On Fri, Aug 23, 2013 at 3:48 AM, Stefan Behrens <sbehr...@giantdisaster.de> wrote: > On Wed, 21 Aug 2013 08:44:55 -0500, Mitch Harder wrote: >> I've had a hard time assembling a portable reproducer for this issue. >> >> I discovered that my reproducer was highly dependent on a local >> archive of out-of-date git kernel sources. My efforts to reproduce >> the error with a portable set of scripts with publicly available >> kernel git sources weren't successful. >> >> It seems like this issue is related to a corner-case workload that is >> difficult to reproduce. >> >> So I've bisected the error I was seeing with my local script, and >> identified the following commit as triggering my issue: >> >> commit: 3c64a1aba7cfcb04f79e76f859b3d66660275d59 >> Btrfs: cleanup: don't check the same thing twice >> https://git.kernel.org/cgit/linux/kernel/git/mason/linux-btrfs.git/commit/fs/btrfs?h=for-linus&id=3c64a1aba7cfcb04 >> >> I tested a kernel which reverted this change, and also added WARN_ON >> lines to provide a back trace. > [...] >> diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c >> index cd46e2c..a1091f7 100644 >> --- a/fs/btrfs/inode.c >> +++ b/fs/btrfs/inode.c >> @@ -2302,6 +2302,12 @@ static noinline int >> relink_extent_backref(struct btrfs_path *path, >> return 0; >> return PTR_ERR(root); >> } >> + if (btrfs_root_refs(&root->root_item) == 0) { >> + srcu_read_unlock(&fs_info->subvol_srcu, index); >> + /* parse ENOENT to 0 */ >> + WARN_ON(1); >> + return 0; >> + } > [...] >> [ 1616.886868] ------------[ cut here ]------------ >> [ 1616.886912] WARNING: at fs/btrfs/inode.c:2308 >> relink_extent_backref+0x103/0x721 [btrfs]() >> [ 1616.887050] Call Trace: >> [ 1616.887064] [<ffffffff8161a34a>] dump_stack+0x19/0x1b >> [ 1616.887071] [<ffffffff8103035a>] warn_slowpath_common+0x67/0x80 >> [ 1616.887077] [<ffffffff8103038d>] warn_slowpath_null+0x1a/0x1c >> [ 1616.887100] [<ffffffffa019ea82>] relink_extent_backref+0x103/0x721 >> [ 1616.887205] [<ffffffffa019f7e2>] btrfs_finish_ordered_io+0x742/0x829 > > Mitch, > > Thank you for this excellent work to find the cause of the issue. I've sent a > patch "Btrfs: fix for patch "cleanup: don't check the same thing twice"" and > would appreciate if you could repeat your test, just to make sure, because I > was never able to reproduce this issue myself. >
Thanks. I've tested my "special" workload with your patch on the latest 3.11_rc6 kernel, and the patch corrects the errors I was encountering. -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
