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From: Jeff Moyer <jmoyer@redhat.com>
To: majianpeng <majianpeng@gmail.com>
Cc: axboe <axboe@kernel.dk>, viro <viro@zeniv.linux.org.uk>,
	LKML <linux-kernel@vger.kernel.org>,
	linux-fsdevel <linux-fsdevel@vger.kernel.org>
Subject: Re: [PATCH V2 0/2] Auto stop async-write on block device when device removed.
Date: Wed, 25 Sep 2013 11:44:58 -0400	[thread overview]
Message-ID: <x49siwsewhx.fsf@segfault.boston.devel.redhat.com> (raw)
In-Reply-To: <201309250932532670454@gmail.com> (majianpeng@gmail.com's message of "Wed, 25 Sep 2013 09:32:55 +0800")

majianpeng <majianpeng@gmail.com> writes:

>>The bigger question is whether we want to change this long-standing
>>behaviour of how our write-back cache works.  I don't know that it's
>>really worth it, honestly.  If you want to ensure data is on disk, you
>>open the file O_SYNC or you issue an fsync, and those calls will return
>>an error for a removed block device.  So, I guess I'll ask the same
>>question again: why are you looking at this?  Is there some application
>>you care about that does buffered I/O to the block device and never does
>>an fsync?
>>
> Yes, for my company, we used our filesystem in userspace on block-device.
> For the performance, we used buffer-wrtite not sync-write.
> For my workload, we allow user to remove disk whether disk working or not.
> Now, we check the state of disk from /proc/partitions at the same interval.
>
> This patchset don't change write-back cache works.It only let vfs know
> the state of lower-device.  I think it make a sense.

I'm still curious to know how you maintain a consistent file system
without the use of fsync, but that's an unrelated issue.

I looked at the rescan partition code path more closely, and it will
only really trigger if the partitions themselves aren't open.  So, I
don't think there is a problem in your approach.

I'll ack patch 1.  I still think patch 2 is not neessary.  Please
correct me if I'm wrong.

Cheers,
Jeff

  reply	other threads:[~2013-09-25 15:45 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2013-09-17  3:21 [PATCH V2 0/2] Auto stop async-write on block device when device removed majianpeng
2013-09-23 14:47 ` Jeff Moyer
2013-09-24  3:07   ` majianpeng
2013-09-24 13:54     ` Jeff Moyer
2013-09-25  1:32       ` majianpeng
2013-09-25 15:44         ` Jeff Moyer [this message]
2013-09-29  8:46       ` majianpeng

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