From patchwork Tue Mar 1 09:33:46 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Patrick Steinhardt X-Patchwork-Id: 12764400 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7C11FC433EF for ; Tue, 1 Mar 2022 09:34:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232098AbiCAJex (ORCPT ); Tue, 1 Mar 2022 04:34:53 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53372 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233877AbiCAJeu (ORCPT ); Tue, 1 Mar 2022 04:34:50 -0500 Received: from out2-smtp.messagingengine.com (out2-smtp.messagingengine.com [66.111.4.26]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6BF5B5F8F4 for ; Tue, 1 Mar 2022 01:33:49 -0800 (PST) Received: from compute4.internal (compute4.nyi.internal [10.202.2.44]) by mailout.nyi.internal (Postfix) with ESMTP id 3EA785C021A; Tue, 1 Mar 2022 04:33:48 -0500 (EST) Received: from mailfrontend1 ([10.202.2.162]) by compute4.internal (MEProxy); Tue, 01 Mar 2022 04:33:48 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=pks.im; h=cc:cc :content-type:date:date:from:from:in-reply-to:in-reply-to :message-id:mime-version:references:reply-to:sender:subject :subject:to:to; s=fm3; bh=342M7DnLmCkA4aADhmXNC72DSdxDUizWZpcAKm iiTdE=; b=Jn7246bPmfjiRKIDmHmO7Nng5GPPdg5C34/z0MkvkWcKciQbWCH1cK /KEmmqN4icndt4DOy8te9+acQDZlE9EhZon4oxfZDmcddNIggqNLgN8x44GhBSNI hfbIYSqU+orETTF0q/2VQIvPUJnOg7TvPc89//eyzmYsoYwv0EnqMcxliPONm9Hq CJzN9A+F9AFMrys5PNCtlpNXJpV4esGfENSeLolg1Az3h+XsMflDVPNVBbNiTFqY MUPIzpwbZiAxTgJr/2t1RJEhlACkIKKpoRMmvSbUGOywqsThtYtVcdoBgmAG6prs brhG3m7eYlNt5Vfd0AyXt5DbLb/uZ8tw== DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d= messagingengine.com; h=cc:cc:content-type:date:date:from:from :in-reply-to:in-reply-to:message-id:mime-version:references :reply-to:sender:subject:subject:to:to:x-me-proxy:x-me-proxy :x-me-sender:x-me-sender:x-sasl-enc; s=fm2; bh=342M7DnLmCkA4aADh mXNC72DSdxDUizWZpcAKmiiTdE=; b=j8jOwqp0QhFktk9C45Qo5qhhLJqlK3Iqf iLOJW70XoTWP3hVzllLhlCzlcFWsZggTN56004RbVp6Ku2Ph7wM5WCQfw+640crW 4RNbfwYignLT31HYrqqNfsq2GFI8yK9o8giiZuVj+oCEOk2AyQhPL+Wq2XaB8r2T 4UO5yj2t03qFAt2mW5p3BOpC4XzVDIYQDCSrFpRaf6yebYTGqEHiIovfXdvvZw+Q IjwR/XtGEpKWPI3lnrMxyoByr7dlTu1cvUn+oNaxuZM78HvYLromwd44sBELU2Fb UUAugtTGxD/oKw7MDHC1QIRttGiAa8z2XD64c1nKYjHa8f5hk+eog== X-ME-Sender: X-ME-Received: X-ME-Proxy-Cause: gggruggvucftvghtrhhoucdtuddrgedvvddruddtvddgtdefucetufdoteggodetrfdotf fvucfrrhhofhhilhgvmecuhfgrshhtofgrihhlpdfqfgfvpdfurfetoffkrfgpnffqhgen uceurghilhhouhhtmecufedttdenucesvcftvggtihhpihgvnhhtshculddquddttddmne cujfgurhepfffhvffukfhfgggtuggjsehgtderredttddvnecuhfhrohhmpefrrghtrhhi tghkucfuthgvihhnhhgrrhguthcuoehpshesphhkshdrihhmqeenucggtffrrghtthgvrh hnpeehgefhtdefueffheekgfffudelffejtdfhvdejkedthfehvdelgfetgfdvtedthfen ucevlhhushhtvghrufhiiigvpedtnecurfgrrhgrmhepmhgrihhlfhhrohhmpehpshesph hkshdrihhm X-ME-Proxy: Received: by mail.messagingengine.com (Postfix) with ESMTPA; Tue, 1 Mar 2022 04:33:47 -0500 (EST) Received: from localhost (ncase [10.192.0.11]) by vm-mail.pks.im (OpenSMTPD) with ESMTPSA id c950ba61 (TLSv1.3:TLS_AES_256_GCM_SHA384:256:NO); Tue, 1 Mar 2022 09:33:47 +0000 (UTC) Date: Tue, 1 Mar 2022 10:33:46 +0100 From: Patrick Steinhardt To: git@vger.kernel.org Cc: Derrick Stolee Subject: [PATCH v2 3/5] refs: add ability for backends to special-case reading of symbolic refs Message-ID: <29eb81d37c8fef63858d8e066795e308692d219c.1646127015.git.ps@pks.im> References: MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org Reading of symbolic and non-symbolic references is currently treated the same in reference backends: we always call `refs_read_raw_ref()` and then decide based on the returned flags what type it is. This has one downside though: symbolic references may be treated different from normal references in a backend from normal references. The packed-refs backend for example doesn't even know about symbolic references, and as a result it is pointless to even ask it for one. There are cases where we really only care about whether a reference is symbolic or not, but don't care about whether it exists at all or may be a non-symbolic reference. But it is not possible to optimize for this case right now, and as a consequence we will always first check for a loose reference to exist, and if it doesn't, we'll query the packed-refs backend for a known-to-not-be-symbolic reference. This is inefficient and requires us to search all packed references even though we know to not care for the result at all. Introduce a new function `refs_read_symbolic_ref()` which allows us to fix this case. This