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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id DC6B61075280 for ; Thu, 19 Mar 2026 09:14:24 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 0E1A46B044C; Thu, 19 Mar 2026 05:14:24 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 0B9A56B044E; Thu, 19 Mar 2026 05:14:24 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id F384D6B044F; Thu, 19 Mar 2026 05:14:23 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0017.hostedemail.com [216.40.44.17]) by kanga.kvack.org (Postfix) with ESMTP id E61736B044C for ; Thu, 19 Mar 2026 05:14:23 -0400 (EDT) Received: from smtpin06.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay03.hostedemail.com (Postfix) with ESMTP id A8516B9815 for ; Thu, 19 Mar 2026 09:14:23 +0000 (UTC) X-FDA: 84562251606.06.22C39A2 Received: from out-183.mta0.migadu.com (out-183.mta0.migadu.com [91.218.175.183]) by imf21.hostedemail.com (Postfix) with ESMTP id C1F121C0004 for ; Thu, 19 Mar 2026 09:14:21 +0000 (UTC) Authentication-Results: imf21.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=E8KC75sI; spf=pass (imf21.hostedemail.com: domain of lance.yang@linux.dev designates 91.218.175.183 as permitted sender) smtp.mailfrom=lance.yang@linux.dev; dmarc=pass (policy=none) header.from=linux.dev ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1773911662; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=gYXkNav1+HQX/FrEJ8HsLP07xF9bB7aK4BPpIVJxRmg=; b=vpLSqgnVM8Jq2wTOCXBz+MkxU/E+e86hhnSvI5SSHmne9zKH6aSjnsamRepJbnLE9l0Q8s gshvI3uHxBzLzPBK3EdGVYotk5Ao/pCkmViNManLOzKft0OC7GHFj7XhL/FfVGxDjMIrTz kajy7ERnjf7aOVH4oM2TA7wuQ3qIiVM= ARC-Authentication-Results: i=1; imf21.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=E8KC75sI; spf=pass (imf21.hostedemail.com: domain of lance.yang@linux.dev designates 91.218.175.183 as permitted sender) smtp.mailfrom=lance.yang@linux.dev; dmarc=pass (policy=none) header.from=linux.dev ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1773911662; a=rsa-sha256; cv=none; b=SzytBe54Z4M39iL0ZNbxMAIbKiYz9TZzzk1NJMuWm2sb6+YserCeG/FKuTqCR6XPclGT1Z 0mFi7mx7o3sVVbHGeBV9yy7XRuTjszCaNmPlz7hO98jpykCgXezc0nRkzDBQGwmGE1uFA6 6CGgWFaJ3s1GDypu5GsPF/8hpFMh71A= Message-ID: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1773911659; 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: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=gYXkNav1+HQX/FrEJ8HsLP07xF9bB7aK4BPpIVJxRmg=; b=E8KC75sIn/igZd6wRapbByk/rIhF7KrGPQPN9fafPCaBRxPbu3ogIttiA+zoTIx+GELYXF USlQ35JZjtQYZCRexz7VHtTpRufNnX7u9/o/1WSXAUYzgLFcTdCmKmKUiFM7/LOmaWKnMl tpXn4ok3Bi+POS7vZBoGQOhjnUXA2EI= Date: Thu, 19 Mar 2026 17:14:06 +0800 MIME-Version: 1.0 Subject: Re: [syzbot] [mm?] kernel BUG in collapse_scan_file Content-Language: en-US To: "David Hildenbrand (Arm)" , "Lorenzo Stoakes (Oracle)" Cc: syzbot , willy@infradead.org, baolin.wang@linux.alibaba.com, npache@redhat.com, linux-mm@kvack.org, baohua@kernel.org, ryan.roberts@arm.com, syzkaller-bugs@googlegroups.com, dev.jain@arm.com, ziy@nvidia.com, linux-kernel@vger.kernel.org, Liam.Howlett@oracle.com, akpm@linux-foundation.org References: <69bba3c0.050a0220.227207.002b.GAE@google.com> <10e5f1d6-077d-4783-aa16-6c8b98cb9e74@lucifer.local> X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Lance Yang In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Migadu-Flow: FLOW_OUT X-Rspam-User: X-Rspamd-Queue-Id: C1F121C0004 X-Rspamd-Server: rspam08 X-Stat-Signature: r6ukqcgkbsxdee43fid37dbh7as81h1f X-HE-Tag: 1773911661-966892 X-HE-Meta: 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 5JgCAv2N 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 2026/3/19 17:00, David Hildenbrand (Arm) wrote: > On 3/19/26 09:53, Lorenzo Stoakes (Oracle) wrote: >> On Thu, Mar 19, 2026 at 04:05:38PM +0800, Lance Yang wrote: >>> Ccing Willy >>> >>> IIUC, this is a dup of the earlier report[1], which I looked into back >>> in January. The root cause is the same: collapse_file() calls >>> xas_lock_irq() without resetting the xas state first, tripping the >>> XAS_INVALID() assertion: >>> >>> #define xas_lock_irq(xas) xa_lock_irq(XAS_INVALID(xas)->xa) >>> >>> static inline struct xa_state *XAS_INVALID(struct xa_state *xas) >>> { >>> XA_NODE_BUG_ON(xas->xa_node, xas_valid(xas)); >>> return xas; >>> } >>> >>> Added by commit: >>> >>> commit 43b00759f21b10142094d1ae5ff65cbb368953a3 >>> Author: Matthew Wilcox (Oracle) >>> Date: Sun Dec 14 10:53:31 2025 -0500 >>> >>> XArray: Add extra debugging check to xas_lock and friends >>> >>> While tracking down a recent bug, we discovered somewhere that had >>> forgotten to call xas_reset() before calling xas_lock(). Add a debug >>> check to be sure that doesn't happen in future and fix all the places in >>> the test suite which were carelessly doing just this. >>> >>> Suggested-by: Linus Torvalds >>> Signed-off-by: Matthew Wilcox (Oracle) >>> >>> I posted a HACK fix at the time[2], but David pointed out that Willy >>> had mentioned it likely needs more thought[3]. >> >> Hmm we shouldn't leave this bug in place while working for a fancier fix?? >> >> Can we get _something_ going as an upstream fix? We can improve whatever we do >> later right? >> >> David, thoughts? > > I recall Willy mentioning that the issue is likely a false positive. > > IIUC, that commit is not upstream? So it only triggers in linux-next. Right. That does not appear to be in upstream, I only see it in linux-next :) > Which means: > > 1) If it's a false positive, upstream is not effected (no XA_NODE_BUG_ON) > > 2) If it's not a false positive, upstream is effected but does not > trigger the XA_NODE_BUG_ON Yep. So this particular BUG_ON is not affecting upstream directly. That said, syzbot will likely keep hitting it in linux-next and generating noise for us until it is addressed there ...