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Date: Tue, 19 Jul 2011 12:56:39 -0400
From: Christoph Hellwig <hch@infradead.org>
To: Jan Kara <jack@suse.cz>
Cc: Curt Wohlgemuth <curtw@google.com>, Christoph Hellwig <hch@infradead.org>,
        Al Viro <viro@zeniv.linux.org.uk>, linux-fsdevel@vger.kernel.org,
        linux-kernel@vger.kernel.org, fengguang.wu@intel.com
Subject: Re: [PATCH] writeback: Don't wait for completion in
 writeback_inodes_sb_nr
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On Fri, Jul 15, 2011 at 01:08:54AM +0200, Jan Kara wrote:
>   Actually, it's the other way around writeback_inodes_sb() is superfluous
> because of wakeup_flusher_threads(). So something like attached patch could
> improve sync times (especially in presence of other IO). So far I have only
> checked that sync times look reasonable with it but didn't really compare
> them with original kernel...

This changes the order in which ->quota_sync is called relatively to
other operations, see my other mail about it.  Also the code gets really
confusing at this point, I think you're better of stopping to try to
shared code between syncfs, umount & co and sys_sync with these bits.

You're also skipping the ->sync_fs and quotasync calls the first round.
I know for XFS sync_fs without wait is already mostly a no-op, but we'll
need to benchmark and document this change, and apply it to the non-sync
caller as well.