From: Christoph Hellwig <hch@infradead.org>
To: Andreas Dilger <adilger@sun.com>
Cc: Quentin Barnes <qbarnes@yahoo-inc.com>, linux-fsdevel@vger.kernel.org
Subject: Re: real_lookup() lock contention causes poor performance
Date: Tue, 26 Jan 2010 02:55:41 -0500 [thread overview]
Message-ID: <20100126075541.GA14602@infradead.org> (raw)
In-Reply-To: <12CBE910-64A3-4A3A-BB6D-B1B2AAFF5067@sun.com>
On Mon, Jan 25, 2010 at 04:15:03PM -0700, Andreas Dilger wrote:
> We have had something similar for Lustre patched into ext3/ext4 for a
> long time -"__iopen__/{inum}", which depends on a mount option "iopen"
> to allow this functionality, and "iopen_nopriv" to allow access to non-
> root users.
>
> The problem we had in the past is that this needed a bunch of changes in
> ext3/4 and the VFS in order to handle subtle races in the dcache. We're
> moving away from changing ext3/4 and changing the API to use export
> methods (i.e. ext4_get_dentry()) on each filesystem, which should
> simplify this a lot, though I'm not sure it will solve your scalability
> problem.
the get_dentry export operation is long gone. Take a look at
xfs_handle_to_dentry() and friends for a semi-sane (not the horribe
legacy ABI but the implementation) open by handle implementation using
the full exportfs infrastructure. It's still going to hit the dcache
locking quite hard, though.
prev parent reply other threads:[~2010-01-26 7:55 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-01-25 17:09 real_lookup() lock contention causes poor performance Quentin Barnes
2010-01-25 23:15 ` Andreas Dilger
2010-01-26 7:55 ` Christoph Hellwig [this message]
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