On Thu, Oct 26, 2017 at 11:41 AM, Roman Mamedov <rm@xxxxxxxxxxx> wrote: > On Thu, 26 Oct 2017 09:40:19 -0600 > Cheyenne Wills <cheyenne.wills@xxxxxxxxx> wrote: > >> Briefly when I upgraded a system from 4.0.5 kernel to 4.9.5 (and >> later) I'm seeing a blocked task timeout with heavy IO against a >> multi-lun btrfs filesystem. I've tried a 4.12.12 kernel and am still >> getting the hang. > > There is now 4.9.58 (fifty three versions later!) and 4.12 series is long > abandoned and gone from the charts altogether. So just in case, did you check > with the latest kernels? > > Also, keep in mind the 120 second warnings are just that, and not an error > condition by themselves. You can disable them or increase the maximum timeout > in sysctl settings. And it is not clear from your reports if you only get > warnings and after the load subsides everything is back to normal, or the FS > locks out "for good", i.e. with all access attempts hanging indefinitely and > no way to unmount the FS or otherwise recover. > > -- > With respect, > Roman Just tried a 4.13 kernel and it appears to have fixed the problem (at least the scrub hasn't locked up). Because the system didn't lock up, I was able to obtain some additional information and it appears that the core problem was a shortage of xen grant table frames. By increasing the gnttab_max_frames value in the xen host, I was not able to cause a system hang (even with some of the prior kernels -- well at least a 4.12.12 kernel). I ended up closing the above mentioned issue. I included in the issue some of the information that I found so that if other folks are having the same problem there is some discussion on a possible solution. When the system wasn't hanging with the 4.13 kernel, I was getting an error message about the grant tables. Doing some searches with that information, I was able to find a discussion on "I/O to LUNs hang / stall under high load when using xen-blkfront" Turns out that the number of grant tables has a relationship with the number of devices attached to a xen guest. Thanks for the assistance :) Cheyenne Wills -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
