linux-kernel - Re: [patch] RFC directio: partial writes support

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Message-ID: <87vddj6ij8.fsf@openvz.org>
Date:	Sat, 27 Feb 2010 14:10:35 +0300
From:	Dmitry Monakhov <dmonakhov@...nvz.org>
To:	"linux-kernel\@vger.kernel.org" <linux-kernel@...r.kernel.org>
Cc:	"linux-fsdevel\@vger.kernel.org" <linux-fsdevel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [patch] RFC directio: partial writes support

Dmitry Monakhov <dmonakhov@...nvz.org> writes:

> Can someone please describe me why directio deny partial writes.
> For example if someone try to write 100Mb but file system has less
> data it return ENOSPC in the middle of block allocation.
> All allocated blocks will be truncated (it may be 100Mb -4k) end
> ENOSPC will be returned. As far as i remember direct_io always act
> like this, but i never asked why?
> Why do we have to give up all the progress we made?
> In fact partial writes are possible in case of holes, when we 
> fall back to buffered write. XFS implemented partial writes.
>
> I've done trivial changes and it works like charm. 
> Let's enable partial writes support and allow caller to define
> this behavior.
add Andrew to cc:
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