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

[Andrew Price <anprice@redhat.com>]

On 09/04/2019 13:21, Steven Whitehouse wrote:
> 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. 

Is it the functions that aren't sensible or the use of the gfs2_ondisk.h 
structs as the containers for the native endian data? I'm not sure I get 
why the kernel functions like gfs2_dinode_in() are considered sensible 
and gfs2-utils' gfs2_dinode_in(), which does a similar thing but with a 
different struct, isn't sensible.

> 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.

Okay, I'll add back the bitwise annotations through typedefs to stdint.h 
types in a new header but I don't want to name it linux/types.h to avoid 
picking up the wrong one, so I'll just change that #include in 
gfs2_ondisk.h.

Andy