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 2DD4FC433FE for ; Fri, 25 Mar 2022 01:10:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1357146AbiCYBLe (ORCPT ); Thu, 24 Mar 2022 21:11:34 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:38280 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1357153AbiCYBL0 (ORCPT ); Thu, 24 Mar 2022 21:11:26 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3CB4764BCB for ; Thu, 24 Mar 2022 18:09:54 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id C258F6177D for ; Fri, 25 Mar 2022 01:09:53 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 25AF1C340EC; Fri, 25 Mar 2022 01:09:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1648170593; bh=ScfNCgSDD6pedCbQrNdSqkDjkRn4PGxjSfzYW38zyu8=; h=Date:To:From:In-Reply-To:Subject:From; b=ME5XJuqNdtRNxpyTqyXPwaigsRpJfLz/OY6ZQZyQ8ELJWN6h+HYH6srxnJkv3RMYX tUPC0QxonVrI0z/LZLfHK6Zmhuf4gzcdlyEb+EZxd3T8wOUqPpN11SJBqIhrmpjoVQ AtzWLIKrWfKpKATY5+tBiG1dmxdyqGGDcZ7Em2Fo= Date: Thu, 24 Mar 2022 18:09:52 -0700 To: willy@infradead.org, hughd@google.com, akpm@linux-foundation.org, patches@lists.linux.dev, linux-mm@kvack.org, mm-commits@vger.kernel.org, torvalds@linux-foundation.org, akpm@linux-foundation.org From: Andrew Morton In-Reply-To: <20220324180758.96b1ac7e17675d6bc474485e@linux-foundation.org> Subject: [patch 026/114] mm: filemap_unaccount_folio() large skip mapcount fixup Message-Id: <20220325010953.25AF1C340EC@smtp.kernel.org> Precedence: bulk Reply-To: linux-kernel@vger.kernel.org List-ID: X-Mailing-List: mm-commits@vger.kernel.org From: Hugh Dickins Subject: mm: filemap_unaccount_folio() large skip mapcount fixup The page_mapcount_reset() when folio_mapped() while mapping_exiting() was devised long before there were huge or compound pages in the cache. It is still valid for small pages, but not at all clear what's right to check and reset on large pages. Just don't try when folio_test_large(). Link: https://lkml.kernel.org/r/879c4426-4122-da9c-1a86-697f2c9a083@google.com Signed-off-by: Hugh Dickins Cc: Matthew Wilcox Signed-off-by: Andrew Morton --- mm/filemap.c | 26 +++++++++++++------------- 1 file changed, 13 insertions(+), 13 deletions(-) --- a/mm/filemap.c~mm-filemap_unaccount_folio-large-skip-mapcount-fixup +++ a/mm/filemap.c @@ -152,25 +152,25 @@ static void filemap_unaccount_folio(stru VM_BUG_ON_FOLIO(folio_mapped(folio), folio); if (!IS_ENABLED(CONFIG_DEBUG_VM) && unlikely(folio_mapped(folio))) { - int mapcount; - pr_alert("BUG: Bad page cache in process %s pfn:%05lx\n", current->comm, folio_pfn(folio)); dump_page(&folio->page, "still mapped when deleted"); dump_stack(); add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE); - mapcount = page_mapcount(&folio->page); - if (mapping_exiting(mapping) && - folio_ref_count(folio) >= mapcount + 2) { - /* - * All vmas have already been torn down, so it's - * a good bet that actually the folio is unmapped, - * and we'd prefer not to leak it: if we're wrong, - * some other bad page check should catch it later. - */ - page_mapcount_reset(&folio->page); - folio_ref_sub(folio, mapcount); + if (mapping_exiting(mapping) && !folio_test_large(folio)) { + int mapcount = page_mapcount(&folio->page); + + if (folio_ref_count(folio) >= mapcount + 2) { + /* + * All vmas have already been torn down, so it's + * a good bet that actually the page is unmapped + * and we'd rather not leak it: if we're wrong, + * another bad page check should catch it later. + */ + page_mapcount_reset(&folio->page); + folio_ref_sub(folio, mapcount); + } } } _