Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965052Ab2EOCRL (ORCPT ); Mon, 14 May 2012 22:17:11 -0400 Received: from mail.windriver.com ([147.11.1.11]:49004 "EHLO mail.windriver.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S964869Ab2EOCQJ (ORCPT ); Mon, 14 May 2012 22:16:09 -0400 From: Paul Gortmaker To: , Subject: [34-longterm 012/179] jbd: fix fsync() tid wraparound bug Date: Mon, 14 May 2012 22:11:48 -0400 Message-ID: <1337048075-6132-13-git-send-email-paul.gortmaker@windriver.com> X-Mailer: git-send-email 1.7.9.6 In-Reply-To: <1337048075-6132-1-git-send-email-paul.gortmaker@windriver.com> References: <1337048075-6132-1-git-send-email-paul.gortmaker@windriver.com> MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3098 Lines: 78 From: Ted Ts'o ------------------- This is a commit scheduled for the next v2.6.34 longterm release. http://git.kernel.org/?p=linux/kernel/git/paulg/longterm-queue-2.6.34.git If you see a problem with using this for longterm, please comment. ------------------- commit d9b01934d56a96d9f4ae2d6204d4ea78a36f5f36 upstream. If an application program does not make any changes to the indirect blocks or extent tree, i_datasync_tid will not get updated. If there are enough commits (i.e., 2**31) such that tid_geq()'s calculations wrap, and there isn't a currently active transaction at the time of the fdatasync() call, this can end up triggering a BUG_ON in fs/jbd/commit.c: J_ASSERT(journal->j_running_transaction != NULL); It's pretty rare that this can happen, since it requires the use of fdatasync() plus *very* frequent and excessive use of fsync(). But with the right workload, it can. We fix this by replacing the use of tid_geq() with an equality test, since there's only one valid transaction id that is valid for us to start: namely, the currently running transaction (if it exists). Reported-by: Martin_Zielinski@McAfee.com Signed-off-by: "Theodore Ts'o" Signed-off-by: Jan Kara Signed-off-by: Paul Gortmaker --- fs/jbd/journal.c | 16 +++++++++++++--- 1 file changed, 13 insertions(+), 3 deletions(-) diff --git a/fs/jbd/journal.c b/fs/jbd/journal.c index bd224ee..45905ff 100644 --- a/fs/jbd/journal.c +++ b/fs/jbd/journal.c @@ -435,9 +435,12 @@ int __log_space_left(journal_t *journal) int __log_start_commit(journal_t *journal, tid_t target) { /* - * Are we already doing a recent enough commit? + * The only transaction we can possibly wait upon is the + * currently running transaction (if it exists). Otherwise, + * the target tid must be an old one. */ - if (!tid_geq(journal->j_commit_request, target)) { + if (journal->j_running_transaction && + journal->j_running_transaction->t_tid == target) { /* * We want a new commit: OK, mark the request and wakup the * commit thread. We do _not_ do the commit ourselves. @@ -449,7 +452,14 @@ int __log_start_commit(journal_t *journal, tid_t target) journal->j_commit_sequence); wake_up(&journal->j_wait_commit); return 1; - } + } else if (!tid_geq(journal->j_commit_request, target)) + /* This should never happen, but if it does, preserve + the evidence before kjournald goes into a loop and + increments j_commit_sequence beyond all recognition. */ + WARN_ONCE(1, "jbd: bad log_start_commit: %u %u %u %u\n", + journal->j_commit_request, journal->j_commit_sequence, + target, journal->j_running_transaction ? + journal->j_running_transaction->t_tid : 0); return 0; } -- 1.7.9.6 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/