Re: [PATCH 06/10] powerpc/mm/slice: implement slice_check_range_fits

[Nicholas Piggin <npiggin@gmail.com>]

On Tue, 6 Mar 2018 15:41:00 +0100
Christophe LEROY <christophe.leroy@c-s.fr> wrote:

> Le 06/03/2018 à 14:25, Nicholas Piggin a écrit :


> > +static bool slice_check_range_fits(struct mm_struct *mm,
> > +			   const struct slice_mask *available,
> > +			   unsigned long start, unsigned long len)
> >   {
> > -	DECLARE_BITMAP(result, SLICE_NUM_HIGH);
> > -	/*
> > -	 * Make sure we just do bit compare only to the max
> > -	 * addr limit and not the full bit map size.
> > -	 */
> > -	unsigned long slice_count = GET_HIGH_SLICE_INDEX(mm->context.slb_addr_limit);
> > +	unsigned long end = start + len - 1;
> > +	u64 low_slices = 0;
> >   
> > -	if (!SLICE_NUM_HIGH)
> > -		return (mask->low_slices & available->low_slices) ==
> > -		       mask->low_slices;
> > +	if (start < SLICE_LOW_TOP) {
> > +		unsigned long mend = min(end, (SLICE_LOW_TOP - 1));  
> 
> See slice_range_to_mask()
> 
> You'll have an issue here with PPC32, you have to cast (SLICE_LOW_TOP - 
> 1) to unsigned long because SLICE_LOW_TOP is unsigned long long on PPC32

Okay thanks. Forgot to cross compiled it on 8xx, so I'll do that next
time.

> > +
> > +		low_slices = (1u << (GET_LOW_SLICE_INDEX(mend) + 1))
> > +				- (1u << GET_LOW_SLICE_INDEX(start));
> > +	}
> > +	if ((low_slices & available->low_slices) != low_slices)
> > +		return false;
> > +
> > +	if (SLICE_NUM_HIGH && ((start + len) > SLICE_LOW_TOP)) {
> > +		unsigned long start_index = GET_HIGH_SLICE_INDEX(start);
> > +		unsigned long align_end = ALIGN(end, (1UL << SLICE_HIGH_SHIFT));
> > +		unsigned long count = GET_HIGH_SLICE_INDEX(align_end) - start_index;
> > +		unsigned long i;
> >   
> > -	bitmap_and(result, mask->high_slices,
> > -		   available->high_slices, slice_count);
> > +		for (i = start_index; i < start_index + count; i++) {
> > +			if (!test_bit(i, available->high_slices))
> > +				return false;
> > +		}  
> 
> What about using bitmap_find_next_zero_area()

I'll look at it. Perhaps in another patch, because existing
loops are not using bitmap range operations either. A series
to convert those is a good idea.

> > @@ -562,15 +571,11 @@ unsigned long slice_get_unmapped_area(unsigned long addr, unsigned long len,
> >   #endif
> >   
> >   	/* First check hint if it's valid or if we have MAP_FIXED */
> > -	if (addr != 0 || fixed) {
> > -		/* Build a mask for the requested range */
> > -		slice_range_to_mask(addr, len, &mask);
> > -		slice_print_mask(" mask", &mask);
> > -
> > +	if (addr || fixed) {  
> 
> It is cleanup, should it really be part of this patch ?



> > @@ -596,10 +601,11 @@ unsigned long slice_get_unmapped_area(unsigned long addr, unsigned long len,
> >   	slice_or_mask(&potential_mask, &good_mask);
> >   	slice_print_mask(" potential", &potential_mask);
> >   
> > -	if ((addr != 0 || fixed) &&
> > -			slice_check_fit(mm, &mask, &potential_mask)) {
> > -		slice_dbg(" fits potential !\n");
> > -		goto convert;
> > +	if (addr || fixed) {
> > +		if (slice_check_range_fits(mm, &potential_mask, addr, len)) {
> > +			slice_dbg(" fits potential !\n");
> > +			goto convert;
> > +		}  
> 
> Why not keep the original structure and just replacing slice_check_fit() 
> by slice_check_range_fits() ?
> 
> I believe cleanups should not be mixed with real feature changes. If 
> needed, you should have a cleanup patch up front the serie.

For code that is already changing, I think minor cleanups are okay if
they're very simple. Maybe this is getting to the point of needing
another patch. You've made valid points for a lot of other unnecessary
cleanups though, so I'll fix all of those.

Thanks,
Nick