linux-kernel - Re: [PATCH 17/19] fs: Reduce inode I

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Message-ID: <20101017051310.GA22060@amd>
Date:	Sun, 17 Oct 2010 16:13:10 +1100
From:	Nick Piggin <npiggin@...nel.dk>
To:	Nick Piggin <npiggin@...nel.dk>
Cc:	Dave Chinner <david@...morbit.com>,
	Christoph Hellwig <hch@...radead.org>,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 17/19] fs: Reduce inode I_FREEING and factor inode
 disposal

On Sun, Oct 17, 2010 at 03:35:14PM +1100, Nick Piggin wrote:
> On Sun, Oct 17, 2010 at 03:13:13PM +1100, Dave Chinner wrote:
> > On Sun, Oct 17, 2010 at 01:49:23PM +1100, Nick Piggin wrote:
> > > On Sat, Oct 16, 2010 at 09:30:47PM -0400, Christoph Hellwig wrote:
> > > > >   * inode->i_lock is *always* the innermost lock.
> > > > >   *
> > > > > + * inode->i_lock is *always* the innermost lock.
> > > > > + *
> > > > 
> > > > No need to repeat, we got it..
> > > 
> > > Except that I didn't see where you fixed all the places where it is
> > > *not* the innermost lock. Like for example places that take dcache_lock
> > > inside i_lock.
> > 
> > I can't find any code outside of ceph where the dcache_lock is used
> > within 200 lines of code of the inode->i_lock. The ceph code is not
> > nesting them, though.
> 
> You mustn't have looked very hard? From ceph:
> 
>        spin_unlock(&dcache_lock);
>        spin_unlock(&inode->i_lock);
> 
> (and yes, acquisition side does go in i_lock->dcache_lock order)

A really quick grep reveals cifs is using GlobalSMBSeslock inside i_lock
too.

Everything uses i_size seqlock inside it, but I guess that's *always*
the inner innermost lock so it doesn't really count.
 
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