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 2FAB5C7EE2A for ; Tue, 23 May 2023 20:51:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238594AbjEWUvI (ORCPT ); Tue, 23 May 2023 16:51:08 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43884 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232531AbjEWUvG (ORCPT ); Tue, 23 May 2023 16:51:06 -0400 Received: from galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 68861DA for ; Tue, 23 May 2023 13:51:04 -0700 (PDT) From: Thomas Gleixner DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1684875061; 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; bh=xu3lh9FcdoeNVU96OzSdewnm6QGeZvQPxHHm1nN5R3o=; b=tSDD3fTqiWMazlzB0uscOaBYvMfkKxQ9Yr4u8hfs1K6DD8rg61sijq43Zt/QDRlF/fKD8l LdVdWgrNYPDr0EZ2IZj0uGiWiTEEJ4ufALsq/BlBFGTkHF8ALeaJc4Feb8FKsrvxdJgMAY xdbWK4lyC1JaSA9JJHvphcdDraUL+RWAlvmxFc2LTfRBcK77dlhyOjZ1M4uUMxA3MjWE3X YEWrrKkpjY+I/ITc6mzewzZLbKv8W8apJvXb0z4w4TYsHh28TwOFuy5VRJmLkYHiB4Hajn F6lCgkh/XcHysdEgZdDiqyoD9b/I4SeM4cogvr0RhgKlKirBZMG9mU2YJ7pAbQ== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1684875061; 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; bh=xu3lh9FcdoeNVU96OzSdewnm6QGeZvQPxHHm1nN5R3o=; b=kEoXdNpAMbORtwLPhvlREk3m9evosE9L6C3idDDMP4pPPX91PJFznyv0UwrE7alOmVf9FK uMwqzrRGezeT6TAQ== To: "Liam R. Howlett" Cc: LKML , Matthew Wilcox , linux-mm@kvack.org, Shanker Donthineni Subject: [PATCH v2] maple_tree: Fix a few documentation issues In-Reply-To: <20230523134646.gelsru64qvny3fi7@revolver> Date: Tue, 23 May 2023 22:51:01 +0200 Message-ID: <87ttw2n556.ffs@tglx> MIME-Version: 1.0 Content-Type: text/plain Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The documentation of mt_next() claims that it starts the search at the provided index. That's incorrect as it starts the search after the provided index. The documentation of mt_find() is slightly confusing. "Handles locking" is not really helpful as it does not explain how the "locking" works. 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. Fix similar issues for mt_find_after() and mt_prev(). Reword the confusing "Note: Will not return the zero entry." comment on mt_for_each() and document @__index correctly. Signed-off-by: Thomas Gleixner --- V2: Address review feedback. Add pointer to documentation, reword the zero entry and the index explanations. - Liam --- include/linux/maple_tree.h | 5 +++-- lib/maple_tree.c | 26 +++++++++++++++++++++----- 2 files changed, 24 insertions(+), 7 deletions(-) --- a/include/linux/maple_tree.h +++ b/include/linux/maple_tree.h @@ -659,10 +659,11 @@ 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 iterator skips all entries, which resolve to a NULL pointer, + * e.g. entries which has been reserved with XA_ZERO_ENTRY. */ #define mt_for_each(__tree, __entry, __index, __max) \ for (__entry = mt_find(__tree, &(__index), __max); \ --- a/lib/maple_tree.c +++ b/lib/maple_tree.c @@ -5947,7 +5947,11 @@ EXPORT_SYMBOL_GPL(mas_next); * @index: The start index * @max: The maximum index to check * - * Return: The entry at @index or higher, or %NULL if nothing is found. + * Takes RCU read lock internally to protect the search, which does not + * protect the returned pointer after dropping RCU read lock. + * See also: Documentation/core-api/maple_tree.rst + * + * Return: The entry higher than @index or %NULL if nothing is found. */ void *mt_next(struct maple_tree *mt, unsigned long index, unsigned long max) { @@ -6012,7 +6016,11 @@ EXPORT_SYMBOL_GPL(mas_prev); * @index: The start index * @min: The minimum index to check * - * Return: The entry at @index or lower, or %NULL if nothing is found. + * Takes RCU read lock internally to protect the search, which does not + * protect the returned pointer after dropping RCU read lock. + * See also: Documentation/core-api/maple_tree.rst + * + * Return: The entry before @index or %NULL if nothing is found. */ void *mt_prev(struct maple_tree *mt, unsigned long index, unsigned long min) { @@ -6487,9 +6495,15 @@ EXPORT_SYMBOL(mtree_destroy); * mt_find() - Search from the start up until an entry is found. * @mt: The maple tree * @index: Pointer which contains the start location of the search - * @max: The maximum value to check + * @max: The maximum value of the search range * - * Handles locking. @index will be incremented to one beyond the range. + * Takes RCU read lock internally to protect the search, which does not + * protect the returned pointer after dropping RCU read lock. + * See also: Documentation/core-api/maple_tree.rst + * + * In case that an entry is found @index is updated to point to the next + * possible entry independent whether the found entry is occupying a + * single index or a range if indices. * * Return: The entry at or after the @index or %NULL */ @@ -6548,7 +6562,9 @@ EXPORT_SYMBOL(mt_find); * @index: Pointer which contains the start location of the search * @max: The maximum value to check * - * Handles locking, detects wrapping on index == 0 + * Same as mt_find() except that it checks @index for 0 before + * searching. If @index == 0, the search is aborted. This covers a wrap + * around of @index to 0 in an iterator loop. * * Return: The entry at or after the @index or %NULL */