Re: [PATCH] Fix EXT4_FEATURE_RO_COMPAT_HUGE_FILE check

[Eric Sandeen <sandeen@redhat.com>]

Andreas Dilger wrote:

> This isn't the first time that we've had problems like this, and it
> won't be the last time unless there is a better API for checking
> these flags.

*nod*
 
> I've long thought about having something like:

Same thing crossed my mind; seems like a very good idea.

> #define EXT4_CHECK_COMPAT(sb, flag)    ((super)->s_feature_compat &     \
>                                           EXT4_FEATURE_COMPAT_ ## flag)
> #define EXT4_CHECK_RO_COMPAT(sb, flag) ((super)->s_feature_ro_compat &     \
>                                           EXT4_FEATURE_RO_COMPAT_ ## flag)
> #define EXT4_CHECK_INCOMPAT(sb, flag)  ((super)->s_feature_incompat &     \
>                                           EXT4_FEATURE_INCOMPAT_ ## flag)
> #define EXT4_SET_COMPAT(sb, flag)    do { (super)->s_feature_compat |=     \
>                                          EXT4_FEATURE_COMPAT_ ## flag; } while(0)
> #define EXT4_SET_RO_COMPAT(sb, flag) do { (super)->s_feature_ro_compat |=     \
>                                          EXT4_FEATURE_RO_COMPAT_ ##flag;} while(0)
> #define EXT4_SET_INCOMPAT(sb, flag)  do { (super)->s_feature_incompat |=     \
>                                          EXT4_FEATURE_INCOMPAT_ ## flag;} while(0)
> 
> This will produce a compile error if the flag name and the macro name
> don't match. Unfortunately, for e2fsprogs we will need 3 sets of such
> macros because the feature flags are named EXT2_*, EXT3_*, and
> EXT4_*, depending on when they were added. For the kernel code that
> wouldn't be needed.

Time to name them consistently in e2fsprogs, then, I think?

-Eric

> Cheers, Andreas