linux-kernel - Re: [PATCH] issue storage device flush via sync

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Message-ID: <49CADCCC.4000902@redhat.com>
Date:	Wed, 25 Mar 2009 21:39:24 -0400
From:	Ric Wheeler <rwheeler@...hat.com>
To:	Jeff Garzik <jeff@...zik.org>
CC:	Eric Sandeen <sandeen@...deen.net>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Theodore Tso <tytso@....edu>, Ingo Molnar <mingo@...e.hu>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Arjan van de Ven <arjan@...radead.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Nick Piggin <npiggin@...e.de>, David Rees <drees76@...il.com>,
	Jesper Krogh <jesper@...gh.cc>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] issue storage device flush via sync_blockdev() (was Re:
 Linux 2.6.29)

Jeff Garzik wrote:
> Jeff Garzik wrote:
>> Ric Wheeler wrote:
>> What do you think sync_blockdev() does?  What is its purpose?
>
>> Twofold:
>> (1) guarantee all user data is flushed out before a major event 
>> (unmount, journal close, unplug, poweroff, explosion, ...)
>
>> (2) As a sledgehammer hack for simple or legacy filesystems that do 
>> not wish or need the complexity of transactional protection. 
>> sync_blockdev() is intentionally used in lieu of complexity for the 
>> following filesystems: HFS, HFS+, ADFS, AFFS, FAT, bfs, UFS, NTFS, qnx4.
>
>> My patch adds needed guarantees, only for the above filesystems, 
>> where none were present before.
>
> To be specific, I was referring to fsync(2) guarantees being added to 
> HFS, HFS+, ADFS, AFFS, FAT, bfs, UFS, NTFS, and qnx4.
>
> Other filesystems, besides those in the list, gain the 
> flush-on-unmount action (a rare but useful addition) with my patch.
>
>     Jeff
>
>
>
Sorry for misunderstanding the scope of this before - this is certainly 
a net win for the file systems that don't have proper barrier support 
baked in already. Thanks!

Ric


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