On Wed, Oct 26, 2016 at 11:56:07AM +1100, Dave Chinner wrote:
> On Tue, Oct 25, 2016 at 04:05:17PM -0700, Darrick J. Wong wrote:
> > By default, libxfs will use the kernel/system headers to define struct
> > fsxattr. Unfortunately, this creates a problem for developers who are
> > writing new features but building xfsprogs on a stable system, because
> > the stable kernel's headers don't reflect the new feature. In this
> > case, we want to be able to use the internal fsxattr definition while
> > the kernel headers catch up, so provide some configure magic to allow
> > developers to force the use of the internal definition.
> >
> > Signed-off-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
> ....
> > #include <stdio.h>
> > #include <asm/types.h>
> > #include <mntent.h>
> > +#ifdef OVERRIDE_SYSTEM_FSXATTR
> > +# define fsxattr sys_fsxattr
> > +#endif
> > #include <linux/fs.h> /* fsxattr defintion for new kernels */
> > +#ifdef OVERRIDE_SYSTEM_FSXATTR
> > +# undef fsxattr
> > +#endif
>
> messy, but I can't think of a cleaner way of doing this.
> >
> > static __inline__ int xfsctl(const char *path, int fd, int cmd, void *p)
> > {
> > @@ -175,7 +181,7 @@ static inline void platform_mntent_close(struct mntent_cursor * cursor)
> > * are a copy of the definitions moved to linux/uapi/fs.h in the 4.5 kernel,
> > * so this is purely for supporting builds against old kernel headers.
> > */
> > -#ifndef FS_IOC_FSGETXATTR
> > +#if !defined FS_IOC_FSGETXATTR || defined OVERRIDE_SYSTEM_FSXATTR
> > struct fsxattr {
> > __u32 fsx_xflags; /* xflags field value (get/set) */
> > __u32 fsx_extsize; /* extsize field value (get/set)*/
> > @@ -184,7 +190,9 @@ struct fsxattr {
> > __u32 fsx_cowextsize; /* cow extsize field value (get/set) */
> > unsigned char fsx_pad[8];
> > };
> > +#endif
> >
> > +#ifndef FS_IOC_FSGETXATTR
> > /*
> > * Flags for the fsx_xflags field
> > */
>
> Hmmm - what happens if all we are doing is introducing new flags?
> Doesn't the overide need to cover them as well?
As I did in the next patch, my intent is for the include/ header files to
define any flag that isn't picked up by the system headers. IOWs, the
OVERRIDE_SYSTEM_FSXATTR only helps us pick up changes to the struct
fsxattr definition.
#ifndef FS_XFLAG_MOOCOW
# define FS_XFLAG_MOOCOW 0xBEEF
#endif
(Inelegant, but oh well.)
--D
>
> Cheers,
>
> Dave.
> --
> Dave Chinner
> david@xxxxxxxxxxxxx
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