Re: 2.5.67-mm3

William Lee Irwin III
2003-04-15T04:39:47Z

William Lee Irwin III <wli@holomorphy.com> wrote:
>> + for (; addr < (unsigned long)uaddr + size && !ret; addr += PAGE_SIZE)
>> + ret = __put_user(0, (char *)max(addr, (unsigned long)uaddr));

On Mon, Apr 14, 2003 at 09:31:14PM -0700, Andrew Morton wrote:
> This hurts my brain. If anything, it should be formulated as a do-while loop.
> But I'm not sure we should really bother, because relatively large amounts of
> stuff is broken for PAGE_SIZE != PAGE_CACHE_SIZE anyway. tmpfs comes to
> mind...
> If page clustering needs to redo this code (and I assume it does) then that
> would be an argument in favour.

Page clustering wants something similar but slightly different. The
unit it wants as its stride (MMUPAGE_SIZE) isn't present so this doesn't
really help or hurt it. I believe I actually dodged this bullet by
ensuring (or incorrectly assuming) the callers used sizes <= MMUPAGE_SIZE
and left it either unaltered and suboptimal or (worst-case) buggy.

I'm just going down the list of FIXME's in the VM I turned up by grepping.
Should we do the following instead?

-- wli

diff -urpN mm3-2.5.67-2/include/linux/pagemap.h mm3-2.5.67-2A/include/linux/pagemap.h
--- mm3-2.5.67-2/include/linux/pagemap.h 2003-04-07 10:30:34.000000000 -0700
+++ mm3-2.5.67-2A/include/linux/pagemap.h 2003-04-14 21:24:52.000000000 -0700
@@ -169,7 +169,7 @@ extern void end_page_writeback(struct pa
/*
* Fault a userspace page into pagetables. Return non-zero on a fault.
*
- * FIXME: this assumes that two userspace pages are always sufficient. That's
+ * This assumes that two userspace pages are always sufficient. That's
* not true if PAGE_CACHE_SIZE > PAGE_SIZE.
*/
static inline int fault_in_pages_writeable(char *uaddr, int size)