On Wed, 20 Mar 2013 15:56:03 -0500 Brassow Jonathan <jbrassow@xxxxxxxxxx> wrote: > > On Mar 19, 2013, at 9:46 PM, NeilBrown wrote: > > > On Tue, 19 Mar 2013 16:15:35 -0500 Brassow Jonathan <jbrassow@xxxxxxxxxx> > > wrote: > > > >> > >> On Mar 17, 2013, at 6:49 PM, NeilBrown wrote: > >> > >>> On Wed, 13 Mar 2013 12:29:24 -0500 Jonathan Brassow <jbrassow@xxxxxxxxxx> > >>> wrote: > >>> > >>>> Neil, > >>>> > >>>> I've noticed that when too many devices fail in a RAID arrary that > >>>> addtional I/O will hang, yielding an endless supply of: > >>>> Mar 12 11:52:53 bp-01 kernel: Buffer I/O error on device md1, logical block 3 > >>>> Mar 12 11:52:53 bp-01 kernel: lost page write due to I/O error on md1 > >>>> Mar 12 11:52:53 bp-01 kernel: sector=800 i=3 (null) (null) > >>>> (null) (null) 1 > >>> > >>> This is the third report in as many weeks that mentions that WARN_ON. > >>> The first two where quite different causes. > >>> I think this one is the same as the first one, which means it would be fixed > >>> by > >>> md/raid5: schedule_construction should abort if nothing to do. > >>> > >>> which is commit 29d90fa2adbdd9f in linux-next. > >> > >> Sorry, I don't see this commit in linux-next: > >> (the "for-next" branch of) git://github.com/neilbrown/linux.git > >> or git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git > >> > >> Where should I be looking? > > > > Sorry, I probably messed up. > > I meant this commit: > > http://git.neil.brown.name/?p=md.git;a=commitdiff;h=ce7d363aaf1e28be8406a2976220944ca487e8ca > > Yes, I found this patch in 'for-next'. I tested 3.9.0-rc3 with and without this patch. The good news is that my issue with RAID5 appears to be fixed with this patch. To test, I simply created a 1GB RAID array, let it sync, killed all of the devices and then issued a 40M write request (4M block size). Before the patch, I would see the kernel warnings and it would take 7+ minutes to finish the 40M write. After the patch, I don't see the kernel warnings or call traces and it takes < 1 sec to finish the 40M write. That's good. Will this patch make it back to 3.[78]? > > However, I also found that RAID1 can take 2.5 min to perform the write and RAID10 can take 9+ min. Hung task messages with call traces and many many errors are the result. This is bad. I haven't figured out why these are so slow yet. What happens if you take RAID out of the picture? i.e. write to a single device, then "kill" that device, then try issuing a 40M write request to it. If that takes 2.5 minutes to resolve, then I think it is correct for RAID1 to also take 2.5 minutes to resolve. If it resolves much more quickly than it does with RAID1, then that is a problem we should certainly address. > > On a different topic, I've noticed the following commits in 'for-next': > 90584fc MD: Prevent sysfs operations on uninitialized kobjects > e3620a3 MD RAID5: Avoid accessing gendisk or queue structs when not available > but these are not in 3.9.0-rc3. They should make their way into 3.9.0 as well as 3.8.0. (They apply cleanly to the 3.8 kernel, but I hadn't bothered to notify 'stable' - only mention the regression was introduced in 3.8-rc1.) They are due to be sent to Linus today. The second one is tagged for -stable and will go to 3.8.x (I think 3.7.x is closed). The first isn't - my quick examination suggested that the current code is safe but not ideal. If you think it is appropriate for -stable (i.e. fixes a real bug that could hurt users) let me know why and I'll make sure it goes to -stable. NeilBrown
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