linux-kernel - Re: [PATCH v4 2/2] fs/dcache.c: fix spin lockup issue on nlru->lock

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Date:   Fri, 30 Jun 2017 08:46:57 +0530
From:   Sahitya Tummala <stummala@...eaurora.org>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     Alexander Polakov <apolyakov@...et.ru>,
        Vladimir Davydov <vdavydov.dev@...il.com>,
        Jan Kara <jack@...e.cz>, viro@...iv.linux.org.uk,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH v4 2/2] fs/dcache.c: fix spin lockup issue on nlru->lock


On 6/30/2017 4:18 AM, Andrew Morton wrote:
>
>> --- a/fs/dcache.c
>> +++ b/fs/dcache.c
>> @@ -1133,11 +1133,12 @@ void shrink_dcache_sb(struct super_block *sb)
>>   		LIST_HEAD(dispose);
>>   
>>   		freed = list_lru_walk(&sb->s_dentry_lru,
>> -			dentry_lru_isolate_shrink, &dispose, UINT_MAX);
>> +			dentry_lru_isolate_shrink, &dispose, 1024);
>>   
>>   		this_cpu_sub(nr_dentry_unused, freed);
>>   		shrink_dentry_list(&dispose);
>> -	} while (freed > 0);
>> +		cond_resched();
>> +	} while (list_lru_count(&sb->s_dentry_lru) > 0);
>>   }
>>   EXPORT_SYMBOL(shrink_dcache_sb);
> I'll add a cc:stable to this one - a large dentry list is a relatively
> common thing.
>
> I'm assumng that [1/2] does not need to be backported, OK?

I think we should include [1/2] as well along with this patch, as this patch
is using list_lru_count(), which can return incorrect count if [1/2] is 
not included.

Also, all the previous patches submitted for fixing this issue must be 
dropped i.e,
mm/list_lru.c: use cond_resched_lock() for nlru->lock must be dropped.

-- 
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