What will happen on attempt to write to read-only page when CONFIG_MEM_SOFT_DIRTY is off ?

[Lev Olshvang]

Hello all,
Please help me to clarify what will page fault handler do (if any)

File arch/x86/include/asm/pgtable_types.h have following comment for  2  PAGE_DIRTY_BITs

#define _PAGE_BIT_DIRTY		6	/* was written to (raised by CPU) */
_PAGE_BIT_SOFT_DIRTY	_PAGE_BIT_SOFTW3 /* software dirty tracking */

While documentation clearly explains that Page Fault handler sets second flag
https://www.kernel.org/doc/Documentation/vm/soft-dirty.txt

I do not have idea what will happen when tracking Soft Dirty flags is off, I suppose the answer is in mm/gup.c 
but I was not able to track it to page handler.

Thanks you all.
Lev.