Re: [PATCH] vfs: fix statfs64() returning impossible EOVERFLOW for 64-bit f_files

From: Linus Torvalds
Date: Thu Oct 05 2017 - 21:31:36 EST

On Thu, Oct 5, 2017 at 4:06 PM, Al Viro <viro@xxxxxxxxxxxxxxxxxx> wrote:
> Just to make sure we are on the same page: out of kstatfs fields
> we have 5 u64 ones (see above; all of them are u64 is struct statfs64
> on all architectures), an opaque 64bit f_fsid and 5 fields that
> are long: f_type (magic numbers, all 32bit), f_namelen (max filename
> length), f_frsize (0 on most of filesystems, always fits into 32 bits),
> f_flags (guaranteed to be 32bit) and f_bsize.

Please just use that FITS_IN() kind of macro regardless.

If the sizes match, the compiler will optimize the test away.

If the sizes don't match, that FITS_IN() will do the right thing.

Do *not* manually go and say "these fields are ok, because..". The
whole bug was because people were confused about the field widths.