linux-kernel - Re: [PATCH 3/4] vfs: count unlinked inodes

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Date:	Mon, 21 Nov 2011 06:34:16 -0500
From:	Christoph Hellwig <hch@...radead.org>
To:	Miklos Szeredi <miklos@...redi.hu>
Cc:	viro@...IV.linux.org.uk, hch@...radead.org,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	jack@...e.cz, akpm@...ux-foundation.org,
	toshi.okajima@...fujitsu.com, mszeredi@...e.cz
Subject: Re: [PATCH 3/4] vfs: count unlinked inodes

On Mon, Nov 21, 2011 at 12:11:32PM +0100, Miklos Szeredi wrote:
> Do not WARN_ON if set_nlink is called with zero count, just do a
> ratelimited printk.  This happens on xfs and probably other
> filesystems after an unclean shutdown when the filesystem reads inodes
> which already have zero i_nlink.  Reported by Christoph Hellwig.

Given that this is part of the normal recovery process printing anything
seems like a bad idea.  I also don't think the code for this actually
is correct.

Remember when a filesystem recovery from unlinked but open inodes the
following happens:

 - we walk the list of unlinked but open inodes, and read them into
   memory, remove the linkage and then iput it.

With the current code that won't ever increment s_remove_count, but
decrement it from __destroy_inode.  I suspect the right fix is to
simply not warn for a set_nlink to zero, but rather simply increment
s_remove_count for that case.

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