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Re: [RFC] freeing unlinked file indefinitely delayed

From Al Viro <viro@ZenIV.linux.org.uk>
Newsgroups linux.kernel
Subject Re: [RFC] freeing unlinked file indefinitely delayed
Date 2015-07-12 17:10 +0200
Message-ID <pLr3b-1lE-5@gated-at.bofh.it> (permalink)
References <pJMEN-4OM-3@gated-at.bofh.it> <pJZVn-4A0-5@gated-at.bofh.it>
Organization linux.* mail to news gateway

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On Wed, Jul 08, 2015 at 10:41:43AM -0500, Ben Myers wrote:

> The bug rings a bell for me so I will stick my neck out instead of
> lurking.  Don't you need to sample that link count under the filesystems
> internal lock in order to avoid an unlink/iget race?  I suggest creating
> a helper to prune disconnected dentries which a filesystem could call in
> .unlink.  That would avoid the risk of unintended side effects with the
> d_alloc/d_free/icache approach and have provable link count correctness.

For one thing, this patch does *not* check for i_nlink at all.  For another,
there's no such thing as 'filesystems internal lock' for i_nlink protection -
that's handled by i_mutex...  And what does iget() have to do with any of that?
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Re: [RFC] freeing unlinked file indefinitely delayed Al Viro <viro@ZenIV.linux.org.uk> - 2015-07-12 17:10 +0200

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