On Mon, Dec 12, 2011 at 09:13:49AM -0500, Christoph Hellwig wrote: > The only reason that xfs_log_space_wake had to do opportunistic wakeups > was that the old xfs_log_move_tail calling convention didn't allow for > exact wakeups when not updating the log tail LSN. Man, that's a doosey. when you called xfs_log_move_tail... if you passed tail_lsn = 1 it would: not move the tail ignore strict accounting and wake only 1 if you passed tail_lsn = 0 it would: get tail_lsn from l_last_sync_lsn move the tail pay attention to strict accounting wake as many as is correct if you passed tail_lsn = !1, !0 it would: move the tail pay attention to strict accounting wake as many as is correct. The important thing to understand is that the opportunistic wakeups would ignore the the test (free_bytes < need_bytes) in xfs_log_move_tail, so you could wake a process regardless of whether there is sufficient space in the log for it. No wonder they had to pepper the code with opportunistic wakeups to prevent log space hangs... > Since this issue has > been fixed we can do exact wakeups now. > > Signed-off-by: Christoph Hellwig <hch@xxxxxx> > > --- > fs/xfs/xfs_log.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > Index: xfs/fs/xfs/xfs_log.c > =================================================================== > --- xfs.orig/fs/xfs/xfs_log.c 2011-12-11 15:30:49.977750776 +0100 > +++ xfs/fs/xfs/xfs_log.c 2011-12-11 17:49:00.692836117 +0100 > @@ -2748,7 +2748,7 @@ xlog_ungrant_log_space(xlog_t *log, > > trace_xfs_log_ungrant_exit(log, ticket); > > - xfs_log_space_wake(log->l_mp, true); > + xfs_log_space_wake(log->l_mp, false); Yeah, he's doing an _exact_ wakeup now. Reviewed-by: Ben Myers <bpm@xxxxxxx> _______________________________________________ xfs mailing list xfs@xxxxxxxxxxx http://oss.sgi.com/mailman/listinfo/xfs
