From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758572Ab2CMBEY (ORCPT ); Mon, 12 Mar 2012 21:04:24 -0400 Received: from mail.windriver.com ([147.11.1.11]:46772 "EHLO mail.windriver.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758007Ab2CMAR5 (ORCPT ); Mon, 12 Mar 2012 20:17:57 -0400 From: Paul Gortmaker To: stable@kernel.org, linux-kernel@vger.kernel.org Cc: stable-review@kernel.org, Artem Bityutskiy , Paul Gortmaker Subject: [34-longterm 032/196] UBIFS: fix debugging failure in dbg_check_space_info Date: Mon, 12 Mar 2012 20:12:40 -0400 Message-Id: <1331597724-31358-33-git-send-email-paul.gortmaker@windriver.com> X-Mailer: git-send-email 1.7.9.3 In-Reply-To: <1331597724-31358-1-git-send-email-paul.gortmaker@windriver.com> References: <1331597724-31358-1-git-send-email-paul.gortmaker@windriver.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Artem Bityutskiy ------------------- This is a commit scheduled for the next v2.6.34 longterm release. If you see a problem with using this for longterm, please comment. ------------------- commit 7da6443aca9be29c6948dcbd636ad50154d0bc0c upstream. This patch fixes a debugging failure with which looks like this: UBIFS error (pid 32313): dbg_check_space_info: free space changed from 6019344 to 6022654 The reason for this failure is described in the comment this patch adds to the code. But in short - 'c->freeable_cnt' may be different before and after re-mounting, and this is normal. So the debugging code should make sure that free space calculations do not depend on 'c->freeable_cnt'. A similar issue has been reported here: http://lists.infradead.org/pipermail/linux-mtd/2011-April/034647.html This patch should fix it. For the -stable guys: this patch is only relevant for kernels 2.6.30 onwards. Signed-off-by: Artem Bityutskiy Signed-off-by: Paul Gortmaker --- fs/ubifs/debug.c | 41 ++++++++++++++++++++++++++++++++++++----- 1 file changed, 36 insertions(+), 5 deletions(-) diff --git a/fs/ubifs/debug.c b/fs/ubifs/debug.c index c2a68ba..923d697 100644 --- a/fs/ubifs/debug.c +++ b/fs/ubifs/debug.c @@ -961,11 +961,39 @@ void dbg_dump_index(struct ubifs_info *c) void dbg_save_space_info(struct ubifs_info *c) { struct ubifs_debug_info *d = c->dbg; - - ubifs_get_lp_stats(c, &d->saved_lst); + int freeable_cnt; spin_lock(&c->space_lock); + memcpy(&d->saved_lst, &c->lst, sizeof(struct ubifs_lp_stats)); + + /* + * We use a dirty hack here and zero out @c->freeable_cnt, because it + * affects the free space calculations, and UBIFS might not know about + * all freeable eraseblocks. Indeed, we know about freeable eraseblocks + * only when we read their lprops, and we do this only lazily, upon the + * need. So at any given point of time @c->freeable_cnt might be not + * exactly accurate. + * + * Just one example about the issue we hit when we did not zero + * @c->freeable_cnt. + * 1. The file-system is mounted R/O, c->freeable_cnt is %0. We save the + * amount of free space in @d->saved_free + * 2. We re-mount R/W, which makes UBIFS to read the "lsave" + * information from flash, where we cache LEBs from various + * categories ('ubifs_remount_fs()' -> 'ubifs_lpt_init()' + * -> 'lpt_init_wr()' -> 'read_lsave()' -> 'ubifs_lpt_lookup()' + * -> 'ubifs_get_pnode()' -> 'update_cats()' + * -> 'ubifs_add_to_cat()'). + * 3. Lsave contains a freeable eraseblock, and @c->freeable_cnt + * becomes %1. + * 4. We calculate the amount of free space when the re-mount is + * finished in 'dbg_check_space_info()' and it does not match + * @d->saved_free. + */ + freeable_cnt = c->freeable_cnt; + c->freeable_cnt = 0; d->saved_free = ubifs_get_free_space_nolock(c); + c->freeable_cnt = freeable_cnt; spin_unlock(&c->space_lock); } @@ -982,12 +1010,15 @@ int dbg_check_space_info(struct ubifs_info *c) { struct ubifs_debug_info *d = c->dbg; struct ubifs_lp_stats lst; - long long avail, free; + long long free; + int freeable_cnt; spin_lock(&c->space_lock); - avail = ubifs_calc_available(c, c->min_idx_lebs); + freeable_cnt = c->freeable_cnt; + c->freeable_cnt = 0; + free = ubifs_get_free_space_nolock(c); + c->freeable_cnt = freeable_cnt; spin_unlock(&c->space_lock); - free = ubifs_get_free_space(c); if (free != d->saved_free) { ubifs_err("free space changed from %lld to %lld", -- 1.7.9.3