linux-kernel - Re: [PATCH 15/17] fs: inode per-cpu last

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Message-ID: <1285833189.2615.31.camel@edumazet-laptop>
Date:	Thu, 30 Sep 2010 09:53:09 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Dave Chinner <david@...morbit.com>, linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 15/17] fs: inode per-cpu last_ino allocator

Le jeudi 30 septembre 2010 à 07:36 +0200, Eric Dumazet a écrit :
> Le mercredi 29 septembre 2010 à 21:53 -0700, Andrew Morton a écrit :

> > > +static unsigned int last_ino_get(void)
> > > +{
> > > +	static unsigned int last_ino;
> > > +
> > > +	return ++last_ino;
> > > +}
> > 
> > This is racy with CONFIG_PREEMPT on some architectures, I suspect.  I'd
> > suggest conversion to atomic_t with, of course, an explanatory comment ;)
> > 
> 

In fact this code was OK when I submitted my original patch back in
2008, since it replaced fs/inode.c

	inode->i_ino = ++last_ino;

And this was protected by a surrounding spinlock
(spin_lock(&inode_lock); at that time)

Even after Nick patches, preemption is still disabled (by two
spinlocks... spin_lock(&sb_inode_list_lock); /
spin_lock(&inode->i_lock);)

So patch 15/17 seems good to me, I re-sign it as-is ;)

Signed-off-by: Eric Dumazet <eric.dumazet@...il.com>

If it happens preemption is re-enabled later (with future patches), we
might need to change last_ino_get() too.

Thanks !


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