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]) by smtp.lore.kernel.org (Postfix) with ESMTP id 2FBC7CCA479 for ; Mon, 18 Jul 2022 22:13:39 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 32A406B0071; Mon, 18 Jul 2022 18:13:39 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 2B2896B0073; Mon, 18 Jul 2022 18:13:39 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 12D176B0074; Mon, 18 Jul 2022 18:13:39 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0013.hostedemail.com [216.40.44.13]) by kanga.kvack.org (Postfix) with ESMTP id F11076B0071 for ; Mon, 18 Jul 2022 18:13:38 -0400 (EDT) Received: from smtpin11.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay06.hostedemail.com (Postfix) with ESMTP id BBC743583E for ; Mon, 18 Jul 2022 22:13:38 +0000 (UTC) X-FDA: 79701623316.11.F6E91D8 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by imf08.hostedemail.com (Postfix) with ESMTP id 5666B160071 for ; Mon, 18 Jul 2022 22:13:37 +0000 (UTC) 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 B300861538; Mon, 18 Jul 2022 22:13:36 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id DFF3AC341C0; Mon, 18 Jul 2022 22:13:35 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1658182415; bh=6sNH6sal5TicDehq4BhVSgQxonrBdrjzj1qkQO3IpZc=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=Jep36cTrn9SQVYkmm3O3YLkoKbgaTEQTGa57ZmONF0Bn98aLslFIPI+aeMMDnTFWD QViGm3mbzPGm09ShDjupZINzYt9Vsurt1GHosk/tD5N9X8kwevHYf9+gPf4C6aVMze iOwQYXF2yrxcMUdbj1PUUIEUjoih8j7FXXaEKhQGSRZWJeLS8bUHTOtYoXCw2480U8 VsefHX40HcAtybwFIwScOKBqvzI4ZQ+29sNii2cFxjQ+yivnOmDotFWs+SPPo862kG t5CeD5mjEJD6SzRwp4rFxxpWrbXyFv+mLhaAHpi7FwhaNX5D8zC0FcfiAeA8WZ0+ez oKDpiVX3ROzNA== Date: Mon, 18 Jul 2022 15:13:35 -0700 From: "Darrick J. Wong" To: Dan Williams Cc: "ruansy.fnst@fujitsu.com" , "linux-kernel@vger.kernel.org" , "linux-xfs@vger.kernel.org" , "nvdimm@lists.linux.dev" , "linux-mm@kvack.org" , "linux-fsdevel@vger.kernel.org" , "david@fromorbit.com" , "hch@infradead.org" , "jane.chu@oracle.com" Subject: Re: [RFC PATCH v6] mm, pmem, xfs: Introduce MF_MEM_REMOVE for unbind Message-ID: References: <20220410171623.3788004-1-ruansy.fnst@fujitsu.com> <20220714103421.1988696-1-ruansy.fnst@fujitsu.com> <62d05eb8e663c_1643dc294fa@dwillia2-xfh.jf.intel.com.notmuch> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <62d05eb8e663c_1643dc294fa@dwillia2-xfh.jf.intel.com.notmuch> ARC-Authentication-Results: i=1; imf08.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=Jep36cTr; dmarc=pass (policy=none) header.from=kernel.org; spf=pass (imf08.hostedemail.com: domain of djwong@kernel.org designates 139.178.84.217 as permitted sender) smtp.mailfrom=djwong@kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1658182418; 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: in-reply-to:in-reply-to:references:references:dkim-signature; bh=ZuLDXyqTl5dqqKEobSJu5+tlBHVV8KiQt+FSUAcxH18=; b=USUg5y/iApm+9xEY6LTxhPe3y8Qhv2p0EQTXMA33EPXWpddYVK1BNrRY7Nd18onL4DETdI +GN/GlTdZ/mgZuZCGDCLptJcin8KyKg0Uv7l2oeNpWrH52BBbdSISlFHg91XpE2MKzMwsj tHYJQBfjTGJ3iyGZkEy7heq6t786YKI= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1658182418; a=rsa-sha256; cv=none; b=xuv6N+MiPlCNq9/r1QFxGwA0jsbKZRMOnzSwitoypx43P45cf8HiGiJxc6cbbEoGrXyJt9 Pn9LPUUoq40/O5AcYFGqvokB7oytfpRjaQqFIO+Q/Eh2hXWTL9rQU8XkilWSfYMrHWzXBr 10TyKbvW+O4apnxsSWbKiDolIOQIMwI= X-Stat-Signature: dgamt87dhzwa63w4ck6bufftk9u34m8h X-Rspamd-Queue-Id: 5666B160071 X-Rspamd-Server: rspam08 Authentication-Results: imf08.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=Jep36cTr; dmarc=pass (policy=none) header.from=kernel.org; spf=pass (imf08.hostedemail.com: domain of djwong@kernel.org designates 139.178.84.217 as permitted sender) smtp.mailfrom=djwong@kernel.org X-Rspam-User: X-HE-Tag: 1658182417-791956 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Thu, Jul 14, 2022 at 11:21:44AM -0700, Dan Williams wrote: > ruansy.fnst@fujitsu.com wrote: > > This patch is inspired by Dan's "mm, dax, pmem: Introduce > > dev_pagemap_failure()"[1]. With the help of dax_holder and > > ->notify_failure() mechanism, the pmem driver is able to ask filesystem > > (or mapped device) on it to unmap all files in use and notify processes > > who are using those files. > > > > Call trace: > > trigger unbind > > -> unbind_store() > > -> ... (skip) > > -> devres_release_all() # was pmem driver ->remove() in v1 > > -> kill_dax() > > -> dax_holder_notify_failure(dax_dev, 0, U64_MAX, MF_MEM_PRE_REMOVE) > > -> xfs_dax_notify_failure() > > > > Introduce MF_MEM_PRE_REMOVE to let filesystem know this is a remove > > event. So do not shutdown filesystem directly if something not > > supported, or if failure range includes metadata area. Make sure all > > files and processes are handled correctly. > > > > == > > Changes since v5: > > 1. Renamed MF_MEM_REMOVE to MF_MEM_PRE_REMOVE > > 2. hold s_umount before sync_filesystem() > > 3. move sync_filesystem() after SB_BORN check > > 4. Rebased on next-20220714 > > > > Changes since v4: > > 1. sync_filesystem() at the beginning when MF_MEM_REMOVE > > 2. Rebased on next-20220706 > > > > [1]: https://lore.kernel.org/linux-mm/161604050314.1463742.14151665140035795571.stgit@dwillia2-desk3.amr.corp.intel.com/ > > > > Signed-off-by: Shiyang Ruan > > --- > > drivers/dax/super.c | 3 ++- > > fs/xfs/xfs_notify_failure.c | 15 +++++++++++++++ > > include/linux/mm.h | 1 + > > 3 files changed, 18 insertions(+), 1 deletion(-) > > > > diff --git a/drivers/dax/super.c b/drivers/dax/super.c > > index 9b5e2a5eb0ae..cf9a64563fbe 100644 > > --- a/drivers/dax/super.c > > +++ b/drivers/dax/super.c > > @@ -323,7 +323,8 @@ void kill_dax(struct dax_device *dax_dev) > > return; > > > > if (dax_dev->holder_data != NULL) > > - dax_holder_notify_failure(dax_dev, 0, U64_MAX, 0); > > + dax_holder_notify_failure(dax_dev, 0, U64_MAX, > > + MF_MEM_PRE_REMOVE); > > > > clear_bit(DAXDEV_ALIVE, &dax_dev->flags); > > synchronize_srcu(&dax_srcu); > > diff --git a/fs/xfs/xfs_notify_failure.c b/fs/xfs/xfs_notify_failure.c > > index 69d9c83ea4b2..6da6747435eb 100644 > > --- a/fs/xfs/xfs_notify_failure.c > > +++ b/fs/xfs/xfs_notify_failure.c > > @@ -76,6 +76,9 @@ xfs_dax_failure_fn( > > > > if (XFS_RMAP_NON_INODE_OWNER(rec->rm_owner) || > > (rec->rm_flags & (XFS_RMAP_ATTR_FORK | XFS_RMAP_BMBT_BLOCK))) { > > + /* Do not shutdown so early when device is to be removed */ > > + if (notify->mf_flags & MF_MEM_PRE_REMOVE) > > + return 0; > > xfs_force_shutdown(mp, SHUTDOWN_CORRUPT_ONDISK); > > return -EFSCORRUPTED; > > } > > @@ -174,12 +177,22 @@ xfs_dax_notify_failure( > > struct xfs_mount *mp = dax_holder(dax_dev); > > u64 ddev_start; > > u64 ddev_end; > > + int error; > > > > if (!(mp->m_sb.sb_flags & SB_BORN)) { > > xfs_warn(mp, "filesystem is not ready for notify_failure()!"); > > return -EIO; > > } > > > > + if (mf_flags & MF_MEM_PRE_REMOVE) { > > + xfs_info(mp, "device is about to be removed!"); > > + down_write(&mp->m_super->s_umount); > > + error = sync_filesystem(mp->m_super); > > + up_write(&mp->m_super->s_umount); > > Are all mappings invalidated after this point? No; all this step does is pushes dirty filesystem [meta]data to pmem before we lose DAXDEV_ALIVE... > The goal of the removal notification is to invalidate all DAX mappings > that are no pointing to pfns that do not exist anymore, so just syncing > does not seem like enough, and the shutdown is skipped above. What am I > missing? ...however, the shutdown above only applies to filesystem metadata. In effect, we avoid the fs shutdown in MF_MEM_PRE_REMOVE mode, which enables the mf_dax_kill_procs calls to proceed against mapped file data. I have a nagging suspicion that in non-PREREMOVE mode, we can end up shutting down the filesytem on an xattr block and the 'return -EFSCORRUPTED' actually prevents us from reaching all the remaining file data mappings. IOWs, I think that clause above really ought to have returned zero so that we keep the filesystem up while we're tearing down mappings, and only call xfs_force_shutdown() after we've had a chance to let xfs_dax_notify_ddev_failure() tear down all the mappings. I missed that subtlety in the initial ~30 rounds of review, but I figure at this point let's just land it in 5.20 and clean up that quirk for -rc1. > Notice that kill_dev_dax() does unmap_mapping_range() after invalidating > the dax device and that ensures that all existing mappings are gone and > cannot be re-established. As far as I can see a process with an existing > dax mapping will still be able to use it after this runs, no? I'm not sure where in akpm's tree I find kill_dev_dax()? I'm cribbing off of: https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git/tree/fs/xfs/xfs_notify_failure.c?h=mm-stable --D