Messages in this thread | | | Subject | Re: [mm PATCH v5 7/7] mm: Use common iterator for deferred_init_pages and deferred_free_pages | From | Alexander Duyck <> | Date | Mon, 12 Nov 2018 07:12:13 -0800 |
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On 11/9/2018 8:13 PM, Pavel Tatashin wrote: > On 18-11-05 13:20:01, Alexander Duyck wrote: >> +static unsigned long __next_pfn_valid_range(unsigned long *i, >> + unsigned long end_pfn) >> { >> - if (!pfn_valid_within(pfn)) >> - return false; >> - if (!(pfn & (pageblock_nr_pages - 1)) && !pfn_valid(pfn)) >> - return false; >> - return true; >> + unsigned long pfn = *i; >> + unsigned long count; >> + >> + while (pfn < end_pfn) { >> + unsigned long t = ALIGN(pfn + 1, pageblock_nr_pages); >> + unsigned long pageblock_pfn = min(t, end_pfn); >> + >> +#ifndef CONFIG_HOLES_IN_ZONE >> + count = pageblock_pfn - pfn; >> + pfn = pageblock_pfn; >> + if (!pfn_valid(pfn)) >> + continue; >> +#else >> + for (count = 0; pfn < pageblock_pfn; pfn++) { >> + if (pfn_valid_within(pfn)) { >> + count++; >> + continue; >> + } >> + >> + if (count) >> + break; >> + } >> + >> + if (!count) >> + continue; >> +#endif >> + *i = pfn; >> + return count; >> + } >> + >> + return 0; >> } >> >> +#define for_each_deferred_pfn_valid_range(i, start_pfn, end_pfn, pfn, count) \ >> + for (i = (start_pfn), \ >> + count = __next_pfn_valid_range(&i, (end_pfn)); \ >> + count && ({ pfn = i - count; 1; }); \ >> + count = __next_pfn_valid_range(&i, (end_pfn))) > > Can this be improved somehow? It took me a while to understand this > piece of code. i is actually end of block, and not an index by PFN, ({pfn = i - count; 1;}) is > simply hard to parse. Why can't we make __next_pfn_valid_range() to > return both end and a start of a block?
One thing I could do is flip the direction and work from the end to the start. If I did that then 'i' and 'pfn' would be the same value and I wouldn't have to do the subtraction. If that works for you I could probably do that and it may actually be more efficient.
Otherwise I could probably pass pfn as a reference, and compute it in the case where count is non-zero.
> The rest is good: > > Reviewed-by: Pavel Tatashin <pasha.tatashin@soleen.com> > > Thank you, > Pasha >
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