Re: [PATCH RFC 00/15] decouple pagefault_disable() from preempt_disable()

[David Hildenbrand <dahi@linux.vnet.ibm.com>]

> > This series therefore does 2 things:
> > 
> > 
> > 1. Decouple pagefault_disable() from preempt_enable()
> > 
> > ...
> > 
> > 2. Reenable might_sleep() checks for might_fault()
> 
> All seems sensible to me.  pagefault_disabled has to go into the
> task_struct (rather than being per-cpu) because
> pagefault_disabled_inc() doesn't disable preemption, yes?
> 

Right, we can now get scheduled while in pagefault_disable() (if preemption
hasn't been disabled manually). So we have to store it per task/thread not per
cpu.

Actually even the preempt disable counter is only per-cpu for x86 and lives in
thread_info for all other archs (which is also not 100% clean but doesn't
matter at that point).

I had that pagefault disable counter in thread_info before, but that required
messing with asm-offsets of some arch (I had a proper version but this one
feels cleaner).

Thanks for having a look!

David