git@vger.kernel.org mailing list mirror (one of many)
 help / color / mirror / code / Atom feed
From: Jeff King <peff@peff.net>
To: Michael Haggerty <mhagger@alum.mit.edu>
Cc: "Junio C Hamano" <gitster@pobox.com>,
	"Nguyễn Thái Ngọc Duy" <pclouds@gmail.com>,
	"David Turner" <novalis@novalis.org>,
	git@vger.kernel.org
Subject: Re: [PATCH 04/20] refs_verify_refname_available(): implement once for all backends
Date: Mon, 20 Mar 2017 13:42:40 -0400	[thread overview]
Message-ID: <20170320174240.gykldqzbqyva6kbs@sigill.intra.peff.net> (raw)
In-Reply-To: <22abd274bfdada94b3654a811ee209822640765f.1490026594.git.mhagger@alum.mit.edu>

On Mon, Mar 20, 2017 at 05:33:09PM +0100, Michael Haggerty wrote:

> It turns out that we can now implement
> `refs_verify_refname_available()` based on the other virtual
> functions, so there is no need for it to be defined at the backend
> level. Instead, define it once in `refs.c` and remove the
> `files_backend` definition.

Does this mean that backends can no longer provide storage for
D/F-conflicted refnames (i.e., "refs/foo" and "refs/foo/bar")? It looks
like the global verify_refname_available() has that logic baked in.

I know that was a complex subject because of the potential compatibility
issues (e.g., fetching from a server with a more capable backend), but
I'd just worry we are shutting a door on some options. OTOH, it probably
wouldn't be that hard for the global function to check a flag specific
to the ref_store, and allow such refs when it is set.

>  int refs_verify_refname_available(struct ref_store *refs,
>  				  const char *refname,
> -				  const struct string_list *extra,
> +				  const struct string_list *extras,
>  				  const struct string_list *skip,
>  				  struct strbuf *err)
>  {
> [...]
> +		/*
> +		 * We are still at a leading dir of the refname (e.g.,
> +		 * "refs/foo"; if there is a reference with that name,
> +		 * it is a conflict, *unless* it is in skip.
> +		 */
> +		if (skip && string_list_has_string(skip, dirname.buf))
> +			continue;
> +
> +		if (!refs_read_raw_ref(refs, dirname.buf, oid.hash, &referent, &type)) {
> +			strbuf_addf(err, "'%s' exists; cannot create '%s'",
> +				    dirname.buf, refname);
> +			goto cleanup;
> +		}

We don't really care about reading the ref value here; we just care if
it exists. Does that matter for efficiency (e.g., for the files backend
it's a stat() versus an open/read/close)? I guess the difference only
matters when it _does_ exist, which is the uncommon error case.

(Also, I suspect the loose ref cache always just reads everything in the
current code, though with the iterator approach in theory we could stop
doing that).

-Peff

  reply	other threads:[~2017-03-20 17:43 UTC|newest]

Thread overview: 38+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-03-20 16:33 [PATCH 00/20] Separate `ref_cache` into a separate module Michael Haggerty
2017-03-20 16:33 ` [PATCH 01/20] get_ref_dir(): don't call read_loose_refs() for "refs/bisect" Michael Haggerty
2017-03-20 16:33 ` [PATCH 02/20] refs_read_raw_ref(): new function Michael Haggerty
2017-03-20 16:33 ` [PATCH 03/20] refs_ref_iterator_begin(): " Michael Haggerty
2017-03-20 16:33 ` [PATCH 04/20] refs_verify_refname_available(): implement once for all backends Michael Haggerty
2017-03-20 17:42   ` Jeff King [this message]
2017-03-20 22:20     ` Michael Haggerty
2017-03-20 16:33 ` [PATCH 05/20] refs_verify_refname_available(): use function in more places Michael Haggerty
2017-03-20 16:33 ` [PATCH 06/20] Rename `add_ref()` to `add_ref_entry()` Michael Haggerty
2017-03-20 16:33 ` [PATCH 07/20] Rename `find_ref()` to `find_ref_entry()` Michael Haggerty
2017-03-20 16:33 ` [PATCH 08/20] Rename `remove_entry()` to `remove_entry_from_dir()` Michael Haggerty
2017-03-20 16:33 ` [PATCH 09/20] refs: split `ref_cache` code into separate files Michael Haggerty
2017-03-20 17:49   ` Jeff King
2017-03-20 19:47     ` Junio C Hamano
2017-03-20 20:35       ` Stefan Beller
2017-03-20 22:40         ` Junio C Hamano
2017-03-20 16:33 ` [PATCH 10/20] ref-cache: introduce a new type, ref_cache Michael Haggerty
2017-03-20 16:33 ` [PATCH 11/20] refs: record the ref_store in ref_cache, not ref_dir Michael Haggerty
2017-03-20 17:51   ` Jeff King
2017-03-20 22:39     ` Michael Haggerty
2017-03-20 16:33 ` [PATCH 12/20] ref-cache: use a callback function to fill the cache Michael Haggerty
2017-03-20 16:33 ` [PATCH 13/20] refs: handle "refs/bisect/" in `loose_fill_ref_dir()` Michael Haggerty
2017-03-20 16:33 ` [PATCH 14/20] do_for_each_entry_in_dir(): eliminate `offset` argument Michael Haggerty
2017-03-20 16:33 ` [PATCH 15/20] get_loose_ref_dir(): function renamed from get_loose_refs() Michael Haggerty
2017-03-20 16:33 ` [PATCH 16/20] get_loose_ref_cache(): new function Michael Haggerty
2017-03-20 16:33 ` [PATCH 17/20] cache_ref_iterator_begin(): make function smarter Michael Haggerty
2017-03-20 16:33 ` [PATCH 18/20] commit_packed_refs(): use reference iteration Michael Haggerty
2017-03-20 18:05   ` Jeff King
2017-03-22  8:42     ` Michael Haggerty
2017-03-22 13:06       ` Jeff King
2017-03-20 16:33 ` [PATCH 19/20] files_pack_refs(): " Michael Haggerty
2017-03-20 16:33 ` [PATCH 20/20] do_for_each_entry_in_dir(): delete function Michael Haggerty
2017-03-20 17:25 ` [PATCH 00/20] Separate `ref_cache` into a separate module Junio C Hamano
2017-03-20 18:12 ` Jeff King
2017-03-20 18:24 ` Ævar Arnfjörð Bjarmason
2017-03-20 18:30   ` Jeff King
2017-03-20 22:32 ` Junio C Hamano
2017-03-20 22:48   ` Michael Haggerty

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

  List information: http://vger.kernel.org/majordomo-info.html

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20170320174240.gykldqzbqyva6kbs@sigill.intra.peff.net \
    --to=peff@peff.net \
    --cc=git@vger.kernel.org \
    --cc=gitster@pobox.com \
    --cc=mhagger@alum.mit.edu \
    --cc=novalis@novalis.org \
    --cc=pclouds@gmail.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body.
Code repositories for project(s) associated with this public inbox

	https://80x24.org/mirrors/git.git

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).