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Subject: Re: [PATCH 2/4] fs/dcache: Report negative dentry number in
 dentry-state
To: Matthew Wilcox <willy@infradead.org>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>,
        Jonathan Corbet <corbet@lwn.net>, linux-kernel@vger.kernel.org,
        linux-doc@vger.kernel.org, linux-fsdevel@vger.kernel.org,
        "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Ingo Molnar <mingo@kernel.org>, Miklos Szeredi <mszeredi@redhat.com>
References: <1500298773-7510-1-git-send-email-longman@redhat.com>
 <1500298773-7510-3-git-send-email-longman@redhat.com>
 <20170717140934.GA14983@bombadil.infradead.org>
From: Waiman Long <longman@redhat.com>
Organization: Red Hat
Message-ID: <be481c43-c1ea-f2e9-8a64-09ee9c319ede@redhat.com>
Date: Mon, 17 Jul 2017 10:39:11 -0400
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On 07/17/2017 10:09 AM, Matthew Wilcox wrote:
> On Mon, Jul 17, 2017 at 09:39:31AM -0400, Waiman Long wrote:
>> @@ -63,9 +63,10 @@ struct qstr {
>>  struct dentry_stat_t {
>>  	long nr_dentry;
>>  	long nr_unused;
>> -	long age_limit;          /* age in seconds */
>> -	long want_pages;         /* pages requested by system */
>> -	long dummy[2];
>> +	long nr_negative;	/* # of negative dentries */
>> +	long age_limit;		/* age in seconds */
>> +	long want_pages;	/* pages requested by system */
>> +	long dummy;
>>  };
>>  extern struct dentry_stat_t dentry_stat;
> You can't just insert a field in the middle like that.  It'll break any code
> parsing /proc/sys/fs/dentry-state.  You have to put it at the end:
>
>  	long age_limit;          /* age in seconds */
>  	long want_pages;         /* pages requested by system */
> -	long dummy[2];
> +	long nr_negative;	/* # of negative dentries */
> +	long dummy;
>  };

My mistake. I will send out an updated patches later on after collecting
more feedback to make the new field go to the end.

Cheers,
Longman