NVM and swap device

[Matthew Wilcox]

On Wed, Jan 13, 2016 at 09:26:29AM +0100, Hannes Reinecke wrote:
> On 01/13/2016 04:40 AM, Stephen Hemminger wrote:
> >I have a nice shiny new Intel NVM PCI card; decided to use it for a filesystem and swap.
> >The filesystem (btrfs) is doing fine, but the swap device was throwing occasional
> >random errors. Suspect a driver problem rather than hardware.
> >
> >I am using 4.4 kernel without patches.
> >
> >kern.log:Jan 12 08:11:57 xeon-e3 kernel: [159474.037390] Read-error on swap-device (259:0:17597808)
> >kern.log.1:Jan  7 08:32:10 xeon-e3 kernel: [87938.855526] Read-error on swap-device (259:0:11355648)
> >kern.log.1:Jan  7 08:32:10 xeon-e3 kernel: [87938.855530] Read-error on swap-device (259:0:11355656)
> >kern.log.1:Jan  7 08:32:10 xeon-e3 kernel: [87939.855467] Read-error on swap-device (259:0:16180824)
> >kern.log.1:Jan  8 08:24:07 xeon-e3 kernel: [63670.777981] Read-error on swap-device (259:0:32690768)
> >kern.log.1:Jan  9 09:25:02 xeon-e3 kernel: [153720.919325] Read-error on swap-device (259:0:220488)
> >kern.log.1:Jan  9 16:40:05 xeon-e3 kernel: [179820.957675] Read-error on swap-device (259:0:24476232)
> >kern.log.1:Jan  9 16:40:05 xeon-e3 kernel: [179820.962673] Read-error on swap-device (259:0:33292816)
> >
> >The swap device was being added via /etc/fstab by UUID.
> >
> >I gave up and went back to spinning rust for swap device for stabilty.
> >
> >Device partitions are:
> >
> >Disk /dev/nvme0n1: 781422768 sectors, 372.6 GiB
> >Logical sector size: 512 bytes
> >Disk identifier (GUID): 304117A4-18EF-4B51-92F4-8015758B5CB0
> >Partition table holds up to 128 entries
> >First usable sector is 34, last usable sector is 781422734
> >Partitions will be aligned on 8-sector boundaries
> >Total free space is 0 sectors (0 bytes)
> >
> >Number  Start (sector)    End (sector)  Size       Code  Name
> >    1              34            2047   1007.0 KiB  EF02  BIOS boot partition
> >    2            2048        33556479   16.0 GiB    8200  Linux swap
> >    3        33556480       781422734   356.6 GiB   8300  Linux filesystem
> >
> Ouch.
> 
> 34 sectors is aligned to basically nothing, and is guaranteed to trip any
> alignment issues there are.

Maybe, but that's the BIOS boot partition; who cares?  The swap partition
is aligned to 2048 sectors which should be good enough for anyone (it's 1MB).

Can you run a straight 'dd' from that partition, to see if you get errors?