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

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Date:	Mon, 19 Dec 2011 14:38:42 +0000
From:	Steven Whitehouse <swhiteho@...hat.com>
To:	Al Viro <viro@...IV.linux.org.uk>
Cc:	Miklos Szeredi <miklos@...redi.hu>, 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

Hi,

On Sat, 2011-12-17 at 07:36 +0000, Al Viro wrote:
> On Mon, Nov 21, 2011 at 12:11:32PM +0100, Miklos Szeredi wrote:
> > @@ -241,6 +242,11 @@ void __destroy_inode(struct inode *inode)
> >  	BUG_ON(inode_has_buffers(inode));
> >  	security_inode_free(inode);
> >  	fsnotify_inode_delete(inode);
> > +	if (!inode->i_nlink) {
> > +		WARN_ON(atomic_long_read(&inode->i_sb->s_remove_count) == 0);
> > +		atomic_long_dec(&inode->i_sb->s_remove_count);
> > +	}
> 
> Umm...  That relies on ->destroy_inode() doing nothing stupid; granted,
> all work on actual file removal should've been done in ->evice_inode()
> leaving only (RCU'd) freeing of in-core, but there are odd ones that
> do strange things in ->destroy_inode() and I'm not sure that it's not
> a Yet Another Remount Race(tm).  OTOH, it's clearly not worse than what
> we used to have; just something to keep in mind for future work.
> 
GFS2 is one of those cases. The issue is that when we enter
->evict_inode() with i_nlink 0, we do not know whether any other node
still has the inode open. If it does, then we do not deallocate it in
->evict_inode() but instead just forget about it, just as if i_nlink was
> 0 leaving the remaining opener(s) to do the deallocation later,

Steve.


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