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From:   ebiederm@xmission.com (Eric W. Biederman)
To:     Al Viro <viro@zeniv.linux.org.uk>
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Date:   Thu, 20 Feb 2020 17:39:14 -0600
In-Reply-To: <20200220230309.GS23230@ZenIV.linux.org.uk> (Al Viro's message of
        "Thu, 20 Feb 2020 23:03:09 +0000")
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Subject: Re: [PATCH 4/7] proc: Use d_invalidate in proc_prune_siblings_dcache
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Al Viro <viro@zeniv.linux.org.uk> writes:

> On Thu, Feb 20, 2020 at 10:54:20PM +0000, Al Viro wrote:
>> On Thu, Feb 20, 2020 at 02:49:53PM -0600, Eric W. Biederman wrote:
>> > 
>> > The function d_prune_aliases has the problem that it will only prune
>> > aliases thare are completely unused.  It will not remove aliases for
>> > the dcache or even think of removing mounts from the dcache.  For that
>> > behavior d_invalidate is needed.
>> > 
>> > To use d_invalidate replace d_prune_aliases with d_find_alias
>> > followed by d_invalidate and dput.  This is safe and complete
>> > because no inode in proc has any hardlinks or aliases.
>> 
>> s/no inode.*/it's a fucking directory inode./
>
> Wait... You are using it for sysctls as well?  Ho-hum...  The thing is,
> for sysctls you are likely to run into consequent entries with the
> same superblock, making for a big pile of useless playing with
> ->s_active...  And yes, that applied to mainline as well

Which is why I worked to merge the two cases since they were so close.
Fewer things to fix and more eyeballs on the code.

Eric