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=-15.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=unavailable 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 45E59C11F65 for ; Tue, 29 Jun 2021 02:35:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2B93561A1D for ; Tue, 29 Jun 2021 02:35:07 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231809AbhF2Chd (ORCPT ); Mon, 28 Jun 2021 22:37:33 -0400 Received: from mail.kernel.org ([198.145.29.99]:58204 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231805AbhF2Chc (ORCPT ); Mon, 28 Jun 2021 22:37:32 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 1678661A1D; Tue, 29 Jun 2021 02:35:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1624934105; bh=dc9u2zMjO0eTHghh8btbujdaSiOGNJ1liWXelQc8B9Y=; h=Date:From:To:Subject:In-Reply-To:From; b=h0Im7+dlglw6z1mqp7ydbCEb5B0rqKAMHBa+QWiArtrtuLkI3G2zHatLgBfjc5lTG a8grNNP91r5ZdSzGiP0X1OzccnHGZqqGDwzE4j6Rvykmj8YMSsmg/sjyQSgKpUShLd 6lDAoRkSXlhjq611phgdi5S2Dal36fWgf9YzCvx8= Date: Mon, 28 Jun 2021 19:35:04 -0700 From: Andrew Morton To: akpm@linux-foundation.org, aneesh.kumar@linux.ibm.com, dan.j.williams@intel.com, jack@suse.cz, linux-mm@kvack.org, mm-commits@vger.kernel.org, torvalds@linux-foundation.org, willy@infradead.org Subject: [patch 034/192] dax: fix ENOMEM handling in grab_mapping_entry() Message-ID: <20210629023504.arpzMvPnv%akpm@linux-foundation.org> In-Reply-To: <20210628193256.008961950a714730751c1423@linux-foundation.org> User-Agent: s-nail v14.8.16 Precedence: bulk Reply-To: linux-kernel@vger.kernel.org List-ID: X-Mailing-List: mm-commits@vger.kernel.org From: Jan Kara Subject: dax: fix ENOMEM handling in grab_mapping_entry() grab_mapping_entry() has a bug in handling of ENOMEM condition. Suppose we have a PMD entry at index i which we are downgrading to a PTE entry. grab_mapping_entry() will set pmd_downgrade to true, lock the entry, clear the entry in xarray, and decrement mapping->nrpages. The it will call: entry = dax_make_entry(pfn_to_pfn_t(0), flags); dax_lock_entry(xas, entry); which inserts new PTE entry into xarray. However this may fail allocating the new node. We handle this by: if (xas_nomem(xas, mapping_gfp_mask(mapping) & ~__GFP_HIGHMEM)) goto retry; however pmd_downgrade stays set to true even though 'entry' returned from get_unlocked_entry() will be NULL now. And we will go again through the downgrade branch. This is mostly harmless except that mapping->nrpages is decremented again and we temporarily have an invalid entry stored in xarray. Fix the problem by setting pmd_downgrade to false each time we lookup the entry we work with so that it matches the entry we found. Link: https://lkml.kernel.org/r/20210622160015.18004-1-jack@suse.cz Fixes: b15cd800682f ("dax: Convert page fault handlers to XArray") Signed-off-by: Jan Kara Reviewed-by: Dan Williams Cc: Matthew Wilcox Cc: "Aneesh Kumar K.V" Signed-off-by: Andrew Morton --- fs/dax.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) --- a/fs/dax.c~dax-fix-enomem-handling-in-grab_mapping_entry +++ a/fs/dax.c @@ -488,10 +488,11 @@ static void *grab_mapping_entry(struct x struct address_space *mapping, unsigned int order) { unsigned long index = xas->xa_index; - bool pmd_downgrade = false; /* splitting PMD entry into PTE entries? */ + bool pmd_downgrade; /* splitting PMD entry into PTE entries? */ void *entry; retry: + pmd_downgrade = false; xas_lock_irq(xas); entry = get_unlocked_entry(xas, order); _