linux-kernel - Re: replace() system call needed (was Re: EXT4-ish "fixes" in UBIFS)

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Date:	Sun, 29 Mar 2009 16:57:06 +0300
From:	Artem Bityutskiy <Artem.Bityutskiy@...ia.com>
To:	Pavel Machek <pavel@....cz>
CC:	Artem Bityutskiy <dedekind@...dex.ru>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: replace() system call needed (was Re: EXT4-ish "fixes" in	UBIFS)

ext Pavel Machek wrote:
> On Sun 2009-03-29 16:07:35, Artem Bityutskiy wrote:
>> Pavel Machek wrote:
>>> On Sun 2009-03-29 16:00:45, Artem Bityutskiy wrote:
>>>> Pavel Machek wrote:
>>>>>>>> 2. create/write/rename leads to empty files
>>>>>>> ..but this should not be. If we want to make that explicit, we should
>>>>>>> provide "replace()" operation; where replace is rename that makes sure
>>>>>>> that source file is completely on media before commiting the rename.
>>>>>> Well, OK, we can fsync() before rename, we just need clean rules
>>>>>> for this, so that all Linux FSes would follow them. Would be nice
>>>>>> to have final agreement on all this stuff.
>>>>> My proposal is 
>>>>>
>>>>> rename() stays.
>>>> It stays and:
>>>>
>>>> 1. does _not_ fsync
>>> Does not fsync. If someone wants to make sure one of the files is on
>>> the disk, he should use replace(). [On non-linux systems, replace()
>>> should be implemented as fsync/rename in libc or something.]
>> I would be happy with these rules. But the fact is, application
>> people just refuse to add fsync before rename. They say that the
>> FS has to do this. And they say that even Linus supports them,
> 
> That's good. fsync before rename would be ugly regression (on ext3 at
> least). We should get them to use replace() syscall, not get them to
> add fsyncs. [Of course, that means we need replace syscall first. :-)]

I'd say it is better to fix ext3 then.

-- 
Best Regards,
Artem Bityutskiy (Артём Битюцкий)
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