On Fri, Jun 16, 2017 at 12:24:45PM -0700, Darrick J. Wong wrote: > On Fri, Jun 16, 2017 at 08:35:10PM +0200, Luis R. Rodriguez wrote: > > On Fri, Jun 16, 2017 at 12:54:45PM +0200, Carlos Maiolino wrote: > > > When a buffer has been failed during writeback, the inode items into it > > > are kept flush locked, and are never resubmitted due the flush lock, so, > > > if any buffer fails to be written, the items in AIL are never written to > > > disk and never unlocked. > > > > > > This causes unmount operation to hang due these items flush locked in AIL, > > > > What type of hang? If it has occurred in production is there a trace somewhere? > > what does it look like? > > > > You said you would work on an xfstest for this, how's that going? Otherewise > > a commit log description of how to reproduce would be useful. > > I'm curious for an xfstest too, but I think Carlos /did/ tell us how to > reproduce -- create a thinp device, format XFS, fill it up, and try to > unmount. Well he did mention to create a Dm-thin device with a fileystem larger than the real device. You seem to have say just filling up a filsystem? Do both cases trigger the issue? > I don't think there /is/ much of a trace, just xfsaild doing > nothing and a bunch of ail items that are flush locked and stuck that way. OK so no hung task seek, no crash, just a system call that never ends? Is the issue recoverable? So unmount just never completes? Can we CTRL-C (SIGINT) out of it? > > > but this also causes the items in AIL to never be written back, even when > > > the IO device comes back to normal. > > > > > > I've been testing this patch with a DM-thin device, creating a > > > filesystem larger than the real device. > > > > > > When writing enough data to fill the DM-thin device, XFS receives ENOSPC > > > errors from the device, and keep spinning on xfsaild (when 'retry > > > forever' configuration is set). > > > > > > At this point, the filesystem can not be unmounted because of the flush locked > > > items in AIL, but worse, the items in AIL are never retried at all > > > (once xfs_inode_item_push() will skip the items that are flush locked), > > > even if the underlying DM-thin device is expanded to the proper size. > > > > Jeesh. > > > > If the above issue is a real hang, shoudl we not consider a sensible stable fix > > to start off with ? > > Huh? I thought this series is supposed to be the fix. It seems like a rather large set of changes, if the issue was sevee I was hoping for a stable candidate fix first. If its not fixing a severe issue then sure. Luis -- To unsubscribe from this list: send the line "unsubscribe linux-xfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
