From: Ted Ts'o <tytso@mit.edu>
To: Christoph Hellwig <hch@lst.de>
Cc: 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 17:25:34 -0400 [thread overview]
Message-ID: <20100815212534.GE20124@thunk.org> (raw)
In-Reply-To: <20100815190230.GA11416@lst.de>
On Sun, Aug 15, 2010 at 09:02:30PM +0200, Christoph Hellwig wrote:
> 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.
OK, now I understand why I'm confused. I thought the proposal was to
change sb_issue_discard() to make it be asynchronous? Really, what
we're talking about here is eliminating the explicit
barrier/SYNCHRONIZE CACHE from the discard, correct? The
sb_issue_discard() call will still remain synchronous.
- Ted
next prev parent reply other threads:[~2010-08-15 21:25 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
2010-08-15 21:25 ` Ted Ts'o [this message]
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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