linux-ext4 - Re: [RFC,PATCH 2/2] Direct IO for holes and fallocate

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Message-ID: <20090818001831.GB1215@mit.edu>
Date:	Mon, 17 Aug 2009 20:18:31 -0400
From:	Theodore Tso <tytso@....edu>
To:	Mingming <cmm@...ibm.com>
Cc:	linux-ext4@...r.kernel.org, Eric Sandeen <sandeen@...hat.com>,
	Jan Kara <jack@...e.cz>, Curt Wohlgemuth <curtw@...gle.com>,
	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
Subject: Re: [RFC,PATCH 2/2] Direct IO for holes and fallocate

Here's my suggest rewrite of the patch description:

ext4: Direct IO for holes and fallocate: unwritten extents spt for DIO

From: Mingming <cmm@...ibm.com>

When writing into an unitialized extent via direct I/O, and the direct
I/O doesn't exactly cover the unitialized extent, split the extent
into uninitialized and initialized extents before submitting the I/O.
The reason for doing this is to avoid needing to deal with an ENOSPC
error in the end_io callback that gets used for direct I/O.

Singed-Off-By: Mingming Cao <cmm@...ibm.com> 
Signed-off-by: "Theodore Ts'o" <tytso@....edu>

------------------

As mentioned in my comments for the previous patch,
ext4_convert_unwritten_extents() needs to be defined in the previous
patch.  This may requiring dragging in substantial portions of this
patch.

The other observation is there seems to be quite a bit of overlap
between ext4_split_unwritten_extents() and
ext4_ext_convert_to_initialized().  Is there some way we can do some
code factorization?

						- Ted
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