From: Dave Chinner <david@fromorbit.com>
To: Christoph Hellwig <hch@infradead.org>
Cc: xfs@oss.sgi.com
Subject: Re: [PATCH 06/11] xfs: replace i_flock with a sleeping bitlock
Date: Wed, 14 Dec 2011 09:19:17 +1100 [thread overview]
Message-ID: <20111213221917.GD3179@dastard> (raw)
In-Reply-To: <20111208155918.493178782@bombadil.infradead.org>
On Thu, Dec 08, 2011 at 10:58:01AM -0500, Christoph Hellwig wrote:
> We almost never block on i_flock, the exception is synchronous inode
> flushing. Instead of bloating the inode with a 16/24-byte completion
> that we abuse as a semaphore just implement it as a bitlock that uses
> a bit waitqueue for the rare sleeping path. This primarily is a
> tradeoff between a much smaller inode and a faster non-blocking
> path vs faster wakeups, and we are much better off with the former.
>
> A small downside is that we will lose lockdep checking for i_flock, but
> given that it's always taken inside the ilock that should be acceptable.
I didn't think we had lockdep checking on the i_flock because it
uses completions rather than real lock primitives. Either way, I'm
not concerned about this aspect of the change - lockdep doesn't pick
up the typical sort of holdoff problems that i_flock vs delwri
trigger...
> Note that for example the inode writeback locking is implemented in a
> very similar way.
....
> +
> +static inline void xfs_ifunlock(struct xfs_inode *ip)
> +{
> + xfs_iflags_clear(ip, XFS_IFLOCK);
> + wake_up_bit(&ip->i_flags, __XFS_IFLOCK_BIT);
> +}
Should the wakeup be done whilst the ip->i_flags_lock is still held?
The VFS code does the __I_SYNC wakeup while still holding the
inode->i_lock so that the clear and wakeup are atomic, similarly the
__I_NEW bit....
Cheers,
Dave.
--
Dave Chinner
david@fromorbit.com
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next prev parent reply other threads:[~2011-12-13 22:19 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-12-08 15:57 [PATCH 00/11] inode shrink and misc updates Christoph Hellwig
2011-12-08 15:57 ` [PATCH 01/11] xfs: remove xfs_itruncate_data Christoph Hellwig
2011-12-13 21:23 ` Dave Chinner
2011-12-08 15:57 ` [PATCH 02/11] xfs: cleanup xfs_iomap_eof_align_last_fsb Christoph Hellwig
2011-12-13 21:25 ` Dave Chinner
2011-12-08 15:57 ` [PATCH 03/11] xfs: remove the unused dm_attrs structure Christoph Hellwig
2011-12-08 15:57 ` [PATCH 04/11] xfs: remove the if_ext_max field in struct xfs_ifork Christoph Hellwig
2011-12-13 21:59 ` Dave Chinner
2011-12-08 15:58 ` [PATCH 05/11] xfs: make i_flags an unsigned long Christoph Hellwig
2012-01-13 19:07 ` Ben Myers
2012-01-24 18:03 ` Christoph Hellwig
2011-12-08 15:58 ` [PATCH 06/11] xfs: replace i_flock with a sleeping bitlock Christoph Hellwig
2011-12-13 22:19 ` Dave Chinner [this message]
2011-12-18 18:11 ` Christoph Hellwig
2011-12-08 15:58 ` [PATCH 07/11] xfs: replace i_pin_wait with a bit waitqueue Christoph Hellwig
2011-12-13 22:21 ` Dave Chinner
2011-12-08 15:58 ` [PATCH 08/11] xfs: remove the i_size field in struct xfs_inode Christoph Hellwig
2011-12-13 22:58 ` Dave Chinner
2011-12-08 15:58 ` [PATCH 09/11] xfs: remove the i_new_size " Christoph Hellwig
2011-12-13 23:16 ` Dave Chinner
2011-12-14 13:30 ` Christoph Hellwig
2011-12-08 15:58 ` [PATCH 10/11] xfs: always return with the iolock held from xfs_file_aio_write_checks Christoph Hellwig
2011-12-13 23:20 ` Dave Chinner
2011-12-14 13:27 ` Christoph Hellwig
2011-12-08 15:58 ` [PATCH 11/11] xfs: cleanup xfs_file_aio_write Christoph Hellwig
2011-12-13 23:28 ` Dave Chinner
-- strict thread matches above, loose matches on Subject: below --
2011-12-18 20:00 [PATCH 00/11] inode shrink and misc updates V2 Christoph Hellwig
2011-12-18 20:00 ` [PATCH 06/11] xfs: replace i_flock with a sleeping bitlock Christoph Hellwig
2012-01-13 21:49 ` Ben Myers
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