Build failure of 6.2.1.102 against 4.19.10 kernel

[brettwooldridge]

I am getting the following compilation error using tag 6.2.1.102 against kernel version 4.19.10:

In file included from /kvdo/vdo/../uds/memoryAlloc.h:30,
                 from /kvdo/vdo/kernel/histogram.c:24:
/kvdo/vdo/kernel/histogram.c: In function 'makeLogarithmicJiffiesHistogram':
/kvdo/vdo/../uds/permassert.h:114:5: error: duplicate case value
     case expr:              \
     ^~~~
/kvdo/vdo/kernel/histogram.c:600:3: note: in expansion of macro 'STATIC_ASSERT'
   STATIC_ASSERT((MSEC_PER_SEC % HZ) == 0);
   ^~~~~~~~~~~~~
/kvdo/vdo/../uds/permassert.h:113:5: note: previously used here
     case 0:                 \
     ^~~~
/kvdo/vdo/kernel/histogram.c:600:3: note: in expansion of macro 'STATIC_ASSERT'
   STATIC_ASSERT((MSEC_PER_SEC % HZ) == 0);
   ^~~~~~~~~~~~~
make[2]: *** [scripts/Makefile.build:303: /kvdo/vdo/kernel/histogram.o] Error 1
make[2]: *** Waiting for unfinished jobs....
make[1]: *** [scripts/Makefile.build:544: /kvdo/vdo] Error 2
make: *** [Makefile:1517: _module_/kvdo] Error 2
make: Leaving directory '/usr/src/linux-4.19.10'

[ghost]

Related: https://aur.archlinux.org/packages/kvdo-dkms/

[bgurney-rh]

For this system with kernel 4.19.10, what's the full kernel string? (In other words, what would you see if you ran "uname -r" in this kernel?)

Looking at the arch link above, if the kernel config has "CONFIG_HZ=300", this will result in 3.333333333333 milliseconds per jiffy

[bgurney-rh]

Note that the CONFIG_HZ kernel option can be different between Linux distributions; Fedora uses CONFIG_HZ=1000, and on checking an older Debian system, I see CONFIG_HZ=250.

[brettwooldridge]

Yeah, we figured that out. We’re recompiling the kernel with HZ=250.

Looking at the code it appears it needs to be refactored to dynamically calculate the histogram interval. Comments in the code seem to note this improvement requirement.

[corwin]

We will be fixing this in a future version, but it will be a few months before we get around to it. In the mean time, if recompiling the kernel with a different HZ setting is not a good long-term solution, removing the failing assertion should be safe. The only downside is that the histograms and possibly some other timing-related statistics may be inaccurate. The actual functioning of the device should be unaffected.

[brettwooldridge]

@corwin Thanks. We recompiled the kernel with HZ=250 and as a result are able to compile kvdo successfully. We are still having issues creating a volume, but it seems unrelated to this issue, so I am closing this for now.