On 10/24/2012 12:23 AM, Theodore Ts'o wrote: > On Tue, Oct 23, 2012 at 11:27:09PM -0500, Eric Sandeen wrote: >> >> Ok, fair enough. If the BBU is working, nobarrier is ok; I don't trust >> journal_async_commit, but that doesn't mean this isn't a regression. > > Note that Toralf has reported almost exactly the same set of symptoms, > but he's using an external USB stick --- and as far as I know he > wasn't using nobarrier and/or the journal_async_commit. Toralf, can > you confirm what, if any, mount options you were using when you saw > it. > > I've been looking at this some more, and there's one other thing that > the short circuit code does, which is neglects setting the > JBD2_FLUSHED flag, which is used by the commit code to know when it > needs to reset the s_start fields in the superblock when we make our > next commit. However, this would only happen if the short circuit > code is getting hit some time other than when the file system is > getting unmounted --- and that's what Eric and I can't figure out how > it might be happening. Journal flushes outside of an unmount does > happen as part of online resizing, the FIBMAP ioctl, or when the file > system is frozen. But it didn't sound like Toralf or Nix was using > any of those features. (Toralf, Nix, please correct me if my > assumptions here is wrong). If I freeze w/ anything in the log, then s_start !=0 and we proceed normally. If I re-freeze w/o anything in the log, it's already set to FLUSHED (which makes sense) so not re-setting it doesn't matter. So I don't see that that's an issue. As for FIBMAP I think we only do journal_flush if it's data=journal. In other news, Phoronix is on the case, so expect escalating freakouts ;) -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
