On Mon, 2018-06-11 at 17:56 -0400, Bryan Gurney wrote: > On Mon, Jun 11, 2018 at 1:00 PM, Anthony Youngman > <anthony@xxxxxxxxxxxxxxx> wrote: > > On 11/06/18 16:06, James Bottomley wrote: > > > Well, this is the problem: a 4k logical (presumably 4k physical) > > > drive cannot be addressed in block sectors that are not divisible > > > by 8. This type of drive configuration is very unusual (although > > > it was something we tested years ago before the industry realised > > > it had to ship drives with 4k physical but 512 byte logical > > > sectors because of the legacy problem). > > > > I understood these drives were now becoming much more common, > > especially enterprise-grade drives. I know there were problems > > switching from 512/512 drives to 512/4096, but as you say I thought > > they were pretty much addressed. > > As soon as I saw the model number "HGST HUH721010AL", and did a > search, I said, "Oh, it's _this_ drive." > > The HGST Ultrastar He10 has both "512e Format" and "4K Native Format" > part numbers, so it's easy to potentially buy the wrong type of drive > (e.g.: accidentally buy a 4K Native drive, and discover some obscure > I/O failures). > > FYI, in my experience, when an application sends a > smaller-than-4096-bytes I/O to a 4096-bytes block device, the usual > error code that's sent by the driver is EINVAL (or "Invalid > argument"), so see if there's a log message citing that error code. We've done the work to make this function. However, it was a while ago and I don't believe anyone tests regularly now (particularly with the corner cases) so errors can creep back into the stack. > > I think it must be a couple of years ago now though, that I heard > > (on LWN) enterprise drives were apparently switching over to > > 4096/4096. With NO 512 emulation fall-back. > > Some drive manufacturers seem to be more eager than others, but > there's still work to be done. For example, try this with a 4K- > native drive: > > 1. Write an ISO image to the drive with the command "dd > if=isofile.iso of=/dev/testdevice bs=4096 oflag=direct" > > 2. Create a test directory (for example, "/mnt/testdir"), then > attempt to mount the device with "mount /dev/testdevice /mnt/testdir" This is a textbook case of something that can never work: The requirement for a 4k drive is that the stack must be aligned, meaning 4k or multiple of 4k block size all the way up and down. The isofs you're copying only has a 2k block size. You get the same failure with any non 4k multiple filesystem block size. Fortunately most modern filesystems have had 4k, or multiple thereof, block sizes for a while now, so you're unlikely to see this on your old ext4 devices but, in principle, it could happen. James > When I tried it on RHEL 7.5, I saw this: "kernel: isofs_fill_super: > bread failed, dev=testdevice, iso_blknum=17, block=-2147483648" > > Note that ISO filesystems have a 2048-byte block size (maximum), but > in this test, it's stored on a block device with a block size of 4096 > bytes. > > There may be more issues out there, but they have to be found first. > And finding the issues is difficult, due to the obscurity of the > error messages seen. > > > Thanks, > > Bryan >
