From mboxrd@z Thu Jan 1 00:00:00 1970 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 826CFC433EF for ; Tue, 8 Mar 2022 14:35:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1344020AbiCHOgU (ORCPT ); Tue, 8 Mar 2022 09:36:20 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43804 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234344AbiCHOgT (ORCPT ); Tue, 8 Mar 2022 09:36:19 -0500 Received: from smtp-out1.suse.de (smtp-out1.suse.de [195.135.220.28]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 8DDF54BB99 for ; Tue, 8 Mar 2022 06:35:22 -0800 (PST) Received: from relay2.suse.de (relay2.suse.de [149.44.160.134]) by smtp-out1.suse.de (Postfix) with ESMTP id 3EAB7210EF; Tue, 8 Mar 2022 14:35:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_rsa; t=1646750121; h=from:from:reply-to:reply-to:date:date:message-id:message-id:to:to: cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=rM0sU9QLUWYsWg9WE7UFGxX4tQZaPJ2aOPYyKrTgOx4=; b=HYNdFZYMQQPLx1bypQ56L6Y0yHf8hj43lnB7AtOXuyqaDT6ToJKx+u10GSRg+Y2jtdwy2c NWA2yowu6NooaREXEO1zV+0ld3LaGMPWUFFEKaZyDhYUNuzhM0U4i5oP+yxbWpeEF+a4bt IBClI2l8GCdx1Jd5M3BHrTKrqPO8lvw= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_ed25519; t=1646750121; h=from:from:reply-to:reply-to:date:date:message-id:message-id:to:to: cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=rM0sU9QLUWYsWg9WE7UFGxX4tQZaPJ2aOPYyKrTgOx4=; b=jPGEkMHEVHjxyq3DmzjqpBKj4YeSIvS2MSltosC0bft+z7+QAHVjLmvKppcLKVE2+O/T9U T7n6Tdj+VAbkLdCA== Received: from ds.suse.cz (ds.suse.cz [10.100.12.205]) by relay2.suse.de (Postfix) with ESMTP id 36784A3B88; Tue, 8 Mar 2022 14:35:21 +0000 (UTC) Received: by ds.suse.cz (Postfix, from userid 10065) id 2D519DA823; Tue, 8 Mar 2022 15:31:26 +0100 (CET) Date: Tue, 8 Mar 2022 15:31:26 +0100 From: David Sterba To: Gabriel Niebler Cc: linux-btrfs@vger.kernel.org, dsterba@suse.com, Marcos Paulo de Souza Subject: Re: [PATCH v3 01/14] btrfs: Introduce btrfs_for_each_slot iterator macro Message-ID: <20220308143126.GL12643@twin.jikos.cz> Reply-To: dsterba@suse.cz Mail-Followup-To: dsterba@suse.cz, Gabriel Niebler , linux-btrfs@vger.kernel.org, dsterba@suse.com, Marcos Paulo de Souza References: <20220302164829.17524-1-gniebler@suse.com> <20220302164829.17524-2-gniebler@suse.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220302164829.17524-2-gniebler@suse.com> User-Agent: Mutt/1.5.23.1-rc1 (2014-03-12) Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org On Wed, Mar 02, 2022 at 05:48:16PM +0100, Gabriel Niebler wrote: > There is a common pattern when searching for a key in btrfs: > > * Call btrfs_search_slot to find the slot for the key > * Enter an endless loop: > * If the found slot is larger than the no. of items in the current leaf, > check the next leaf > * If it's still not found in the next leaf, terminate the loop > * Otherwise do something with the found key > * Increment the current slot and continue > > To reduce code duplication, we can replace this code pattern with an iterator > macro, similar to the existing for_each_X macros found elsewhere in the kernel. > This also makes the code easier to understand for newcomers by putting a name > to the encapsulated functionality. > > Signed-off-by: Marcos Paulo de Souza > Signed-off-by: Gabriel Niebler > --- > fs/btrfs/ctree.c | 33 +++++++++++++++++++++++++++++++++ > fs/btrfs/ctree.h | 24 ++++++++++++++++++++++++ > 2 files changed, 57 insertions(+) > > diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c > index a7db3f6f1b7b..d735bd472616 100644 > --- a/fs/btrfs/ctree.c > +++ b/fs/btrfs/ctree.c > @@ -2277,6 +2277,39 @@ int btrfs_search_backwards(struct btrfs_root *root, struct btrfs_key *key, > return ret; > } > > +/* Search for a valid slot for the given path. Multi-line comments should start with /* * Text ... * ... */ > + * > + * @root: The root node of the tree. > + * @key: Will contain a valid item if found. > + * @path: The starting point to validate the slot. Please align the descriptions, an example is here https://btrfs.wiki.kernel.org/index.php/Development_notes#Comments > + * > + * Return 0 if the item is valid, 1 if not found and < 0 if error. > + */ > +int btrfs_get_next_valid_item(struct btrfs_root *root, struct btrfs_key *key, > + struct btrfs_path *path) > +{ > + while (1) { > + int ret; > + const int slot = path->slots[0]; > + const struct extent_buffer *leaf = path->nodes[0]; Newline between declarations and statements. > + /* this is where we start walking through the path */ The comments should read like a sentence, so the first letter should be uppercase unless it's an identifier. > + if (slot >= btrfs_header_nritems(leaf)) { > + /* > + * if we've reached the last slot in this leaf we need > + * to go to the next leaf and reset the path > + */ > + ret = btrfs_next_leaf(root, path); > + if (ret) > + return ret; > + continue; > + } > + /* store the found, valid item in key */ > + btrfs_item_key_to_cpu(leaf, key, slot); > + break; > + } > + return 0; > +} > + > /* > * adjust the pointers going up the tree, starting at level > * making sure the right key of each node is points to 'key'. > diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h > index 947f04789389..98091334b749 100644 > --- a/fs/btrfs/ctree.h > +++ b/fs/btrfs/ctree.h > @@ -2976,6 +2976,30 @@ int btrfs_next_old_leaf(struct btrfs_root *root, struct btrfs_path *path, > int btrfs_search_backwards(struct btrfs_root *root, struct btrfs_key *key, > struct btrfs_path *path); > > +int btrfs_get_next_valid_item(struct btrfs_root *root, struct btrfs_key *key, > + struct btrfs_path *path); > + > +/* Search in @root for a given @key, and store the slot found in @found_key. > + * > + * @root: The root node of the tree. > + * @key: The key we are looking for. > + * @found_key: Will hold the found item. > + * @path: Holds the current slot/leaf. > + * @iter_ret: Contains the value returned from btrfs_search_slot or > + * btrfs_get_next_valid_item, whichever was executed last. > + * > + * The iter_ret is an output variable that will contain the return value of > + * btrfs_search_slot, if it encountered an error, or the value returned from > + * btrfs_get_next_valid_item, otherwise. That return value can be 0, if a valid > + * slot was found, 1 if there were no more leaves, and <0 if there was an error. > + */ > +#define btrfs_for_each_slot(root, key, found_key, path, iter_ret) \ > + for (iter_ret = btrfs_search_slot(NULL, root, key, path, 0, 0); \ > + iter_ret >= 0 && \ > + (iter_ret = btrfs_get_next_valid_item(root, found_key, path)) == 0; \ > + path->slots[0]++ \ As the arguments can be more than just an identifier it's safer to put them in ( ) in the definition, ie root/key/found_key/path/iter_ret shouls be all (root) etc