From 7da6443aca9be29c6948dcbd636ad50154d0bc0c Mon Sep 17 00:00:00 2001 From: Artem Bityutskiy Date: Mon, 4 Apr 2011 17:16:39 +0300 Subject: UBIFS: fix debugging failure in dbg_check_space_info 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 Cc: stable@kernel.org [2.6.30+] --- 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 645737769c98..004d3745dc45 100644 --- a/fs/ubifs/debug.c +++ b/fs/ubifs/debug.c @@ -972,11 +972,39 @@ 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); } @@ -993,12 +1021,15 @@ 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", -- cgit v1.2.3