From: Nick Piggin <npiggin@kernel.dk>
To: Christoph Hellwig <hch@infradead.org>
Cc: Nick Piggin <npiggin@kernel.dk>,
Dave Chinner <david@fromorbit.com>,
linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 04/19] fs: Implement lazy LRU updates for inodes.
Date: Sun, 17 Oct 2010 13:09:51 +1100 [thread overview]
Message-ID: <20101017020951.GC3162@amd> (raw)
In-Reply-To: <20101017004710.GC1614@infradead.org>
On Sat, Oct 16, 2010 at 08:47:10PM -0400, Christoph Hellwig wrote:
> On Sun, Oct 17, 2010 at 04:29:24AM +1100, Nick Piggin wrote:
> > > I don't think the pointer check will work either. By the time we retake
> > > the lru lock the inode might already have been reaped through a call
> > > to invalidate_inodes. There's no way we can do anything with it after
> >
> > I don't think you're right. If we re take inode_lock, ensure it is on
> > the LRU, and call the can_unuse checks, there is no more problem than
> > the regular loop taking items from the LRU, AFAIKS.
>
> As long as we have the global inode lock it should indeed be safe.
> But once we have a separate lru lock (global or per-zone, with or
> without i_lock during the addition) there is nothing preventing the
> inode from getting reused and re-added to the lru in the meantime.
> Sure this is an extremly unlikely case, but there is no locking to
> prevent it once inode_lock is gone.
No. There is nothing preventing that exact reuse from happening in
mainline _today_ either, because the inode_lock is dropped there too.
The point is that it is a heuristic that works (apparently) most of the
time but if it gets it wrong then it's not a big deal, it's only the LRU
position anyway. It would work exactly the same with separate global or
per-zone lru locks.
next prev parent reply other threads:[~2010-10-17 2:09 UTC|newest]
Thread overview: 62+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-10-16 8:13 Inode Lock Scalability V4 Dave Chinner
2010-10-16 8:13 ` [PATCH 01/19] fs: switch bdev inode bdi's correctly Dave Chinner
2010-10-16 9:30 ` Nick Piggin
2010-10-16 16:31 ` Christoph Hellwig
2010-10-16 8:13 ` [PATCH 02/19] kernel: add bl_list Dave Chinner
2010-10-16 9:51 ` Nick Piggin
2010-10-16 16:32 ` Christoph Hellwig
2010-10-16 8:13 ` [PATCH 03/19] fs: Convert nr_inodes and nr_unused to per-cpu counters Dave Chinner
2010-10-16 8:29 ` Eric Dumazet
2010-10-16 10:04 ` Dave Chinner
2010-10-16 10:04 ` Dave Chinner
2010-10-16 10:27 ` Eric Dumazet
2010-10-16 10:27 ` Eric Dumazet
2010-10-16 17:26 ` Peter Zijlstra
2010-10-17 1:09 ` Dave Chinner
2010-10-17 1:12 ` Christoph Hellwig
2010-10-17 2:16 ` Dave Chinner
2010-10-16 8:13 ` [PATCH 04/19] fs: Implement lazy LRU updates for inodes Dave Chinner
2010-10-16 9:29 ` Nick Piggin
2010-10-16 16:59 ` Christoph Hellwig
2010-10-16 17:29 ` Nick Piggin
2010-10-16 17:34 ` Nick Piggin
2010-10-17 0:47 ` Christoph Hellwig
2010-10-17 0:47 ` Christoph Hellwig
2010-10-17 2:09 ` Nick Piggin [this message]
2010-10-17 1:53 ` Dave Chinner
2010-10-16 8:13 ` [PATCH 05/19] fs: inode split IO and LRU lists Dave Chinner
2010-10-16 8:14 ` [PATCH 06/19] fs: Clean up inode reference counting Dave Chinner
2010-10-16 8:14 ` [PATCH 07/19] exofs: use iput() for inode reference count decrements Dave Chinner
2010-10-16 8:14 ` [PATCH 08/19] fs: rework icount to be a locked variable Dave Chinner
2010-10-16 8:14 ` [PATCH 09/19] fs: Factor inode hash operations into functions Dave Chinner
2010-10-16 8:14 ` [PATCH 10/19] fs: Introduce per-bucket inode hash locks Dave Chinner
2010-10-16 8:14 ` [PATCH 11/19] fs: add a per-superblock lock for the inode list Dave Chinner
2010-10-16 8:14 ` [PATCH 12/19] fs: split locking of inode writeback and LRU lists Dave Chinner
2010-10-16 8:14 ` [PATCH 13/19] fs: Protect inode->i_state with the inode->i_lock Dave Chinner
2010-10-16 8:14 ` [PATCH 14/19] fs: introduce a per-cpu last_ino allocator Dave Chinner
2010-10-16 8:14 ` [PATCH 15/19] fs: Make iunique independent of inode_lock Dave Chinner
2010-10-16 8:14 ` [PATCH 16/19] fs: icache remove inode_lock Dave Chinner
2010-10-16 8:14 ` [PATCH 17/19] fs: Reduce inode I_FREEING and factor inode disposal Dave Chinner
2010-10-17 1:30 ` Christoph Hellwig
2010-10-17 2:49 ` Nick Piggin
2010-10-17 4:13 ` Dave Chinner
2010-10-17 4:35 ` Nick Piggin
2010-10-17 5:13 ` Nick Piggin
2010-10-17 6:52 ` Dave Chinner
2010-10-17 7:05 ` Nick Piggin
2010-10-17 23:39 ` Dave Chinner
2010-10-18 21:27 ` Sage Weil
2010-10-19 3:54 ` Nick Piggin
2010-10-16 8:14 ` [PATCH 18/19] fs: split __inode_add_to_list Dave Chinner
2010-10-16 8:14 ` [PATCH 19/19] fs: do not assign default i_ino in new_inode Dave Chinner
2010-10-16 9:09 ` Eric Dumazet
2010-10-16 9:09 ` Eric Dumazet
2010-10-16 16:35 ` Christoph Hellwig
2010-10-18 9:11 ` Eric Dumazet
2010-10-18 14:48 ` Christoph Hellwig
2010-10-16 17:55 ` Inode Lock Scalability V4 Nick Piggin
2010-10-17 2:47 ` Dave Chinner
2010-10-17 2:55 ` Nick Piggin
2010-10-17 2:57 ` Nick Piggin
2010-10-17 6:10 ` Dave Chinner
2010-10-17 6:34 ` Nick Piggin
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