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=-16.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,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 134F6C11F67 for ; Wed, 14 Jul 2021 03:37:04 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E82986127C for ; Wed, 14 Jul 2021 03:37:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237729AbhGNDjy (ORCPT ); Tue, 13 Jul 2021 23:39:54 -0400 Received: from mail104.syd.optusnet.com.au ([211.29.132.246]:49842 "EHLO mail104.syd.optusnet.com.au" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237758AbhGNDjw (ORCPT ); Tue, 13 Jul 2021 23:39:52 -0400 Received: from dread.disaster.area (pa49-181-34-10.pa.nsw.optusnet.com.au [49.181.34.10]) by mail104.syd.optusnet.com.au (Postfix) with ESMTPS id CA6C2864373 for ; Wed, 14 Jul 2021 13:36:58 +1000 (AEST) Received: from discord.disaster.area ([192.168.253.110]) by dread.disaster.area with esmtp (Exim 4.92.3) (envelope-from ) id 1m3Vhi-006IgD-3m for linux-xfs@vger.kernel.org; Wed, 14 Jul 2021 13:36:58 +1000 Received: from dave by discord.disaster.area with local (Exim 4.94) (envelope-from ) id 1m3Vhh-00B03J-SK for linux-xfs@vger.kernel.org; Wed, 14 Jul 2021 13:36:57 +1000 From: Dave Chinner To: linux-xfs@vger.kernel.org Subject: [PATCH 5/5] xfs: order CIL checkpoint start records Date: Wed, 14 Jul 2021 13:36:56 +1000 Message-Id: <20210714033656.2621741-6-david@fromorbit.com> X-Mailer: git-send-email 2.31.1 In-Reply-To: <20210714033656.2621741-1-david@fromorbit.com> References: <20210714033656.2621741-1-david@fromorbit.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Optus-CM-Score: 0 X-Optus-CM-Analysis: v=2.3 cv=F8MpiZpN c=1 sm=1 tr=0 a=hdaoRb6WoHYrV466vVKEyw==:117 a=hdaoRb6WoHYrV466vVKEyw==:17 a=e_q4qTt1xDgA:10 a=20KFwNOVAAAA:8 a=0SoGSWBIiDR9d1GlltwA:9 Precedence: bulk List-ID: X-Mailing-List: linux-xfs@vger.kernel.org From: Dave Chinner Because log recovery depends on strictly ordered start records as well as strictly ordered commit records. This is a zero day bug in the way XFS writes pipelined transactions to the journal which is exposed by fixing the zero day bug that prevents the CIL from pipelining checkpoints. This re-introduces explicit concurrent commits back into the on-disk journal and hence out of order start records. The XFS journal commit code has never ordered start records and we have relied on strict commit record ordering for correct recovery ordering of concurrently written transactions. Unfortunately, root cause analysis uncovered the fact that log recovery uses the LSN of the start record for transaction commit processing. Hence, whilst the commits are processed in strict order by recovery, the LSNs associated with the commits can be out of order and so recovery may stamp incorrect LSNs into objects and/or misorder intents in the AIL for later processing. This can result in log recovery failures and/or on disk corruption, sometimes silent. Because this is a long standing log recovery issue, we can't just fix log recovery and call it good. This still leaves older kernels susceptible to recovery failures and corruption when replaying a log from a kernel that pipelines checkpoints. There is also the issue that in-memory ordering for AIL pushing and data integrity operations are based on checkpoint start LSNs, and if the start LSN is incorrect in the journal, it is also incorrect in memory. Hence there's really only one choice for fixing this zero-day bug: we need to strictly order checkpoint start records in ascending sequence order in the log, the same way we already strictly order commit records. Signed-off-by: Dave Chinner --- fs/xfs/xfs_log.c | 1 + fs/xfs/xfs_log_cil.c | 69 +++++++++++++++++++++++++++++++++++-------- fs/xfs/xfs_log_priv.h | 1 + 3 files changed, 58 insertions(+), 13 deletions(-) diff --git a/fs/xfs/xfs_log.c b/fs/xfs/xfs_log.c index f41c6f388456..98d8fea6a83b 100644 --- a/fs/xfs/xfs_log.c +++ b/fs/xfs/xfs_log.c @@ -3777,6 +3777,7 @@ xlog_force_shutdown( * avoid races. */ spin_lock(&log->l_cilp->xc_push_lock); + wake_up_all(&log->l_cilp->xc_start_wait); wake_up_all(&log->l_cilp->xc_commit_wait); spin_unlock(&log->l_cilp->xc_push_lock); xlog_state_shutdown_callbacks(log); diff --git a/fs/xfs/xfs_log_cil.c b/fs/xfs/xfs_log_cil.c index 18a2d6a9f26e..5ef47aed10f9 100644 --- a/fs/xfs/xfs_log_cil.c +++ b/fs/xfs/xfs_log_cil.c @@ -587,6 +587,7 @@ xlog_cil_committed( */ if (abort) { spin_lock(&ctx->cil->xc_push_lock); + wake_up_all(&ctx->cil->xc_start_wait); wake_up_all(&ctx->cil->xc_commit_wait); spin_unlock(&ctx->cil->xc_push_lock); } @@ -640,7 +641,14 @@ xlog_cil_set_ctx_write_state( ASSERT(!ctx->commit_lsn); if (!ctx->start_lsn) { spin_lock(&cil->xc_push_lock); + /* + * The LSN we need to pass to the log items on transaction + * commit is the LSN reported by the first log vector write, not + * the commit lsn. If we use the commit record lsn then we can + * move the tail beyond the grant write head. + */ ctx->start_lsn = lsn; + wake_up_all(&cil->xc_start_wait); spin_unlock(&cil->xc_push_lock); return; } @@ -682,10 +690,16 @@ xlog_cil_set_ctx_write_state( * relies on the context LSN being zero until the log write has guaranteed the * LSN that the log write will start at via xlog_state_get_iclog_space(). */ +enum _record_type { + _START_RECORD, + _COMMIT_RECORD, +}; + static int xlog_cil_order_write( struct xfs_cil *cil, - xfs_csn_t sequence) + xfs_csn_t sequence, + enum _record_type record) { struct xfs_cil_ctx *ctx; @@ -708,19 +722,47 @@ xlog_cil_order_write( */ if (ctx->sequence >= sequence) continue; - if (!ctx->commit_lsn) { - /* - * It is still being pushed! Wait for the push to - * complete, then start again from the beginning. - */ - xlog_wait(&cil->xc_commit_wait, &cil->xc_push_lock); - goto restart; + + /* Wait until the LSN for the record has been recorded. */ + switch (record) { + case _START_RECORD: + if (!ctx->start_lsn) { + xlog_wait(&cil->xc_start_wait, &cil->xc_push_lock); + goto restart; + } + break; + case _COMMIT_RECORD: + if (!ctx->commit_lsn) { + xlog_wait(&cil->xc_commit_wait, &cil->xc_push_lock); + goto restart; + } + break; } } spin_unlock(&cil->xc_push_lock); return 0; } +/* + * Write out the log vector change now attached to the CIL context. This will + * write a start record that needs to be strictly ordered in ascending CIL + * sequence order so that log recovery will always use in-order start LSNs when + * replaying checkpoints. + */ +static int +xlog_cil_write_chain( + struct xfs_cil_ctx *ctx, + struct xfs_log_vec *chain) +{ + struct xlog *log = ctx->cil->xc_log; + int error; + + error = xlog_cil_order_write(ctx->cil, ctx->sequence, _START_RECORD); + if (error) + return error; + return xlog_write(log, ctx, chain, ctx->ticket, XLOG_START_TRANS); +} + /* * Write out the commit record of a checkpoint transaction to close off a * running log write. These commit records are strictly ordered in ascending CIL @@ -746,6 +788,10 @@ xlog_cil_write_commit_record( if (xlog_is_shutdown(log)) return -EIO; + error = xlog_cil_order_write(ctx->cil, ctx->sequence, _COMMIT_RECORD); + if (error) + return error; + error = xlog_write(log, ctx, &vec, ctx->ticket, XLOG_COMMIT_TRANS); if (error) xfs_force_shutdown(log->l_mp, SHUTDOWN_LOG_IO_ERROR); @@ -955,11 +1001,7 @@ xlog_cil_push_work( */ wait_for_completion(&bdev_flush); - error = xlog_write(log, ctx, &lvhdr, tic, XLOG_START_TRANS); - if (error) - goto out_abort_free_ticket; - - error = xlog_cil_order_write(ctx->cil, ctx->sequence); + error = xlog_cil_write_chain(ctx, &lvhdr); if (error) goto out_abort_free_ticket; @@ -1364,6 +1406,7 @@ xlog_cil_init( spin_lock_init(&cil->xc_push_lock); init_waitqueue_head(&cil->xc_push_wait); init_rwsem(&cil->xc_ctx_lock); + init_waitqueue_head(&cil->xc_start_wait); init_waitqueue_head(&cil->xc_commit_wait); INIT_LIST_HEAD(&ctx->committing); diff --git a/fs/xfs/xfs_log_priv.h b/fs/xfs/xfs_log_priv.h index f74e3968bb84..400471fa12d2 100644 --- a/fs/xfs/xfs_log_priv.h +++ b/fs/xfs/xfs_log_priv.h @@ -271,6 +271,7 @@ struct xfs_cil { xfs_csn_t xc_push_seq; struct list_head xc_committing; wait_queue_head_t xc_commit_wait; + wait_queue_head_t xc_start_wait; xfs_csn_t xc_current_sequence; struct work_struct xc_push_work; wait_queue_head_t xc_push_wait; /* background push throttle */ -- 2.31.1