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 X-Spam-Level: X-Spam-Status: No, score=-19.4 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,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 788BFC49EB7 for ; Mon, 28 Jun 2021 14:38:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6392E61CB1 for ; Mon, 28 Jun 2021 14:38:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234324AbhF1OlE (ORCPT ); Mon, 28 Jun 2021 10:41:04 -0400 Received: from mail.kernel.org ([198.145.29.99]:43572 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234600AbhF1Oi1 (ORCPT ); Mon, 28 Jun 2021 10:38:27 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id DBCF761CBB; Mon, 28 Jun 2021 14:31:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1624890664; bh=3hFt1p4Ipc5Usu0ADBa83BW6ndkZm9KgKlZUaxK4YJ4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Kxv+l8n7XVbK1S1gBW+9QD0DdH70v6rzZa2Dsp9P/cyfS7+ZiV+LZZaPr7CiWY7Qd 4+ELk6nHMY1TyPs853gbMhpevNitSWiEX2bD5OktTplfAeLVwYmks/0BOdVZsrWr2r eOjmcV0saLrqzQGUTOwYGzvCr1nf8e9pyuJy21fQzMsvgOWMSvgtLdO6+3M+cv6Nza a6fXbSE7L1H0WuiUjQKoE8Pn4PnqH81EFnKqdQce7Hj5DOUaW9YAB7CEReIwWIDXQ2 l2gfSV0J1CMk7RdR9KxeXZGe5DITZeZklbG2vAn85EDlnlSymxuc/EF+NDLA85SnQ1 2QHyY5MOJCKbw== From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Yang Shi , Zi Yan , "Kirill A . Shutemov" , Hugh Dickins , Alistair Popple , Jan Kara , Jue Wang , "Matthew Wilcox (Oracle)" , Miaohe Lin , Minchan Kim , Naoya Horiguchi , Oscar Salvador , Peter Xu , Ralph Campbell , Shakeel Butt , Wang Yugui , Andrew Morton , Linus Torvalds , Greg Kroah-Hartman Subject: [PATCH 5.4 55/71] mm: thp: replace DEBUG_VM BUG with VM_WARN when unmap fails for split Date: Mon, 28 Jun 2021 10:29:48 -0400 Message-Id: <20210628143004.32596-56-sashal@kernel.org> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20210628143004.32596-1-sashal@kernel.org> References: <20210628143004.32596-1-sashal@kernel.org> MIME-Version: 1.0 X-KernelTest-Patch: http://kernel.org/pub/linux/kernel/v5.x/stable-review/patch-5.4.129-rc1.gz X-KernelTest-Tree: git://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable-rc.git X-KernelTest-Branch: linux-5.4.y X-KernelTest-Patches: git://git.kernel.org/pub/scm/linux/kernel/git/stable/stable-queue.git X-KernelTest-Version: 5.4.129-rc1 X-KernelTest-Deadline: 2021-06-30T14:29+00:00 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Yang Shi [ Upstream commit 504e070dc08f757bccaed6d05c0f53ecbfac8a23 ] When debugging the bug reported by Wang Yugui [1], try_to_unmap() may fail, but the first VM_BUG_ON_PAGE() just checks page_mapcount() however it may miss the failure when head page is unmapped but other subpage is mapped. Then the second DEBUG_VM BUG() that check total mapcount would catch it. This may incur some confusion. As this is not a fatal issue, so consolidate the two DEBUG_VM checks into one VM_WARN_ON_ONCE_PAGE(). [1] https://lore.kernel.org/linux-mm/20210412180659.B9E3.409509F4@e16-tech.com/ Link: https://lkml.kernel.org/r/d0f0db68-98b8-ebfb-16dc-f29df24cf012@google.com Signed-off-by: Yang Shi Reviewed-by: Zi Yan Acked-by: Kirill A. Shutemov Signed-off-by: Hugh Dickins Cc: Alistair Popple Cc: Jan Kara Cc: Jue Wang Cc: "Matthew Wilcox (Oracle)" Cc: Miaohe Lin Cc: Minchan Kim Cc: Naoya Horiguchi Cc: Oscar Salvador Cc: Peter Xu Cc: Ralph Campbell Cc: Shakeel Butt Cc: Wang Yugui Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Note on stable backport: fixed up variables in split_huge_page_to_list(), and fixed up the conflict on ttu_flags in unmap_page(). Signed-off-by: Hugh Dickins Signed-off-by: Greg Kroah-Hartman --- mm/huge_memory.c | 24 +++++++----------------- 1 file changed, 7 insertions(+), 17 deletions(-) diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 9cb4e1e7e282..87a07aa61be0 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -2462,15 +2462,15 @@ static void unmap_page(struct page *page) { enum ttu_flags ttu_flags = TTU_IGNORE_MLOCK | TTU_IGNORE_ACCESS | TTU_RMAP_LOCKED | TTU_SPLIT_HUGE_PMD | TTU_SYNC; - bool unmap_success; VM_BUG_ON_PAGE(!PageHead(page), page); if (PageAnon(page)) ttu_flags |= TTU_SPLIT_FREEZE; - unmap_success = try_to_unmap(page, ttu_flags); - VM_BUG_ON_PAGE(!unmap_success, page); + try_to_unmap(page, ttu_flags); + + VM_WARN_ON_ONCE_PAGE(page_mapped(page), page); } static void remap_page(struct page *page) @@ -2749,7 +2749,7 @@ int split_huge_page_to_list(struct page *page, struct list_head *list) struct deferred_split *ds_queue = get_deferred_split_queue(page); struct anon_vma *anon_vma = NULL; struct address_space *mapping = NULL; - int count, mapcount, extra_pins, ret; + int extra_pins, ret; bool mlocked; unsigned long flags; pgoff_t end; @@ -2811,7 +2811,6 @@ int split_huge_page_to_list(struct page *page, struct list_head *list) mlocked = PageMlocked(page); unmap_page(head); - VM_BUG_ON_PAGE(compound_mapcount(head), head); /* Make sure the page is not on per-CPU pagevec as it takes pin */ if (mlocked) @@ -2834,9 +2833,7 @@ int split_huge_page_to_list(struct page *page, struct list_head *list) /* Prevent deferred_split_scan() touching ->_refcount */ spin_lock(&ds_queue->split_queue_lock); - count = page_count(head); - mapcount = total_mapcount(head); - if (!mapcount && page_ref_freeze(head, 1 + extra_pins)) { + if (page_ref_freeze(head, 1 + extra_pins)) { if (!list_empty(page_deferred_list(head))) { ds_queue->split_queue_len--; list_del(page_deferred_list(head)); @@ -2857,16 +2854,9 @@ int split_huge_page_to_list(struct page *page, struct list_head *list) } else ret = 0; } else { - if (IS_ENABLED(CONFIG_DEBUG_VM) && mapcount) { - pr_alert("total_mapcount: %u, page_count(): %u\n", - mapcount, count); - if (PageTail(page)) - dump_page(head, NULL); - dump_page(page, "total_mapcount(head) > 0"); - BUG(); - } spin_unlock(&ds_queue->split_queue_lock); -fail: if (mapping) +fail: + if (mapping) xa_unlock(&mapping->i_pages); spin_unlock_irqrestore(&pgdata->lru_lock, flags); remap_page(head); -- 2.30.2