linux-kernel - Re: The bug of iput() removal from flusher thread?

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Message-ID: <20121121170850.GD30250@quack.suse.cz>
Date:	Wed, 21 Nov 2012 18:08:50 +0100
From:	Jan Kara <jack@...e.cz>
To:	Dave Chinner <david@...morbit.com>
Cc:	Jan Kara <jack@...e.cz>,
	OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>,
	Al Viro <viro@...iv.linux.org.uk>,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: The bug of iput() removal from flusher thread?

On Wed 21-11-12 13:44:05, Dave Chinner wrote:
> On Wed, Nov 21, 2012 at 02:48:51AM +0100, Jan Kara wrote:
> > 
> > diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
> > index 51ea267..3e3422f 100644
> > --- a/fs/fs-writeback.c
> > +++ b/fs/fs-writeback.c
> > @@ -228,6 +228,8 @@ static void requeue_io(struct inode *inode, struct bdi_writeback *wb)
> >  static void inode_sync_complete(struct inode *inode)
> >  {
> >  	inode->i_state &= ~I_SYNC;
> > +	/* If inode is clean an unused, put it into LRU now... */
> > +	inode_add_lru(inode);
> >  	/* Waiters must see I_SYNC cleared before being woken up */
> >  	smp_mb();
> >  	wake_up_bit(&inode->i_state, __I_SYNC);
> > diff --git a/fs/inode.c b/fs/inode.c
> > index b03c719..8f6396f 100644
> > --- a/fs/inode.c
> > +++ b/fs/inode.c
> > @@ -408,6 +408,19 @@ static void inode_lru_list_add(struct inode *inode)
> >  	spin_unlock(&inode->i_sb->s_inode_lru_lock);
> >  }
> >  
> > +/*
> > + * Add inode to LRU if needed (inode is unused and clean).
> > + *
> > + * Needs inode->i_lock held.
> > + */
> > +void inode_add_lru(struct inode *inode)
> > +{
> > +	if (!(inode->i_state & (I_DIRTY | I_FREEING | I_SYNC)) &&
> > +	    !atomic_read(&inode->i_count) && inode->i_sb->s_flags & MS_ACTIVE)
> > +		inode_lru_list_add(inode);
> 
> Needs to avoid I_WILL_FREE as well. There's no point putting it on
> the LRU if we are writing from iput_final()....
  Yeah, it won't cause any real problems but you are right it's not useful
to put such inodes into the LRU. I'll send v3 in a moment, now as a proper
patch submission since we seem to agree...

								Honza
-- 
Jan Kara <jack@...e.cz>
SUSE Labs, CR
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