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 E033BC77B7D for ; Mon, 15 May 2023 21:16:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S245491AbjEOVQX (ORCPT ); Mon, 15 May 2023 17:16:23 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46518 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S245496AbjEOVQS (ORCPT ); Mon, 15 May 2023 17:16:18 -0400 Received: from galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E4934A5C1 for ; Mon, 15 May 2023 14:16:14 -0700 (PDT) From: Thomas Gleixner DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1684185372; h=from:from:reply-to:subject:subject: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=DZHhrNE+lQbMd0iIV/PZ3+/ZDJKPK1+e6kKnPQuIdO4=; b=mjIcxdOMt117Z/QHUdcxvAHXIzHvqhmCiIOD4xmpVwTwKEFP3bAbA4CeE0Rbf7q97sD5xa XT5sPi25X90ACLaZuBUj533X3Gof2ZS+mkXZNl3+nGiDJy5Kxx71nsbfFeOn0UCx2gvHZr bowCkjef4fchr61EnWxh1gz2NK8ot5IByR204y7wZY966ZtDpEx7jKYbsjeBUvhMLBL1B/ 26Tr9LWuCQhQG06+xDS+u6Bn1jfRFhMeGO1F3R/QLLegky7enBvgqwzgRUqPCvLUdyozhT MrX4wCGrt2CwEEh1vKnNwG+ytq9epy97LtAeaEXtw1fs2LPN4GYU/rRfO+cUHw== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1684185372; h=from:from:reply-to:subject:subject: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=DZHhrNE+lQbMd0iIV/PZ3+/ZDJKPK1+e6kKnPQuIdO4=; b=mIWjKwOGTdaUTvRCsI5Y8rW11BO2lZGkbtLM/DOu1MtM/HOODl+KJnMyb5AEdyu4eunqr4 QNdFSjbS7c4xzpCg== To: "Liam R. Howlett" Cc: LKML , Matthew Wilcox , linux-mm@kvack.org, Shanker Donthineni Subject: Re: your mail In-Reply-To: <20230515192708.sypitem5hzycdois@revolver> References: <87mt2cxb7y.ffs@tglx> <20230515192708.sypitem5hzycdois@revolver> Date: Mon, 15 May 2023 23:16:11 +0200 Message-ID: <87wn198fdw.ffs@tglx> MIME-Version: 1.0 Content-Type: text/plain Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Liam! On Mon, May 15 2023 at 15:27, Liam R. Howlett wrote: > * Thomas Gleixner [230510 15:01]: >>Also the >> documentation of index talks about a range, while in reality the index >> is updated on a succesful search to the index of the found entry plus one. > > This is a range based tree, so the index is incremented beyond the last > entry which would return the entry. That is, if you search for 5 and > there is an entry at 4-100, the index would be 101 after the search - > or, one beyond the range. If you have single entries at a specific > index, then index would be equal to last and it would be one beyond the > index you found - but only because index == last in this case. Thanks for the explanation >> >> Fix similar issues for mt_find_after() and mt_prev(). >> >> Remove the completely confusing and pointless "Note: Will not return the >> zero entry." comment from mt_for_each() and document @__index correctly. > > The zero entry concept is an advanced API concept which allows you to > store something that cannot be seen by the mt_* family of users, so it > will not be returned and, instead, it will return NULL. Think of it as > a reservation for an entry that isn't fully initialized. Perhaps it > should read "Will not return the XA_ZERO_ENTRY" ? That makes actually sense. >> --- a/include/linux/maple_tree.h >> +++ b/include/linux/maple_tree.h >> @@ -659,10 +659,8 @@ void *mt_next(struct maple_tree *mt, uns >> * mt_for_each - Iterate over each entry starting at index until max. >> * @__tree: The Maple Tree >> * @__entry: The current entry >> - * @__index: The index to update to track the location in the tree >> + * @__index: The index to start the search from. Subsequently used as iterator. >> * @__max: The maximum limit for @index >> - * >> - * Note: Will not return the zero entry. > > This function "will not return the zero entry", meaning it will return > NULL if xa_is_zero(entry). Ack. >> + * Takes RCU read lock internally to protect the search, which does not >> + * protect the returned pointer after dropping RCU read lock. >> * >> - * Handles locking. @index will be incremented to one beyond the range. >> + * In case that an entry is found @index contains the index of the found >> + * entry plus one, so it can be used as iterator index to find the next >> + * entry. > > What about: > "In case that an entry is found @index contains the last index of the > found entry plus one" Something like that, yes. Let me try again. Thanks, tglx