Re: [PATCH 3/4] Move CONFIG_XFS handling to meson.build

[Thomas Huth <thuth@redhat.com>]

On 02/11/2021 12.34, Paolo Bonzini wrote:
> On 28/10/21 20:59, Thomas Huth wrote:
>> Checking for xfsctl() can be done more easily in meson.build. Also,
>> this is not a "real" feature like the other features that we provide
>> with the "--enable-xxx" and "--disable-xxx" switches for the
>> configure script, since this does not influence lots of code (it's
>> only about one call to xfsctl() in file-posix.c), so people don't
>> gain much with the ability to disable this with "--disable-xfsctl".
>> Let's rather treat this like the other cc.has_function() checks in
>> meson.build, i.e. don't add a new option for this in meson_options.txt.
>>
>> Signed-off-by: Thomas Huth <thuth@redhat.com>
> 
> I think we should just use ioctl and copy the relevant definitions from Linux:
> 
> struct dioattr {
>          u32           d_mem;          /* data buffer memory alignment */
>          u32           d_miniosz;      /* min xfer size                */
>          u32           d_maxiosz;      /* max xfer size                */
> };
> 
> #define XFS_IOC_DIOINFO        _IOR ('X', 30, struct dioattr)

I've now had a closer look at this idea, but it's getting messy: We'd 
additionally also need the platform_test_xfs_fd() function that is called 
from file-posix.c ... sure it's not big, but the XFS header stuff is 
licensed as LGPL, so it feels wrong to copy this over into file-posix.c that 
has a MIT license. Of course, it could be rewritten, or put into a separate 
file ... but that is already way more cumbersome for such a small benefit. 
So I think I prefer to rather keep my patch in the current shape that has a 
way nicer diffstat with way less risk of messing things up here.

  Thomas