linux-kernel - Re: [PATCH] writeback: Fix broken sync writeback

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Date:	Sun, 27 Jun 2010 18:44:42 +0200 (CEST)
From:	Jan Engelhardt <jengelh@...ozas.de>
To:	Jan Kara <jack@...e.cz>
cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Jens Axboe <jens.axboe@...cle.com>,
	Linux Kernel <linux-kernel@...r.kernel.org>, stable@...nel.org,
	gregkh@...e.de
Subject: Re: [PATCH] writeback: Fix broken sync writeback


Hi Jan Kara,


On Monday 2010-02-15 16:41, Jan Engelhardt wrote:
>On Monday 2010-02-15 15:49, Jan Kara wrote:
>>On Sat 13-02-10 13:58:19, Jan Engelhardt wrote:
>>> >> 
>>> >> This fixes it by using the passed in page writeback count, instead of
>>> >> doing MAX_WRITEBACK_PAGES batches, which gets us much better performance
>>> >> (Jan reports it's up from ~400KB/sec to 10MB/sec) and makes sync(1)
>>> >> finish properly even when new pages are being dirted.
>>> >
>>> >This seems broken.
>>> 
>>> It seems so. Jens, Jan Kara, your patch does not entirely fix this.
>>> While there is no sync/fsync to be seen in these traces, I can
>>> tell there's a livelock, without Dirty decreasing at all.

What ultimately became of the discussion and/or the patch? 

Your original ad-hoc patch certainly still does its job; had no need to 
reboot in 86 days and still counting.
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