linux-kernel - Re: [PATCH] Fix queueing work if !bdi_cap_writeback

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Message-ID: <87627ie8mu.fsf@devron.myhome.or.jp>
Date:	Thu, 13 Sep 2012 15:31:37 +0900
From:	OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>
To:	Fengguang Wu <fengguang.wu@...el.com>
Cc:	viro@...iv.linux.org.uk, jack@...e.cz, hch@....de,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Fix queueing work if !bdi_cap_writeback_dirty()

Fengguang Wu <fengguang.wu@...el.com> writes:

>> >> I tested by custom bdi with BDI_CAP_NO_WRITEBACK - sync(2) blocked
>> >> forever by this reason.
>> >
>> > What's your test script? How do you create/use that custom bdi?
>> 
>> Ah, I wrote my kernel module to test. I guess there is no users in
>> current kernel for now, because it doesn't work.
>
> OK. Got it. So I'd suggest to change the first chunk to a VM_BUG_ON(),
> which should be enough to catch new bad callers. The other two chunks
> look fine.

Hm, if it changed to VM_BUG_ON(), we can't use BDI_CAP_NO_WRITEBACK to
disable the writeback task (but allow inode cache reclaim) after all.

Or you meant we don't allow to disable the writeback task?

Thanks.
-- 
OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>
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