Cache issues

[NIIBE Yutaka]

NIIBE Yutaka wrote:
 > I don't see any reason why we need to flush the cache here.
 > 
 > --- v2.4.6-pre5/mm/memory.c	Mon Jun 25 18:48:10 2001
 > +++ kernel/mm/memory.c	Tue Jun 26 14:48:15 2001
 > @@ -1109,8 +1109,6 @@ static int do_swap_page(struct mm_struct
 >  			return -1;
 >  		}
 >  		wait_on_page(page);
 > -		flush_page_to_ram(page);
 > -		flush_icache_page(vma, page);
 >  	}
 >  
 >  	/*

I've looked thorough all flush_page_to_ram and flush_icache_page calls.
If the architecture support follows the rule of Documentation/cachetlb.txt, 
I think that all the occurrences of flush_page_to_ram and
flush_icache_page are (almost) bogus now.

We have two issues yet:

(1) include/linux/highmem.h:memclear_highpage_flush
    We need to call flush_dcache_page here to remove flush_page_to_ram

(2) kernel/ptrace.c
    We need to call flush_dcache_page here too.
    Special care would be needed here.  I think that we cannot defer
    the flushing here.  There's the case where page->mapping ==
    &swapper_space, thus mapping->i_mmap == NULL 
    && mapping->i_mmap_shared == NULL.

Besides, flush_cache_page in mm/memory.c:{break_cow,do_wp_page}	are
redundant for SH-4.  SH-4's cache is direct mapped, virtually indexed
phisically tagged, so we don't need to flush anything.
--