karthik Nayak
2024-05-07 12:58               ` [PATCH v8 8/8] refs: remove `create_symref` and associated dead code Karthik Nayak
2024-05-07 15:50               ` [PATCH v8 0/8] refs: add support for transactional symref updates phillip.wood123
2024-05-07 16:32               ` Junio C Hamano
2024-05-12 17:17                 ` Karthik Nayak
2024-05-13 17:15                   ` Junio C Hamano

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