linux-ext4 - Re: [PATCH] ext4: block direct I/O writes during ext4

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Message-ID: <20130717182709.GB26859@thunk.org>
Date:	Wed, 17 Jul 2013 14:27:10 -0400
From:	Theodore Ts'o <tytso@....edu>
To:	Jan Kara <jack@...e.cz>
Cc:	Ext4 Developers List <linux-ext4@...r.kernel.org>,
	stable@...r.kernel.org
Subject: Re: [PATCH] ext4: block direct I/O writes during ext4_truncate

On Tue, Jul 16, 2013 at 12:49:42PM -0400, Theodore Ts'o wrote:
> On Tue, Jul 16, 2013 at 05:46:58PM +0200, Jan Kara wrote:
> > and ext4_setattr() does (again under i_mutex):
> >                                         ext4_inode_block_unlocked_dio(inode);
> >                                         inode_dio_wait(inode);
> >                                         ext4_inode_resume_unlocked_dio(inode);
> 
> Ah, I missed this; thanks for pointing this out.

I took a closer look, and there are other code paths which call
ext4_truncate() which don't call ext4_inode_block_unlocked_dio() and
inode_dio_wait().  In particular, the orphan cleanup code and the
SETFLAGS ioctl.

I suspect the right answer is to move these these calls, and possibly
also the truncate_pagecache() call.

The other thing that we probably will want to do as a cleanup for the
next merge window is to look at merging more of the code paths for
ext4_punch_hole() and ext4_truncate().

Cheeers,

						- Ted
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