function will only ever return symbolic references and can thus optimize for the scenario layed out above. By default, if the backend doesn't provide an implementation for it, we just use the old code path and fall back to `read_raw_ref()`. But in case the backend provides its own, more efficient implementation, we will use that one instead. Note that this function is explicitly designed to not distinguish between missing references and non-symbolic references. If it did, we'd be forced to always search the packed-refs backend to see whether the symbolic reference the user asked for really doesn't exist, or if it exists as a non-symbolic reference. Signed-off-by: Patrick Steinhardt --- refs.c | 17 +++++++++++++++++ refs.h | 3 +++ refs/debug.c | 1 + refs/files-backend.c | 1 + refs/packed-backend.c | 1 + refs/refs-internal.h | 16 ++++++++++++++++ 6 files changed, 39 insertions(+) diff --git a/refs.c b/refs.c index 1598fb13e2..0b79bdd7c3 100644 --- a/refs.c +++ b/refs.c @@ -1673,6 +1673,23 @@ int refs_read_raw_ref(struct ref_store *ref_store, const char *refname, type, failure_errno); } +int refs_read_symbolic_ref(struct ref_store *ref_store, const char *refname, + struct strbuf *referent) +{ + struct object_id oid; + int ret, failure_errno = 0; + unsigned int type = 0; + + if (ref_store->be->read_symbolic_ref) + return ref_store->be->read_symbolic_ref(ref_store, refname, referent); + + ret = refs_read_raw_ref(ref_store, refname, &oid, referent, &type, &failure_errno); + if (ret || !(type & REF_ISSYMREF)) + return -1; + + return 0; +} + const char *refs_resolve_ref_unsafe(struct ref_store *refs, const char *refname, int resolve_flags, diff --git a/refs.h b/refs.h index 1ae12c410a..23479c7ee0 100644 --- a/refs.h +++ b/refs.h @@ -82,6 +82,9 @@ int read_ref_full(const char *refname, int resolve_flags, struct object_id *oid, int *flags); int read_ref(const char *refname, struct object_id *oid); +int refs_read_symbolic_ref(struct ref_store *ref_store, const char *refname, + struct strbuf *referent); + /* * Return 0 if a reference named refname could be created without * conflicting with the name of an existing reference. Otherwise, diff --git a/refs/debug.c b/refs/debug.c index 2b0771ca53..c590d37720 100644 --- a/refs/debug.c +++ b/refs/debug.c @@ -435,6 +435,7 @@ struct ref_storage_be refs_be_debug = { debug_ref_iterator_begin, debug_read_raw_ref, + NULL, debug_reflog_iterator_begin, debug_for_each_reflog_ent, diff --git a/refs/files-backend.c b/refs/files-backend.c index f59589d6cc..f3428a9f12 100644 --- a/refs/files-backend.c +++ b/refs/files-backend.c @@ -3286,6 +3286,7 @@ struct ref_storage_be refs_be_files = { files_ref_iterator_begin, files_read_raw_ref, + NULL, files_reflog_iterator_begin, files_for_each_reflog_ent, diff --git a/refs/packed-backend.c b/refs/packed-backend.c index 27dd8c3922..f56e2cc635 100644 --- a/refs/packed-backend.c +++ b/refs/packed-backend.c @@ -1684,6 +1684,7 @@ struct ref_storage_be refs_be_packed = { packed_ref_iterator_begin, packed_read_raw_ref, + NULL, packed_reflog_iterator_begin, packed_for_each_reflog_ent, diff --git a/refs/refs-internal.h b/refs/refs-internal.h index 6e15db3ca4..001ef15835 100644 --- a/refs/refs-internal.h +++ b/refs/refs-internal.h @@ -649,6 +649,21 @@ typedef int read_raw_ref_fn(struct ref_store *ref_store, const char *refname, struct object_id *oid, struct strbuf *referent, unsigned int *type, int *failure_errno); +/* + * Read a symbolic reference from the specified reference store. This function + * is optional: if not implemented by a backend, then `read_raw_ref_fn` is used + * to read the symbolcic reference instead. It is intended to be implemented + * only in case the backend can optimize the reading of symbolic references. + * + * Return 0 on success, or -1 on failure. `referent` will be set to the target + * of the symbolic reference on success. This function explicitly does not + * distinguish between error cases and the reference not being a symbolic + * reference to allow backends to optimize this operation in case symbolic and + * non-symbolic references are treated differently. + */ +typedef int read_symbolic_ref_fn(struct ref_store *ref_store, const char *refname, + struct strbuf *referent); + struct ref_storage_be { struct ref_storage_be *next; const char *name; @@ -668,6 +683,7 @@ struct ref_storage_be { ref_iterator_begin_fn *iterator_begin; read_raw_ref_fn *read_raw_ref; + read_symbolic_ref_fn *read_symbolic_ref; reflog_iterator_begin_fn *reflog_iterator_begin; for_each_reflog_ent_fn *for_each_reflog_ent;