Messages in this thread | | | Subject | Re: scsi: myrs: warning fix, was: [GIT PULL] first round of SCSI updates for the 4.19+ merge window | From | Hannes Reinecke <> | Date | Fri, 26 Oct 2018 16:28:14 +0200 |
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On 10/26/18 10:16 AM, Arnd Bergmann wrote: > On Wed, Oct 24, 2018 at 1:00 PM James Bottomley > <James.Bottomley@hansenpartnership.com> wrote: >> >> James Bottomley (1): >> scsi: myrs: fix build failure on 32 bit > > Hi James and Hannes, > > Since James mentioned 32-bit compiles during the kernel summit, > I'd like to confirm that I hit this on my randconfig builder now, > with some latency since the last linux-next tree I tested before > flying to Edinburgh did not have the bug, and the latest > linux-next tree that is available now (dated last Friday) does, and > I see your tree is fixed. During normal times, I should catch these > within a short time of the patch getting into scsi-next. > > However, while looking at this bug, I found two more issues related > to the specific computation: > > percent_complete = ldev_info->rbld_lba * 100 / ldev_info->cfg_devsize; > > I see that both rbld_lba and cfg_devsize are reported by the > device, but only the former is 64 bit but the latter is 32 bit and > also intended to be the larger of the two. I suspect this is a > bug, and the same is also present in the old DAC960.c. > cfg_devsize is followed by four reserved bytes in the header, > so I suppose it was meant to be 64-bit? > If you divide two 64-bit numbers, you also have to use div_u64_64() > instead of do_div(). > > On top of that, I see we get those values from the device but > never do any endianess conversion on them. It seems likely > that they are all little-endian and require a le32_to_cpu() > conversion to also work on big-endian kernel builds. Alternatively > we could make the Kconfig symbol as > 'depends on !CPU_BIG_ENDIAN || COMPILE_TEST'. > It _really_ is questionable if these device ever work on big-endian machines, as they rely on the BIOS to start up the RAID engine; I've had a hard enough time getting them to work on normal machines :-)
Plus the firmware refused to handle any drive larger than 4GB (!), so it's really a purely theoretical issue whether 'cfgsize' was meant to be 64 bit ...
Cheers,
Hannes
-- Dr. Hannes Reinecke zSeries & Storage hare@suse.com +49 911 74053 688 SUSE LINUX GmbH, Maxfeldstr. 5, 90409 Nürnberg GF: F. Imendörffer, J. Smithard, D. Upmanyu, G. Norton HRB 21284 (AG Nürnberg)
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