On Mon, Jul 24, 2006 at 03:57:30PM +1000, Nathan Scott wrote:
> Hi,
>
> I started running the QA tests with an external log on a ramdisk &
> now constantly see situations where xlog_state_so_callback reports:
>
> Filesystem "sda2": xlog_state_do_callback: looping 10
> Filesystem "sda2": xlog_state_do_callback: looping 20
> Filesystem "sda2": xlog_state_do_callback: looping 10
> Filesystem "sda2": xlog_state_do_callback: looping 10
> Filesystem "sda2": xlog_state_do_callback: looping 10
> Filesystem "sda2": xlog_state_do_callback: looping 20
>
> on the system console. Tim and I looked into this further, and remembered
> long ago list discussion on the topic, after others reported this too (also
> on ramdisks interestingly):
> http://oss.sgi.com/archives/xfs/2005-02/msg00108.html
> http://oss.sgi.com/archives/xfs/2005-02/msg00109.html
>
> So, it seems Glen added this to try detect infinte loops on systems where
> we do log callback processing in interrupt context (i.e. IRIX). It seems
> that with ramdisks its causing spurious warnings due to how quickly the
> completion handlers will be run (immediate, sync) though. We can quite
> easily still keep the same infinite loop check but bump up the reporting
> threshold to something that wont happen for ramdisks/raid caches ... and
> report each several-thousand iterations instead of each tenth one. It
> does still seems worthwhile to keep the infinte loop detection though, so
> at this stage I've left that in there.
>
> Tim also insisted I optimise away the modulo operation that we do in the
> callback processing loop, while I was fixing this other issue, and he's
> pointed out an easy way to do that...
ok
> Index: xfs-linux/xfs_log.c
> ===================================================================
> --- xfs-linux.orig/xfs_log.c 2006-07-20 12:06:56.455633750 +1000
> +++ xfs-linux/xfs_log.c 2006-07-20 12:17:19.819492000 +1000
> @@ -2243,9 +2243,13 @@ xlog_state_do_callback(
>
> iclog = iclog->ic_next;
> } while (first_iclog != iclog);
> - if (repeats && (repeats % 10) == 0) {
> +
> + if (repeats > 5000) {
> + flushcnt += repeats;
> + repeats = 0;
> xfs_fs_cmn_err(CE_WARN, log->l_mp,
> - "xlog_state_do_callback: looping %d", repeats);
> + "%s: possible infinite loop (%d iterations)",
> + __FUNCTION__, flushcnt);
> }
> } while (!ioerrors && loopdidcallbacks);
>
> @@ -2277,6 +2281,7 @@ xlog_state_do_callback(
> }
> #endif
>
> + flushcnt = 0;
> if (log->l_iclog->ic_state & (XLOG_STATE_ACTIVE|XLOG_STATE_IOERROR)) {
> flushcnt = log->l_flushcnt;
> log->l_flushcnt = 0;
>
>
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