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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id CA8C5C433EF for ; Tue, 12 Oct 2021 19:08:23 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id AC2BC60F3A for ; Tue, 12 Oct 2021 19:08:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232654AbhJLTKY (ORCPT ); Tue, 12 Oct 2021 15:10:24 -0400 Received: from mail.kernel.org ([198.145.29.99]:33398 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231751AbhJLTKY (ORCPT ); Tue, 12 Oct 2021 15:10:24 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 94BFA601FA; Tue, 12 Oct 2021 19:08:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1634065702; bh=xOsh0JSmkemRR5j1SF7p4r6ObbaUNKO/TXYXQqJydek=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=ifFDF/Zcnh7mo+8rlB+3RqUQs9SXYjw9ODVyRO7Wkx9LlmtfW0bqNgh7vsBhpIQ8m arjY4H3UYEj76wxHAhPvFPmqUSEnr2MURVBWk82ShY3SD1+nBLYHJFRTClKReFCK+w atpewWtdSwIqlT0/eGWSS6J4Mq2cEN4JdX7U2lM/jAzYiIIN0s6xOFY0kGDJzddDnS /8xvRwWdFhruVR3L6VOeOP7Abitg5Oo7+GbP8M45G8zDyuCxRhpfrxYYMVfPZEtEwB IE88W0G9KjUhsEI3Q2JgOzFA9uuZXbNAJTfR/gXx2XdcxN5RYYtSXVTLua9uulrnzT LtbFI3YBe4AbA== Date: Tue, 12 Oct 2021 12:08:22 -0700 From: "Darrick J. Wong" To: Brian Foster Cc: linux-xfs@vger.kernel.org Subject: Re: [PATCH v2 3/4] xfs: terminate perag iteration reliably on agcount Message-ID: <20211012190822.GN24307@magnolia> References: <20211012165203.1354826-1-bfoster@redhat.com> <20211012165203.1354826-4-bfoster@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20211012165203.1354826-4-bfoster@redhat.com> Precedence: bulk List-ID: X-Mailing-List: linux-xfs@vger.kernel.org On Tue, Oct 12, 2021 at 12:52:02PM -0400, Brian Foster wrote: > The for_each_perag_from() iteration macro relies on sb_agcount to > process every perag currently within EOFS from a given starting > point. It's perfectly valid to have perag structures beyond > sb_agcount, however, such as if a growfs is in progress. If a perag > loop happens to race with growfs in this manner, it will actually > attempt to process the post-EOFS perag where ->pag_agno == > sb_agcount. This is reproduced by xfs/104 and manifests as the > following assert failure in superblock write verifier context: > > XFS: Assertion failed: agno < mp->m_sb.sb_agcount, file: fs/xfs/libxfs/xfs_types.c, line: 22 > > Update the corresponding macro to only process perags that are > within the current sb_agcount. Does this need a Fixes: tag? Also ... should we be checking for agno <= agcount-1 for the initial xfs_perag_get in the first for loop clause of for_each_perag_range? I /think/ the answer is that the current users are careful enough to check that race, but I haven't looked exhaustively. Welcome back, by the way. :) --D > Signed-off-by: Brian Foster > --- > fs/xfs/libxfs/xfs_ag.h | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/fs/xfs/libxfs/xfs_ag.h b/fs/xfs/libxfs/xfs_ag.h > index cf8baae2ba18..b8cc5017efba 100644 > --- a/fs/xfs/libxfs/xfs_ag.h > +++ b/fs/xfs/libxfs/xfs_ag.h > @@ -142,7 +142,7 @@ struct xfs_perag *xfs_perag_next( > (pag) = xfs_perag_next((pag), &(agno))) > > #define for_each_perag_from(mp, agno, pag) \ > - for_each_perag_range((mp), (agno), (mp)->m_sb.sb_agcount, (pag)) > + for_each_perag_range((mp), (agno), (mp)->m_sb.sb_agcount - 1, (pag)) > > > #define for_each_perag(mp, agno, pag) \ > -- > 2.31.1 >