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Subject: Re: [PATCH v3 0/5] fs/dcache: Limit # of negative dentries
To: "Wangkai (Kevin,C)" <wangkai86@huawei.com>,
        Alexander Viro <viro@zeniv.linux.org.uk>,
        Jonathan Corbet <corbet@lwn.net>
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        "linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>,
        "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
        Andrew Morton <akpm@linux-foundation.org>,
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From: Waiman Long <longman@redhat.com>
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Date: Fri, 18 Aug 2017 10:10:17 -0400
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On 08/18/2017 05:59 AM, Wangkai (Kevin,C) wrote:
>
>>> In my patch the DCACHE_FILE_REMOVED flag was to distinguish the
>>> removed file and The closed file, I found there was no difference of a
>>> dentry between the removed file and the closed File, they all on the lru list.
>> There is a difference between removed file and closed file. The type field of
>> d_flags will be empty for a removed file which indicate a negative dentry.
>> Anything else is a positive dentry. Look at the inline function d_is_negative()
>> [d_is_miss()] and you will see how it is done.
> After the file was removed, the dentry flag was not MISS, the flag was:
> DCACHE_REFERENCED | DCACHE_RCUACCESS | DCACHE_LRU_LIST | DCACHE_REGULAR_TYPE
> So, the dentry never be freed, until the kernel reclaim the slab memory.

The dentry_unlink_inode() function will clear DCACHE_REGULAR_TYPE.

Cheers,
Longman