From: Christoph Hellwig <hch@lst.de>
To: "Ted Ts'o" <tytso@mit.edu>
Cc: Christoph Hellwig <hch@lst.de>,
hughd@google.com, hirofumi@mail.parknet.co.jp,
chris.mason@oracle.com, swhiteho@redhat.com,
linux-fsdevel@vger.kernel.org, jaxboe@fusionio.com,
martin.petersen@oracle.com
Subject: Re: discard and barriers
Date: Sun, 15 Aug 2010 21:02:30 +0200 [thread overview]
Message-ID: <20100815190230.GA11416@lst.de> (raw)
In-Reply-To: <20100815173906.GA20124@thunk.org>
On Sun, Aug 15, 2010 at 01:39:06PM -0400, Ted Ts'o wrote:
> So after these ordering flush/ordering change that have been proposed,
> if the block device layer is free to reorder the discard and a
> subsequent write to a discard block, I will need to add a *new* wait
> for the discard to complete before I can free the busy extent list.
> And this will be true for all file systems that are currently issuing
> discards. Again, am I missing something?
The above is correct, except for the *new* part. sb_issue_discard at
the moment is synchronous, so you're already waiting for it to finish.
> So that means we need to add the end-io callbacks to the discard
> operations *first*, before we remove the implicit flush/ordering
> guarantees.
Doing the discard asynchronous and with and end_io callback defintivel
is an optimization over waiting for it synchronously, and it's in fact
what I'm doing in XFS. It's however unrelated to getting rid of the
barriers.
next prev parent reply other threads:[~2010-08-15 19:03 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-08-14 11:56 discard and barriers Christoph Hellwig
2010-08-14 14:14 ` Ted Ts'o
2010-08-14 14:52 ` Christoph Hellwig
2010-08-14 15:46 ` Chris Mason
2010-08-14 17:22 ` Christoph Hellwig
2010-08-14 20:11 ` Hugh Dickins
2010-08-15 17:39 ` Ted Ts'o
2010-08-15 19:02 ` Christoph Hellwig [this message]
2010-08-15 21:25 ` Ted Ts'o
2010-08-15 21:30 ` Christoph Hellwig
2010-08-16 9:41 ` Steven Whitehouse
2010-08-16 11:26 ` Christoph Hellwig
2010-08-17 10:59 ` Steven Whitehouse
2010-08-23 16:42 ` Christoph Hellwig
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