From patchwork Tue Jun 8 18:27:35 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg KH X-Patchwork-Id: 457686 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-18.9 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER, INCLUDES_PATCH, MAILING_LIST_MULTI, SPF_HELO_NONE, SPF_PASS, URIBL_BLOCKED, USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id D70C1C4743D for ; Tue, 8 Jun 2021 18:48:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id BA81461461 for ; Tue, 8 Jun 2021 18:48:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233945AbhFHSup (ORCPT ); Tue, 8 Jun 2021 14:50:45 -0400 Received: from mail.kernel.org ([198.145.29.99]:42400 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235688AbhFHSrI (ORCPT ); Tue, 8 Jun 2021 14:47:08 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 3B11361417; Tue, 8 Jun 2021 18:38:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1623177481; bh=4FcyaguISM1PgqqomZKvZuyeUf7ahnUYCUJk4+qmEZA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=xfjl0IfjYSemaaOqsPEHIRTfUsExeWkQJcfWOumTJX1NSNE7fS7utTZZ9qF22UptG vQIgz0xVj8GXl1IqoJz1GnaU6d6gopucpmQ15ZawOIcL/QIAPcksFBEP7KuDekZU5t iqJJAob60SUKnLY3PF4LLjgQMFvbWXrc4OWH4v+g= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Greg Kroah-Hartman , "Matthew Wilcox (Oracle)" , Andrew Morton , "Kirill A . Shutemov" , Qian Cai , Song Liu , Linus Torvalds Subject: [PATCH 5.4 66/78] XArray: add xa_get_order Date: Tue, 8 Jun 2021 20:27:35 +0200 Message-Id: <20210608175937.496153693@linuxfoundation.org> X-Mailer: git-send-email 2.32.0 In-Reply-To: <20210608175935.254388043@linuxfoundation.org> References: <20210608175935.254388043@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: "Matthew Wilcox (Oracle)" commit 57417cebc96b57122a2207fc84a6077d20c84b4b upstream Patch series "Fix read-only THP for non-tmpfs filesystems". As described more verbosely in the [3/3] changelog, we can inadvertently put an order-0 page in the page cache which occupies 512 consecutive entries. Users are running into this if they enable the READ_ONLY_THP_FOR_FS config option; see https://bugzilla.kernel.org/show_bug.cgi?id=206569 and Qian Cai has also reported it here: https://lore.kernel.org/lkml/20200616013309.GB815@lca.pw/ This is a rather intrusive way of fixing the problem, but has the advantage that I've actually been testing it with the THP patches, which means that it sees far more use than it does upstream -- indeed, Song has been entirely unable to reproduce it. It also has the advantage that it removes a few patches from my gargantuan backlog of THP patches. This patch (of 3): This function returns the order of the entry at the index. We need this because there isn't space in the shadow entry to encode its order. [akpm@linux-foundation.org: export xa_get_order to modules] Signed-off-by: Matthew Wilcox (Oracle) Signed-off-by: Andrew Morton Cc: "Kirill A . Shutemov" Cc: Qian Cai Cc: Song Liu Link: https://lkml.kernel.org/r/20200903183029.14930-1-willy@infradead.org Link: https://lkml.kernel.org/r/20200903183029.14930-2-willy@infradead.org Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- include/linux/xarray.h | 9 +++++++++ lib/test_xarray.c | 21 +++++++++++++++++++++ lib/xarray.c | 40 ++++++++++++++++++++++++++++++++++++++++ 3 files changed, 70 insertions(+) --- a/include/linux/xarray.h +++ b/include/linux/xarray.h @@ -1470,6 +1470,15 @@ void xas_pause(struct xa_state *); void xas_create_range(struct xa_state *); +#ifdef CONFIG_XARRAY_MULTI +int xa_get_order(struct xarray *, unsigned long index); +#else +static inline int xa_get_order(struct xarray *xa, unsigned long index) +{ + return 0; +} +#endif + /** * xas_reload() - Refetch an entry from the xarray. * @xas: XArray operation state. --- a/lib/test_xarray.c +++ b/lib/test_xarray.c @@ -1649,6 +1649,26 @@ static noinline void check_account(struc #endif } +static noinline void check_get_order(struct xarray *xa) +{ + unsigned int max_order = IS_ENABLED(CONFIG_XARRAY_MULTI) ? 20 : 1; + unsigned int order; + unsigned long i, j; + + for (i = 0; i < 3; i++) + XA_BUG_ON(xa, xa_get_order(xa, i) != 0); + + for (order = 0; order < max_order; order++) { + for (i = 0; i < 10; i++) { + xa_store_order(xa, i << order, order, + xa_mk_index(i << order), GFP_KERNEL); + for (j = i << order; j < (i + 1) << order; j++) + XA_BUG_ON(xa, xa_get_order(xa, j) != order); + xa_erase(xa, i << order); + } + } +} + static noinline void check_destroy(struct xarray *xa) { unsigned long index; @@ -1697,6 +1717,7 @@ static int xarray_checks(void) check_reserve(&array); check_reserve(&xa0); check_multi_store(&array); + check_get_order(&array); check_xa_alloc(); check_find(&array); check_find_entry(&array); --- a/lib/xarray.c +++ b/lib/xarray.c @@ -1592,6 +1592,46 @@ unlock: return xas_result(&xas, NULL); } EXPORT_SYMBOL(xa_store_range); + +/** + * xa_get_order() - Get the order of an entry. + * @xa: XArray. + * @index: Index of the entry. + * + * Return: A number between 0 and 63 indicating the order of the entry. + */ +int xa_get_order(struct xarray *xa, unsigned long index) +{ + XA_STATE(xas, xa, index); + void *entry; + int order = 0; + + rcu_read_lock(); + entry = xas_load(&xas); + + if (!entry) + goto unlock; + + if (!xas.xa_node) + goto unlock; + + for (;;) { + unsigned int slot = xas.xa_offset + (1 << order); + + if (slot >= XA_CHUNK_SIZE) + break; + if (!xa_is_sibling(xas.xa_node->slots[slot])) + break; + order++; + } + + order += xas.xa_node->shift; +unlock: + rcu_read_unlock(); + + return order; +} +EXPORT_SYMBOL(xa_get_order); #endif /* CONFIG_XARRAY_MULTI */ /**