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Date: Fri, 9 Nov 2018 23:13:38 -0500
From: Pavel Tatashin <pasha.tatashin@soleen.com>
Subject: Re: [mm PATCH v5 7/7] mm: Use common iterator for
 deferred_init_pages and deferred_free_pages
Message-ID: <20181110041338.7ttram7po7a2ssz7@xakep.localdomain>
References: <154145268025.30046.11742652345962594283.stgit@ahduyck-desk1.jf.intel.com>
 <154145280115.30046.13334106887516645119.stgit@ahduyck-desk1.jf.intel.com>
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Sender: owner-linux-mm@kvack.org
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To: Alexander Duyck <alexander.h.duyck@linux.intel.com>
Cc: akpm@linux-foundation.org, linux-mm@kvack.org, sparclinux@vger.kernel.org, linux-kernel@vger.kernel.org, linux-nvdimm@lists.01.org, davem@davemloft.net, pavel.tatashin@microsoft.com, mhocko@suse.com, mingo@kernel.org, kirill.shutemov@linux.intel.com, dan.j.williams@intel.com, dave.jiang@intel.com, rppt@linux.vnet.ibm.com, willy@infradead.org, vbabka@suse.cz, khalid.aziz@oracle.com, ldufour@linux.vnet.ibm.com, mgorman@techsingularity.net, yi.z.zhang@linux.intel.com

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?

The rest is good:

Reviewed-by: Pavel Tatashin <pasha.tatashin@soleen.com>

Thank you,
Pasha