Theodore Tso wrote: > On Tue, Oct 21, 2008 at 02:03:01PM -0400, Eric Paris wrote: > >> I can consistently get the below backtrace any time I try to shutdown my >> machine. This machine has ext4 as it's root FS. This is 100% >> reproducible. I backed out commit >> 3e624fc72fba09b6f999a9fbb87b64efccd38036 and it fixed the problem. >> >> This is a regression. >> > > Can you send me your .config, please? I'm trying to duplicate it on > my end. > > - Ted > Ted, you probably need some slab debugging on to hit it. I think the problem is that jbd2_journal_commit_transaction may call __jbd2_journal_drop_transaction(journal, commit_transaction) if the checkpoint lists are NULL, and this frees the commit_transaction. However, the call to ->j_commit_callback() tries to use it after that. I'm out of time for now to be sure this is the right fix, but something like this perhaps? Index: linux-2.6/fs/jbd2/commit.c =================================================================== --- linux-2.6.orig/fs/jbd2/commit.c 2008-10-27 11:24:42.000000000 -0500 +++ linux-2.6/fs/jbd2/commit.c 2008-10-27 17:19:22.771063324 -0500 @@ -992,15 +992,15 @@ restart_loop: commit_transaction->t_cpprev->t_cpnext = commit_transaction; } + if (journal->j_commit_callback) + journal->j_commit_callback(journal, commit_transaction); + + trace_mark(jbd2_end_commit, "dev %s transaction %d head %d", + journal->j_devname, commit_transaction->t_tid, + journal->j_tail_sequence); } spin_unlock(&journal->j_list_lock); - if (journal->j_commit_callback) - journal->j_commit_callback(journal, commit_transaction); - - trace_mark(jbd2_end_commit, "dev %s transaction %d head %d", - journal->j_devname, commit_transaction->t_tid, - journal->j_tail_sequence); jbd_debug(1, "JBD: commit %d complete, head %d\n", journal->j_commit_sequence, journal->j_tail_sequence); Also, I'm not certain that it matters, but the loop in release_blocks_on_commit() is kfreeing list entries w/o taking them off the list; I suppose maybe this is safe if the whole thing is getting discarded when we're done, but just to keep things sane, would this make sense (also, I think we need to double-check use of s_md_lock; it's taken when adding things to the list, but not when freeing/removing ... if it's needed, isn't it needed on both ends...): Index: linux-2.6/fs/ext4/mballoc.c =================================================================== --- linux-2.6.orig/fs/ext4/mballoc.c 2008-10-27 11:24:41.000000000 -0500 +++ linux-2.6/fs/ext4/mballoc.c 2008-10-27 17:19:43.401064490 -0500 @@ -2644,6 +2644,7 @@ static void release_blocks_on_commit(jou struct super_block *sb = journal->j_private; struct ext4_buddy e4b; struct ext4_group_info *db; + struct ext4_sb_info *sbi = EXT4_SB(sb); int err, count = 0, count2 = 0; struct ext4_free_data *entry; ext4_fsblk_t discard_block; @@ -2683,6 +2684,9 @@ static void release_blocks_on_commit(jou (unsigned long long) discard_block, entry->count); sb_issue_discard(sb, discard_block, entry->count); + spin_lock(&sbi->s_md_lock); + list_del(&entry->list); + spin_unlock(&sbi->s_md_lock); kmem_cache_free(ext4_free_ext_cachep, entry); ext4_mb_release_desc(&e4b); } -Eric -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
