linux-kernel - RE: [PATCH] incorrect direct io error handling

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Date:	Mon, 18 Dec 2006 11:56:36 -0800
From:	"Chen, Kenneth W" <kenneth.w.chen@...el.com>
To:	"'Dmitriy Monakhov'" <dmonakhov@...nvz.org>,
	<linux-kernel@...r.kernel.org>
Cc:	<devel@...nvz.org>, "Andrew Morton" <akpm@...l.org>,
	<xfs@....sgi.com>
Subject: RE: [PATCH] incorrect direct io error handling

Dmitriy Monakhov wrote on Monday, December 18, 2006 5:23 AM
> This patch is result of discussion started week ago here:
> http://lkml.org/lkml/2006/12/11/66
> changes from original patch:
>  - Update wrong comments about i_mutex locking.
>  - Add BUG_ON(!mutex_is_locked(..)) for non blkdev. 
>  - vmtruncate call only for non blockdev
> LOG:
> If generic_file_direct_write() has fail (ENOSPC condition) inside 
> __generic_file_aio_write_nolock() it may have instantiated
> a few blocks outside i_size. And fsck will complain about wrong i_size
> (ext2, ext3 and reiserfs interpret i_size and biggest block difference as error),
> after fsck will fix error i_size will be increased to the biggest block,
> but this blocks contain gurbage from previous write attempt, this is not 
> information leak, but its silence file data corruption. This issue affect 
> fs regardless the values of blocksize or pagesize.
> We need truncate any block beyond i_size after write have failed , do in simular
> generic_file_buffered_write() error path. If host is !S_ISBLK i_mutex always
> held inside generic_file_aio_write_nolock() and we may safely call vmtruncate().
> Some fs (XFS at least) may directly call generic_file_direct_write()with 
> i_mutex not held. There is no general scenario in this case. This fs have to 
> handle generic_file_direct_write() error by its own specific way (place).      


I'm puzzled that if ext2 is able to instantiate some blocks, then why does it
return no space error?  Where is the error coming from?
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