Re: Regression: Disk corruption with dm-crypt and kernels >= 4.0

[Abelardo Ricart III <aricart@memnix.com>]

On Fri, 2015-05-01 at 18:24 -0400, Abelardo Ricart III wrote:
> On Fri, 2015-05-01 at 17:17 -0400, Mike Snitzer wrote:
> > On Fri, May 01 2015 at 12:37am -0400,
> > Abelardo Ricart III <aricart@memnix.com> wrote:
> > 
> > > I made sure to run a completely vanilla kernel when testing why I was 
> > > suddenly
> > > seeing some nasty libata errors with all kernels >= v4.0. Here's a 
> > > snippet:
> > > 
> > > -------------------->8--------------------
> > > [  165.592136] ata5.00: exception Emask 0x60 SAct 0x7000 SErr 0x800 
> > > action 
> > > 0x6
> > > frozen
> > > [  165.592140] ata5.00: irq_stat 0x20000000, host bus error
> > > [  165.592143] ata5: SError: { HostInt }
> > > [  165.592145] ata5.00: failed command: READ FPDMA QUEUED
> > > [  165.592149] ata5.00: cmd 60/08:60:a0:0d:89/00:00:07:00:00/40 tag 12 
> > > ncq 
> > > 4096
> > > in
> > >                         res 40/00:74:40:58:5d/00:00:00:00:00/40 Emask 0x60
> > > (host bus error)
> > > [  165.592151] ata5.00: status: { DRDY }
> > > -------------------->8--------------------
> > > 
> > > After a few dozen of these errors, I'd suddenly find my system in read
> > > -only
> > > mode with corrupted files throughout my encrypted filesystems (seemed like
> > > either a read or a write would corrupt a file, though I could be 
> > > mistaken). 
> > > I
> > > decided to do a git bisect with a random read-write-sync test to narrow 
> > > down
> > > the culprit, which turned out to be this commit (part of a series):
> > > 
> > > # first bad commit: [cf2f1abfbd0dba701f7f16ef619e4d2485de3366] dm crypt: 
> > > don't
> > > allocate pages for a partial request
> > > 
> > > Just to be sure, I created a patch to revert the entire nine patch series 
> > > that
> > > commit belonged to... and the bad behavior disappeared. I've now been 
> > > running
> > > kernel 4.0 for a few days without issue, and went so far as to stress 
> > > test 
> > > my
> > > poor SSD for a few hours to be 100% positive.
> > > 
> > > Here's some more info on my setup.
> > > 
> > > -------------------->8--------------------
> > > $ lsblk -f
> > > NAME         FSTYPE      LABEL MOUNTPOINT
> > > sda                  
> > > ├─sda1       vfat              /boot/EFI
> > > ├─sda2       ext4              /boot
> > > └─sda3       LVM2_member
> > >   ├─SSD-root crypto_LUKS
> > >   │ └─root   f2fs              /
> > >   └─SSD-home crypto_LUKS
> > >     └─home   f2fs              /home
> > > 
> > > $ cat /proc/cmdline
> > > BOOT_IMAGE=/vmlinuz-linux-memnix cryptdevice=/dev/SSD/root:root:allow
> > > -discards
> > > root=/dev/mapper/root acpi_osi=Linux security=tomoyo
> > > TOMOYO_trigger=/usr/lib/systemd/systemd intel_iommu=on
> > > modprobe.blacklist=nouveau rw quiet
> > > 
> > > $ cat /etc/lvm/lvm.conf | grep "issue_discards"
> > > issue_discards = 1
> > > -------------------->8--------------------
> > > 
> > > If there's anything else I can do to help diagnose the underlying 
> > > problem, 
> > > I'm
> > > more than willing.
> > 
> > The patchset in question was tested quite heavily so this is a
> > surprising report.  I'm noticing you are opting in to dm-crypt discard
> > support.  Have you tested without discards enabled?
> 
> I've disabled discards universally and rebuilt a vanilla kernel. After running
> my heavy read-write-sync scripts, everything seems to be working fine now. I
> suppose this could be something that used to fail silently before, but now
> produces bad behavior? I seem to remember having something in my message log
> about "discards not supported on this device" when running with it enabled
> before.

Forgive me, but I spoke too soon. The corruption and libata errors are still
there, as was evidenced when I went to reboot and got treated to an eye full of
"read-only filesystem" and ata errors.

So no, disabling discards unfortunately did nothing to help.