[Cluster-devel] [PATCH] libgfs2: Import gfs2_ondisk.h

[Steven Whitehouse <swhiteho@redhat.com>]

Hi,

On 09/04/2019 13:18, Andrew Price wrote:
> On 09/04/2019 13:03, Christoph Hellwig wrote:
>> On Tue, Apr 09, 2019 at 10:41:53AM +0100, Andrew Price wrote:
>>> Give gfs2-utils its own copy of gfs2_ondisk.h which uses userspace
>>> types. This allows us to always support the latest ondisk structures 
>>> and
>>> obsoletes a lot of #ifdef GFS2_HAS_<FEATURE> blocks and configure.ac
>>> checks.
>>>
>>> gfs2_ondisk.h was changed simply by search-and-replace of the kernel 
>>> int
>>> types with the uintN_t, i.e.:
>>>
>>> :%s/__u\(8\|16\|32\|64\)/uint\1_t/g
>>> :%s/__be\(64\|32\|16\|8\)/uint\1_t/g
>>>
>>> and the linux/types.h include replaced with stdint.h
>>
>> Why?
>
> Because I'd like to be able to build gfs2-utils on FreeBSD one day. 
> Plus we get the handy stuff in inttypes.h to use, Linux doesn't have 
> that.
>
>> At least the be types give you really useful type checking with
>> sparse, which can be trivially wired up in userspace as well.
>
> If you mean the bitwise annotations that only sparse checks, we're 
> fairly safe in gfs2-utils in that anything represented by a struct is 
> going to have been parsed through one of the libgfs2/ondisk.c 
> functions so will be the right endianness. I run sparse over this code 
> very rarely anyway.

Those conversion functions are not sensible, thats why we got rid of 
them from the kernel code. It is better to have a set of types that have 
the endianess specified so that we can use sparse. Compile time checking 
is always a good plan where it is possible.


>
>> Also
>> keeping the file 1:1 the same is going to make your life much easier
>> in the future..
>
> It's really no difficulty to run the above substitutions the next time 
> the file changes, but gfs2_ondisk.h changes once in a blue moon anyway 
> so the maintenance overhead is going to be tiny.
>
> Andy
>
Thats true, but lets keep the ability to do endianess checks,

Steve.