[lustre-discuss] Request of Lustre ldiskfs porting to vanilla Linux kernel

[Tung-Han Hsieh]

Dear All,

I hope that this is the right place to post our feature request
of Lustre file system.

Currently Lustre file system with ldiskfs backend server has to
compiled with specified Linux kernel versions of RedHat, or SuSE,
or other distributions which we haven't tried. But this is very
inconvenient and very painful to other distribution e.g. Debian
users. So our request is:

Whether it is possible to have future releases of Lustre file
system with ldiskfs backend server ported to vanilla Linux kernel ?

https://www.kernel.org/

Our reason is the following:

1. Our cluster environments are a bit complicated. We need Lustre
   file system, Infiniband drivers and software, Fibre driver for
   external storages, and almost newest CUDA driver for GPU computing.
   Hence most likely we cannot use the precompiled packages to install
   our clusters. Therefore, we decide to build Linux kernel, CUDA
   driver, Infiniband driver, and Lustre file system from source code,
   and try to get them work together.

2. We often choose vanilla Linux kernel as our source, because it is
   easier to switch, maintain, and available. Actually we cannot always
   use the newest release because sometimes the kernel Fibre driver may
   have abnormal problems (we did encounter these abnormalities several
   times).

3. Among all these, the most challenge part is building Lustre file
   system with ldiskfs server. Although we can build with patchless
   kernel, but ldiskfs itself is highly depending on the Ext4 source
   code of kernel. The build often failed at the source code patches
   in the very earily stage. We have done many times tring to figure
   out the conflicts of the patches, modify kernel source codes and
   patch files based on our best guesses, which of course is highly
   risky since we don't know whether our modification would break
   important functions or not.

4. We also tried to get the compatible Linux kernel source to build
   and run under Debian, e.g., SuSE Linux kernels. But these kernels
   are hardly to find, especially Lustre often referred to specifiec
   versions.  Further, RedHat kernel often cannot be compiled under
   Debian, because of the gcc version and feature problems.

Therefore, we are really hope that Lustre file system with ldiskfs
could have porting to the vanilla Linux kernel. They are very easily
available, very actively developped and updated. Actually, there are
several "longterm" maintained series, like 4.4.XXX, 4.9.XXX, 4.14.XXX,
etc. We would suggest that Lustre development team can target on a few
"longterm" maintained series for the porting. For example, for a specific
release of Lustre, it can target on, say, 4.4.250, 4.9.250, and 4.14.181.
Then that would be very enough and appreciate for our usage.

Best Regards,

T.H.Hsieh