Well, then, at least fix the comment, from the rather oddly phrased:

#define __GFP_USER	0x40000u /* User is a userspace user */

to something more accurate such as:

#define __GFP_USER	0x40000u /* User and other really easily reclaimed pages */

This was a cleverly designed trick to push me over the 80 column per line limit. 
   I've seen through your ruse and added:

#define __GFP_USER     0x40000u /* User & other really easily reclaimed pages */

And consider adding a comment to its use in fs/buffer.c, where marking
a page obviously destined for kernel space __GFP_USER seems strange.
I doubt I will be the last person to look at the line of code and
scratch my head.

Done.  Patch with the two updated comments attached.

I think all hairs have been split and we can merge this one now.