linux-kernel - Re: [PATCH v3 04/11] readahead: rework loop in page_cache_ra

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Date: Tue, 26 Mar 2024 10:39:02 +0100
From: Hannes Reinecke <hare@...e.de>
To: Matthew Wilcox <willy@...radead.org>,
 "Pankaj Raghav (Samsung)" <kernel@...kajraghav.com>
Cc: linux-xfs@...r.kernel.org, linux-fsdevel@...r.kernel.org,
 gost.dev@...sung.com, chandan.babu@...cle.com, mcgrof@...nel.org,
 djwong@...nel.org, linux-mm@...ck.org, linux-kernel@...r.kernel.org,
 david@...morbit.com, akpm@...ux-foundation.org,
 Pankaj Raghav <p.raghav@...sung.com>
Subject: Re: [PATCH v3 04/11] readahead: rework loop in
 page_cache_ra_unbounded()

On 3/25/24 19:41, Matthew Wilcox wrote:
> On Wed, Mar 13, 2024 at 06:02:46PM +0100, Pankaj Raghav (Samsung) wrote:
>> @@ -239,8 +239,8 @@ void page_cache_ra_unbounded(struct readahead_control *ractl,
>>   			 * not worth getting one just for that.
>>   			 */
>>   			read_pages(ractl);
>> -			ractl->_index++;
>> -			i = ractl->_index + ractl->_nr_pages - index - 1;
>> +			ractl->_index += folio_nr_pages(folio);
>> +			i = ractl->_index + ractl->_nr_pages - index;
>>   			continue;
>>   		}
>>   
>> @@ -252,13 +252,14 @@ void page_cache_ra_unbounded(struct readahead_control *ractl,
>>   			folio_put(folio);
>>   			read_pages(ractl);
>>   			ractl->_index++;
>> -			i = ractl->_index + ractl->_nr_pages - index - 1;
>> +			i = ractl->_index + ractl->_nr_pages - index;
>>   			continue;
>>   		}
> 
> You changed index++ in the first hunk, but not the second hunk.  Is that
> intentional?

Hmm. Looks you are right; it should be modified, too.
Will be fixing it up.

Cheers,

Hannes